Looking for some opinions here

3.75 stroke, 6 inch rod, 4.030 bore
+7cc domed SRP pistons, almost .010 above deck
76cc chamber on heads

Currently running felpro gaskets, 4.125 bore, .039 compressed

When this was first put together the pistons actually were going to hit the chambers, I had to take off a fraction inside the chambers so it cleared.

Now I am going to a big solid roller, going to measure and notch the pistons (have the tool already).

I was looking at Mr Gasket head gaskets instead of the felpro but am worried about a few things.

First, quality. Will they hold a 600+ NA motor, how about some n20 ontop of that? Ive searched and havent found any opinions. A cometic or something of that likes is out of the question for now.

Second, they are a 4.100 bore and .026 compressed versus the felpros 4.125 and .039. That will yield a touch more compression (even after notching). How will this effect the quench, flame travel, hotspots etc. Positively, negatively? Just looking for a little more static compression, the dynamic is well within reason.

Thanks

 

You want about .035" quench. Any less and you will get pistons kissing the heads at temp and high RPM.

If it is .01 out the hole then you should go with at least a .039 probably a .045 gasket.

 

Yeah, you definitely don't wanna go with a .026 gasket, when you are .010 out of the hole!

 

Jared, don't do that. Considering that the iron block will tighten up the quench as it gets hot you are going to have something touch and that WILL break something, rod, piston, pin, crank, valve etc....

Why did you mill the block so much?

Bret

 

I thought this went without saying but YOU HAVE TO PAY TO PLAY. 600 hp and budget don't go in the same sentence. There isn't a standard/shelf/cheap- gasket that I would trust in an application like that(providing you didn't have clearance issues). The custom gasket guys are calling your name.

Bringing the gasket bore in closer to the cylinder bore will only help quench and flame travel. It also puts some more meat between the cylinders(never a bad thing). You can get a gasket made in just about any size that you want. Try a gasket with a 4.060 overbore/ .050 thick and see how your calculations come out. You could also mill the heads a little if it comes down to it.

Good luck,

James

 

I dont mind an expensive gasket (never said anything about cheap, this motor has plenty of $$ into already, lol), just have heard a few too many horror stories about some gaskets (cometic) leaking coolant. Ive always used the felpros with good results, had no experience with Mr gasket stuff. Can felpro do the custom stuff, if not who should I be contacting.

The block wasnt originally mine. It was a 15:1 race gas/track only motor that my buddy had built by BES. He ran it down the track like 15 passes and decided he wanted a street car instead of a track car. My AFRs that I had on order gave me the chance to have the compression be streetable again. So thats a long winded reply on the deck height situation.

A 4.060 bore and .050 thickness would drop me about .3 before the pistons are even notched. :/ How tight is too tight to bring the gasket into the bore. Maybe Ill stick with the .039 range and bring in the bore as much as possible. Trying to avoid head milling as they are really touchy with the single plane intake thats on there. Already had them off and angle milled because the intake gaskets werent sealing and sucking oil. Really a touchy setup.

Anyways, thanks for all the replies so far, keep them comming!

 

Lookup SCE performance gaskets...they make the good stuff.

 

A .039 gasket will still be too close. That's only gonna give you .029-.030 quench...sorta too close for comfort!

 

Thats what has been on the motor for almost 5k miles without any issues.

Looked up SCE, all their composite gaskets are no more. Summit is cross referencing them to Felpro numbers. They dont make anything other than copper (none self sealing) for LT1s.

I did manage my way to cometics page, yuck. However 4.040 bore with .040 thickness looks rather like what i want. Reading up on them now from searching, anyone can throw in their .02 on them too.

 

Make sure you have stiff wrist pins, and not too much running bore clearance. You can check piston rock with the heads off, but it won't tell you much about what happens when the pistons warm up. If you get by with it, you'll be a hero of sorts. I was in a position with a former job to be able to ask major successful engine builders about this subject and couldn't get a single one of them to go any tighter than .034" on a high performance motor. A friend of mine builds his own asphalt oval track engines and has gone as tight as .029" and had the pistons leave the part number in the quench of the head. While I never saw it, I do believe him. I have been interested in how tight you could run the piston to head clearance on a steel rod small block for a long time as I think you could get away with more compression on pump gas that way. Good luck.
By the way, the composite MrGasket Ultra Seal head gaskets provide an excellent seal. The problem comes when you want to take the heads off. Cleaning those gaskets off can make you hate life. I am not a believer in using scotchlock pads on an engine.

 

Ah I just cant bring myself to do the cometic or copper gaskets.

Is there any standard type gasket in a .037-.045 range on a tighter bore than 4.125? Anyone who can custom make them?

 

Well I'll let you know what I find on mine if anything when its pulled apart. Should have been .029 too. Im going to clay it though and find out exactly what it was.

 

Jared,

I came up with these two part numbers from SCE, still a copper gasket but read below.

011064LT(4.06x.043) if you are still wanting to live dangerously

011065LT(4.06x.050) if a few hp lost to compression is worth the piece of mind

I do things differently than most people but while I was trying to find a part number I came across a bit on Milodens website that confirms what I have practiced and preached for years. Here's the cut and paste:


Regardless of the type of use, these gaskets are reusable with proper handling and installation, for many engine rebuilds. These gaskets can be used with or without stainless steel 0-ring wire installed in the block. They are totally acceptable for street use, as long as a THIN bead of silicone is applied on both sides of the gasket around ALL the water passageway holes. Copper gaskets may cost more initially, but the improved sealing and reusability make these well worth the investment in the long run. O-ring wire is not needed unless actual compression ratio is 14:1 and over. This included blown and turbo engines. On engines using water cooling, as opposed to dry Top Fuel, etc engines, a thin bead of silicone must be applied around all water passageways on both sides of the gasket. Nothing is needed to seal the compression.


I have also used copper coat on these gaskets instead of the silicone or hylomar with no leaks. If it will make cometics seal then it has to work on anything, right?

Hope this helps,
James

 

Yeah - and when they mean thin...they mean thin, that stuff spreads a lot when torqued.

So SCE does not list composite anymore? We just got a really nice set for a turbo 302 car.

 

Ya SCE only lists them on one part of their website, and by the looks of it it shouldnt even be listed there (error in web design?) Also summit has most of their part numbers cross referenced to felpro stuff.
http://store.summitracing.com/defaul...=egnsearch.asp
Either way, nothing is LT1 available.

Thanks for looking up those part numbers for the copper stuff. If Im going to take a chance with something copper, IMO i might as well go cometic and spray the heads and deck with copper spray and hope it seals. I have no idea what my head or deck surface rufness is though.