I'm trying to solve an engine problem and I'm going through the process of elemination; Two quick questions.
#1- Is the correct firing order for a BB 427, 1-8-4-3-6-5-7-2 ...?

#2- Does the distributor rotor turn clockwise ?

Thanks a ton :thumbsup:

I'm trying to solve an engine problem and I'm going through the process of elemination; Two quick questions.
#1- Is the correct firing order for a BB 427, 1-8-4-3-6-5-7-2 ...?

#2- Does the distributor rotor turn clockwise ?

Thanks a ton :thumbsup:
=
Yes
Yes

Yes and yes.

Gary Anderson

Hey guys....... Thanks!!! Well I guess I'll have to keep looking to find the problem. :sad:

Which would be.......???

Hey Fred, well since you asked... :)
The engine seems to lunge and buck when I coast and am off the gas pedal, this happens while in any gear (4-spd) at any speed below 45mph.
It's the same feeling as when you coast to a stop and forget to step on the clutch while in 4th gear, I've checked a bunch of things and can't find the problem.

-427ci rebuilt by previous owner to L-72 specs
-solid cam/lifter, roller rockers
-12"-14" of vacuum at 950-1000rpm idle
-Holley 4160 750cfm, single pump-double feed
vacuum secondary, electric choke,
5.5 power valve, 70 prim. jet - 21 secondary plate(=75 jets)
-Edlebrock Performer RPM intake
-GM HEI, 12volt from panel box -12ga. wire
-M-20 4-speed
-3:55 posi, 12 bolt
-Power drum brakes (11" booster)

Bowl fuel level checked
New 5.5 power valve
Fuel mixure adjusted
Choke properly adjusted
Firing order correct
Plug good (EKG)
Wires good (Taylor Spiro pro 8mm silicone)
No vacuum leaks

I'm at my witts end ....:( . I'm thinking maybe a valve adjustment or a problem with the drive-train somewhere.

Jim,70 prim/75 sec jets for a perf 427 is too lean IMHO,esp the secondarys @ 75's.

I would start with 72-73 prim/82 ish secondary.

Also,what intial & total timing are you running?

Most perf cams like approx 16-18 deg btdc intiaql and a total ofapprox 36-38 deg btdc total timinAnd your setup would benefit from a vacuum advance on the street too.

Your 5.5 power valve may be ok but with 12-14 inches idle vacuum i would like to see 6.5-7.0 power valve/s as the lowest i would go .This is because the 5.5 P/V opens up a little later then the 7.0 which could possiblky lean things out just a tad too much additing to driveability issue esp with your carb jetting being way to lean too not tomention if your timing is retarded too.

The carb is very lean and if your timing is retarded too thoses things can make the buck like you stated.

So dial in the carb & timing better and your motor will be happier.

By the way what are your cam specs which is also important info we need to better assist/advise you?

Scott

Hey Scott;
Thanks for the response. First let me start off with the cam issue, I don't have any specs on the cam at all, all the previous owner could tell me is that it was a L-72 solid lifter cam.
My timing is set at 16* to 18* intial, and I'm running a HEI with vacuum advance, taking full manifold vacuum from front bottom port of carb.
I changed the power valve from the 6.5 that came with the carb to a 5.5 because;
#1- The old plugs I took out were wet with fuel and the PV may have been bad or #2- The 6.5 PV was opening at idle due to the low vacuum causing a load up of fuel.
I will take your advise and change the Jets,.... but I'm still confused about the power valve issue, according to Holley the PV value should be 1/2 of the lowest idle vacuum reading..... 1/2 of 12" vac is 6, so I went with 5.5 to be safe, I may be wrong and reading it wrong, if so I'll change the PV as well. Thanks for your time Scott I really appreciate your help!

If none of the "normal" stuff being possibly wrong fixes it, I had an old truck that did that and it was the fuel filter so maybe it's a fuel delivery issue, filter, pump, tank sock? Just a thought. Pete

Hi Pete;
That fuel issue came to mind as well, but it would have created other problems as well..... The engine is fine in all other conditions.

Jim,you stated your idle vacuum was 12-14 inches with that cam then the 6.5 pwr valve/s should have never opened up at idle unless they were blown/ bad or something else is wrong with the carb.

The 6.5 p/valve is not supposed to start opening untill the intake vacuum falls close to 6.5 so with 12-14 inches of idle vacuum as you stated you had that should not happen,there has to be something else wrong with the carb.

Take an avg of your 12-14 idle vac you say your motor has which is 13,1/ 2 of 13 is 6.5 which is what holley recommends (approx 1/2 of idle vacuum) and what i also recommended in my above post.

You could have a cracked or pourus metering block,bad/shrunken metering block gasket/s (Prim or Sec) causing extra fuel to be sucked in which can & does happen at times with holley's leading to over rich mixture,float lvl too high,defective float,defective leaking needle & seat or dirt in the needle & seat,fuel pressure too high, all of which can possibly lead to over rich mixture.

But a 5.5 p/valve is what you would generally run in a motor with approx 9-10 inches idle vac and not with a motor with 12-14 inches of idle vacuum IMHO.

Your inital timing is ok @ 16 deg btd try 18 deg btdc with that cam along with getting the jetting where it belongs too. Make sure the total does not go over 38 deg btdc and if so get the dist recurved to accomidate 18 deg btdc intial timing.

By the way,what brand & heat range plugs are you running?

Scott

Scott;
I did have to adjust the float levels, they were a bit high, that may have been the reason for the wet plugs. I will install a 65 PV and rejet to 73 prim/82 sec and see what happens, I'll also bring the timing to 18*.... the plugs are NGK's UR5.

Jim,let us know how the motor responds to the power valve & jetting changes along with a few more deg initial timing.

Scott

Scott,
I will surely do that ...... It will be in a couple of days, Wifes got me doing afew things around the house and I need to close the pool first. Thanks again for the help it's deeply appreciated!..:thumbsup: