Thread: last ? on compression

Tweet

is 10:1 compression ok on a 400 if i run premium

Originally Posted by maineevent

is 10:1 compression ok on a 400 if i run premium

I hope you have a dished piston in there.
With a flat top piston 64cc head you will have 11.5 to 1 comp. ratio.
This will not run on pump gas.

Just make sure the intake valve closing point is about 65 -70 degree abdc.

Originally Posted by shawnlee28

Just make sure the intake valve closing point is about 65 -70 degree abdc.

I think there might be a few more varibles than just the cam timing.

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

oh yeah the dished pistons spec say 10:1 compession with 64 cc heads

Originally Posted by maineevent

oh yeah the dished pistons spec say 10:1 compession with 64 cc heads

Yes,that will run on pump gas with the dished pistons.

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?

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.

[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

Originally Posted by techinspector1

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.

According to Comp Cams that cam will work with a static comp. ratio of 10,or 9 to 1.
They also go on to say that 11 to 12 to 1 can cause detonation.

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!!

Originally Posted by shawnlee28

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!!

If you are refering to the XE 274H it will work, but he will need to run a 2,200 stall or more.

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

Why are you so hung up on 10.1:1 compression?