327 vs 283

[67chevygary]

Has anyone flow or tack tested the different powerpack heads?

[Dan Fahey]

Originally Posted by 67chevygary

Has anyone flow or tack tested the different powerpack heads?

Think the 520's are the ones you want..
On the fronts of the heads they have a Rectangle with a Small tiangle on top of it.
If it is just a Rectangle they are they earlier 61 heads.

Damn this was a long time ago ..1973 ran a 64 Impala SS M/S
With a mucie m20 tranny..and pumpkin rear.

Choice of Carter WCFB or Rochester4bbl which were 450 cfm at best.
But were really responsive.

I am CarbonDating myself...

D

[67chevygary]

I started a thread about a month ago about what I need to get my '57-150 ready for class racing in either n/s or m/sa. I've talked to a few people about which parts to aquire. but still looking for as much input as I can get. so far i think i've got the right block-the correct single 4 barrell-but need input on heads-intake-rear end & trans-still looking for a correct 2x4 set-up. all input is much appreciated as I've forgotten way more than I ever knew.

[Dan Fahey]

Originally Posted by 67chevygary

I started a thread about a month ago about what I need to get my '57-150 ready for class racing in either n/s or m/sa. I've talked to a few people about which parts to aquire. but still looking for as much input as I can get. so far i think i've got the right block-the correct single 4 barrell-but need input on heads-intake-rear end & trans-still looking for a correct 2x4 set-up. all input is much appreciated as I've forgotten way more than I ever knew.

Find a 55-57 Chevy Forum..You should be able anything you want !!

Suggest sending the carbs to Val Headworth and have them fix them up right!

For camshafts recommend Bullet Cams.
They have many of the experienced Cam Makers from Lunati, Comp, Crane and others.
That also know your combination and history on making those cars run.

D

[Jeff Lee]

As a VERY BASIC rule of thumb, 1 HP per CID, all else being equal. In this case, your talking 44 cubic inches or 44 HP. That's "pretty close" to what Brad said; 2 1/2 tenths. And he has real world experience. That just allows you to do some quick calculations to determine if the CID increase cancells out the HP or weight increase. And of course you should easily make 1.25+ HP per CID for any class engine.

[Joe Schweigert]

Originally Posted by Brad Zaskowski

In my SS car with the car weight real close to the same the 327 250/258 is about 2.5 tenths faster than the 283 220/230 which uses the same heads, intake and carb. I don't know the actual HP numbers but that is what they are on the track for our car and motors.
The 283 makes the power about 1000 rpm higher than the 327.

Brad I tired this several years ago and it was a about 4 tenths than with an automatic the 283 responds better with the stick

[Corvette Guy]

Originally Posted by Dan Fahey

YES..
62/64 327 ran 283 Power Pack heads with 1.72/1.42 valves

65 - 327 used larger 1.94/1.5 valves which are perfect valve size for that size engine.

D

Dan,

are you saying 327 runs better with a 1.94/1.50 than with 2.02/1.60 valves ???

[Dan Fahey]

Originally Posted by Corvette Guy

Dan,

are you saying 327 runs better with a 1.94/1.50 than with 2.02/1.60 valves ???

In Stock the basic ..929 class cams are right about .400 inch..Not much Lift.
The 2.02/1.60 will not show much performance improvement because the port sizes are near identical. Go with a high lift high rpm SS cam and you can see the difference.

There is a similar battle between the 441 and 492 heads for the 350/255 and 350/290 SBC engines..
There is less that a tenth difference between the head though the Compression is a bit more with the 492's. NHRA lowered the HP but the 290/300 is not as competitive an engine and class difference.

In 2009 spoke with Joe Mondello (rip) at length about SBC and LT1 Iron Heads.
(Read every article he ever wrote on cylinder heads, porting and bought his head porting kit.)

He said the 1.94/1.50 valves are near perfect for stock SBC heads.
Adding the 2.02 intake would reduce low speed flow and low end torque for a 350.
Though the 1.60 exhaust would benefit a SBC head.
For a 383 Stroker the larger intake will get that high speed flow back where you need it.

From his instructions carefully port/chamber/polished a set of LT 1 Irons and used Stock sized high flow valves without using a flow bench. I did use a wetted string..!

Installed them on our PINKS car with a junk yard 350.
The car ran 8 tenths quicker over their modified LT 1 Aluminum Heads they used later.

Another nice benefit of a 327 is the Rod Stroke Ratio.
The heads have the same port size and configuration of the 350.
For some reason the 327 produces near the same HP as a 350.
Mostly because the shorter stroke it and near identical port volume the 327 rev higher to make up some of the lost torque of the 350.

Hope this OVER the Top View helpes ;-)



D