I just got my prc stage 2.5 5.3 heads milled to 59cc and am going to run the .40 cometic gaskets, will i need new smaller pushrods or will the 7.4 chrome moly i have work? I am running a 224r tsp cam

 

Same heads..same gaskets... when I measured my PR length it came to 7.350 with preload.

Only way to tell for sure is to measure.

R/

Frat

 

You also better measure PTVC
and most important if your cam is a 112+4 LSA and you are on stock block, you are in dangerous DCR territory.
You are looking at 11.8 SCR and 9.40 DCR

With stock MLS you would be OK on premium gas only with 1 step colder plugs(like TR6).

 

so im going to need smaller pushrods, the came is just a 112 lsa no advance ground in, i also went with tr55 plugs

 

Yeah to keep the same lifter preload after milled heads/small gaskets you need to get a smaller pushrod.

 

Calculating still over 9.0 DCR and with those plugs you will have some detonating issues. Go 1 step colder and watch your timing on 93/94 octane

Go with stock MLS and you'll be safe on premium

How did you get 11:1 CR in your sig?
And cometics are .040 not .40

 

lol, i added the 11:1 compression to sound cool, haha, so i need one step colder plugs? im not to smart when it comes to this stuff, so whats the next step colder plugs and also i cannot use the cometics?

 

Screaming, If you do not do this right you could loose your whole motor. 9+ DCR, those plugs and bad gas with the valve events of that cam and you could blow a hole in your piston the size of your fist.

Do not use the Cometics, just run GM MLS and you'll be at 11.3 SCR and 8.7 DCR for a nice strong combination.

If you don't believe me ask around, PM Patrick G he will explain the same thing. I'm just trying to save you from making a HUUUUGE mistake.

 

You can use the cometics, but what he is saying is you might be better running like a 0.045 or 0.050 gasket. But then again, decreasing compression by increasing quench isn't optimal in my oppinion. I think your best bet would be to have the pistons notched for the intake valves to avoid issues.

 

I just saw Predator reply while I was typing....

What he's saying is you are on the edge of having to run race gas (greater than 94 octane) to avoid detonation with your motor combo as it sites. Stock mls gaskets are a compressed 0.056" which will help lower your static and dynamic compression.

 

Yeah 9+ of compression is a little much for the typical street setup, you will wind up fighting detonation on pump gas, its worth it to pull the compression down some by swapping to a thicker gasket or flycutting the piston tops.

 

im running the same setup, with the exception of 1. MS4 and 2. GM MLS gaskets. same heads same chamber size. also i am cutting the pistons, (obviously), am i going to be in DCR danger? i dont want to risk my motor.

 

So what would happen if you were running an LS6 Head with 59cc and .050 gaskets with 7.375 pushrods? would you be ok on the stock bottom end?

 

theres a crapload of people who have done the heads im doing milled with thinner gaskets, and ive never heard of them having issues, i dont get it, my compression ratio isnt 11:1i just put that in my sig cause i had seen it around others sig's

 

The issue isn't static compression, it's the dynamic compression ratio which takes into account your valve events based on the camshaft. Since you are running a relatively smaller camshaft, you have less valve overlap of the intake valve being open during the compression stroke which helps to bleed off some compression. Dynamic compression takes into account when the intake valve actually closes, which with a smaller camshaft means more compression. That's good up to a certain point. To much and you cause detonation. Since you milled the heads and have a small combustion chamber size, your dynamic compression ratio has now gone up dramatically.

That's what Predator-Z was trying to tell you earlier. Usually when you mill a head that much, it's to gain back some dynamic compression after going with a monster cam.

 

i see so when i get te car tuned...cant i remove some timing?

 

AAAAAAAHHHHHHHH Just listen to the man!!! (Predator) He knows his **** as good as anybody on here. Just run a GM stock MLS and and your 8.7 DCR is PERFECT for pump gas

 

lol, im ordering them as we speak, so with the gm stock mls gaskets, i can still run the tr55 plugs? Jon from texas speed said with te heads milled the 7.4 pushrods will still work?

 

the preload will just be higher than normal

 

lol, thanks guys, ive finally started to understand what you were telling me, i just odered it through speed inc, i went with the 7.35 pushrods, gm mls gaskets and the tr6 plugs....what do you think Predator Z.....should be good to go now?