Restoration-Mini

Technical Forums => Restorations => Daves Garage => Topic started by: MiniDave on March 01, 2021, 01:31:53 PM

Title: Sprite Race Engine Rebuild for Dave L
Post by: MiniDave on March 01, 2021, 01:31:53 PM
Watch this space - it promises to be ugly based on the description!

No compression on #3, and it was blowing out a whole lot of oil, so my guess is a hole in #3 piston.

We need a quick turnaround on this one, he has a race in 3 weeks at Hallet and since he didn't finish his weekend at Houston - it ran great for 2 1/2 days! -  they won't punch his ticket till he runs one more event.

His other option is to pull the motor and gearbox out of his Lotus 7, which is the one with the straight cut gears I built a short while ago, but we'd also need to change the cylinder head as it's aluminum and he can't run that.

We'll see in a couple of days when he hauls it over and I tear it down.....I already made arrangements with the machine shop to slide it in ahead of other work so we can get it right back out again.....but three weeks might be cutting it close, depending on how long it takes to get parts.

Really miss my local Brit parts supplier, Victoria British!

Clancy sold his spare race car, so if this engine runs well I may get to build another for him, he already asked me to build him up another straight cut gearbox so I have another set of gears on the way.
Title: Re: Sprite Race Engine Rebuild
Post by: cstudep on March 01, 2021, 02:54:31 PM
Sounds like you will at least stay busy for a while! Whether that is a good thing or a bad thing we will just have to wait and see I guess. 77.gif
Title: Re: Sprite Race Engine Rebuild
Post by: pbraun on March 01, 2021, 03:40:22 PM
so he needs to finish and drive safe, build a street motor, or minor mods.
Title: Re: Sprite Race Engine Rebuild
Post by: MiniDave on March 01, 2021, 04:28:50 PM
Yes, I have no idea how built up this motor is, what cam it runs or how much head work has been done. I also don't know if he has a wideband on it so he can see if it leans out at higher RPM - which could have caused the piston to burn.

I won't know for sure till I see it and tear it down.

The biggest concern is whether it damaged the cylinder walls.....
Title: Re: Sprite Race Engine Rebuild
Post by: MiniDave on March 04, 2021, 02:34:08 PM
Well, this engine turned out not to be so dire after all - it still will need major surgery but once I got the head off I expected to see a hole in the piston or the side melted off - none of that happened!

The engine is a bit of a mystery in that the parts list of race parts dates from 2009, and I'm not sure all those parts are still in it. It does still have the $600 flywheel and clutch tho!

For example, 2 of the pistons had pretty good marks on them where a valve has hit, one of the intake valves is different than the others, although it's not in either of the cylinders that have the valve marks on them. One of the pushrods is bent, tho none of the valves are stuck, all the guide look good etc. and one of the 8 pushrods is different than the others! The front two pistons have different markings on them than the back two.

Also, stem seals are on the list, but not on the head....

So, it may have started out pretty racey and has been bodged a time or two over the years.

We're trying to get a set of +40 pistons, if we can't we'll get some +60 and bore the block. If we can get the +40 then we'll just give it a light hone....as long as the cylinders measure out OK, there is no damage to the cylinder walls at least.

The cam is supposed to be a "scatter" cam, but I sure can't see any difference in it other than the lobe width - the cam is undamaged, but several of the lifters are showing damage, as do the rear main bearing, the rear cam bearing and the oil pressure relief valve, which was stuck solid and full of metal bits.
 
Another interesting tidbit, normally the piston crown comes up to about 5 thou below the deck surface, #1 piston was 3 thou below, all the others were 5 thou over the top of the deck!

The owner is taking the block, head, pistons and cam up to Kent Prather tonight to have him take a look and make some recommendations, but I think it will be a pretty simple rebuild. The owner has no idea about what his timing, valve clearances or air fuel ratio were......so he has some work to do to learn this motor.

