My From Start to Finish 6.0L Build

[RAMurphy]

Do you have a good LS Series engine build book? I bought this one on recommendation of a member here. It’s got a section on head gaskets. I know you need to determine thickness needed so you can calculate compression ratio. Cosmetic seems to be the go-to gasket for most but I have also heard they can take quite awhile to get. There’s others here who have experience, I have only dreamed so far.

Thank you. I actually have that book and one other. Will be diving deep in those books again.

 

[RAMurphy]

Reached out to Cometics and had a nice discussion with them about head gaskets. They are recommending their C5751 series - which is 4.060". We discussed different thicknesses depending on the heads I want to use. If I go with the 243 heads the standard thickness would be more than sufficient. I asked about the 862 heads, and he recommended the same size bore with a thickness of .092" which would bring my compression ratio down one point. Essentially the equation is an increase of gasket thickness of .010" for every .25 pt of compression. So, I'm back to thinking I want to use my 862 heads. I'm burning 93 octane right now with my current engine and tune. Thoughts?

 

[iamdub]

Reached out to Cometics and had a nice discussion with them about head gaskets. They are recommending their C5751 series - which is 4.060". We discussed different thicknesses depending on the heads I want to use. If I go with the 243 heads the standard thickness would be more than sufficient. I asked about the 862 heads, and he recommended the same size bore with a thickness of .092" which would bring my compression ratio down one point. Essentially the equation is an increase of gasket thickness of .010" for every .25 pt of compression. So, I'm back to thinking I want to use my 862 heads. I'm burning 93 octane right now with my current engine and tune. Thoughts?

On a NA street build, I'm all for as high of compression as you can afford (tuning- and octane-wise). I like 9.5 at the bare minimum but really prefer 10.0 or more. You can easily safely tune around the preferred octane grade you wanna run with ~10:1 CR. DCR (dynamic compression ratio) is a thing, but not so critical with a stock or mild cam so I wouldn't muddy up the waters with that factor. Besides the CR, mind the quench height. This is where gasket thickness comes into play. I aimed for .037" for mine. Might be pushing it for an older engine spinning 6K, but it's been fine so far and I haven't babied it. Factor this in if you're still debating what head to use.

You'd need to know how much, if any the piston comes "outta the hole" with your new rotating assembly. 862s have a smaller chamber, that's why they recommended such thick gaskets. Although, .092" sounds excessive. But I haven't ran any calcs. You're sacrificing quench height in addition to that one point of compression. Swirl from a tight quench is one of the LS head's best characteristics. Speaking of, what are the CRs we're talking about here?

 

[RAMurphy]

Good question. BBP estimated my compression ratio with dished pistons around 11:1 utilizing the 862 heads (93 octane fuel territory with the potential to knock under heavy load (like towing)). 243 heads with dished pistons at 10:5ish range. Sounds like you think a slightly thinner gasket might be the sweet spot.

 

[iamdub]

Good question. BBP estimated my compression ratio with dished pistons around 11:1 utilizing the 862 heads (93 octane fuel territory with the potential to knock under heavy load (like towing)). 243 heads with dished pistons at 10:5ish range. Sounds like you think a slightly thinner gasket might be the sweet spot.

I wouldn't go thicker than stock gasket and especially not .041" thicker. I'd go slightly thinner if the piston height allows and that 10.5 is nice. But, it depends on the rotating assembly, pistons, etc. I doubt you'll have pistons coming outta the hole .055" to where .092" gaskets would yield a good quench height.

 

[RAMurphy]

I wouldn't go thicker than stock gasket and especially not .041" thicker. I'd go slightly thinner if the piston height allows and that 10.5 is nice. But, it depends on the rotating assembly, pistons, etc. I doubt you'll have pistons coming outta the hole .055" to where .092" gaskets would yield a good quench height.

I've been doing some compression calculations on my own and other research, and I agree with your thoughts/suggestions. Thank you.

 

[RAMurphy]

I just finished up conversations with an engine builder I have utilized in the past and with Tech Support from Texas Speed. Both have stated that the engine I want to build utilizing the rotating assembly I purchased (with flathead pistons) utilizing either the 862 or 243 heads should not be a problem (using premium fuel). As I stated in an earlier thread - I already burn Premium. Texas Speed recommends the 243 heads because they breath better at higher RPMs but said 862 should not be a problem. My engine builder also stated yes 243 heads breath better but since I'm looking at lower RPMs that should not be a problem. Even Roger from Vinci Hi-Performance, who I received my upgraded camshaft from, had no issue with my build. Not sure why BBP has such a concern. The type of heads I end up using is not critical at this point - I may even use after market heads (highly unlikely (cost) but possible). Both conversations included their computation of CR and were similar to what I computed. Texas Speed recommended and computed compression ratio based on the standard head gasket thickness of .051". @iamdub - based on the rotating assembly I ordered there should not be pistons out of the hole. More research to follow.

 

[RAMurphy]

Well I have tomorrow off and the rest of the weekend. My plan is to install the TBSS intake on my current engine.

 

[RAMurphy]

Got started this morning.


About 90 minutes later. Believe it or not, it took me about 20 minutes to remove two fuel injector plugs. Lots of room in the front of these engines - not so much in the back.

 

[RAMurphy]

Injectors and fuel rail installed on TBSS.