Drops 500 RPM when I put it in gear

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440+6scamp

440+6scamp

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Fresh rebuilt 440 w/ new Holley carbs (6 pack). I did not adjust the carbs out of the box other then the idle. Idles fine in park (727) and the timing is good. When I put it in gear it drops 500 RPM and wants to die. I give it a little gas and it revs up but drops right back down when I let off. Can the kickdown adjustment affect this? Due to the shifter linkage I'm using the kickdown lever can't return all the way (but it's close). Or is this more likely a carb issue? I have yet to drive the car and I'd like to iron this out before I do so.
 
We just put a 6 bbl setup in my dads gtx and we had to rejet the carbs right out of the box. This might have something to do with it
 
timing....converter....and cam shaft will effect the idle.....
 
Cam is .454 lift w/ 218 duration at .050. 2200 converter. Timing is set at 12 to 13*.
 
Sounds either lean at idle, or not enough intial timing. The intake bolted on with no trouble getting the bolts started? That is a small cam so I'd be inclined to say it's carb tuning related.
 
Had a little trouble getting the intake bolts started. I'll try to adjust the carbs tonight (have to swap them front to rear to get to the screws!). The plugs seem to indicate that it's a little lean although I'm not real sure what I'm looking for.
 
if its a lean mixture you will have a bigger rpm drop.

fatten the idle and see what it does.
 
Will do.

Could it be a vacuum leak? I'll check that too.
 
Ran home during lunch to mess w/ it.

Checked for vacuum leak 1st... all good.

Bumped the timing up a couple degs... nothing. Went a couple more degs... nothing.

Opened just the front carb mixture screws a 1/2 turn... cut the RPM drop in 1/2. Opened them another 1/2 turn and it only dropped 100 RPM. Each time I opened them the motor picked up which I assume means it was too lean.

So, what should the initial timing be? I've been told to set the total timing around 35 to 36 and let the initial timing fall where it may (somewhere around 14).

I'll set all the mixture screws by maxing out the vacuum. Is this correct?
 
440+6scamp said:
Ran home during lunch to mess w/ it.

Checked for vacuum leak 1st... all good.

Bumped the timing up a couple degs... nothing. Went a couple more degs... nothing.

Opened just the front carb mixture screws a 1/2 turn... cut the RPM drop in 1/2. Opened them another 1/2 turn and it only dropped 100 RPM. Each time I opened them the motor picked up which I assume means it was too lean.

So, what should the initial timing be? I've been told to set the total timing around 35 to 36 and let the initial timing fall where it may (somewhere around 14).
Click to expand...
For now just set your total timing and let the initial fall where it may - do you have an MP dist? mines around 17 initial with it set up at 34 total.

440+6scamp said:
I'll set all the mixture screws by maxing out the vacuum. Is this correct?
Click to expand...

YES! it will raise your rpm as well.
 
Good tool to have when adjusting the idle mixture screws is a vacuum guage....the better the vacuum the better the idle mixture is...
 
Worked on it last night. Set total timing at 34. This made the initial 16 (MSD dist). It reaches the total timing around 2700 to 2800 RPM. Then I adjusted the front and rear carbs by maxing out the vacuum gauge. The max reading I was able to obtain on the vac gauge was 15.5 (little low?).

I have yet to drive it but hope to do so this Sunday.
 
Make sure the float level on the center carb is where is should be if it's too low it will cause a lean condition. I would think with that cam you would pull 18-20" of vacume at 800 rpm or so.
 
It still drops 100 RPM. Is it normal to drop a little?
 
440+6scamp said:
Worked on it last night. Set total timing at 34. This made the initial 16 (MSD dist). It reaches the total timing around 2700 to 2800 RPM. Then I adjusted the front and rear carbs by maxing out the vacuum gauge. The max reading I was able to obtain on the vac gauge was 15.5 (little low?). 16 pounds is about all you can get at idle...

I have yet to drive it but hope to do so this Sunday.
Click to expand...

440+6scamp said:
It still drops 100 RPM. Is it normal to drop a little?
Click to expand...
Mine idles at 900 and drops to 750 in gear...it's the torque convertor loading up and 100 is good
 
yea it always drops. you are putting the motor under a load. The only way you could have it not drop in rpm is with and EFI air controller to compensate for the load.
 
Thanks guys. I feel good about it now. Timing is 16 initial, 34 total. All 6 mixture screws have been adjusted to max out the vacuum gauge (15.5 is still as high as I can get... no vacuum leaks anywhere). All 3 floats are set so that fuel barely trickles out of the site plugs.

I'm going to drive it tonight for the 1st time since it had a slant six 5 years ago!
 
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