Now - the damage. #3 piston - which had the lowest compression - has no tension on the top ring, it has a slight amount of burning damage on the side above the top ring, but nothing else and the top ring was not stuck. #4 piston had a broken top ring, but no other damage, the other two were also fine. Not so bad, huh? However if this engine is running 13-1 compression like he thinks, that will pressurize the crankcase pretty quickly at 7500 rpm!

The engine does have some pretty racy bits on it, like a 4 bolt center main cap, all ARP studs and nuts on the rods, mains and head, and an 11 bolt head.

Should be a fairly easy rebuild, given that I've enlisted the owner to clean all the bits before we put it back together.
Title: Re: Sprite Race Engine Rebuild
Post by: MiniDave on March 05, 2021, 09:30:30 AM
The owner has decided to see if he can find some 40 over pistons, turns out one of the pistons had a broken ring land under the ring, pretty much like WillieB's engine did. If he can't find the 40's Kent Prather has a set of 60 over he can buy. Still looking for a rimflow intake valve to replace the oddball one.

He's taking the block back up to Kent's shop on Tuesday to do some of Kent's secret modifications (they're not that secret - I told him about them already  ;D ) to make it more durable as a race engine. We're really trying to get it ready in time for the race at Hallet on March 19-21, but that's a big ask if we have to wait for parts. We also need to get the block over to the machine shop either to get honed or bored depending on which pistons he goes with.

I really think this engine has been cobbled up some over the years since it was first built so we're going to straighten it all out - the bones are good, we just need to get everything set up correctly.
Title: Re: Sprite Race Engine Rebuild
Post by: Willie_B on March 05, 2021, 10:09:30 AM
https://www.ebay.com/itm/New-Set-of-Genuine-AE-Pistons-MG-Midget-Austin-Sprite-1275-8-8-to-1-040-Over-40/114519037824?hash=item1aa9ddd780:g:L9sAAOSw5T5fsCeF

These are dished.

Title: Re: Sprite Race Engine Rebuild
Post by: MiniDave on March 05, 2021, 10:17:15 AM
Low compression, cast pistons. We need flat top, forged pistons....
Title: Re: Sprite Race Engine Rebuild
Post by: MiniDave on March 09, 2021, 08:02:50 PM
all righty then, lots done on this race motor, care of Kent Prather (who's also retired but failing at it too :-) )  Today they overbored the oil gallery holes, then threaded them for allen grub screws. They found a couple of bad valves so they changed them all and did a light three angle cleanup of the seats.

He also supplied the owner with new push rods, gasket sets, rod and cam bearings and a few other bits and bobs. main bearings are on the way and will be here Fri I'm told.

He also decided to go with the 60 over pistons Kent had, so we'll be sending it off to be bored and finish honed tomorrow - I'm hopeful my buddy at the machine shop can slide us in and get it done by Friday afternoon, he said he thought he could but if he's slammed he may not be able to get to it as quickly as he hoped.

They also balanced the rotating assembly, so once all the stuff arrives it should be an easy assembly process.
Title: Re: Sprite Race Engine Rebuild
Post by: MiniDave on March 10, 2021, 10:31:12 AM
OK, the block and old rods/pistons went to the machine shop today, I'm hopeful he can get it done by Friday, but we won't have rings and rod bearings till Monday, so that will slow things down a bit too.

Kent apparently found a lot of things wrong in the head, bad valves, one seat that needed to be recut and so on. He also said no two lobes on the cam were the same lift, so a new cam will be in the works for the next time it gets torn down. :(

This engine definitely shows signs of detonation, and it has been bodged together with an assortment of oddball parts, two pistons that were different from the other two and so on, but if you want to piss with the big dogs you have to lift your leg as they say, so he's buying the good stuff and he'll get more as the season goes along. The pistons he got from Kent were forged and 70 thou oversized custom made pistons - the max you can do without offset boring the block. Kent has used them for years, so they're a known quantity....that's the kind of stuff you need to do if you're going to win races - and Kent's engines win races - and championships.

