Is This Too Close To The Edge?
Thread Starter
Melting Slicks
Joined: Apr 2000
Posts: 2,145
Likes: 1
From: Ft. Walton Beach, Fl USA
Is This Too Close To The Edge?
I know I've been asking alot of questions lately but I want as much info as I can get before I start putting this motor together. I got my shortblock yesterday and I'm ready to get started.
396SBC, alum heads, single pattern 244@.050 hydraulic roller, 11.43CR, 8.57DCR, .036 quench (.006 deck) very good cooling system and cold air intake. Too much compression?? To high DCR??
396SBC, alum heads, single pattern 244@.050 hydraulic roller, 11.43CR, 8.57DCR, .036 quench (.006 deck) very good cooling system and cold air intake. Too much compression?? To high DCR??
Melting Slicks
Joined: Jul 2005
Posts: 2,060
Likes: 46
From: winter haven florida
St. Jude Donor '12
i am not an expert but i think you are at the extreame limit for pump gas for a steet car. you may get some detonation depending on fuel quality. i went with a slightly smaller cam and 10.5 to 1 comp to get my dcr at 8.27. i also have a 396 sbc. i would want a little buffer due to the unpredictable fuel quality we have here along with the heat. i may be leaving a little bit of potential hp on the table but i would rather have a very drivable and safe combo over absolute max hp for a street motor. i had a very similar comp ratio with my 383 and it would detonate like crazy with 93 octane sometimes. it had lots of power but was not worth it in the end because it was hit and miss with the detonation depending on the fuel i got. some tanks would be fine and others would be terrible.
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,444
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Over the years i have built two motors that were on the verge DCR wise with pump gas. In each one the fix was a longer duration cam. Your 244 is pretty big. Generally 8.5 DCR is the limit. I would try it and see.
Is your exhaust really free flowing? What is the cams LSA?
Is your exhaust really free flowing? What is the cams LSA?
Race Director
Joined: Oct 2000
Posts: 14,991
Likes: 79
From: central FL, near the beach.
sounds good but u need
1. good gas as frcz19 notes, some 91-93 tanks really have 87 in them!
2. best forged pistons- i've seen the skirts break off at 12:1. so i dont like piston rock
3.quiet enough exhaust that u can hear ping.
4. willingness to do individual cyl. tuning, if necessary
1. good gas as frcz19 notes, some 91-93 tanks really have 87 in them!
2. best forged pistons- i've seen the skirts break off at 12:1. so i dont like piston rock
3.quiet enough exhaust that u can hear ping.
4. willingness to do individual cyl. tuning, if necessary
Last edited by Matt Gruber; Oct 10, 2007 at 07:13 AM.
Thread Starter
Melting Slicks
Joined: Apr 2000
Posts: 2,145
Likes: 1
From: Ft. Walton Beach, Fl USA
i am not an expert but i think you are at the extreame limit for pump gas for a steet car. you may get some detonation depending on fuel quality. i went with a slightly smaller cam and 10.5 to 1 comp to get my dcr at 8.27. i also have a 396 sbc. i would want a little buffer due to the unpredictable fuel quality we have here along with the heat. i may be leaving a little bit of potential hp on the table but i would rather have a very drivable and safe combo over absolute max hp for a street motor. i had a very similar comp ratio with my 383 and it would detonate like crazy with 93 octane sometimes. it had lots of power but was not worth it in the end because it was hit and miss with the detonation depending on the fuel i got. some tanks would be fine and others would be terrible.
Thread Starter
Melting Slicks
Joined: Apr 2000
Posts: 2,145
Likes: 1
From: Ft. Walton Beach, Fl USA
My exhaust is Hooker Sidepipes.
Thread Starter
Melting Slicks
Joined: Apr 2000
Posts: 2,145
Likes: 1
From: Ft. Walton Beach, Fl USA
sounds good but u need
1. good gas as frcz19 notes, some 91-93 tanks really have 87 in them!
2. best forged pistons- i've seen the skirts break off at 12:1. so i dont like piston rock
3.quiet enough exhaust that u can hear ping.
4. willingness to do individual cyl. tuning, if necessary
1. good gas as frcz19 notes, some 91-93 tanks really have 87 in them!
