[25stevem]

Tim I feel your distress!

Here’s how I view what going on with your motor, but my first concern would be to pull the pan and find out why at high flow rates your oil pressure is slipping .

In terms of your motors level of power your cam only has a mire 8 degrees more intake duration @ .050” then the factory 068 cam has, and I think that with the way your heads are ported that you do not need a single pattern cam.

To gain more power I would get a half set of 1.65 rockers to put on the intake side.

You would need to confirm that the springs where then good to .556” lift and that the valve train clearances where good.

You would need to check the geometry again also.

I would also like to see you swap that Tomahawk out for a performer rpm.
The added port velocity will produce a higher level of average torque and Hp while not cutting into the peak Hp numbers.

I see your ported heads for sure are helping above 5200 rpm since you motor is still holding onto darn close to 400 Hp even up at 5800 with that small intake duration cam!

Here are some dyno test results that you may recall from a 9.4 comp 455 from the June 1992 issue of HPP.

This 455 used stock heads, ( 6X and 1971 # 96 ) a performer intake and a cam far bigger then yours.
The cam was 236/244 @ .050”.

Even with a cam this big and stock heads the HP took a nose dive at 5400 rpm where your 442 is still going strong.

Is there a chassis dyno you could get the car out to once the motors in the car?

[Stan Weiss]

Tim,
If this was my engine, just by looking at the dyno results I don't know that I would want to just start changing parts. I would see if there was someone else in the area with a dyno. I would explain to him what happened with the last dyno tests and see what he thinks about the results and if he thinks it might be a dyno problem and not an engine problem. I know dyno testing is not cheap but it may turn out that another dyno session somewhere else is the answer.

Stan

[KEN CROCIE]

Upor rethink ing the HP drop, pulling a plug wire at that instant, would drop the power by 50HP.

[Tim Corcoran]

could I have a sticking exhaust valve?

[25stevem]

I will post this story here just keeping this possibility open.
David Vizard during a chassis dyno test session of a customers motor had a shock when he found the he was down some 80 to 100 hp from where he should have been, but yet the motor sounded very healthy.

After spending hours going over everything to the point of even degreeing the cam again he put things back together to make another run.

During the check out session the Champion plugs got very wet.
All he had on hand was a set of Autolites , but they where not a racing plug, be he went with them anyway.
On the next pull he made 85 hp showed up like magic !
To confirm that these results where not a fluke the Champions where put back to make the next pull and the motor was back to a 85 Hp loss.

[PAUL K]

Originally Posted by Tim Corcoran

could I have a sticking exhaust valve?

Usually a sticking valve gets unstuck when the piston hits it and bent in the process. A quick compression test will tell you if the valve is bent or sticking.

[25stevem]

Also at idle a sticking exh valve for example would be heard as a miss out the exh system on whatever bank it was in, where as a hanging up intake valve would be making a backfire out the carb.
Another test out for the possibility of either valve being off it’s seat even without making a compression test is to just kill the spark and crank the motor over.

If a cylinder has very low or no compression you will hear the rate of cranking speed up as the motor tolls passed that low cylinder.

[Tim Corcoran]

Just as a side note the shop owner that was running the dyno said that his brake on the dyno was quite worn and he did rebuild the brake shortly after this. I also suspect the dyno was not acting right. He also was fighting an input wire signal into one of his control boxes he had to mess with the wire to get it to connect. This is not a race car it's a street car so having oil pressure drop above 5,000 RPM doesn't worry me. It has nice torque to pull the 3.08:1 rear gear with a 28" tire hopefully I can drive it on the freeway without revving up the motor too much. I never felt comfortable driving on the freeway with the engine turning above 3,000 RPM for long periods.