Thread: last ? on compression
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10-30-2006 06:05 AM #1
last ? on compression
is 10:1 compression ok on a 400 if i run premium
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10-30-2006 06:52 AM #2
Originally Posted by maineevent
With a flat top piston 64cc head you will have 11.5 to 1 comp. ratio.
This will not run on pump gas.
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10-30-2006 10:00 AM #3
Just make sure the intake valve closing point is about 65 -70 degree abdc.Its gunna take longer than u thought and its gunna cost more too(plan ahead!)
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10-30-2006 10:16 AM #4
Originally Posted by shawnlee28
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10-31-2006 07:28 AM #5
im buying a rubuild kit with 12.5 cc 5.7 dished pistons I'm going to sell my flat top pistons plan on using comp xtreme 268 cam my going to have my crank turned it should hold up well or is it necessary to buy a scat replacment crank plus since yuo all say vortec heads vortecs it shall be
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10-31-2006 07:33 AM #6
oh yeah the dished pistons spec say 10:1 compession with 64 cc heads
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10-31-2006 08:44 AM #7
Originally Posted by maineevent
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10-31-2006 11:33 AM #8
9.96 to 1 static and 8.31 to 1 dynamic with the cam you specified and stock deck height,I do not know how well the vortecs are for 400,may be rpm limited,maybe some one with more exsperiance can chime in on vortecs on a 400?Its gunna take longer than u thought and its gunna cost more too(plan ahead!)
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10-31-2006 02:28 PM #9
If you're nailed down to that cam, I think I'd drop down some on the static compression ratio. 8.31 DCR would seem to be a little dicey on pump gas in my opinion, but then, what do I know?
I would also think the Vortecs would be all the head you would need in a street motor with a short cam.
Build the motor with a tight squish, 0.035" to 0.040 to make it more octane tolerant. Juggle your deck height and gasket thickness to make it happen.
Drill the Vortecs for steam holes and use 400 head gaskets.PLANET EARTH, INSANE ASYLUM FOR THE UNIVERSE.
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10-31-2006 02:41 PM #10
[QUOTE=techinspector1] 8.31 DCR would seem to be a little dicey on pump gas in my opinion, but then, what do I know?
Quite a bit more than most of us"aerodynamics are for people who cant build engines"
Enzo Ferrari
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10-31-2006 02:48 PM #11
Originally Posted by techinspector1
They also go on to say that 11 to 12 to 1 can cause detonation.
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10-31-2006 04:25 PM #12
Go one cam size bigger,xe 270,after all it is a 400 , and its sounds like you should have a tire fryin motor!!!With the right tires and gears I think its goin to feel like the front left tire is coming off the ground when you get on it!!Your lookin at about 1100 to 1200 bucks for the heads,intake ,cam lifters and springs.These are new retail prices,used heads and intake will lower this alot!!Its gunna take longer than u thought and its gunna cost more too(plan ahead!)
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10-31-2006 05:43 PM #13
Originally Posted by shawnlee28
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10-31-2006 09:36 PM #14
so you think going with the dish pistons and a exterme 270 cam would be better than the 268 an i'll still get the 10:1:1 compression an can run pump gas
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11-01-2006 09:49 AM #15
Why are you so hung up on 10.1:1 compression?PLANET EARTH, INSANE ASYLUM FOR THE UNIVERSE.
Welcome to CHR. I think that you need to hook up your vacuum advance. At part throttle when cruising you have less air and fuel in each cylinder, and the air-fuel mixture is not as densely packed...
MSD 8360 distributor vacuum advance