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Race Engine Setup Advice

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ChrisS

ChrisS

Jedi Knight
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I need some practical advice from the race folks. I’m gearing up to build my first race engine and would like to run my setup by you to see what I’m wasting money on and what I’m missing. This will be for time trials and autocross this year, preparing for wheel to wheel next year.

1275 block, 0.060” overbore (max rules limit)
Polished and balanced crank (is it worth wedging?)
Stock rods
ARP rod bolts
AE 21253 8cc dish pistons
Stock 9 bolt head, (I need a recommendation on valve sizes, I was thinking of using SS Cooper S race valves, 1.401” intake, 1.22” exhaust, is it worth going with rimflow valves?)
Upgraded valve springs
Stock cam (race rules, I have a spare Isky MM55 cam as well which is 268’ duration for autocross)
Stock lifters, push rods and rockers
Stock timing chain / gears with offset keys as needed
ARP studs for the head (is it necessary to add holes / tap block for 11 studs?)
Stock intake manifold
Smoothed SU’s through intake to head (major porting not allowed)
LCB header
Crane HI-6 CD Ignition box (it will fire from a Pertronix trigger most likely)
Lightened flywheel (exaggerate the step between the friction surface and the ring gear)

So does this sound like a safe starting point? What have others done?

Thanks
 
You may want to balance the entire setup (not just the crank). Otherwise, it sounds good. If you are just running the autocross or just starting wheel-to-wheel, the big valves could wait,especially if you're on a budget.

A crank scraper will buy you about 5 HP almost for free.

And set up engine rich at first....always safer. Also, 30 degrees total ignition advance is plenty to start out.

Actually, my favorite item for the engine is a shift light. Real easy to keep track of RPMs, thus engine lasts longer. Mine was $35 at Summit. I never use the tach anymore and am considering deleting it from the instruments.
 
crank scraper ??? What is this?
 
Jack,
A crank scraper is a piece of metal that is contoured to the rotating diameter of the crank and rod big ends that helps ‘scrape’ the oil off the crank and keep it in the pan. It doesn’t actually touch the crank, it is just really close. Keeping the oil off the crank reduces the rotating mass and helps reduce power losses.

Nial,
I haven’t seen one for the A series in my travels. Are they part of a competition oil pan? I can make it, but there is a lot of planning and cutting that leads to a lot of scrap.

Chris
 
With that cam and the proper build methods. You should not need a shift light.(Won't over rev) I use rod bolts for a chevy big block.(use 454 torque values) They work great and only cost 25 bucks. Much better than the 100 bucks for ARP stuff for a 1275. Heck you can even get ARP stuff for the big block for 30 bucks... I think. Plus you get enough to do two engines. The knurled shank on the chevy stuff goes into the rod cap and really holds the assembly together. The machinist can help you do it. I would also recommend a scatter pattern cam. It will give you more low and mid torque. You don't need arp head studs for the head. Use stock ones and only torque it to 40 #.(I run 14 to 1 and only torque to 40) The extra bolts won't hurt but if you are running less than 10 to 1 they are not needed. Run a fat mix on the carbs 12 parts air to 1 part fuel. Maybe a #5 needle on the stock carbs should do it.
Run a 4.5 rear gear. If you can get one try a 4.8 or 5.3 rear gear.
With that cam stock valves will work great. Don't waste your money. Balanced crank is fine forget the other stuff. Forget the rim flow stuff.Too much $$$$ Only bore to .060 if needed. You will see very little HP gain going from say .020 to .060. De-stress and shot peen the rods. Flux the crank for cracks. My head is hurting I will stop now. good luck.
 
scatter pattern cam?? Someone tell me about this?
 
Basically a scatter pattern cam is a cam to limit the cylinder to cylinder scavenging that occurs between cyl's 1 and 2 cyl's 3 and 4. The #2 cylinder will steal the intake charge from #1 in the siamese port. Sooooo, ya move the #2 intake lobe forward bout 7 to 15+-(depends on who ya talk to)degrees and ya move the #1 lobe backwards about the same.( I think that is it) This tends to isolate the to actions a bit.
The effect is to get good charges to both pistons. Kinda helps in the mid to upper rpm range of the cam and improve volumetric efficency.( no there in a mouth full, is that spelled right?) There is more to it, but I think I have it right...now my head really hurts. I could tell ya more but then I would have to kill myself.
 
