DCR vs. Quench - Team Camaro Tech
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post #1 of 36 (permalink) Old Jan 10th, 08, 01:25 PM Thread Starter
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DCR vs. Quench

Trying to put a parts list together for a head swap and am wondering which head gasket would work out the best.

Old setup has 64cc chambers with dome pistons. 8.3ish DCR .064 quench. It actually runs fine on 91 octane.

New setup has 67cc chambers with same dome pistons.

1) 8.05 DCR and .064 quench with the same .039 gasket
2) 8.48 DCR and .044 quench with .018-.020 gasket

My question is would the tighter quench offset the increased DCR enough to avoid detonation?

If I were to always stay close to home I'd run the tighter quench, mix in some race gas and not give it a second thought. I'd like to be able to go on road trips and not have to worry though.

Or a 3rd 'middle of the road' option would be .028 gasket for a DCR of 8.28 and .053 quench.

Thanks for any insight or opinions.

Mark

68 327 4-speed 3.42 posi and a sunroof
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best so far... 13.25 at 106mph

78 Firebird 350/T350 3.23 posi
65 Mustang convert. 6 cyl. 3-speed
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post #2 of 36 (permalink) Old Jan 10th, 08, 01:36 PM
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Re: DCR vs. Quench

I assume you are checking quench and your piston is 0 deck? if it is, I would go with the .039. We are talking quench here . You did not mention deck. If you want to run on the edge with steel rods , you could use the .028 gasket , but thats close.

if the block had never been decked, I would also guess your piston can be in the hole .020-.040., so best you can do here is steel shim at maybe .015-.017.

You need to know what cc your piston is. You already know what the head volumes are so maybe you can juggle something around .
here is something that may help you do that. http://members.uia.net/pkelley2/crc.htm

Don
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post #3 of 36 (permalink) Old Jan 10th, 08, 01:45 PM Thread Starter
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Re: DCR vs. Quench

Don

I'm assuming, yeah I know, that the pistons are .025ish in the hole. That's what I'm doing my calculations with. Never been decked, but haven't measured it yet either. Using +6cc for piston dome volume.

I wanted to cut the quench down to where it should be, but it jacks my compression up significantly. I wanted to know if the better quench is going to offset the increased compression enough to go with the shim gaskets.

Mark

68 327 4-speed 3.42 posi and a sunroof
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best so far... 13.25 at 106mph

78 Firebird 350/T350 3.23 posi
65 Mustang convert. 6 cyl. 3-speed
66 Mustang coupe 6 cyl. auto
80 Chevy C10 406 4-speed

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post #4 of 36 (permalink) Old Jan 10th, 08, 01:50 PM
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Re: DCR vs. Quench

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Originally Posted by mbrekke View Post
Don

I'm assuming, yeah I know, that the pistons are .025ish in the hole. That's what I'm doing my calculations with. Never been decked, but haven't measured it yet either. Using +6cc for piston dome volume.

I wanted to cut the quench down to where it should be, but it jacks my compression up significantly. I wanted to know if the better quench is going to offset the increased compression enough to go with the shim gaskets.

Mark
You are basically where I was and I ran the thin gasket, .020-.030 in the hole with 6cc pistons and 64 cc heads. I think keeping the quench down is the idea to controlling detonation in your case. Maybe Pdq will drop by soon.
Your cam overlap also comes into play here too. Too much will bleed off excessive compression, not so much will help you retain.

Don
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post #5 of 36 (permalink) Old Jan 10th, 08, 01:54 PM
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Re: DCR vs. Quench

I got about 10.2 comp using stock 350 specs and your heads with .017 gasket. You did not say what material the heads were, if alloy, you can get away with a lot.

Don
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post #6 of 36 (permalink) Old Jan 10th, 08, 01:56 PM Thread Starter
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Re: DCR vs. Quench

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Originally Posted by zdld17 View Post
You are basically where I was and I ran the thin gasket, .020-.030 in the hole with 6cc pistons and 64 cc heads. I think keeping the quench down is the idea to controlling detonation in your case. Maybe Pdq will drop by soon.
Your cam overlap also comes into play here too. Too much will bleed off excessive compression, not so much will help you retain.
Thanks for the quick replies Don. "Maybe pdq will drop by soon." Yeah, he'll chew me out for not going with bigger heads.

Mark

68 327 4-speed 3.42 posi and a sunroof
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best so far... 13.25 at 106mph

78 Firebird 350/T350 3.23 posi
65 Mustang convert. 6 cyl. 3-speed
66 Mustang coupe 6 cyl. auto
80 Chevy C10 406 4-speed

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post #7 of 36 (permalink) Old Jan 10th, 08, 02:01 PM Thread Starter
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Re: DCR vs. Quench

Quote:
Originally Posted by zdld17 View Post
I got about 10.2 comp using stock 350 specs and your heads with .017 gasket. You did not say what material the heads were, if alloy, you can get away with a lot.

Cast iron heads. About 10.2:1 static (8.05 DCR) with the .039 gasket and huge quench. 10.7:1ish (8.48 DCR) with shim gaskets and tight quench.

I think I just talked myself into the 'middle of the road' option...

