Lewspike69

We're they straight steel shims or were they coated in rubber? But that's very assuring especially the 87 octane part.
For me 89 would be goal

camarito

They are coated with the quench at 0.040 and a decent size cam you'll be fine with 89

Orr89RocZ

iTrader: (20)

Afr's with right plug heat range and timing should tolerate 89 no problem under 10.5 to 1. My 11 to 1 383 with good quench and roughly 8.3 to 1 dcr ran temporarily on a 89-93 mix, mostly 89 that was 7 months old. Abit less comp and right tuneup should handle 89. My car handled 93 with as much as 39 deg timing at wot no issue. Thats alot of chamber pressure and heat. New AFR heads have good chambers imo

Lewspike69

I just calculated my dynamic compression ratio to be 8:1.
So what would you guys do?
Use the thinner, less safer gasket to achieve better quench and higher compression
Or
Use safer thicker for less compression and less efficient quench?

I don't want to change head gaskets I'f I don't have to

skinny z

10.2:1 and .040" piston to head clearence in a heartbeat. Provided you develop a good tune and don't let it overheat, detonation shouldn't be a concern especially with the aluminum head. Leaks aren't a concern with any of the gaskets discussed provided the block and head sealing surfaces are true.
Once you've establsihed how far the piston is below deck, you may want consider one of the .026" gaskets mentioned. While some may argue that the quench is not the be all and end all of your build, if you can establish a desirable quench with no additional outlay of funds, then why not. It'll only help.

skinny z

8:1 DCR isn't a problem. At least I haven't found it to be even with iron heads. I'm running 10.25 scr and 8.3 dcr with iron heads.
There's nothing "unsafe" about any of the gaskets mentioned. I've used a Victor Reinz (or Cometic) .026" gasket on aluminum and iron and have never experienced a failure. I can't imagine that you would have any trouble.

Orr89RocZ

iTrader: (20)

Split thedifference with a .026-.028 gasket. I doubt you will see huge difference in power either way. How much power were you shooting for again? 350whp+ can and has been done with cam heads L98's with under 10 to 1 comp

skinny z

That was suggested in the last post however it's contingent on the piston position at tdc. If the piston is .025" down, then the .026" gasket (Victor Reinz 5746 for example) is certainly a better choice than a .040" gasket.
I think we're waiting until some measured values are posted.
Agreed the power gain may be minimal however if the risk of detonantion or other trouble is zero (in achieving 10.25:1 scr and a .040" quench) then why not do it. There's only an upside.

Orr89RocZ

iTrader: (20)

I never used a thin shin with aluminum heads on a undecked block. I would have some concern with that. Atleast a coated shim with that copper spray should be considered. I have only used mls gaskets but hear good things about the GM .028 composite one and also mr gaskets .028". Gives abit more thickness to seal up any surface imperfections.

I dont think he will have a problem with detonation. You can get away with alot on AFR heads imo. With the xe282 roller cam, that should keep dcr nice with 9.5-10.3 to 1 comp and make very good power. 360-380whp should be doable

skinny z

I understand it's the disimilarity between the aluminum head and iron block that causes the problem with a shim type gasket. As you suggest, it's something that should only be considered when it's certain that both sealing surfaces are absolutely true. Having said that, we currently have a.015" rubber coated shim gasket between some new AFRs and a fresh short block. No problems at this point.

[quote=Orr89RocZ;5477915] I have only used mls gaskets but hear good things about the GM .028 composite one and also mr gaskets .028". Gives abit more thickness to seal up any surface imperfections.

If believe GM gasket is either a Victor Reinz or possibly a Cometic. They're both a composite type gasket which I've used with no problems.

camarito

My deck wasn't touched I'm using Procomp heads (not the most perfect ones out there) didnt even spreyed the gaskets and have no problems, Mrgasket has gaskets with 0.020 if I'm not mistaked

Lewspike69

Thanks for all the replies. I'm going to try to get a dial indicator either today or this weekend and get the distance on each cylinder. If it makes any difference, when I did have my block preped the machinest told me that I didn't need my block decked. This of course he just eye balled and probably didn't know I was going to use a thin shim gasket but experienced eyes did say the surface was alright.

And this is exactly where my goal is set. Near 350-400 horses at the wheel. I want to do this as reliable as possible. The more efficient the better.

This is where my thinking is at. If no one had a problem using these shim .015 thick gaskets before, then why not take advantage of the more more efficient cylinders it will create.

That's why I love this site, a first time engine person like me is able to get opinions from people who had been there and done that before.