I don't know how many races a season he's planning to do (or can afford to do!) but this will get him thru the weekend and get his license punched.

Funny thing is, he went racing without checking the timing, fuel ratio or pretty much anything before he hit the track! I wonder if he even checked his tire pressures! Oh well, you learn you grow! ;)
Title: Re: Sprite Race Engine Rebuild
Post by: pbraun on March 10, 2021, 11:03:08 AM
Hummmmm  more fun!  71.gif 11.gif
Title: Re: Sprite Race Engine Rebuild
Post by: MiniDave on March 10, 2021, 05:39:44 PM
Surprisingly, my guy got the Sprite block bored and finish honed this afternoon, tomorrow he'll hone the wrist pin holes in the pistons and I should be able to pick it all up tomorrow. He did us a real favor getting it pushed in ahead of some other work, but he said he had a opening pop up in his schedule, so he slid us in and got it done.

I still have lots of things to do to the block before it's ready to assemble, and if the bearings and such come in for the 998 I'll build it up this weekend first. I'm still waiting for the transmission and head to come back for the 998, so all I can do is the block build up on it for now.

We won't have rings or rod bearings for the Sprite motor till Monday at best, so it will wait till then, but I should have everything ready to go together, so it will be a quick assembly and into the engine stand for a lite break in, retorque and re-adjust of the valves.

Then he can haul it off and drop it back in the car, but the actual break in will happen when he hits the track. Kent says he can run the first session on the break-in oil, keeping the revs below 6K, then drain and change the oil and go for it in the second session.

I'll have pics when everything comes back to me.
Title: Re: Sprite Race Engine Rebuild
Post by: MiniDave on March 12, 2021, 10:33:34 AM
The block came back from the machine shop pretty clean, but I still spent a good part of the day using a scotchbrite pad on all the bearing surfaces, running a tap in every hole - some of which were really crudded up - and getting rid of the last tiny bits of red RTV (man I hate that stuff!)

Once it was all clean and ready I went ahead and installed the new cam bearings - by the way, 998 and 1275 cam bearings are different after all. I never paid a lot of attention to how since they use the same camshafts, but since the block is smaller, the rear cam bearing on 998's is about half as wide as those used in a 1275, and the middle bearing is smaller too. That's the only difference that I can find.....

With the cam bearings in I cleaned out the lifter holes with a rotary wire brush just to make sure they were completely clean and slipped the new lifters in, then installed the cam and oil pump.

There's not much more I can do in the block till the piston rings and main bearings get here, but I have plenty to do on the cylinder head yet. I'll lightly reface the rocker arms as we're going to reuse these standard arms, then Kent supplied us with a "competition" rocker arm shaft, so I'll install that and get them all set up.

I've already cleaned all the main parts, but I'll still need to clean up the threads on all the bolts.

I'm hopeful that the rings and bearings will hit today, but if we don't have them by Monday there's little to no hope of making the race next weekend. If we do get it done I'm thinking of going, it's only a four hour drive and I have a lot of friends going, I could help Clancy with his sales efforts too. He's taking his trailer - he's developed a gig to go to the races and sell parts and such - he's a Griot's dealer, Milwaukee Fuel tools, and lots of specialized Sprite race parts, including the transmissions I build for him. I applaud him for his entrepreneurship!

A few shots of the cam tool in action - thanks again to WillieB for making the last bushing I needed to complete the set. The paint marks help me align the holes in the bearings to match the oil ports in the block. You also have to watch to make sure the bearing doesn't rotate as it's going in - I've had that happen a couple of times.
Title: Re: Sprite Race Engine Rebuild
Post by: Willie_B on March 12, 2021, 11:22:49 AM
Glad to see that it does the job.
Title: Re: Sprite Race Engine Rebuild
Post by: MiniDave on March 12, 2021, 12:27:00 PM
It's a bit fiddly on the inside bearing, but it works perfectly!

