The other day my brother let me take his '89 formula, which as been sitting around forever, to the tire rack to run an autocross. I took 3rd place and the car was a lot of fun to drive. Anyway, the car has always been plagued with problems. The engine has always had a strange vibration that i think is something serious like the crank out of balance. And the rear 2 cylinders have been full of rain water... thats a long story .

We were thinking about rebuilding the engine and have it bored .030 over if the compression is bad. That would require new pistons, but we dont know anything about picking new pistons. How do you choose pistons? Any recommendations for this application? We still want to run pump gas so we dont want crazy compression.

He is also running a Accel 219 single profile cam. I hear this is a really popular cam but i dont know if this is well suited to him because this is a road race/autox car that is always in the high rpms. I thought this cam is better for low-end torque and not high rpm power. Is there a better cam for this car? we still need to have enough vacuum to operate the brakes, so the cam cant be to crazy.
We also want to spin this engine a little faster then the OEM redline, up around 6000-6500. Hes got that AFR "Hydra Rev" kit installed with stronger springs; is that enough to go into that rpm range safely? if not, what else do i need?


This are his mods so far.
AFR 190cc heads with a 58cc chamber.
Accel 219° cam
LT1 intake
short tube headers (i think edelbrock)

Plus new injectors and all the fuel mods and bolt-ons.

I know that the computer isnt tuned right and is not using these mods to their full capacity. We were thinking DFI, but we will do that later. right now, we just want to get this built correctly and fix its problems. After those are taken care of, then we can tune.

I'm a noob to small blocks so any pointers would be great!

 

lets get some more info here;

'89 formula
tranny?
ENGINE SIZE? 305? 350?



are you ready to tear it down and rebuild it, or do you want to do more tuning with it now? Staying naturally aspirated, or perhaps N20 in the future?

speed pro flat top hyper pistons are very popular, and for good reason. Strong enough for most NA motors, and pretty cheap. But this kinda depends if it's a 305 or 350, if i'd recommend flat tops. Or rebuilding it at all

Welcome to the boards _OC.

 

Its a 350 and it has a T-56 tranny out of a 4th gen. Its going to be a N/A motor all the way, no N2O or anything. They wont let you run N2O on a road course.

We are thinking about rebuilding since there may be something physicaly wrong with the engine. Like low compression on the back 2 cylinders and the balance of the engine. We havent checked the compression yet, but we will do that soon.

 

bump

 

Your favorite brand of hypereutectic pistons would be fine. Probably flat tops for decent compression with whatever heads you use. Order the pistons after you've had the block machined, so you'll know what overbore to get.

 

Exactly. The only issue my machinist had with that, is that you finish hone the cylinders based on what the pistons spec it at. So a forged needs a bigger bore then a hyper. Not sure if all hypers are created equal. My machinist insisted basically that I buy my pistons from what he had in stock... Not a big deal, just doubled the price for them due to his markup.

Either way, i'd bring in the block for hot tank, bore, align hone, etc etc. Then pick pistons based on those heads, to get the CR you want. I think you'll need a decent sized dish to lower your CR with teeny 58cc heads. Especially if you have to deck the block at all.
Remember, you can port the chambers to open them up a bit.


You bumped the thread, why don't you list off a numbered list of exactly what questions you want answered?

 

It depends on the piston. Some are specified such that they have the correct clearance when put into a nominal bore. Either way, you don't necessarily need to have the pistons in your hand when the block is bored.

 

my machinist insisted that i order pistons, before he did ANY work on the block. Could also be that he was just putting off work for me though?

 

It could be that he didn't want to have a half-finished project laying around that had to be stopped while waiting for parts and then restarted again.

 

Never looked at it that way.

 

yea, that or that he could measure your bores, bore them as needed, tell you need x over bore pistons... then he moves you block to the corner, then you hand him the pistons, and he resets it back up to be honed again...

 

I think that some sealed power hypers with the dur-o-shield coating(same as mine) would be great for your engine and at $16 a piece it isn't such a bad deal. For the cam, even though you autoX it, streetability should still be a concern, so don't go to big, and if you could afford you should go roller(no break in, or flat lobe concerns).

 

This is all great guys, im a total nub when it comes to pistons and cams. Most of my automotive experience has centered around suspension and chassis setup. There have always been tons of people around that knew enough about engines and such, so I really didn’t concern myself too much with that. But now that I have a few real projects of my own, its turned into a whole different story. I always felt we had a lack of chassis guys in this country, so I went that way Some of the things I read in the suspension/chassis forum make me want to cry!

One of the main reasons we want to rebuild this engine is this strange vibration its had. This vibration was always there, but became more apparent after my bro swapped in a t-56 trans; the trans mounts had hard urethane bushings that transmitted the vibration more.
I have been trying to research what this vibration could be, but I really don’t know. I was thinking that maybe the cam timing is off; but then I thought if it was, the engine would probably have had more trouble by now. I came across one source saying that they had a similar problem and found it was a bad bearing on the crank. But I guess we wont really know until we take it apart. You can feel the engine shake through the chassis with each revolution it makes, at rpm, it makes you worry.

 

even when in neutral? not moving? or when moving, when you put it in neutral, it'll settle down, even while rolling fast?
motor mounts would be the first thing to check. After that, go wrenchin'!

 

yup.. you can be in neutral and feel it. its like someone taking a deadblow mallet and hits the engine once per rev.