JimV

iTrader: (1)

Yes, just for one pull. It will tell you if the cam is to big or not matched to the heads. Make sure the fuel delievery is ok(pressure and volume) and ignition system is OK. By adding lash it will pull some lift and duration out. If the motor goes rich with the same jets I would suspect the heads are a problem. A 2.300 intake valve should flow about 400 CFM @ .700 lift. The 1.900 exhaust valve can be hurting as well. Knowing those exports, it's hard to get 250 CFM out of them and when you do their usually over ported.

Turbojack

I would say it depends on how they checked the air/fuel ratio. If they used O2 sensors then you may need to rejet. If they used the mass air flow sennsor then I would say NO & start looking at some of the other items brougth up above.

Strip Poker 388

iTrader: (6)

[QUOTE=rmbuilder]I apologize for the long post but this is very good information that will hopefully shed some light on the subject courtesy of Larry Meaux.
BSFC and Exhaust Gas Temperature (EGT) Information ;
In the old days of dyno testing , the dyno instrumentation
back then consisted of measuring Torque and engine RPM .
The dyno "luxury options" were also the ability to measure
fuel flow and exhaust gas temperatures , now these options
are standard equipment on modern dynos.

Bob how do you know Larry Meaux ?

If this is the same Larry from Meaux La. I would assume from the info and the last name . I used him on Dynoing My Chevelle motors . He is pretty sharp!!

Rob

mtm

iTrader: (4)

Iv found the Crane lifters to be noise and they quite down after oil gets hot

Michael1

Have you checked your cam timing by any chance? Maybe it is over advanced.

Michael

Pismo10

Whatever happened? What is the final verdict?

rmbuilder

Rob,
Yes. One in the same. Larry is very sharp, your Chevelle was in good hands!
boatman 747,
While your A/F ratio may appear correct there are multiple factors at work that can easily lead to false conclusions. Because of the excessive duration, overlap and possible cylinder head problems you are experiencing low intake signal at the carb. The low signal will pull less fuel per given orifice hence you had to jet up to make the correct A/F. This results in poor fuel atomization and slowed rate of combustion. As Jim V correctly pointed out, if you add lash to the valvetrain for one pull you will effectively kill some of the duration, increasing the intake signal and making your jetting appear fat. If you jet down then pull the lash, the engine will appear lean on the next pull. Catch 22. I believe there are both mechanical and tuning problems at work here.
Bob

Dredgeking

I had Derebery rebuild an HP 500. When he got done with it, it made less HP on the dyno than a stock HP500. This is after his " improvements" and new headers. I don't trust Leon to work on my stuff anymore.

baja36ft

Ouch!!!!!!!!!!!!!!!!!!!!!

NOBODY

Are we talking about solid or hyd. lifters?

All hyd. lifters need to be adjusted to 0 lash plus 1/2 turn on BB chevy studs, that way at high RPM the lifter is less likely to hold the valve off the seat. Don't ever Gage your valve adjustments by the sound of the valve train,(unless the sound suddenly changes), just adjust it the valves in proper procedure with the correct lash you're putting in it.

On solid lifters you can't always be guaranteed adding or subtracting valve lash will tell you if the cam is too big or too small. By adding valve lash sometimes causes more valve bounce which starts early in the RPM band and will give you a false reading.

Not bashing just stating facts.