Today - it's raining outside so I'm down to cleaning things up and a little paint here and there.

Oooooh........shiny!

It's just good ol Rusty O'Leum as this is a race motor and I'm sure it will be torn down frequently - in fact I'll bet I'll be tearing it down again this fall for a new cam, some better rockers and some hardened seats and a good race valve job, plus a few other tricks of the trade.
Title: Re: Sprite Race Engine Rebuild
Post by: MiniDave on March 12, 2021, 04:41:02 PM
Oops, found this today.....

This goes hand in hand with the bent pushrod and the "crop circle" in the top of the piston. Funny that they ran it like this because, look how far out the adjuster is to compensate for the bent pushrod.

Title: Re: Sprite Race Engine Rebuild
Post by: MPlayle on March 12, 2021, 05:38:37 PM
Looks like it was also compensating for a bend in the rocker arm.

Title: Re: Sprite Race Engine Rebuild
Post by: gr8kornholio on March 13, 2021, 12:13:29 AM
Something oddly satisfying about tapping holes.  Itís so nice when you can thread your bolts smoothly all the way in. 
Title: Re: Sprite Race Engine Rebuild
Post by: MiniDave on March 15, 2021, 10:12:57 AM
The owner knew that his engine was running pig rich, but when he tried to adjust the mixture (done by raising or lowering the jet on a SU carb) the jet wouldn't stay up. On looking at it I could see that the choke linkage was holding the jet down and that it was bent in all sorts of weird ways - that's how the choke works - it drops the jet down to richen the mixture and the return spring in the linkage draws the jet back up and holds it against the adjuster. So I took the link off and reconfigured it and viola! now it works! I had to straighten the bend on the end where it attaches to the jet, square the first bend coming off the linkage as it was only about 60*, then re-bend the jet end in a different place to shorten it. It was actually a little tough to do as this metal is pretty stiff, I couldn't bend it with pliers, I had to use a hammer and the vise. Which tells me someone bent it that way to begin with, and/or these carbs have been messed with like everything else on this engine so far.

One more thing off the list.

Still waiting for main bearings and rings so I can build the block. The head is done, I rebuilt the rocker arm assembly with a new shaft and refaced the surface of the rocker that hits the valve, so the head is ready to go on when the block is done. This rocker assy is a short term solution, when we re-do with the head later in the year or post season with new hardened seats and new valves we'll put some new roller tip rockers on it.
Title: Re: Sprite Race Engine Rebuild
Post by: MiniDave on March 15, 2021, 03:35:42 PM
Well, as often happens when you want to get things done quickly....parts orders get screwed up and sent to the wrong address and so on ....bottom line rings and bearing won't be here till Thursday at the soonest, so there's no way we can make the race at Hallett this weekend. Too bad, since it's close enough I might have been able to go....still might but it's unlikely at this point.

The next race is at Gingerman, in Michigan, towards the end of April, so that gives us more time for break in and tuning. I won't be going to that one, it's more like a 10-12 hour drive and if I felt like I could do that I would be up for the Texas run.
Title: Re: Sprite Race Engine Rebuild
Post by: Scargo on March 15, 2021, 04:42:51 PM
Dave...

I assume the race at Gingerman that you mentioned is the VSCDA event over the May 1 & 2 weekend. (There is also a drivers school there the last couple of days in April.)

If this engine being built for Clancy, I have to ask if he is also planning the run in the VSCDA Sprite/Midget Racing Series season finale at Grattan Raceway in Michigan in mid-August. The reason being, I will be there and if Clancy will be there as well, I will look for him.

Title: Re: Sprite Race Engine Rebuild
Post by: MiniDave on March 15, 2021, 04:57:25 PM
No, THIS black engine is for another guy, so that he can finish his school at Gingerman (now - he was going to finish at Hallett this weekend) but Clancy also wants me to build HIM an engine, for the weekend at Gingerman. That one's a long shot, as all he has is a block, crank and rods at this point.....I have a head he could use but it's just a stock 12G940 head.

