Maximum Compression Ratio-Aluminum Head

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sarnett346
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Maximum Compression Ratio-Aluminum Head

Post #1 by sarnett346 » Mon May 14, 2018 7:48 am

I've been thinking about going with an aluminum head on my 200 build. What is the highest static compression ratio I can run on 91 octane pump gas at 5280 feet above sea level with the aluminum head? This isn't going to be a daily driver, I'm leaning towards a performance build.
Thanks!

drag-200stang
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Re: Maximum Compression Ratio-Aluminum Head

Post #2 by drag-200stang » Mon May 14, 2018 9:07 am

I cannot help you , someone here can but they will need to know the cam spec,s and maybe what is fueling it.
66 Mustang Coupe
200 turbo w/lenco 4-spd
stock adj. rockers, stock timing set, ARP studs
best 1/4 mile ET 9.85/best mph 139 on 8 lbs progressing to 15 lbs boost
Went 9's when 10's was fast.

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62Cometman
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Re: Maximum Compression Ratio-Aluminum Head

Post #3 by 62Cometman » Mon May 14, 2018 9:33 am

Once again specs on the cam specs, timing to be run, combustion chamber size and what not will make a difference but about 10:1-10.5:1 is achievable with 91, 11:1 would be pushing it but if running cool enough could be possible but that would be the absolutely highest i would go.
1962 Mercury Comet 170 ci, 2.77 Trans, 3.20:1 7.25 rear.
She ain't fast but she's fun. 8)

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Re: Maximum Compression Ratio-Aluminum Head

Post #4 by rbohm » Mon May 14, 2018 12:54 pm

i agree with the others, in most cases you can run as much as a point higher compression ratio with the aluminum head as with an iron head. but as noted, cam timing, ignition timing, cooling system temps, piston dome shape, among other things all conspire to change the actual compression ratio you can run.

all that said, my advice would be to run 10.5:1 compression, maximum for a street engine, with the aluminum head.
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chad
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What's the maximum CR I can run with my Aluminum Head

Post #5 by chad » Tue May 15, 2018 10:15 am

little understanding or knowledge here:

would the head itself (non - O-ringed) not B the ultimate limiting factor
(along w/the stated 91 C8H18) ?
These 2 factors were the 'givens', we can 'manipulate' all others?

Was it Gene who just hada fastener pop? So the hardware too (head bolts). :?:
Thnx !
"Big thing is only make one change at a time. Change 2 or more things at a time it becomes difficult to figure which change helped or hurt" turbo2256b » 1/16/2017
Chad - '70 LUEB on '77 frame (i.e. PS, D44, trapezoidal BB 9", 4.11), 250, NV 3550 & DSII to B transplanted, "T" D20/PTO, 2" SL, 1" BL, 4 discs, 33"X15", etc. Seeking: Hydraulic gear motor for Koenig pto. chrlsful@aol.com (413) 259-1749

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Re: Maximum Compression Ratio-Aluminum Head

Post #6 by drag-200stang » Tue May 15, 2018 10:39 am

O rings are not a fix for a knocking engine. :nono:
No bolts were harmed , just the pedestal threads. :wink:
66 Mustang Coupe
200 turbo w/lenco 4-spd
stock adj. rockers, stock timing set, ARP studs
best 1/4 mile ET 9.85/best mph 139 on 8 lbs progressing to 15 lbs boost
Went 9's when 10's was fast.

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chad
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Re: Maximum Compression Ratio-Aluminum Head

Post #7 by chad » Tue May 15, 2018 10:54 am

talkin bout 'explosion' here, not knock...
Anyway I'm way off, scuse me...
"Big thing is only make one change at a time. Change 2 or more things at a time it becomes difficult to figure which change helped or hurt" turbo2256b » 1/16/2017
Chad - '70 LUEB on '77 frame (i.e. PS, D44, trapezoidal BB 9", 4.11), 250, NV 3550 & DSII to B transplanted, "T" D20/PTO, 2" SL, 1" BL, 4 discs, 33"X15", etc. Seeking: Hydraulic gear motor for Koenig pto. chrlsful@aol.com (413) 259-1749

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Re: Maximum Compression Ratio-Aluminum Head

Post #8 by fast64ranchero » Mon Jun 11, 2018 9:58 am

In real life with a 200 it will be hard to reach above 10 to 1 without decking the crap out of the head. I have true flat tops (no valve reliefs) and zero deck and I'm not even at that compression ratio.
63 Ranchero,1965 Mercury Comet Convert V-8, 1978 Fairmont small six, mill'd off intake, 62-1 ET 12.332 @ 123.49 mph (gone)

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Re: Maximum Compression Ratio-Aluminum Head

Post #9 by sarnett346 » Thu Jun 14, 2018 11:09 pm

How thick is the head gasket though?