Mark

68 327 4-speed 3.42 posi and a sunroof
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best so far... 13.25 at 106mph

78 Firebird 350/T350 3.23 posi
65 Mustang convert. 6 cyl. 3-speed
66 Mustang coupe 6 cyl. auto
80 Chevy C10 406 4-speed

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post #8 of 36 (permalink) Old Jan 10th, 08, 02:04 PM
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Re: DCR vs. Quench

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Originally Posted by mbrekke View Post
Cast iron heads. About 10.2:1 static (8.05 DCR) with the .039 gasket and huge quench. 10.7:1ish (8.48 DCR) with shim gaskets and tight quench.

Mark
which cam? specs?

Don
TC # 349
Zdld17:69 Z/RS,306, NOR141111, 9N554XXX, 12A, X3G, 59/59,723, AFR 195,CCC282/290HR, TKO 600, BU1122B1E Owner since Dec 1968

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post #9 of 36 (permalink) Old Jan 10th, 08, 02:08 PM Thread Starter
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Re: DCR vs. Quench

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Originally Posted by zdld17 View Post
which cam? specs?

Comp 280 magnum. 230 @ .050 .480 lift 110 intake close 66

Mark

68 327 4-speed 3.42 posi and a sunroof
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best so far... 13.25 at 106mph

78 Firebird 350/T350 3.23 posi
65 Mustang convert. 6 cyl. 3-speed
66 Mustang coupe 6 cyl. auto
80 Chevy C10 406 4-speed

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post #10 of 36 (permalink) Old Jan 10th, 08, 02:14 PM
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Re: DCR vs. Quench

Well, thats close to what I had, 282HR with thin gaskets and pistons like yours on my old 355 with old darts. My guess was the cam was bleeding off some cly pressure but quench was tight, i ran pump prem, I ran altitude from 2ft above to 8500 ft sea level ,37 timing . no issues. I see your pain. I would go with thin gaskets, if you have issues, you can back off a little on timing, if it gets real bad, well, pull of cheap thin gaskets and replace with .039 gaskets at $25 a head. Final answer. Lets see if someone else disagrees. Paul? Tim? Home from work yet?

Somewhere I have a little program that figures your fuel with cam and eng specs, tells you what you can get away with. I will look for it and post it later this evening.

Don
TC # 349
Zdld17:69 Z/RS,306, NOR141111, 9N554XXX, 12A, X3G, 59/59,723, AFR 195,CCC282/290HR, TKO 600, BU1122B1E Owner since Dec 1968

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post #11 of 36 (permalink) Old Jan 10th, 08, 02:26 PM Thread Starter
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Re: DCR vs. Quench

Quote:
Originally Posted by zdld17 View Post
Well, thats close to what I had, 282HR with thin gaskets and pistons like yours on my old 355 with old darts. My guess was the cam was bleeding off some cly pressure but quench was tight, i ran pump prem, I ran altitude from 2ft above to 8500 ft sea level ,37 timing . no issues. I see your pain. I would go with thin gaskets, if you have issues, you can back off a little on timing, if it gets real bad, well, pull of cheap thin gaskets and replace with .039 gaskets at $25 a head. Final answer. Lets see if someone else disagrees. Paul? Tim? Home from work yet?

Somewhere I have a little program that figures your fuel with cam and eng specs, tells you what you can get away with. I will look for it and post it later this evening.
Thanks Don

My current setup is about 10.5 static and 8.3 dynamic. It runs on 91 octane. My hope was to tighten up the quench but that puts me at 10.7 static and right at 8.5 dynamic. Pretty high for cast iron.

Mark

68 327 4-speed 3.42 posi and a sunroof
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best so far... 13.25 at 106mph

78 Firebird 350/T350 3.23 posi
65 Mustang convert. 6 cyl. 3-speed
66 Mustang coupe 6 cyl. auto
80 Chevy C10 406 4-speed

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post #12 of 36 (permalink) Old Jan 10th, 08, 02:31 PM
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Re: DCR vs. Quench

Quote:
Originally Posted by mbrekke View Post
Thanks Don

My current setup is about 10.5 static and 8.3 dynamic. It runs on 91 octane. My hope was to tighten up the quench but that puts me at 10.7 static and right at 8.5 dynamic. Pretty high for cast iron.

Mark
Your cam numbers and altitude will play a part, I will post this little link as soon as i got home, bout 5 pm. The numbers sound high but i think the main issue is controlling quench.
The 8.5 dynamic is at the high side of Vizards recommendations but its in the range he talks about , not over into the 9.0

Don
TC # 349
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post #13 of 36 (permalink) Old Jan 10th, 08, 04:19 PM
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Re: DCR vs. Quench

Mark, here is the program I was talking about.
http://www.bid2race.com/DynamicCompr...Calculator.php

Fill in the blanks. Remember that you are dealing with much of the unknown on deck. I presumed my piston were .025 in the hole, when I checked, I found wide variations from .019 to .034.

Don
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post #14 of 36 (permalink) Old Jan 10th, 08, 04:20 PM
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Re: DCR vs. Quench

Dang.....that's some confusing stuff right there......


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post #15 of 36 (permalink) Old Jan 10th, 08, 04:40 PM
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Re: DCR vs. Quench

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Originally Posted by dubs68camaro View Post
Dang.....that's some confusing stuff right there......
Yes, and the engine efficency factor plays too, less efficent your motor is , lowers you fuel requirement , as I am finding out.

Don
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Zdld17:69 Z/RS,306, NOR141111, 9N554XXX, 12A, X3G, 59/59,723, AFR 195,CCC282/290HR, TKO 600, BU1122B1E Owner since Dec 1968

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