Re: HP adjustments after the Dutch - posted
 

Bruce I know its a old car but give me a break . 1.20 under get HP if you make a mistake with wrong heads to bad . Its must have been a advantage if he went 1.20 under

Re: HP adjustments after the Dutch - posted
 

Well Bo, let's see how fast he is with bigger valves.

Re: HP adjustments after the Dutch - posted
 

Lets get this straight, before every key board engine builder gets their pantie in a twist. First and foremost I F---Ked up plain and simple!!I had done the heads for a 396 and when we switched and made it a 402 I never gave the valves a thought. Till dave measured it ! Yes I f--ked up!This is the reason anything that goes 1.200 under should be torn down.Why should he (or other w/ comb) be hit if his was not legal? BO what if I were to put a different blower or pulley on, and wreck your combo? As far as the guys that call themselves engine builders and want to go around the track saying this and that, JUST maybe if you did your own stuff rather than having it trucked in, then maybe you too would make a mistake once in awhile! Yes I'm sure the big valve will slow it down probably will not be able to run the index:)

Re: HP adjustments after the Dutch - posted
 

If brian did this motor and tells u what he did wrong u can take it to the bank he is fair and honest!

Re: HP adjustments after the Dutch - posted
 

I completely agree that every combo that runs fast enough to get hp should be torn down and pass tech. With that said, running 1.2 under with to small of valve would be like running to small of a carburetor. LOL Luckily for him this mistake saved his combo from getting an automatic hit. But will it save it from the review board at the end of the year?

Re: HP adjustments after the Dutch - posted
 

Agreed.

Re: HP adjustments after the Dutch - posted
 

Just curiosity ----The wrong size valve being talked about is the exhaust side at 1.72 vs 1.88 as being the 70 402 which used the same head as a 70 LS6. Am I following this correctly ?

Re: HP adjustments after the Dutch - posted
 

It is not the same philosophy or dynamics.
Also, the intake port does not behave the same way as an intake port.
The Chevy big block exhaust port and valve BBC are already bigger than they need to be.

Due to the lift restrictions in the class, using a smaller valve improves the curtain area by slowing down the flow and velocity.

During scavenging, the pressure recovery is better when the gases expand due to a slower velocity, specifically when you take into account the CID and RPM range limits of the engine.

Therefore, contrary to what many may think, going to a larger exhaust valve may slow down the car.

However, in the case of an intake valve, the rule would be the opposite.

Re: HP adjustments after the Dutch - posted
 

If the smaller valve is indeed the better performer here couldn't you adjust the events of the ex lobe on the cam to get your velocity and scavenging back to where it was?

Re: HP adjustments after the Dutch - posted
 

Was there any repercussions, just curious what, if anything, that would warrant???