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chad
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Re: Maximum Compression Ratio-Aluminum Head

Post #10 by chad » Fri Jun 15, 2018 12:07 am

I use the term "zero deck" only for the block.
set me straight?
"Big thing is only make one change at a time. Change 2 or more things at a time it becomes difficult to figure which change helped or hurt" turbo2256b » 1/16/2017
Chad - '70 LUEB on '77 frame (i.e. PS, D44, trapezoidal BB 9", 4.11), 250, NV 3550 & DSII to B transplanted, "T" D20/PTO, 2" SL, 1" BL, 4 discs, 33"X15", etc. Seeking: Hydraulic gear motor for Koenig pto. chrlsful@aol.com (413) 259-1749

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Re: Maximum Compression Ratio-Aluminum Head

Post #11 by CNC-Dude » Fri Jun 15, 2018 12:41 pm

Yes, it refers to the block only. Check out the recent post in his other thread regarding this subject.
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chad
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Re: Maximum Compression Ratio-Aluminum Head

Post #12 by chad » Fri Jun 15, 2018 8:16 pm

so this is "mill pass", Dude? or what - "Head tolerance', ummm, gee, I can't think ~
"Big thing is only make one change at a time. Change 2 or more things at a time it becomes difficult to figure which change helped or hurt" turbo2256b » 1/16/2017
Chad - '70 LUEB on '77 frame (i.e. PS, D44, trapezoidal BB 9", 4.11), 250, NV 3550 & DSII to B transplanted, "T" D20/PTO, 2" SL, 1" BL, 4 discs, 33"X15", etc. Seeking: Hydraulic gear motor for Koenig pto. chrlsful@aol.com (413) 259-1749

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Re: Maximum Compression Ratio-Aluminum Head

Post #13 by CNC-Dude » Fri Jun 15, 2018 8:28 pm

Read the post I'm referring to, it will explain a lot.
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chad
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Re: Maximum Compression Ratio-Aluminum Head

Post #14 by chad » Fri Jun 15, 2018 8:43 pm

"... his other thread ..."
'S OK, couldn't ID it.
I'm all set.
Thnx
"Big thing is only make one change at a time. Change 2 or more things at a time it becomes difficult to figure which change helped or hurt" turbo2256b » 1/16/2017
Chad - '70 LUEB on '77 frame (i.e. PS, D44, trapezoidal BB 9", 4.11), 250, NV 3550 & DSII to B transplanted, "T" D20/PTO, 2" SL, 1" BL, 4 discs, 33"X15", etc. Seeking: Hydraulic gear motor for Koenig pto. chrlsful@aol.com (413) 259-1749

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Re: Maximum Compression Ratio-Aluminum Head

Post #15 by CNC-Dude » Fri Jun 15, 2018 9:22 pm

It's titled "Minimum piston/head clearance-quench"
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Re: Maximum Compression Ratio-Aluminum Head

Post #16 by fast64ranchero » Sun Jul 08, 2018 11:29 pm

10 to 10.5 to 1 at sea level. At 5200 feet you could run 11.5 to 1, with some attention to detail in the chambers and pistons to prevent hot spots maybe 1/2 point higher. The cam will play into it, but it sounds like you will run one on the larger side which will help..
Be hard to get to that compression though.
63 Ranchero,1965 Mercury Comet Convert V-8, 1978 Fairmont small six, mill'd off intake, 62-1 ET 12.332 @ 123.49 mph (gone)

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Re: Maximum Compression Ratio-Aluminum Head

Post #17 by 65coupei6 » Mon Jul 09, 2018 10:09 am

One of the reasons why I am running 9.6 compression on my recent build is because we didn't want to mill a new head. Why take the head down that much when you never know if they will be available again.

Also, look how hard it is to find blocks now. At least in my area. That is why we just squared the block and did not zero deck. Mine is already bored .060 because we couldn't find a block in the time we needed.
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