[steve25]

Lol, your stating extremes in a unrealistic fashion in terms of the 301 comment, and just opinion in your first post.

I am talking in a direct comparison stating proven facts!

Jim the factory thought that the 188 CC port volume of the SD455 heads was the largest they wanted to use in terms of street performance when dealing with the weight of the F body cars and the steepest rear gears they would come with which was 3.42 and with a 6000 rpm limit.

The SD heads flowed peak of some 245 intake cfm, and the Pontiac engineers where always carefull in terms of production motors to keep the Intake port velocity around 350 FPS at peak lift.

Now let's look at your ported aftermarket Round port heads.

At the 325 cfm flow rate with a bigger then out of the box 215 CC Intake runner from any porting work they are producing less then 300 FPS, ( probably around 296 FPS ) so if you want to keep the same throttle responce feel of a 188 CC Intake runner like the SD455 head you need to go with a 15 % larger cid motor, or on average always run it at a 15 % higher rpm.

It's really that simple!

Compression wise with a Carb and HEI set up I would go for 9.8 if you can get 94 octane fuel, if your going with a well calibrated fuel injection set up with a oxygen sensor then I would shoot for 10.25 compression.

[Formulajones]

LOL

[tom s]

383-301 with Daves 260 CNC job on 15 heads is the ticket!Tom

[Gach]

Here’s a combo for you, just and idea. 67 GTO 3600+ # ran 11.50’s on pump gas. 4.21 stroke. Round port E-heads just clean up nice valve job. RPM Dual Plane intake, Clift R Q’jet 3:73 gear. Crower hyd cam

INT/EXH - Dur @ .050” Lift: 231°/240° RR: 1.5/1.5 Gross Lift: .470”/.470” LSA: 112° RPM: 2000 to 4800 Redline: 5300

He went with 1.65 rocker. So .520 lift 3800 stall convertor shifts at 5500 rpms. Guessing heads flow 290-300 cfm. Really just out of box E-heads just cleaned up.

If I remember right 9.50 compression. With more cam easily run low 11’s

[Tom Vaught]

I ran 11.50 at 117 in my convertible, I have the time slip somewhere, with a bit more camshaft, slightly less head flow, 4.33 gear, cleaned up Torquer 1 intake and a well tuned Holley 850 #4781 Holley carb.

It is not really that hard to do. Simple roll bar set-up in the car at the time with swing out arms. Cut all that crap out of the car many years later. Bill Klausing in a Much heavier 63 Pontiac Station Wagon could run 12.06 pass after pass with a small hydraulic camshaft and a 1966 tri-power intake with Holley 2 bbls on the intake.

This was in the late 1990s. Palbykin was running low 7s and high 6s with his race car. I think Rodney Butler had run a high 8 second time by then.

Tom V.