2. best forged pistons- i've seen the skirts break off at 12:1. so i dont like piston rock
3.quiet enough exhaust that u can hear ping.
4. willingness to do individual cyl. tuning, if necessary
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Race Director
Joined: May 2005
Posts: 10,674
Likes: 122
From: Millington Illinois
St. Jude Donor '08-'09
I know I've been asking alot of questions lately but I want as much info as I can get before I start putting this motor together. I got my shortblock yesterday and I'm ready to get started.
396SBC, alum heads, single pattern 244@.050 hydraulic roller, 11.43CR, 8.57DCR, .036 quench (.006 deck) very good cooling system and cold air intake. Too much compression?? To high DCR??
396SBC, alum heads, single pattern 244@.050 hydraulic roller, 11.43CR, 8.57DCR, .036 quench (.006 deck) very good cooling system and cold air intake. Too much compression?? To high DCR??
Melting Slicks
Joined: Jul 2005
Posts: 2,060
Likes: 46
From: winter haven florida
St. Jude Donor '12
you can always try it, i found when i was having problems that upping the gasket size and quench made the detonation much worse. give it a shot and if it doesnt work, change to a longer duration cam. keep the quench around .039.
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,444
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
I'm leaning towards the try it and see right now but... I may set it up as I described and have it dynoed. If I run into detonation probs I can always use different head gaskets. I wanted the quench below .040 that's why I was thinking a .030 head gasket. A .036 would give me 8.45DCR and 11.27CR. A .041 I think would put me outside ideal quench at .047 but the CR would be 11.07 and the DCR 8.30. Maybe thats what I should go with.
My exhaust is Hooker Sidepipes.
My exhaust is Hooker Sidepipes.
Tight quench has more resistance to detonation even with slightly higher compression. Because the flame travel is faster.
You can change the DCR by advancing the cam and or going to higher ratio rocker arms because it adds degrees of duration to the .050 lift point.
You can also thermal coat your piston tops and safely run 1/2 point higher compression like I did in my 383 with 11.2 and only 236/242 SR cam
Last edited by gkull; Oct 11, 2007 at 12:37 AM.
Instructor
Joined: Jan 2005
Posts: 152
Likes: 0
Hi Nastee,
Have you calculated how much TQ/HP you will gain
going all the way up to 11.43 compared to a much safer level like 11:1?
Knowing how much (or little) you will gain makes the decision more easy I think.
Best regards, DK.
Have you calculated how much TQ/HP you will gain
going all the way up to 11.43 compared to a much safer level like 11:1?
Knowing how much (or little) you will gain makes the decision more easy I think.
Best regards, DK.
Thread Starter
Melting Slicks
Joined: Apr 2000
Posts: 2,145
Likes: 1
From: Ft. Walton Beach, Fl USA
Thread Starter
Melting Slicks
Joined: Apr 2000
Posts: 2,145
Likes: 1
From: Ft. Walton Beach, Fl USA
That's my primary concern, getting the quench right. The builder told me the deck would be "about" .010 which it is (.006) but I started gathering parts based on the .010. A little more patience probably would have helped.
Burning Brakes
Joined: Feb 2006
Posts: 1,024
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From: AL
Thread Starter
Melting Slicks
Joined: Apr 2000
Posts: 2,145
Likes: 1
From: Ft. Walton Beach, Fl USA
I'm committed! The cam is in the box in my garage. I'm still within the "return" window though. I'll think about it for a few days. The cam I have and the COMP Magnum304 are both 244@.050 but the advertised events are vastly different. Those are pretty much my choices as single pattern cams go.
Thread Starter
Melting Slicks
Joined: Apr 2000
Posts: 2,145
Likes: 1
From: Ft. Walton Beach, Fl USA
Tight quench has more resistance to detonation even with slightly higher compression. Because the flame travel is faster.
You can change the DCR by advancing the cam and or going to higher ratio rocker arms because it adds degrees of duration to the .050 lift point.
You can also thermal coat your piston tops and safely run 1/2 point higher compression like I did in my 383 with 11.2 and only 236/242 SR cam
You can change the DCR by advancing the cam and or going to higher ratio rocker arms because it adds degrees of duration to the .050 lift point.
You can also thermal coat your piston tops and safely run 1/2 point higher compression like I did in my 383 with 11.2 and only 236/242 SR cam