Nial,
I haven't seen one for the A series in my travels. Are they part of a competition oil pan? I can make it, but there is a lot of planning and cutting that leads to a lot of scrap.
Chris
We make them ourselves.......pretty easy. Last one used a pizza box as a template. I do not have one in the 1500 because it's a tougher shape, but the 1275 is straightforward.

jolly:
Great suggestion on the Chevy harware. My car actutally has Porsche ARP hardware in it (freebies). It's interesting how much of this stuff will interchange. Honestly, you don't need to balance if you are controlling RPM and are only running autocross....I agree on that.
But if you run those gears at Watkins Glen, you better bring a bucket and shovel to pick up all the schrapnel! One of my pals has a nice balanced 1275 (he owns a large machine shop) and he pulled the 4.5 rear out of his car at BeaveRun (back to a 4.22) because he was getting to close to $$$$ in the rev range. The milder, unbalanced 1275 that I occassionally race will easily blow itself to bits in third gear. And it will pull past 7000 RPM in fourth at WG.....it's one thing to do that during a shift, but when it just sits there for a minute or longer, it gets sort of creepy. What do you consider over revving in an unbalanced engine?

Static balancing of rod/piston is pretty easy if you can get a good scale. Not as good as dynamic, but worth the trouble, I'd say.

By-the-by, my own Spridget has a 1500, which is especially sensitive to RPMs. I have the shift light set at 5700 and am running 3.7 rear. Works great for our amatuer club racing.
The other aspect of the shift light that I like is that it helps set "goals" when driving (i.e. If I can get it to go "red" before reaching a braking zone on a certain turn, I know I have gotten better launch out of the previous turn).
 
Jack,
Take a look at https://www.minimania.com/web/SCatagory/C...72/ArticleV.cfm

JR,
I have to use a stock cam to stay in the race rules, although I think I can use any A series cam made by BL, so one of the Metro GT profiles may be beneficial. I have looked at the scatter pattern cams before, but heard that some were great and others dogs. Which profile have you had luck with? I may try it on my street car.

Chris
 
The cool thing about a scatter pattern cam is it will idle smoother. So who is checking cams at an autocross course? I don't believe that there are any "dogs" just improper application and build practices. Well i take that back, I have seen some really rad cams that were just plain stupid.
My experience is mainly racer sorta stuff. A 286 kent type scatter unit can work good on the street....maybe. I hesitate to say this because there are too many variables. There are so many ways to skin a cat.
If you can find a scatter pattern cam maybe 276 duration or so, it might work well on the street. Kinda depends on if you like to spin the engine up a bit. A cruiser might not benefit from a non-stock type cam.
Your results may vary.
 
Wow, more than I ever wanted to know.
 
You are correct that no one will be checking the cam at an autocross; even if they did they wouldn't know what the specs should be on a Spridget anyways. I realize this; my thought pattern is that I time trial with a setup similar to what I would run next year in a wheel to wheel environment. (I can run anything I want time trialing too, I'm only racing myself.) I get the benefit of working out bugs and trying different setups this year. I drive the street Midget on the hard side as well, maybe 6000 for short stints. I have another engine that I’ll be building for that car and I may try the scatter pattern in that engine. Good info to have. Thanks.
Chris
 
[ QUOTE ]

We make them ourselves.......pretty easy. Last one used a pizza box as a template.

[/ QUOTE ]

That works for me. K.I.S.S.
 
I'd recommend a dynamic balance. It doesn't make sense to me to do some simple preventative work to reduce bearing wear, etc. The less inertia the system has, the better. I had my 1500 done a long time ago, and I don't remember what it cost, but I still feel that it is a good investment.
 
I always have mine balanced. They run smoother, last longer and it makes a tiny bit more power..not enough to brag about. But you don't want to go to crazy on the balancing part. Oil is flying all around in there and at any time the weigh on the rotating parts changes quite a bit. I have seen this using a special camera. Scary things happen at speed in the engine. Push rods look like snakes and the crank is twisting all over the place.
 
Oh my word Jolly. Did I need to know that?

You know I had never thought about it before but makes sence in a strange way.
 
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