I don't even know if he has a car to put it in.

I also need to build a transmission for it.......
Title: Re: Sprite Race Engine Rebuild
Post by: Scargo on March 15, 2021, 05:00:36 PM
Dang ....you were too too quick on the rebuttal. Now go back and look at my revised line of questioning.
Title: Re: Sprite Race Engine Rebuild
Post by: MiniDave on March 15, 2021, 05:30:59 PM
Too quick on the keyboard!

Yes, he will be at Grattan, that's one of his every year races. He no longer drives, he's set up a business selling parts and tools to racers now, however they (Gingerman) were looking for a "school car" that they could rent out for that weekend and I think that's how this one came about....I still don't know if we're going to build it yet.

I'm limited on how much I can accomplish right now, a few hours a day seems to be my limit.

He has a new trailer that I haven't seen yet but as you get closer to the event I'll make sure you two meet - he's hard to miss, he's 6'4" and I bet anyone you ask in the paddock will be able to point him out!   77.gif

He sells some slick adjustable lower control arms to allow changes in camber and caster both

Edit: we're not going to build the Gingerman car now, maybe later in the year for next season.
Title: Re: Sprite Race Engine Rebuild
Post by: MiniDave on March 18, 2021, 11:08:21 AM
Well, I got a call this morning that the rings we've been waiting for finally came in, only they're wrong. So, another delay....good thing we're no longer trying to make the race this weekend with this engine.

Edit: Just got a call back, turns out the rings are right, the package was labeled wrong! I'll get the new rings tomorrow, so I can carry on with the build. Now I need to get the other engine out of the stand so I can load this one in when I'm done with the assembly.
Title: Re: Sprite Race Engine Rebuild
Post by: MiniDave on March 20, 2021, 06:41:38 PM
So I took a break from the transmission builds and looked at these rings.....top ring looks like a normal cast chrome edged ring, but the second one.....this is a new one on me! Last time I built a Sprite race motor was in the late 60's (team name - Impecunious Racing) they had no sucha thing!


Anyway, like I said the top ring is a standard looking ring, but the second one.....there is a fairly normal looking ring, but on closer inspection there is a dado in the inner part of it, and in the package - a second ring that goes inside the first, and fits in the dado! It should be interesting trying to fit them as the gaps are supposed to go opposite each other. So I guess fit the inner ring on the piston, then the outer - rotate them and hope that when I use the ring compressor they stay together the way they're supposed to!

I've looked them over a bit, and I don't really see how they go together.....but I'll study them some more.....


Title: Re: Sprite Race Engine Rebuild
Post by: TDA on March 21, 2021, 10:37:24 AM
Is it a Total Seal gapless setup?  Prather uses them in his race engines.

If it is you might check the Total Seal web site for installation tips.
Title: Re: Sprite Race Engine Rebuild
Post by: MiniDave on March 21, 2021, 11:08:45 AM
Yes, that's who supplied them.....I'll look at their website and see what I can learn - thanks!

I also figured I could just call Kent....
Title: Re: Sprite Race Engine Rebuild
Post by: MiniDave on March 26, 2021, 05:07:33 PM
After I cleared out a few other projects and did a bit of cleanup and organizing, today I pulled the Mini engine out of the test stand and installed the brackets for a Sprite motor.

Next up I laid out all the rings so I could custom cut the ring gaps - since this is a race motor Kent (who supplied pistons and rings) said he wanted 15thou endgap rather than the usual 8-12, so each of the top and second rings had to be filed slightly and re-measured several times till just right, and any burrs carefully cleaned off of the edges.

With that done, next up I cleaned up the crank journals and put in the new main bearings, then laid the crankshaft in. Next I installed the thrust washers, then the studs for the mains, then the center main cap got torqued down. The crank turned smoothly so I did the same with the other two mains one at a time, to make sure if there was any binding I knew where it was. The crank rolls smoothly, so all good there.

