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by mag2555
Mon Aug 02, 2021 6:54 pm
Forum: Engine Tech
Topic: Pontiac 400 heads
Replies: 62
Views: 2277

Re: Pontiac 400 heads

When your running a factory Cam of no more then .406” lift like in the average 4 bbl high comp 350 hp 445 ft lb 400 motor, then yes the 14 degree inclination which allowed a 7% bigger intake valve then the old 21 degree angle and also made for a nice reduction in the curvature of the exh ports , the...
by mag2555
Sun Aug 01, 2021 4:52 pm
Forum: Engine Tech
Topic: Straight vs Merge Collector
Replies: 24
Views: 777

Re: Straight vs Merge Collector

I’am thinking that getting your tuned lenght maxed out with the collectors you have now will be your best bang for the buck deal.
by mag2555
Sun Aug 01, 2021 4:42 pm
Forum: Engine Tech
Topic: Pontiac 400 heads
Replies: 62
Views: 2277

Re: Pontiac 400 heads

Well let go back to diving in here a bit with all this talk of Pontiacs horrible chambers and other comments. Let’s look at LF4 400 cid model SBC with a 4 bbl as installed in trucks, this motor and the Pontiac 400 have the same bore and stroke ( I guess Chevy new a good thing when they saw it! ) the...
by mag2555
Sun Aug 01, 2021 4:26 pm
Forum: Engine Tech
Topic: Pontiac 400 heads
Replies: 62
Views: 2277

Re: Pontiac 400 heads

I am flattered beyond words, all I can say is thank you!
by mag2555
Sun Aug 01, 2021 9:15 am
Forum: Engine Tech
Topic: Straight vs Merge Collector
Replies: 24
Views: 777

Re: Straight vs Merge Collector

I don’t think your running enough Cam / overlap to fully make use of the merge collectors making enough vacuum level at TDC to start the intake draw early enough to get a good VE kick!

I mean you will get some boost in power, but to me it hinges on the Dollar to power gain ratio.
by mag2555
Sat Jul 31, 2021 11:06 am
Forum: Engine Tech
Topic: Piston?
Replies: 24
Views: 1091

Re: Piston?

Since these pistons are Hypers and run with cast piston type clearances, they probably do not have any pin offset I would bet!
by mag2555
Fri Jul 30, 2021 1:47 pm
Forum: Engine Tech
Topic: Piston?
Replies: 24
Views: 1091

Re: Piston?

I don’t care for the multiple valve notches .
by mag2555
Sun Jul 25, 2021 8:36 am
Forum: Engine Tech
Topic: what sealant to use on expansion plugs, cam tunnel plug etc
Replies: 15
Views: 828

Re: what sealant to use on expansion plugs, cam tunnel plug etc

Gray form-a-gasket is what I have used for 45 years.
by mag2555
Sun Jul 25, 2021 8:30 am
Forum: Engine Tech
Topic: Non-adjustable valvetrain w/mild performance cam?
Replies: 4
Views: 335

Re: Non-adjustable valvetrain w/mild performance cam?

What are you referring to a shaft mounted valve train? A general answer to your question is yes, as long as 1) you can get the push rod length set for decent geometry since the Roller Cam base circle will be lower then stock. 2) the push rod preloads they lifter some when then needed length is set f...
by mag2555
Sat Jul 24, 2021 7:40 am
Forum: Engine Tech
Topic: Pontiac 400 heads
Replies: 62
Views: 2277

Re: Pontiac 400 heads

All Pontiac ram air production heads had 30 degree seats, I know as I own them, or have owned them all. There are, The 1968 RA1 D port exh cast number 31 The late 1968 round port exh cast number 96. The 1969 and 70 round port exh cast number 722 and 614 respectively. Even the round port exh 1971 and...
by mag2555
Wed Jul 21, 2021 3:04 pm
Forum: Engine Tech
Topic: new spark plug issues.
Replies: 5
Views: 251

Re: new spark plug issues.

Plan old new but bad plugs! You can run the 455s plugs as long as the tip length is close to the same and the heat range / color change over point on the ground strap after a heavy full throttle run is not too far past the bend point on the ground strap. Heat range wise plugs have a 600 degree range...
by mag2555
Wed Jul 21, 2021 8:00 am
Forum: Engine Tech
Topic: Safe exhaust valves clearance
Replies: 9
Views: 797

Re: Safe exhaust valves clearance

The Cam manufacturer likely found that when the expansion of everything is taken into account that there recommendation is still safe and better longevity wise for there lobe profile. Actually when you averaged out the numbers there is only a .0047” difference. If you want to be on the safe side the...
by mag2555
Wed Jul 21, 2021 7:39 am
Forum: Engine Tech
Topic: Air Cooled VW question...
Replies: 6
Views: 416

Re: Air Cooled VW question...

Aluminium heads on a water cooled motor expand at least .004” when up to temp, air cooled ones even more. Running zero lash with steel push rods when cold will get you the needed .006” or so when all is hot. When setting the cold lash on a water cooled race motor or even a street motor with Aluminum...
by mag2555
Mon Jul 19, 2021 7:31 pm
Forum: Engine Tech
Topic: GM 383 oil pump screen installation
Replies: 6
Views: 382

Re: GM 383 oil pump screen installation

Physics 101.
Two objects can not reside in the same place at the same time!
by mag2555
Sat Jul 17, 2021 10:34 am
Forum: Engine Tech
Topic: Pontiac 400 heads
Replies: 62
Views: 2277

Re: Pontiac 400 heads

Here’s my flow test results. The head in this test started life with a 1.960” intake valve with a 30 seat. In the first test listed here I the head for a 2.11” valve with a 30 seat. This seat OD was 2.04”, so still way way under the 2.10” that could have been used and it’s available curtain area! Th...