Sup guys my project is moving a little slower than expected but its moving. My question is I have a chevy 400 block and I want to order the bill mitchell stroker kit from summit to make it a 427. the question I have is I have a holley 144 blower and I want to put a 150 shot of juice with it. What compression should I run I was thinkin 8.5-9:1 would that be good or too high? another question is what heads should I go with. I was lookin at the dart heads wih a 230 cc intake runner 64 or 72 cc combustion chamber not sure yet would these heads be good? I was thinkin that since I am supercharging I wanna flow as much air as possible what do oyu guys think???

 

HI THREAT,
WELL I THINK ALOT OF THINGS ARE TO BE CONSIDERED FIRST:
PUMP GAS NORMALLY OR RACE FUEL? HOW MUCH BOOST THAT BLOWER MAKES? AS FAR AS THE HEADS GO YOU WONT BE NEEDING THE LARGE INTAKE RUNNER BECAUSE YOU ARE FORCING AIR-EXHAUST FLOW SHOULD BE YOU CONCERN - A LARGER INTAKE RUNNER WILL JUST LESSEN BOOST AND RESPONSE FROM BLOWER.

TOM

 

I will be running about 12lbs of boost and I want to run pump gas with octane boost the car isnt gonna be a daily just my night and weekend street racer

 

The Holley blower produces too much extra heat to run 12lbs with pump gas. Probably gonna have to run 100 octane just to keep it from detonating, plus timing retard.

I would go with the 200cc heads and a very mild blowercam with that motor, maybe producing 400hp on the motor. If you add 8lbs of boost on top of that, you should add another 150hp (up to 550hp), then you can add a 150hp nitrous kit and get 700hp without having to rev it or run race gas. It would be a 5500rpm motor that would need 2.73 or 3.08 gears, anything else would overrev the motor on the big end (700hp is good for 135mph).

Or,
You could sell the blower and put the money into a set of AFR race heads and run about 600hp on the motor and a nitrous hit of 200 hp for a total of 800hp, without hood clearance problems.

 

A lot of you guys with superchargers what kind of heads do you run and what compression. IN my opinion the best way to learn if from proven experiance so please gimme some ideas thanks

 

If you want to run an actual 12 lbs boost on pump gas
reliably (92 octane) you would want a cr of 7.5:1 to 8.0:1.
You'll have to spin the 144 blower pretty fast, about 2.47:1
drive ratio to get 12 psi with the combo you mentioned. A boost
retard ignition box will help a bit. Forget the octane booster, it's better and cheaper to mix race gas to raise octane. To add nitrous
to this setup would require race gas. Consider a water/alcohol
injection system. It will allow more boost/compression with less ignition retard, for a said octane fuel.

 

can you expalin the water alchohol injection system

 

Do a search on the net for "water injection" AND "detonation"
there is loads of info there for ya.

 

The 230 cc heads you picked will work fine.
You can't have enough head on a 400-427ci sb.
Don't wimp-out on the cam either.
Summit has hydraulic cams that suite a street blower
motor to a tee. Pick one of the three biggest ones depending
on the power/rpm range you prefer.
I like Summit# SUM-1107 for your application.
234/244 dur@.050 on 112 L/S .488/.510 lift.

 

I agree with paul esp the the last part, please consider also the item I am having problems with. piston availability. I did not follow the K.I.S.S. rule along time ago and now I have to live with the consequences. instead of going with a regular 406 or 412 (both 3.75" stroke) with a 5.7 rod (from a 350).I decided to go with an exotic stroke of 415 (3.835") and when I hurt pistons the only people that can help me is JE pistons because mine are custom made. If I could start all over I would have gone with the "Keep It Simple, Stupid" and not got caught up in the numbers of displacement. Just recently as if to rub it in my face Speed Pro (formerly TRW) came out with a 5.7 rod 3.75 inch stroke for the 4.125, 4.155, and 4.185 inch bores of a 400. it has a dished top and is like all thier pistons which are tough little anvils.

 

I would disagree with you there. there to my opinion would be more of a need for a larger intake there..
if he is boosting he is going to be flowing a lot more air through the system in a whole so if he gets a small intake then it is going to back up inside his intake. yeah boost level might go up but you know power is going to go down.
now if he was able to get a bigger head it is going to flow that boosted air a lot better granted he might not have as high of boost numbers.. BUT.. would you rather look at how many pounds of boost are in the manifold or how much air makes it through the whole system


remember boost is not the whole story you also want to look at flow rates..


and also being he is runnign a 400 or 427 I would think he would want a little bit larger of a intake right there.

 

Rx7speed: I agree with you. Just bolting a blower on a
motor that is under headed and under cammed will only result
in a modest power increase and a high boost guage reading.
The idea is to feed the motor more air/fuel, burn it in the
chamber and then get it out. So having good breathing
induction/heads/ exhaust is very important. The boost guage
will read lower per blower drive ratio because more air will be going in the motor, not backing up in the intake manifold.
Personally I'd build a 377ci motor 400block, 350steel crank. 5.7 rod. Builds a very powerfull, strong motor and off the shelf forged pistons
and head cc combinations are available to build the correct cr
at a reasonable price. I'd build for 8.5/9.0 cr using 215/220cc ported heads, the above summit cam or simular and 7 to 9psi boost on the street with 92 to 94 octane gas and at the track, change the boost /drive ratio 12/15 psi and run 114 octane race gas. This 377ci/144-blower combination works,great, is very street friendly and trouble free.... could even handle a lil juice...

 

well you will get tons of different opinions,and choose what you think is best for you - i was just adding my 2 cents from my (experiences) but like i said flow is important on both sides but the side you will net the most gains from are on the exhaust sides of the heads. you will force plenty of air through a 200 -210 cc head
- now if the heads are not exhausting the (forced air) then that is when you will see astronomical boost levels with no beneifit of power gain.
but again this is only my small opinion if i were you i would call holley and see what they suggest.