The next job was to mount up my dial indicator and check the end play - it should be around 3-5 thou and it was spot on at 3 thou.

The next job will be to install the pistons without the rings and then check all measurements, plastigauge the clearances and check the piston to deck height. When I tore it down 3 of the 4 pistons were proud of the deck by a few thousandths, given how the rods can stretch under high RPM use, you don't want them hitting the head or creating any more "crop circles". If we have that situation I may need to send the pistons off to machine shop to have a little taken off the tops. To that end, I have the old head gasket and I will put some clay on top of the pistons, install and torque the head down and roll it over a few times, then remove the head and see how much room there is - the owner found a deal on some 1.5 roller rockers that he wants to use so I need to make sure the valves and pistons won't meet up!

I also have to CC the heads and then try and compute the compression ratio, he thinks it's about 13:1, and we sure don't want it any higher!

So, still lots to do before it will make noise....his next run is the weekend after our Texas trip so I still have a lot to do.
Title: Re: Sprite Race Engine Rebuild
Post by: MiniDave on March 27, 2021, 04:04:22 PM
Today I did a "dry build", where you put the pistons in without rings so you can measure a bunch of things like rod bearing clearance and how far the pistons are above or below the deck surface. When I tore this engine down one piston was 3 thou below and the others were about 5 thou over the top of the deck.

Today they are all uniformly 25 thou below the deck, which will make all my other calculations much easier - I don't have to worry about the pistons hitting the head or the valves hitting the pistons.

With that done I installed the rings onto the pistons and put the pistons into the block, then bolted up the caps and torqued them down. Everything still turns nice and smoothly so I put the oil pump pickup tube in and installed the oil pan. Next I flipped the motor over so I could set up the dial indicator and set TDC, then set up for checking the cam timing.

I really need to cc these heads, as the calculations I'm coming up with indicate a pretty high compression ratio.....
Title: Re: Sprite Race Engine Rebuild
Post by: MiniDave on March 29, 2021, 05:56:12 PM
Today I had PT and as usual I was pretty whipped when I got home, but I did get a little work done on the engine. Last night I mocked up a few things to make sure they would work in the engine stand. For example since the oil cooler and assorted hoses stayed with the car I had to rig up a standard spin on oil filter setup so I can run it in the test stand. I wasn't sure the oil filter was going to clear the extra oil pan square.....which it does.

I also put the the head on, and found that the extra two studs must have been drilled by hand, they are a long way from square to the block surface! They will work, but I have to put the head on, then insert the studs.....

Then I moved around the the clutch end and found the pilot bearing was worn badly. The trick to getting one of these out is to fill it with grease, then inset the input shaft just started into the bushing and give it a good smack with a dead blow hammer - the hydraulic effect will force the bushing out of the hole. However, this one was so worn out that the grease would have just squirted out around the shaft sooo......I found a piece of allthread that was a little bigger, and carefully ground it down till it just fit the bushing. Then I did the grease trick and it came out - in three pieces. i think the hydraulic force broke it up.

Anyway, the new one went in without any drama, so I installed and torqued up the flywheel, then installed the clutch assembly, using an old input shaft as an alignment too.

I also called the company in California that supplied this cam and got the scoop on where to set the cam timing - where I might usually set one up at 106* ATDC, they recommended 103 for this scatter cam - glad I called.

More as it happens.....

Title: Re: Sprite Race Engine Rebuild
Post by: MiniDave on March 30, 2021, 03:30:31 PM
Progress. Cam timing checked. Front end all buttoned up....even made a little pointer to set the timing. Head is on and torqued down, valves are set. Dizzy is in and approximately set. Starter and alternator on, just about ready to set it into the engine stand.....a lot more to do before I can crank up oil pressure, then see if it will make some (hopefully good) noise....
Title: Re: Sprite Race Engine Rebuild
Post by: MiniDave on March 31, 2021, 05:47:41 PM
Got the engine loaded into the stand this afternoon - today was PT day so that's about all I could do - but I got it mostly wired and plumbed. Filled it with oil, I'm letting it run down for a bit now to see how much it will hold with the added capacity. I already filled up the oil filter. Right now it has 4.5 qts in it, looks like 5 is about all it will take.

