10:2:1 CR to low for 396?
06-01-2006, 02:52 PM
#1
10:2:1 CR to low for 396? Well went and had a long talk with my mechainic today and i opted for an 11:5 CR and he refused to build it.
He says that the atmposphere up here is not going to support an 11:5 on pump gas.
Then i talked to Harold at PortPros and Pecos at LME and they both say its crazy talk to run that low of compression.
The highest my mechanic will go is 10:2!! Is that even worth building?
The main point he had was because i would burn a piston.
He also stated that 10:2 vs 11:5 isnt going to be that big of a difference. Then he goes on about tunning and how its going to be a pain without a Standalone system.
I aslo asked what i would be putting down # wise on motor with 195cc Trick flows, and he said 480-510.
The main reason im asking you guys is becuase he is the only builder in town and he builds AMAZING motors. And his warrantys are great too, i dont want an out of state motor and a crappy warranty, cuz when it breaks whos gona fix it?
He says that the atmposphere up here is not going to support an 11:5 on pump gas.
Then i talked to Harold at PortPros and Pecos at LME and they both say its crazy talk to run that low of compression.
The highest my mechanic will go is 10:2!! Is that even worth building?
The main point he had was because i would burn a piston.
He also stated that 10:2 vs 11:5 isnt going to be that big of a difference. Then he goes on about tunning and how its going to be a pain without a Standalone system.
I aslo asked what i would be putting down # wise on motor with 195cc Trick flows, and he said 480-510.
The main reason im asking you guys is becuase he is the only builder in town and he builds AMAZING motors. And his warrantys are great too, i dont want an out of state motor and a crappy warranty, cuz when it breaks whos gona fix it?
06-01-2006, 03:15 PM
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ask him why he wants you to run less compression then your motor had stock.
i've talked to some dopey machinist. they know how to machine blocks, but know nothing about setting up a good combo
i've talked to some dopey machinist. they know how to machine blocks, but know nothing about setting up a good combo
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06-01-2006, 03:51 PM
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What kind of gas do you have in your area? 91 octane the highest it goes? He may be concerned that you'll fill it up with 91 and then drive to a lower altitude area, and that's where you'd get in to trouble.
My 383 LT1 should be around 10.5:1 when I'm done, but I'm not building it to race, just a driver...
My 383 LT1 should be around 10.5:1 when I'm done, but I'm not building it to race, just a driver...
06-01-2006, 04:40 PM
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The issue becomes needing a high altitude tune and a low altitude tune. I lived in Amarillo - which is 2700 ft, typically 4000-5000 ft DA's. I could run 36-37 degrees of WOT timing up there, and my LT1 just loved it. Crazy stuff. Take that down to sea level on 90 octane (which is what most pumps had as "high octane" in the area), and it'd sure break things. I only went to low altitude once with that setup, and I retuned the car for low altitude before going down the dragstrip.
I can understand his point. It's his *** in the sling as far as motor warranty goes - and he's covering it this way. You tune a car to run at high altitude, then take it to a lower altitude, it *could* cause harm, especially if you're "on the edge".
Sounds like he actually does know what's going on.
I can understand his point. It's his *** in the sling as far as motor warranty goes - and he's covering it this way. You tune a car to run at high altitude, then take it to a lower altitude, it *could* cause harm, especially if you're "on the edge".
Sounds like he actually does know what's going on.
06-01-2006, 04:50 PM
#12
split the diff and do about 10.8 or so...that will still run pretty good on pumpgas and you can boost it later...or just get the compression you want and lie to your engine builder, how the hells he going to know? look at it? does he ahve the tools to check it? id say give him the parst tell him you decited on stock compression 10.5 and dont let him kno otherwise
06-01-2006, 05:14 PM
#14
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Speed, have you discussed cams (valve timing) with your engine guy? The intake valve timing is going to influence the Dynamic Compression Ratio (DCR), so shouldn't he be specifying valve events before y'all decide on a SCR? If that idea bothers him, or he doesn't discuss DCR, he wouldn't be my engine builder.
Additional thoughts:
195 cc heads on a 396? Why bother with all those cubes if you can't feed 'em?
480-510 FWhp right? That's maybe 400-430 RWhp...maybe with 195 cc heads. At what rpm does he expect power to peak?
Wouldn't you be happier with 450++ RWhp? It's available in a very streetable 396 if you do it right. It won't have 195 cc heads, however.
You mentioned the Edelbrock LT1 intake manifold. Was that the first one that never went anywhere?
No offense intended with these comments. There are certainly risk-adverse engine builders out there. Not many of them are very big fish in anything but a tiny pond, however.
If you are committed to this builder and his "warranty", so be it, but you are leaving a lot of torque/power on the table. I would not advise forcing the builder to do things he thinks are wrong, however. You are sorta between a rock and a hard place.
Good luck to you.
Additional thoughts:
195 cc heads on a 396? Why bother with all those cubes if you can't feed 'em?
480-510 FWhp right? That's maybe 400-430 RWhp...maybe with 195 cc heads. At what rpm does he expect power to peak?
Wouldn't you be happier with 450++ RWhp? It's available in a very streetable 396 if you do it right. It won't have 195 cc heads, however.
You mentioned the Edelbrock LT1 intake manifold. Was that the first one that never went anywhere?
No offense intended with these comments. There are certainly risk-adverse engine builders out there. Not many of them are very big fish in anything but a tiny pond, however.
If you are committed to this builder and his "warranty", so be it, but you are leaving a lot of torque/power on the table. I would not advise forcing the builder to do things he thinks are wrong, however. You are sorta between a rock and a hard place.
Good luck to you.
06-01-2006, 05:35 PM
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Find another builder 2800 feet is not high!
I'm running 11.28:1 and I'm at 6200ft shoot I take it above 7200ft a couple of times a week.
Mike
I'm running 11.28:1 and I'm at 6200ft shoot I take it above 7200ft a couple of times a week.
Mike
Last edited by aboatguy; 06-01-2006 at 06:14 PM.
06-01-2006, 06:56 PM
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Yeah, those High Compression people are crazy!!!
Mine is a lowly 12.5 SCR...with a 8.77 DCR...Find another engine builder that actually knows LT1's...also make sure your engine builder knows what SCR and DCR stands for...
By the way, I'm at sea level with 32 degrees total timing (could run more, but the car makes most horse power with).
ALSO...a 220ishcc ported head, has no driveabilty issues in a 396 (as long as it actually has enough compression to run the cam you select...eg. torque). Cam is the issue not heads....unless you go like 230ish cc's head on there(then it will just feel spongie but still make gobs of torque when WOT)
Mine is a lowly 12.5 SCR...with a 8.77 DCR...Find another engine builder that actually knows LT1's...also make sure your engine builder knows what SCR and DCR stands for...
By the way, I'm at sea level with 32 degrees total timing (could run more, but the car makes most horse power with).ALSO...a 220ishcc ported head, has no driveabilty issues in a 396 (as long as it actually has enough compression to run the cam you select...eg. torque). Cam is the issue not heads....unless you go like 230ish cc's head on there(then it will just feel spongie but still make gobs of torque when WOT)
Last edited by jimbob; 06-01-2006 at 07:02 PM.
