Revs fine in park, absolute dog in drive

Posted By: Pat_Whalen

Revs fine in park, absolute dog in drive - 04/12/11 03:14 AM

Kind of curious as to what could cause my current issue.

Put a carb back on my 440 in the interest of getting it running again.

Truck starts and idles fine (albeit a little bumpy, but it always did). AFR is right around ~14.5 at idle. It'll rev quickly in park and doesn't seem to have any issues.

During the pre-drive tuning, the truck was idling on it's own and I heard a loud "POP", the truck dropped it's idle to around 200, almost stalled, sat like that for a couple of seconds, and the came right back up on it's own. Kind of odd.

Transmission is recently rebuilt (less than 300 miles on it) and ran fine before the carb went on (previously EFI).

When I shift into drive and start moving forward, the engine doesn't seem to want to rev, and if I force it, it'll backfire loudly and lurch.

I'm not sure if I'm redicously lean and rich, as I know an O2 sensor can be fooled in the extremes of either situation.

My kickdown is properly set and operating.

My Edelbrock 1406 has the IMS turned 2.5 times out.

Is there anything I can do to try and figure out if this is engine related or transmission related?

Thanks all

Posted By: superbyrd

Re: Revs fine in park, absolute dog in drive - 04/12/11 03:29 AM

what is your initial timing set at?

Posted By: Pat_Whalen

Re: Revs fine in park, absolute dog in drive - 04/12/11 03:34 AM

Quote:

what is your initial timing set at?

~10*

Posted By: superbyrd

Re: Revs fine in park, absolute dog in drive - 04/12/11 03:39 AM

try putting some or alot more initial timing in it and see if it helps or not.

Posted By: Pat_Whalen

Re: Revs fine in park, absolute dog in drive - 04/12/11 03:47 AM

Quote:

try putting some or alot more initial timing in it and see if it helps or not.

Will do

Ill report back in a bit.

Posted By: ph23vo

Re: Revs fine in park, absolute dog in drive - 04/12/11 04:12 AM

...also double ck 5 and 7 plug wires arent crossed its easy to do..

Posted By: Pat_Whalen

Re: Revs fine in park, absolute dog in drive - 04/12/11 04:43 AM

Quote:

...also double ck 5 and 7 plug wires arent crossed its easy to do..

A lot of the simple things are easily eliminated- the truck was running well with the EFI on it. The only thing changed was fuel induction. But I will be checking the little things like plug gap and color.

Posted By: Pat_Whalen

Re: Revs fine in park, absolute dog in drive - 04/12/11 04:45 AM

Bumped timing from 10* to 14* and the truck is much much happier. Still seems a little doggy from an initial stomp, but 35"s and 3.23s are bound to make me feel inadequate in the acceleration department. I know my dist adds 26*, at what I don't know. So at some point my total advance is 40*. Is that too much for an otherwise stock late 70s 440?

Posted By: superbyrd

Re: Revs fine in park, absolute dog in drive - 04/12/11 05:21 AM

the smaller carb will help with throttle response on a late smog-era BB, you will have to find a happy medium with timing between bog and detonation with low compression and 87 octane fuel. trial and error,trial and error.

Posted By: Pat_Whalen

Re: Revs fine in park, absolute dog in drive - 04/12/11 05:22 AM

Quote:

the smaller carb will help with throttle response on a late smog-era BB, you will have to find a happy medium with timing between bog and detonation with low compression and 87 octane fuel. trial and error,trial and error.

So theoretically, I just continue increasing initial timing until things start going downhill? Would 16* be a stretch?? I believe the small blocks start around there somewhere, but I didn't know if a big block likes that much advance.

Posted By: superbyrd

Re: Revs fine in park, absolute dog in drive - 04/12/11 05:29 AM

run as much timing as fuel/octane will allow.timing is free HP. once it starts detonating,back it down. i wouldn't push it past 15 degrees inital. engine running temp will rise slightly with your increase as well. watch all the variables. also,make sure with that eddy carb,that your fuel pressure is at 5psi or under. you might be suprised what a stock mechanical fuel pump puts out. if its over 5psi,get a simple parts-store mr.gasket or holley adjustable pressure regulator. eddys are twitchy at anything over 5psi.

Posted By: Mr.Yuck

Re: Revs fine in park, absolute dog in drive - 04/12/11 12:11 PM

Quote:

run as much timing as fuel/octane will allow.timing is free HP. once it starts detonating,back it down. i wouldn't push it past 15 degrees inital. engine running temp will rise slightly with your increase as well. watch all the variables. also,make sure with that eddy carb,that your fuel pressure is at 5psi or under. you might be suprised what a stock mechanical fuel pump puts out. if its over 5psi,get a simple parts-store mr.gasket or holley adjustable pressure regulator. eddys are twitchy at anything over 5psi.

What he said, I'd also think you might want all your timing in early with a big rig like that...36* all in at 2400???? Sounds like you are working it all out.

Posted By: mikemee1331

Re: Revs fine in park, absolute dog in drive - 04/12/11 12:43 PM

Quote:

Transmission is recently rebuilt (less than 300 miles on it) and ran fine before the carb went on (previously EFI).

maybe it's just me but i would be looking at 'what has changed'.

Posted By: Dodgem

Re: Revs fine in park, absolute dog in drive - 04/12/11 01:32 PM

Sounds like you need to speed up the advance curve.
then you will be idling at say 18 initial and only have 36 total.