captainmorgan

I found that I have dish pistons with a 11.5cc volume .025 in the hole. I was things that they were the L-82 flat top pistons. With the engine in the car, I was just going to replace the heads and camshaft with the following:

Trickflow aluminum heads 67cc
Lunati 60103 268/276, 227/233, .489int/.504ext 110LSA

My calculations show that with the current pistons new heads, cam and .015 gasket the static compression will be about 9.25:1. the quench will be about .04.

Should I just leave the dish pistons or pull them, with the engine left in the car, and replace them with 7cc flat top? I was not planing on the extra work and money, so if I would not get much benefit then I would rather leave the dish pistons in. The engine only has 50,000 miles and the compression checked out at 139psi +/- 6psi on all cylinders.

This car is only used for fun. It is not a daily driver and it will not be raced.

Are my calculations above correct?

The Money Pit

I wouldn't waste the money or time,considering the engine is in the car and as fresh as you say.Might want to drop the cam down to something in the 204/214 @ .050. That will pull very strong off idle to about 5500 or so and be quite fun as a driver.

sxr6

The extra cost of pistons would not be worth it to me, I would would just run some .020 shim type head gaskets which should get your comp very close to 9.5/1 I go.

Vette79C3

I agree! Drop the cam down. I'm running an Extreme CompCams 218/224 with AFR 180 Eliminator Street Heads milled to 60cc. Edlebrock Intake and a performance QJet along with headers. Pretty good setup for me.

captainmorgan

What cc were the chambers before you milled them? How much did you need to remove to get them to 60cc? If you mill the heads do you need to do anything to the intake?

Lynx_6

You don't have enough compression for that cam. I have the Lunati 60102 in GMPP 350/290, with AFR 180 65cc, .015 gskt, same pistons, and it is not enough. The 60103 in your setup would yield ~9.25 scr and ~7.7 dcr, not enough. Throw in the 7cc pistons and you are at ~9.7 scr, and ~8.03 dcr, still not enough in my opinion. If you step down to the 60102 you get ~9.7 scr/~8.08dcr, still low. The only way to get that cam to work you need 4cc flats; ~10.02scr/~8.3dcr. I am a big fan of the Lunatis, not ragging on them at all, they show great potential on Dynosim, giving even similar spec rollers a run for their money. My car runs just ok, the compression deficit is noticeable, wish I knew then what I know now. Bottom line: more compression or less cam!

larrywalk

If I were you, I'd leave the pistons alone and use the cam you've selected. Instead of standard hyd lifters, I'd use Rhodes Lifters on that cam which are a hydraulic lifter with a fast bleed down and increase the dynamic compression ratio at lower rpm - they also sound like solid lifters and increase the rpm range! I've used them on several engines and have really liked the results. Otherwise, I like mechanical roller cams best!

Vette79C3

They were 65cc and I had them milled to 60cc. Your goal is to acquire best compression ratio. Here is a compression calculator to help with what you should purchase. http://www.csgnetwork.com/compcalc.html

VegasJen

are the heads new? the reason i ask is if they're used and you're getting a good deal, you might just have a bit milled on them and use you're thin gasket to give you a bit more CR. i would think you'd probably want your CR closer to 9.5-10:1 with aluminum heads and that cam.
that being said, i think you'd be better off just replacing your pistons with 4v flat tops.

Scott Marzahl

It kind of sounds like you have a L-48 piston there. I would tend to agree with the above poster, personally I would use a two valve relief flat top, Speed Pro H631CP with a -5cc volume.

Either that or just keep it simple and sell these heads and get the 56cc Trick Flows. BTW, the only Trick Flow head I see with 67cc chambers on their site has 215cc intake runners which are pretty big for a mild 350 build.

captainmorgan

This sounds like the easiest and cheapest option. If these work then this would be the way I would like to go. I really do want to try and use the current parts that I have. I assure you that the heads are 190cc/67cc.

I noticed that there are a couple different part numbers for the Rhoades lifters. Which one should I go with?

summitracing.com part numbers:

RHL-8178 - Rhoads Original Hydraulic Flat Tappet Lifters
RHL-8178X - Rhoads V-Max Flat Tappet Lifters
RHL-8178L - Rhoads Original Hydraulic Super Lube Flat Tappet Lifters
RHL-8178XL - Rhoads V-Max Super Lube Flat Tappet Lifters

68/70Vette

If you are going to replace pistons, is there going to be a balance problem if the new pistons weigh differently than the old pistons?

larrywalk

Just went to the Rhoads web site to check out the new variations:
http://www.rhoadslifters.com/

I used the original style and had good experiences - whether you want the additional lube feature or the Vmax option is up to you.

captainmorgan

What if I were to advance the Lunati cam 2 degrees and use the Rhoads lifters? Whould this make sence? That should shift the power curve to the left and give me better low end torque right?

Scott Marzahl

Go over to Team Chevelle and ping Harold, it's his design but I bet he suggest that you to go smaller on the cam.

captainmorgan

I contacted Comp yesterday and they recommended their Magnum 270H cam. I don't know what Lunati's equivalent would be. I will try and see if I can contact Harold and see what he says

VegasJen

i used the comp 276 roller in my build but i built it with a 9.2 CR with iron heads. pulls really nice but i still don't even have the carb/ignition figured out.
if you're running aluminum heads, i still think you're going to want at least 9.5 with that cam.