I just bought a set of the Patriot 243 ported heads which I am haveing milled down to 62cc chambers.I will be useing the tr224 cam with lt headers.This will not be to much compression for 94 octane fuel will it?I have time to change on the milling.Gunnar told me they will not ship for about 2 weeks.
Thanks

 

I think stock 243 heads are 64cc. And it depends on how much you want them milled. I am going to have mine milled about.020 Hopefully that will bring them down below 62cc. And bump up the compression for low end. And as far as 94 octane, that is more than plenty..

lane

 

I believe that stock 243 heads are 65cc's.

Bob K.

 

A stock 243 is approximately 64cc.

 

I also thought the 243s had 65cc combustion chambers

 

243: 64.xx cc
241: 66.xx cc

 

63cc .040 gasket if its a 112+4 Lsa {40 Ivc @.050}

62cc .040 if its a 114+4 Lsa {42 Ivc @.050

which is around 11.0:1 scr - 8.8 dcr

 

I got the Patriot 243 heads, milled to 62cc, and used .040" Cometics with a Comp XER 224/228 111 +2. Runs great on 93 octane.

 

Has anyone had their 243s milled down to 60cc? Will that take too much off? Any issues with 93 octane or valve clearance?

 

I had mine milled .030". Actually after the mill, my tuner measured the deck thickness and said he thinks they're milled .040". So somewhere in there.
As for PTV... depends on your cam. I flycut so it is more drivable.

 

im not trying to be a *****, but what does flycuting have to do with drivability??? Is there something I am missing?

lane

 

If you have a cam with PTV issues, you flycut. Then you can mill to get the best DCR. Proper DCR makes a world of difference in drivability. That's what I was saying.

 

Oh okay, see I know all of that, but I guess I just took what you said in a wrong way. lmao. Im sorry, Like I said I was not trying to be a *****. just wondering what you mint.

lane

 

Doesn't Patriot cut chamber sizes to your specs? If so, just get a smaller chamber instead of milling.

 

If you purchase the Patriot "LS6 style" heads, they start off with 035 castings (which have the same ports as LS6 heads, but larger combustion chambers) and weld up the combustion chambers the bring their volume down...due to the welded chambers, those are available in a variety of chamber volumes without milling the decks.

The Patriot heads refered to in this thread start off with OEM LS6/LS2 243 castings. These have unwelded chambers that are just under 65cc (which is about 2cc smaller than the stock LS1 chambers). They need to be decked if you want to get the the CC volumes down even lower; Patriot will deck them to your desired specs for no additional cost.

 

What is your mean above sea level altitude?
This will influence your final CR.....

 

How is that? A compression ratio is a compression ratio. Fractions don't change by location.

 

https://ls1tech.com/forums/showpost....2&postcount=41

The 243 is a 64.45cc combustion chamber. As for valve clearance, be aware aftermarket valves will kill ur PTV clearance. I'm right within spec with a 224/224 cam, 2.02/1.57, .045 gasket and I milled them .010" Be prepared to flycut if you go more aggresive than that.

 

If that is absolute, then why do people at sea level (14.7 psi atmospheric pressure) post stronger dyno numbers than those who run in Denver (5000+ feet acl)?

Given the same stroke, a 64cc chamber facilitates more chamber pressure than a 70cc chamber due to the same volume of air being compressed in a smaller space. However, as you gain in altitude, you lose air density. In a naturally aspirated motor, this means there is less total available air to compress into the chamber, thus less available power produced.

You will also see that forced induction motors see this same affect between sea level and higher altitudes.

 

Dude, it's still the same compression. You're still compressing what started in the chamber down to 1/8.5th its original size, regardless of density. 1/4th a quart of alcohol is the same volume as 1/4th a quart of motor oil.