I'm using the old header as I sent the new one off to be ceramic coated.

Clancy came up with an old transmission case that I can cut the bellhousing off of and make a cover for the clutch and flywheel, but it will have to be for the next one I build. Too many projects to finish first and this one will be long gone in a couple days or less.

Should be making smoke and noise tomorrow morning sometime.

Title: Re: Sprite Race Engine Rebuild
Post by: 94touring on March 31, 2021, 07:36:30 PM
Did you decide if you're going to run it in with race fuel or not?
Title: Re: Sprite Race Engine Rebuild
Post by: MiniDave on March 31, 2021, 09:03:09 PM
Yes, he pulled a gallon out of his tank for me.....I have it already.

Tomorrow I'll crank up oil pressure then see if it will run. Still a few bits and bobs to do, but the owner is coming over tomorrow morning. I really wish I could fire it up before he comes over.....I hate having the owner watch me in case it doesn't go the first time I try it.




Title: Re: Sprite Race Engine Rebuild
Post by: MiniDave on April 01, 2021, 12:31:05 PM
It runs!

Boy does high compression make a difference!

We cranked up oil pressure - and at first it almost wouldn't turn over - but his carbs were leaking gas into the cylinders and once it got some lube on the rings it spun over fine - BUT - you don't want to use gasoline as a lubricant. I insisted that we pull his carbs off and put mine on. I used a shop rag to soak up all the gas in the ports - and there was quite a bit - then put my HIF44 on it and it started after it cleared out all the wet gas off the plugs.

Once running it sounded great - good oil pressure, temp held right at 180 once it warmed up - I finally convinced him to put the muffler on it so we could hear ourselves think and it actually ran better with the back pressure, smoother and it returned to idle better.

We let it run for 20 min or so to break in the cam and when he left he had a big smile on his face! He still has some work to do to install it in the racecar, and he needs to get his carbs sorted out before he tries to run it on them.

Overall, I'm pretty happy with it now myself. I'll let it cool down overnight, then retorque the head and reset the valves then he can take it home. Sorry about the poor video, I was holding my phone while adjusting the carb.....I usually have the phone in a holder.

Title: Re: Sprite Race Engine Rebuild
Post by: 94touring on April 01, 2021, 01:20:34 PM
So does that mean you added oil to lube?
Title: Re: Sprite Race Engine Rebuild
Post by: MiniDave on April 01, 2021, 01:32:48 PM
Nope, started it dry.....the gas in the upper cylinders burned off immediately when it started, from there on it only has whatever normal lubrication that gets on the walls of the cylinders.

We ran it for 20 min and as it ran it clearly seemed to be loosening up already....
Title: Re: Sprite Race Engine Rebuild
Post by: 94touring on April 01, 2021, 01:35:25 PM
Cool
Title: Re: Sprite Race Engine Rebuild
Post by: MiniDave on April 01, 2021, 01:53:30 PM
Did it seem like it took a long time for your engine to break in?

I've never started one with dry cylinders before, but since both Kent and Ivan think that's the way to do it - I decided to go with their experience.....

