0.1 DCR change = ?% power change?
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Joined: Apr 2006
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From: Naperville, IL
0.1 DCR change = ?% power change? For a 346 cube engine. I am wondering if it is worth a bit of extra trouble/money to try to get the DCR closer to or even over 8.5:1 by milling my heads. I'm not out to squeeze every HP out of it, just a fun driver.. but I don't want to build a dog.
With cometic .040 gaskets and unmilled 243 castings (stock valves), I'm looking at a 10.9:1 SCR and a 8.32:1 DCR. My cam (in sig) is a 228.7/232.6 on LSK/XE-R's, 112+2. I want to be sure it clears PtV of course. Should (Can I even?) I get the heads milled a bit to bring up SCR/DCR?
I don't want to go a different cam route because I had this one ground for me by Geoff @ TR to suit my goals.. which it does perfectly! Peak 6300, shifts around 6500-6600, decent midrange torque but with torque peaking higher in the rpm's to soften the hit on street tires (hopefully less spin, and saving the rear, the car will never have slicks).
So.. I guess I'm asking, with being .2ish under ideal DCR, what am I leaving on the table if I don't mill the heads down because I am PtV paranoid?
With cometic .040 gaskets and unmilled 243 castings (stock valves), I'm looking at a 10.9:1 SCR and a 8.32:1 DCR. My cam (in sig) is a 228.7/232.6 on LSK/XE-R's, 112+2. I want to be sure it clears PtV of course. Should (Can I even?) I get the heads milled a bit to bring up SCR/DCR?
I don't want to go a different cam route because I had this one ground for me by Geoff @ TR to suit my goals.. which it does perfectly! Peak 6300, shifts around 6500-6600, decent midrange torque but with torque peaking higher in the rpm's to soften the hit on street tires (hopefully less spin, and saving the rear, the car will never have slicks).
So.. I guess I'm asking, with being .2ish under ideal DCR, what am I leaving on the table if I don't mill the heads down because I am PtV paranoid?
If the heads were off of the car then I would say it would be worth the trouble. I think you would see less than 10 hp, 10 tq. Probably not enough to even notice. 8.32 DCR is not that bad, you would prob. be thankful for it if you were ever to take your car to the desert in the summer.JMHO
Thread Starter
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Joined: Apr 2006
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From: Naperville, IL
Yeah the heads are off the car. I would mill them just a bit if it was worth it, but I HAVE to maintain PtV, I refuse to flycut. I can have them milled but can't have metal put back on, ya know?
and thx for the reply btw
and thx for the reply btw
Clay the pistons and check your ptv., you may be able to mill some. If you do, remember your pushrod length may change. On that note, if you already have your new pushrods, I wouldn't go through the trouble. I know I already said it once but 8.32 is pretty good.
Thread Starter
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Joined: Apr 2006
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From: Naperville, IL
Yeah, you're right, I'm going to stay as is.
It's still a pretty good DCR and I may take a fun trip or 2 to the strip, but it's my DD and I just wanted to do a simple top end swap. I'm not too worried about 5-6 hp.
Thanks again!
It's still a pretty good DCR and I may take a fun trip or 2 to the strip, but it's my DD and I just wanted to do a simple top end swap. I'm not too worried about 5-6 hp.
Thanks again!
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Ideally, it would be best with an existing combination to work from the cranking compression pressure. (I known, easier done before the heads came off!) David Vizard suggests around 220 psi for a hot street engine, but I expect he's talking iron heads, so that figure would be fairly conservative for an aluminum engine.
Speaking of DCR, many years ago, a friend of mine put a much-milled head from an 850 cc. Morris Minor on his stock-cammed 1,100 cc engine. I don't know what either the SCR or DCR was, but it would pin the gauge on a 300 psi compression tester, and blew head gaskets with great regularity despite being run exclusively on Sunoco 260 (106 octane leaded)
Speaking of DCR, many years ago, a friend of mine put a much-milled head from an 850 cc. Morris Minor on his stock-cammed 1,100 cc engine. I don't know what either the SCR or DCR was, but it would pin the gauge on a 300 psi compression tester, and blew head gaskets with great regularity despite being run exclusively on Sunoco 260 (106 octane leaded)
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Banned
Joined: Apr 2006
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From: Naperville, IL
Thanks guys, glad to know I'm right about where I want to be. I see 8.5:1 alot.. number kinda stuck in my head.
I really like the Edelbrock Headers. The ground clearance is nice though I wish I had filed any casting/welding flash/bumps out of the y-pipe merge. The racer collecters tend to have small exhaust leaks but hey, they slipped right in.
Originally Posted by Stang's Bane
No problem. Sounds like a good combo, well thought out. It should run like a raped ape and be torquey as hell. BTW how do you like the Edelbrock headers?
