High Ports w/2.25 intake valves on .060 over factory block
 

Its a 455 block with the factory chamfers for the intake valves. Gonna be a while before I can put an aftermarket block build under this very nice set of 385CFM heads that were set up with the 2.25 intakes (CNC ported at SD and reworked/hand finished by Dan Barton) The guy I bought the heads from ran them on an aftermarket block 535.

Does anyone foresee any mechanical clearance issues.

I know these heads will not see their potential on top of a 4.211 bore due to the intake shrouding with this cyldr size. The 74cc chamber overlaps the bore on the intake side substantially.

I did put the heads on a .030 over 455 bare block and turned it upside down with an intake valve in place and it does get close to the cyldr wall (will try to get a measurement on this but looked like not more than .030 by eyeballing it)

I'd like to hear from guys running high ports with similar flow specs on a factory block and what kind of horsepower levels reached; ET/MPH, car combo, etc

At what valve lift is that 385 cfm taking place at?

What level of hp are you looking to make ?

How much valve lift are you looking at using?


Depending on if the current valve job done on the heads is maxing out or not at the OD of that 2.250” valve, you may be able to switch over to a safer size 2.19” valve with minor seat work for now.

Also note that to make good use of even 350 cfm no less 385 is going to require a ported Victor , or a BOP intake or such, and a BOP has too much runner area for a .060” over 455 unless it’s built go to 7800 or more.

385cfm@800lift - 374 cfm@.700 lift - 364cfm@.600 - 343cfm@500

Camshaft lift is 750 ..

Hoping to make 750-800 -- cubic inch is 474

I bought the heads with a matched victor

True, I am worried about how much I may need to twist up the RPMs

Engine has a cast Eagle 4.250 strk and SCAT H beams

I am running a 2.20 valve on a .035 over 400, SD Dave High Ports. So the valve to wall I bet is pretty close to your engine. A lot of people say I am better off with a 2.15 valve, I do not think so. Smokey U did a bunch of tests on that and the area next to the cyl wall-intake valve does not flow much anyway. The outer2/3s of the valve is where almost all your flow comes from. So run the biggest valve. Go with ol Smokey.
If you are worried about how much you have to twist your engine, get a cam with the lift you need but keep the @ .050 where it will make power at 7K or lower.
Thats what I have done.
What cam are you running ?

My friend, Smokey was dealing with a 23 degree valve inclination angle head, not 14 degrees as we are dealing with now.
This is one of the main reasons why BBC and Ford C type and big block heads have canted intatke valves.

What I mean is just because our Pontiac heads and SBC heads are both parallel valved with wedged chambers it’s not just a Apples to Apples type deal .

Comp Cams Solid Roller
760 w/1.75
271/275 @ .050
108 lobe separation

Have you ran your combo yet or is it in the works?

The Crower SS shaft rockers should be shipped mid Feb.
Cant' wait.

Are you figuring 7000-7200RPM peak power with that cam ?

What is your CR?

Stan

Not sure "exactly" Stan, as I don't know the the valve relief cc on the pistons.

They are Ross with intake and exhaust reliefs the same size

If the reliefs are around 6 cc I think I figured it to be around 11.2 to 11.5. I was also figuring zero deck height in that calc but I have not checked it yet.

Also not sure of top ring placement and I did not calc that area

Head gaskets will be Felpro 1016 - -

Chamber volume is 74

Bore is 4.211 - Stoke is 4.250

I was hoping for more compression ...what do you think my comp will be with the given info. I will get actual deck height tonight but assuming a zero deck and 6 cc valve relief what do you come up with?

Not sure, but I fear my heads want a little more RPM with "only" 474 cubes.

RBAILEY
I emailed my ROSS pistons part number to ROSS and they sent me back the cc of the valve reliefs. Mine are 4.155 pistons and they have 7.63 cc valve reliefs.

Unless I used a wrong number I get 11.8. Note I used the listed cc's for the head gasket.

Stan

Thank you Stan .. the higher the happier for me .. on compression that is ;)

Whats that 550HP number on your chart?

Thanks...then I'm sure mine are probably close to that.