Kent thinks all that's wrong with the carbs is the wrong needles and jets. We're taking the carbs up to his shop tonight and maybe we'll try the twin carb setup tomorrow after I get the head re-torqued and the engine run again on my carb.
Title: Re: Sprite Race Engine Rebuild
Post by: 94touring on April 01, 2021, 01:57:11 PM
It didn't have many miles on it before we hit the dyno.  500 maybe?  79 wheel horses and about the same torque.
Title: Re: Sprite Race Engine Rebuild
Post by: MiniDave on April 01, 2021, 01:58:50 PM
That's my point, I've never had an engine take forever to bed in the rings when I lube them before I install them, but maybe it does it quicker that way?
Title: Re: Sprite Race Engine Rebuild
Post by: 94touring on April 01, 2021, 02:04:24 PM
I think it ensures maximum compression in a quicker time.  50 miles vs 500 kinda thing.  I know on rotaries sometimes it takes a couple thousand miles if guys baby them too much initially.
Title: Re: Sprite Race Engine Rebuild
Post by: PoolGuy on April 02, 2021, 09:28:00 AM
Sorry if I missed it somewhere, but what flywheel, clutch, cover is that?
Title: Re: Sprite Race Engine Rebuild
Post by: MiniDave on April 02, 2021, 11:15:00 AM
Tilton, super light flywheel - that's partly why it revs so fast. The disc has 6 metallic pucks that are about 1/16th of an inch thick, the pressure plate is a two piece unit, very odd looking. It's strictly and in-out clutch, doesn't slip a bit so there's no feathering it!
Title: Re: Sprite Race Engine Rebuild
Post by: MiniDave on April 02, 2021, 05:03:18 PM
It was 37* at 8 this morning and 61* at noon, so I waited till noon to finish this job....   ;D

I re-torqued the head, reset the valve lash, then I fired it up again, which it did easily and ran sweet - made lots of really good noises too!

so it's ready to go home and get dropped into the car again. That will give him time to get all the little niggling bits sorted, plus he bought a Morroso Accusump and he can get that plumbed in too.

Next race is at Eagles Canyon just north of Dallas at the end of April.

Title: Re: Sprite Race Engine Rebuild
Post by: MiniDave on June 15, 2021, 02:56:01 PM
His second race weekend will be this weekend at Blackhawk Farms in northwest Illinois, I'll try and get some video of him on track if I can. Leaving Thursday early and home Monday afternoon.
Title: Re: Sprite Race Engine Rebuild
Post by: pbraun on June 18, 2021, 09:39:00 AM
Good luck !
Title: Re: Sprite Race Engine Rebuild
Post by: John Gervais on June 21, 2021, 08:15:38 PM
Very interesting thread! 

Thanks Dave!
Title: Re: Sprite Race Engine Rebuild
Post by: MiniDave on June 22, 2021, 11:35:50 AM
So, he's done two race weekends with the motor I built him and so far it's done really well....no issues and makes really good power. He's run as high as 4th (out of 42 entries) and that's with a car that is a long ways from being sorted like the front runners.

This weekend he had a few issues with the car itself, he's been unhappy all along with the exhaust as it exits right where he sits on the driver's side of the car so it's noisy, plus it drags on almost every right turn as the car is so low - and this weekend all but one of the turns was a right - sure enough he spun in someone else's oil and tore the pipe off and damaged his header. So, a new exhaust is on the books now.

He also broke an axle - the bane of all Sprite racers - but thanks to the generosity of the other competitors he was able to get all the parts he needed to get back into action. New axle, new double lipped hub seal, new gasket and o-ring and he was back on track - till he tore off the exhaust.

I'm encouraged that the engine is running so well, I don't think he'll be on track again till September, that will give him time enough to fix the exhaust and install the new trick front adjustable control arms Clancy sold him so he can add a little negative camber to his front tires.

I've been contracted to build two more race motors now - one for Clancy and one for a new fellow out of Wichita.

Title: Re: Sprite Race Engine Rebuild for Dave L
Post by: MiniDave on September 21, 2021, 08:22:09 PM
Dave missed the race in Texas last weekend due to health issues, but he's hoping to make the Lake Garnet Grand Prix in Oct with his Lotus 7. To that end I loaned him a stock cylinder head - he has an aluminum head on it now but he changed to 1.5 rockers and bent all the pushrods, since then even after replacing all the bent parts it hasn't run right, so I loaned him a stock cast iron 12G940 head to make sure that the aluminum one isn't causing the problem. I hope he gets well soon enough to finish the engine and get it running.....