[DenRS]

I finally got my engine apart and I getting ready to intall my new heads and cam. I'm currently painting my block so I haven't installed the heads or cam yet. The head gasket that came in my engine kit is a felpro .041 compressed thickness, but I think this might be to thick. My block was decked at one point since there are no numbers on the front pad, but I don't know how much yet. I do plan on measuring how far my pistons are in the hole, but I have to finish painting the block first. My pistons look like the ones in the link, except my pistons don't have the little circle in the middle. They seemed dished, but how do I figure out how much? I'm trying to figure out how to get my compression ratio around 9.5 to 1 for my cam. Does fel pro make a head gasket that I can use with aluminum heads that is thinner than .039?

http://www.chevelles.com/forums/show...headers&page=2

[Mark .L.W.]

You need to check how far down the pistons are , do you have the heads off now . If it's at zero deck now you can't go much thinner or the pistons will hit the head .
Mark.

[zdld17]

Set some type of straight edge across piston hole with piston at TDC. If this is the best you can do, slip a feeler guage between the straight edge and the outer edge of this piston in the photo. If this is your piston, it looks like you have an outer rim and that would be considered the highest point so use that and not the full dish.

Now , if you can come up with a piston part #, that should solve the rest of the equation. I used the .039 1010 flepro gasket too, thats the thinnest I could find in a composition. .035-.045 would be considered safe by some standards but I have seen steel rod motors with less but you are not from Malvern , Pa, so forget that.

Here is a little program to figure what gas you could run, just input the unknown .
http://www.bid2race.com/DynamicCompr...Calculator.php

Here is a link to a compression program by Pat Kelly. Down at the bottom of this are the programs that you could load and run. Determine Dcr and Scr.
http://cochise.uia.net/pkelley2/DynamicCR.html

If you can get that piston #, it would be easier. Did you say if these were cast , forged, aftermarket? Is there a number stamped on deck? They look like a TRW 2556 piston.,

Using the numbers you provide on a 350, with 12 cc pistons, +- .20 deck, .039 gasket, 62cc head, I keep coming up with 9.3scr / 7.7 dcr with your 268 cam. Your quench is about .060
With the 6 cc piston stuff changes, 8.2 dcr / 9.9 scr. This looks like the piston I had in my 355 and that piston was a 6.1 cc piston.

What did I miss.

[DenRS]

I'll check the piston numbers. Where are the located? Are they on the bottom of the piston?

[pdq67]

I think those are just stock, -12 cc dish pistons .

And you can use Fel-pro's #1094 headgaskets with aluminum heads.

They are the .015" thick, rubber coated shims.

But please don't take my word on the pistons b/c if it was mine, I'd cc both them and each head to be sure.

I use this CR. calculating program.

http://www.campbellenterprises.com/R...alculators.htm

pdq67

[zdld17]

Originally Posted by DenRS

I'll check the piston numbers. Where are the located? Are they on the bottom of the piston?

Usually stamped on top near reliefs, but like Paul said, you may be able to just cc them. Get the piston level and drop some measured fluid into the dished portion. You can use a hypo syringe from a farm store.

[DenRS]

I'll have to clean the tops of the pistons because I didn't see any numbers on them.

I attached my dial indicator to the block and set the indictor to the outer edge of the pistons. When the piston stopped moving up according to the dial indicator, I got out a straight edge and checked the edges to check how for the pistons were down. I measured .030 down. Does this seem correct? I thought stock was .025 down. What did I do wrong? My front pad has no numbers on it, so I would assume that it was decked before the last rebuild. Shouldn't my pistons be less than .025 in the hole? Bear with the stupid questions, this is my first rebuild.

[Everett#2390]

You can use the dial indicator to measure the depth.
Bring piston up to TDC with the Dial Ind.
Move D/I over to the block deck, zero the ind.
Place D/I directly above the wrist pin, front to back on the piston, and measure the depth.

Usually, the OE depth is 0.025", if you are measuring at the side of the piston, 90* to the wrist pin, then piston may be cocked in the bore. 0.030" is not bad, just have to add it to the formula.

Aftermarket numbers are stamped on the top.

[DenRS]

Ok, I measured it at the top of the piston. I'll recheck it later on as I have some errands to run for the rest of the day. I did just finish cleaning off my pistons. The numbers on the pistons are 423NP .060. Just found out I have a 4 bolt main too.

[pdq67]

You might have DITH rebuilder pistons so a deck plane could be done is why they are .030" vs the usual .025".

Like DITH of say a .040" and then a .010" clean up cut leaves them at .030"

Get my drift.

pdq67

[DenRS]

I think my pistons are sealed power cast dished pistons. Does anyone have a sealed power catelog and can look up the dish volume of my pistons. I could not find the dish volume of my pistons. The numbers on the pistons are 423NP .060.

[zdld17]

Originally Posted by DenRS

I think my pistons are sealed power cast dished pistons. Does anyone have a sealed power catelog and can look up the dish volume of my pistons. I could not find the dish volume of my pistons. The numbers on the pistons are 423NP .060.

Sealed power. H423NP .060

http://www.flatlanderracing.com/trwchevy350.html

Part # Notes CIDComp Ratio CompDist PistonShape Price/
Each
58cc 60.5cc 64cc 68cc 72cc 76cc



H423NCP-60 5.7" Rod 361 9.56 - 9.00 8.67 8.36 8.08 1.540 .070 dish $16

[Eric68]

When I used the TFS 23* heads on my old 383 I really had good luck with Victor Reinz Nitroseal gaskets. They have a graphite coating on them that sealed good and did not mark up the heads. Very easy to clean up when taking things apart. They have a few different thicknesses -- I am pretty sure there is one that is 4.100" bore by .026-.028" thick. if you search on "Nitroseal" in the Performance forum I am sure I have posted part numbers and thicknesses in the past.

Make sure you measure your deck height and don't go any tighter than about .033-.034" with your quench. My old 383 was OK at .033" but my new 410" motor was carbon tracking at the same quench and I had to open it up with a thicker gasket.

[DenRS]

Thanks for the link. What does .070 dish convert to in CC's?

[zdld17]

I am gonna guess 15 -18 cc = .070. Not knowing much more than what you have posted. . You could take a vet syringe measured in cc's and fill it with water or varsol and fill up that area and get pretty close.