My engine shop is currently building a 383 for me for my 94 TA. The block is from a 96 Caprice. They bored it 30 over, converted it to a splayed main on the center 3 caps. I went with a Callies Dragonslayer 3.75" Crank, 5.7" Callies Compstar Rods, Custom set of JE pistons (-16cc dish). This will be a street/strip motor, I will be using n2o every now and then, in the future i plan to throw a set of larger CC heads on her and slap on a charger and run both n2o/boost. My issue is, the hellfire ring set I got with my custom JE pistons do not fit my pistons, it seems JE messed up with the machine work and I have to send the pistons back for them to be machined. Thats not the problem, but in my talkings with JE they said make sure you do some extra clearence for the piston to clyinder wall. My machine shop was going all by the paperwork which said .005" piston to clyinder wall clearence, the tech guy at JE told me at that clearence it would be great for N/A but once you start spraying nitrous, it mite expand to much and seize up since alluminum expands fast. He said .005" is not enough for nitrous let along nitrous + supercharger. He said he would go with a piston to wall clearence that will be for your most extreme app down the roda (Nitrous + supercharger) and he said .0065" to .007" piston to wall clearence is what i should use (also said .005 clearence and if a power adder is added more clarence is needed on the job spec sheet). What do you guys think about this? This will be a street motor mostly and some track, will the .007" clearence between the piston and wall effect my drivability and will it effect the motor if I dont spray as often as i thought and run N/A 99.9% of the time? ALSO besides the piston to wall clearence, what other clearences should i make sure have some extra room for when I run the dual power adder? Like I said, for now its NA and N2o, and the CR will be 11.0-11.2, I will be throwing a set of larger heads on and lowering the CR and then putting the charger on. Another issue we ran into was the clearence between the rods and the cam lobes, it was hitting, so they had to shave some off the rods, which isn't a big deal, they also had to clearence the rear of the block for the crank (which i know is normal). I heard some horror stories about berring clearence. What should I tell them to make it? I am NOT taking any chances with this motor, i have to much invested in it already. Besides Piston to Wall clarence, what should i make sure the other clearences are so I can run the dual power adder in the future without any issues. Post away, thanks.

 

First of all, you said you got a custom set of pistons. Are they a 2618 alloy (non-silicon)? Assuming that's the case, which it should be for a blower application, the standard small block clearance is .0035 to .0045". You should add .002" for your proposed "dual power adder" setup for a clearance of ~.006". The top ring end gap is a more critical issue, and here I would go with .020".

Bearing clearances cannot be discussed in detail without knowing what type of oil pan and pump you plan to use. Some engine builders like to set up the main and rods a little loose. This will require an aftermaket pan and a high volume pump. What do you have in mind for a pan and pump?

Rich

 

I'd want .0055-.0065 for piston/wall clearance, .025/.028 1st & 2nd ring gap-end clearance, .0027-.0030 main/rod clearance (h-pressure pump) and .020-.025 rod side.

Does any of that really matter?

Well, it does to me but every engine builder uses what they think is best and most aren't going to change the way they do things just cause a customer asks them to. You put your trust in the builder, you're upfront and honest with your expectations, then you let him/her do their business. If you don't trust them or judge them competent for the job... you go somewhere else.

WRT your worries.... If the ring seal is good, the pistons are well machined, then everything should seal up just fine. I wouldn't lose any sleep over ".0065-.007".

-Mindgame

 

I am going with the Canton 279t oil pan, and a melling HV oil pump. Rk, I am not sure if you ever saw the spec sheet that comes with the rings that JE (SRP) ships out but the engine shop is going to be file'in the rings down for the Street Turbo/Nitrous setting, i forgot what they were, is that what your talking about? I told them to gap it for .007" as per JE, is that ok RK? Or will .006 be better? thanks.

 

JE ought to know, though that seems a little big to me. Split the difference at 0.065"?

Rich

 

ok ill tell them to use .0650 clearence for the piston to wall. What other clearences should i ask him about in regards to running my dual power adder in the future?

 

.0065"

 

yea thats what i meant :-D Berring clearences matter when it comes to N/A and n2o + boost?

 

Hmm, but why the question?

Are you building this engine or is your "builder"?

If he doesn't know what to run, then do you really want his business?
If you tell him what to do..... will he want yours?



-Mindgame