355 Head Gaskets

[Shawn F.]

I am needing to purchase either a kit or all of my gaskets for my 355 build but unsure of what thickness I need to go with. I have TRW flat top pistons in the block now that say with 64cc heads the compression ratio will be 9.6:1 (that is if the deck of the block has not been cut down). I have 64cc Vortec heads I am using but would like to keep the compression down to run mid range pump gas is possible or just pump gas in general. Would 9.6:1 be too much? Also from what I read it did not state what thickness of gaskets will let me achieve this 9.6:1 compression.
Anyways my main concern and question for you guys is, what thickness of head gaskets do you recommend going with? Thanks in advance!

 

[Damon]

Using thicker gaskets (like a typical FelPro blue rebuilder gasket (.039") will kkeep you down in the mid 9s but it really won't help detonation resistance because the quench height (from the top of the piston to the flat quench arear of the combustion chamber) will be wider and therefore, less effective. One of those things where the static compression number doesn't tell the whole story of detonation resistance.

Now, Vortec heads have fairly detonation-resistant chambers to begin with so I wouldn't be overly concerned about pushing up near 10:1 on that engine, especially if you're running a bigger than stock cam.

The ideal head gasket would be a steel shim (about .016" thickness) to bring the quench height in around .040" (.025 piston deck height + .016 for the gasket = .041" total quench height), which is generally considered ideal. However, steel shim head gaksets tend to be more difficult to seal up on imperfect surfaces.

Might want to look at the GMPP .028" composition head gaskets, They are cheap and they work very well every time I've used them, including in the mild blower motor that's currently in my Malibu. That is as thin a compsiition-style gasket as you can get and they are much more forgiving of imperfect sealing surfaces than a steel shim. Compression will come in somewhere in the high 9s, but like I said, I wouldn't be too worried about that with Vortec heads.

 

[SSedan64]

As Damon said the Vortec's Chamber is a very efficient design which is resistant to Detonation.

4.030" Bore X 3.48 Stroke.
4VR 7cc Piston, 64cc Head.
.025" Deck Ht., .041" Gasket, .066" Quench = 9.58Cr
With .028" Gasket, .053" Quench = 9.86Cr
With .015" Shim Gasket, .040" Quench = 10.17Cr
The Embossed/Rubber coated steel Shim Gaskets seal better than plain Shims.

Buddy of mine is running a 10.00Cr Vortec, .045" quench, 383ci, w/268H Cam on 87 & 89 octane with no Ping.
It even has the poorly designed Bowl Dish Pistons that don't have much of a Quench area except on the outer ring. LOL!
Dish Example #1470, 1476, 1487>> http://webpages.charter.net/beckracing/slvpg29.htm

 

[Shawn F.]

Thanks a lot for the info guys... Anymore opinions on these embossed/rubber coated steel shim gaskets? As long as I can run pump gas I will be very happy and hopefully push in the 340-350 HP range. I do not plan to run a big cam, I want a low torque to mid torque range cam for daily driving and work vehicle which is pulling my pressure washing trailer with the washer unit, tools and 125 gallons of water.

 

[SSedan64]

High compression & towing aren't a good combination. An RV/Towing Cam wont like high Compression ratios either. Both will cause high EGT/ExhaustGasTemps / High Chamber temps and can cause Detonation/Pinging. Best to check with a few Cam Co.'s & see what they recommend will work.
Which # Vortecs do you have, 906, 062?
The #906's Inconel insert type Exhaust seat is better than the 062's Induction Hardened Seat for towing.
Vortec Head Bible, LOL!>> http://www.nastyz28.com/forum/showthread.php?t=56505

 

[Shawn F.]

Bump for an OLD thread! I never got notification on this thread so want to answer the last question and bring this back to the top for more info! The heads I have are the 906's and I bought them from a member on these boards I believe if I remember correctly...
I still have not thrown this engine together mostly because I am wrapping up my chopped 49 Ford shoebox. I am hoping to start this build in the next 2 months and if I sell my 92 F150 truck soon then I will be jumping in it even quicker!
I still need to decide on the gaskets for the head and if I should even run these heads with this block and flat top pistons? I want to run mid range pump gas and it will be a daily driver. I wish I had dished pistons now but I do not and cannot afford them at this point. What are your guys' opinions here?
I do have a 350 engine (unknown miles but does run) that was pulled from my friends 80 Camaro that is pretty much stock that I can possibly pull, freshen up and then throw these heads on it but not sure what kind of pistons are in those stock motors...
Any advice here for a nice daily driver with some balls would be appreciated! If I can get 330-350HP I'd be more than happy.

 

[Doober]

As Damon said the Vortec's Chamber is a very efficient design which is resistant to Detonation.

4.030" Bore X 3.48 Stroke.
4VR 7cc Piston, 64cc Head.
.025" Deck Ht., .041" Gasket, .066" Quench = 9.58Cr
With .028" Gasket, .053" Quench = 9.86Cr
With .015" Shim Gasket, .040" Quench = 10.17Cr
The Embossed/Rubber coated steel Shim Gaskets seal better than plain Shims.

Buddy of mine is running a 10.00Cr Vortec, .045" quench, 383ci, w/268H Cam on 87 & 89 octane with no Ping.
It even has the poorly designed Bowl Dish Pistons that don't have much of a Quench area except on the outer ring. LOL!
Dish Example #1470, 1476, 1487>> http://webpages.charter.net/beckracing/slvpg29.htm

I have almost this exact setup except I think I'm around 9-9.5:1... rotating assy. that's original to the 1988 block (had it balanced), junkyard Vortecs and a Comp XE268. Runs on 87 all day, pulls hard all the way to 5k, with the stock .040" gaskets to boot (probably .060" quench! This was before I knew about quench). Like Damon said you will be better equipped with the .015" gasket, and the 268 cam makes for an awesoke driver. Bottom end torque (below 2k or so) suffers a hair, but it more than makes up for it on the top end! The 383 with Vortecs in my truck makes ungodly torque (4000lbs. with 3.08s and it still pulls harder down low than the Malibu), but it doesn't have near as much oomph up top as the 'Bu.

 

[Shawn F.]

He said dished pistons though correct? Mine are flat top... Not sure if that kills it for me or not.

 

[Doober]

Nah, compression will be up a little, but if SS64's friend is running 10:1 with 87 you should be fine.
These are what're in mine:

 

[SSedan64]

If it's a 383ci, the Flat Tops may push the CR. a little too high for Mid grade swill. Towing & high Cr. isn't a good mix.
.015" Gasket = 10.88Cr
.028" """"""""" = 10.55Cr

If it's a .030" over 355 it would be Ok.
.015" """"""""" = 10.17Cr
.028" """"""""" = 9.86Cr
Stock Bore 350 will drop CR about .10 point Cr.
""""""" """"""""" = 10.05Cr
""""""" """"""""" = 9.75Cr