So the background info:
- Has Stock bottom end LM7(5.3L) from 2001 tahoe
- Has 862 heads (which are stock LM7 heads) but machined to fit the larger ~2" OD intake valves from the LS6 I think (whatever non sodium filled ones are). I dont remember how much they milled off when planing heads, but it wasn't a lot as machinist didn't sound concerned at all.
- Planning to run XFI comp cam with .558" int valve lift and 265 duration.
- Want to maintain stock 9.5:1 CR (idk how much bigger or smaller chamber got by installing bigger valves if it did so CR might have changed a lil) in order to run turbo, and possibly E85 in future.
- I want to use MLS head gasket (where I think stock compressed thickness is .051")

Can I/Do I have to use the Chevy performance MLS head gaskets for an LS1 engine because of larger intake valve OD, or do I have to go aftermarket for an MLS headgasket for an LM7? I believe the ones that came off the my LM7 when i took it apart had 5.3/5.7HO stamped into them (I think, dont remember off the top of my head if those were the other headgaskets from a different year LM7 I had before).

I just want to know if I'll have clearance issues with that valve either hitting cylinder wall or head gasket or piston.
To my knowledge, this intake valve upgrade is fairly common, but I'm having trouble finding definitive answers about head gasket type based on my application.

Also Chevy performance LS1 MLS headgaskets are about half the price of the ones for LM7.

Appreciate the help and I hope I gave you the right background info.

 

Your issue with mls gaskets will also be determined by your heads. The early heads had a notch near one of the two middle cylinders. If that notch is present the mls gaskets won't seal up.

041 is usually about right for a head gasket on a stock LS bottom end. That will give you .035" quench which is very good for controlling detonation. Will affect your CR by maybe 0.3, so you'll be at 9.8, but less prone to detonation

 

I will have to check if notch is there.
Makes sense why it could keep it from sealing.

Since these are dished pistons, would you measure quench from center flat of dish or flat higher part of outer edge of piston - to the block/gasket mating surface?

However, I was more asking if there would be any issue with using an LS1 MLS headgasket as opposed to an LM7 MLS gasket (now assuming there is no notch there) due to difference in bore between the 2 gaskets.

The other part is still the clearance issue, will the valves be too wide where they would hit the piston top/top of cylinder wall/bore edge of gasket? I'm pretty sure they are the same length valves, so just the increase in OD of valve face will stretch into the cylinder a little more.
Does that make sense?

 

No issue at all between the two.

As for quench, use the top, flat, outer portion

 

It doesnt look like it has those notches, i got lucky with these 862's!<br/>
SO ill be able to use an MLS gasket!

so there isnt a difference between the two gaskets and I wont see any interference issues?

Looks like I'm picking up some chevy performance LS1 MLS headgaskets on my LM7!!!!

Thanks Darth....btw your picture is highly distracting hahaha

 

Good deal and thanks. Ever been jealous of a camshaft?

 

......oh what, did you say something?
gives a fresh take on 'metal shaft placement' haha

I looked at the old head gasket that was on there, yesterday....I see a vague ghost shadow of something that resembled that notch, so maybe it had it at one point, but maybe the machinist knew that and machined the notches flush with the head when I had them machined?
Do you know how deep the notch is cut into the head, in any dimension? Is it a machinable amount? I feel like it wouldn't be but it just kinda had me worried.

I recently found out this was a mid year change in 2001, along with valve seal styles. So since I got new brian tooley Viton valve seals with my double springs and retainers, and machinist didnt mention anything looking strange on the valve seals, and the notches on the heads seem to not exist, I should be good for the style that uses MLS head gasket.

Does anyone know if there is a difference in head gasket layout/dimensions between 2001 and 2002? Because 2002 came with MLS by default no matter what production month. If I just got a 2002 5.3L MLS head gasket, could I just slap those on without worrying, or are they thinner/thicker than what I want for ideal CR?

 

LOL!!!

I'm not sure how deep the notches were, but I can measure when I get home. I have a notched set on the side. I've heard of machinists filling in the notch with weld and then grinding that whole thing smooth, but I've never seen that in person.

As to the gasket thickness, I tend to go with .041", as the pistons usually have .006 above deck at TDC, which gives .035" quench, and is about perfect.

The stock 2002 gaskets will be fine. I think they run .058", but not positive. If so, figure you'll increase CR by 0.3 if you run the thinner gaskets, but your propensity for detonation will actually be less, because of the tighter quench forcing the mixture into the chamber.

 

These are the ones I wanted to get from an LS1 as they are super affordable and are MLS:
http://www.summitracing.com/parts/nal-12498544/all

The 2002 5.3L gaskets are:
http://shop.advanceautoparts.com/p/f...ket#fragment-2

I'd probably get the 5.3 L ones if they are actually sold as a set rather than individually.

 

summit said the compressed thickness is about .051 so that should still be ok.

I'm gonna get those from summit unless i can get a full gasket deal from advance

thanks for help

 

No problem. Hey, FWIW, the notch on my heads is .082" deep.

 

I feel like that is a crap ton to take off of a head, they would have mentioned that.
So maybe it was just the style of the gasket that made it look like that....I dont know, LS1 MLS headgaskets already came to my house this morning so we'll see.

Now time for more RESEARCH!!!!!!! thanks again for the help and distraction Darth_V8r! haha