Thanks again for the posts. I'll get the numbers up ASAP

skinny z

I like your compression pressure. It goes to show what some research and thoughtful selection of parts can do. (Cam specs?)
Having said that, seeing as this is a thread for someone that's asking advice, I wouldn't suggest the shim head gasket route for an undecked block , especially with aluminum heads. That you've had good results is great but I'd feel terrible if I suggested that to the OP and then his gaskets failed.

skinny z

For what it's worth, some fairly accurate results can be achieved with a true straight edge and a set of feeler gauges. The dial indicator would be handy for determining tdc however it's not essential. Keep in mind that there may be variances from cylinder to cylinder. Not as likely with a quality aftermarket reciprocating assembly but my old OEM bottom end had almost .010" from one cylinder to the next. (.026 to .035 ! )
While you’re at it, take the opportunity to establish the true TDC (piston stop tool or dial indicator depending on how you tool up) and mark that on your balancer. It's nice to know and can save a pile of headaches when you're tuning.
No disrespect to your machinist however it's unlikely that he can spot a deck that's out 4 or 5 thousandths.
Post those numbers!

Lewspike69

XR282HR specs
Cam Style:Hydraulic roller tappet
Basic Operating RPM Range:2,200-5,800
Duration at 050 inch Lift:230 int./236 exh.
Advertised Duration:282 int./288 exh.
Valve Lift with Factory Rocker Arm Ratio:0.510 int./0.520 exh.
Lobe Separation (degrees):110

Orr89RocZ

iTrader: (20)

Sorry if i missed it but what intake manifold you using and is it carbed or efi? Run a 1.6 rocker if you can

Lewspike69

I haven't bought either yet so this is not in stone but an edlebrock performer intake (idk this one or perform rpm) and a Holley 750 with mech secondaries (I believe so, maybe 650cfm)
Open to suggestions though.

Orr89RocZ

iTrader: (20)

Definately performer rpm or similar style. You will be pulling to near 6500 rpm.

I am not a carb guy but i see alot of 700-750 or so sized carbs on 350's running strong. My buddy's old vortec 350 ran best with a 750 double pumper, and it only had a stock lt1 cam but maybe it wasnt tuned right from the beginning?

Lewspike69

With more cubes from my 385 cubic inches that's why I'm leaning twards the 750.

Orr89RocZ

iTrader: (20)

Definately 750. I must have also missed the 385 cubes part. Had to reread from beginning. Sounds like block has been cleaned well and may even had deck resurfaced? Good thin mls style gasket would work great

Lewspike69

Good point. It might have been resurfaced I'm going to ask my machine shop. But will probably be able post measurements this weekend bare with me people lol

cuisinartvette

When you start grinding on the inside of those header flanges be very conservative know you can go through to the surface easy on some headers.

Top/bottom might be able to weld from the outside.

Sides you might be up a creek cause the header bolts may not fit with a bead of weld in the way.
Just do a little if any and walk away.

Lewspike69

Okay I was tired of waiting on the dial indicator so I just eyeballed TDC however I believe I got some accurate data. I then double checked with another feeler gauge set and got +/- .001"
This is what I got

Cylinder
#1 .017"
#2 .017"
#3 .016"
#4 .016"
#5 .016"
#6 .017"
#7 .017"
#8 .016"

I noticed a great deal of piston rock. These measurements are where both sides of the piston measured at. Pushing on one side would easily make one side wider and the opposite shorter. Maybe this is because the rings haven't been seated yet?

So with this I now have a deck height of about .016 inches, making the .015 gasket out of the question.

I am now leaning towards the GM composite of the mr. Gasket .028" thick gasket. This would be a quench height of .044 inches.

What do you guys think?

skinny z

I'm sure either of those gaskets would be fine although I don't have any experience with them.
Almost exclusively, I use the Victor Reinz 5746 gasket. Variously referred to as .025" or .026" compressed thickness.

http://www.cnc-motorsports.com/victo...-per-pack.html

http://www.competitionproducts.com/V...ductinfo/5746/

Lewspike69

You have used them with aluminum heads right?

I like the price too haha. I wonder why they are half the price of fel-pro or mr gasket.

If the material Is going to work well with my aluminum AFRs, I think I found a winner

skinny z

Aluminum and steel. AFRs, Brodix, GM and more.
As for price I haven't even really compared considering these are all of I've used for several years.

cuisinartvette

even if your cranking compression is 185-200 its still gonna run real real good.
Good safe zone for pump gas motors

Lewspike69

These look perfect for my engine. This would give me a .041" quench height and 10.1:1 static compression, both I think ideal for my application.

Lewspike69

Just got my gaskets in the mail! Surprisingly since its a blizzard out here in the north east haha. The mail man literally trouped it in the snow. Are these one way gaskets? Are there a specific way to put these on?

skinny z

Install them with the part number facing up.
Of course you should double check that no openings in the head or block are covered by any part of the gasket.

Lewspike69

Wouldn't 1.6 rockers give me border-line too much lift for my stock afr springs (.550 lift)?

What's your ideas on this?
I was planning on using comp magnum roller tip rockers with molley pushrods.

Lewspike69

Hey guys, a little late but I just wanted to thank you for all of your help!

I just started a thread of my build at https://www.thirdgen.org/forums/memb...83-camaro.html and I realized I never posted these pictures I wanted to here. Thanks for the help on picking these AFRs out as well as the head gasket! I would have never been able to make this decision without your advice.