acceleration ?
Moderator
Joined: Dec 2007
Posts: 7,987
Likes: 104
From: Boise, Idaho
Are you meaning that it accelerates harder when you are at half throttle than when you are at full throttle?
You say you have a '79 carburetor in an '85 year truck. Do you still have the feedback ignition system? Or have you converted it to DuraSpark II or some other aftermarket ignition setup?
You say you have a '79 carburetor in an '85 year truck. Do you still have the feedback ignition system? Or have you converted it to DuraSpark II or some other aftermarket ignition setup?
Lead Driver
Joined: Jul 2009
Posts: 6,477
Likes: 19
From: Sheffield, AL
My first guess is that the OP was indicating that the engine was at about 1/2 of its normal operating range??? If that is correct, the engine likely is @ ~1500 - 1600 RPMs which is right at the maximum torque.
Thread Starter
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Elder User
Joined: Jun 2009
Posts: 907
Likes: 6
From: nw pa.
Abandoned bronco,
I have completely removed the emissions ex for the pvc.
I have a gm hei module...I kept leaving the key on and frying ds 2 modules ! Using a ds2 distributor rebuilt from advance auto.
New fuel pump on the block and filter ,rebuilt carb.
😁
I have completely removed the emissions ex for the pvc.
I have a gm hei module...I kept leaving the key on and frying ds 2 modules ! Using a ds2 distributor rebuilt from advance auto.
New fuel pump on the block and filter ,rebuilt carb.
😁
New User
Joined: Mar 2015
Posts: 23
Likes: 0
If we take your question literally (and I think this is what you mean), you accelerate faster when you're at 50% throttle than at full throttle. I can tell you I observe a similar situation. Here's my gut feeling...with a 1bbl carb there isn't a massive difference in CFM from 50% to 100% throttle opening, ie. the air flow is not twice as much at WOT, it's not a linear relationship. With most vehicles when you mash the gas you expect it to move faster than at part throttle, but our tractor engines don't respond the same way. I doubt it's "faster" at part throttle but it just isn't much faster at WOT. That's just my 100% anecdotal experience.
Then again, it could be something like a worn out bore in the throttle plate that as you open the throttle it exposes more of the leak and causes a highly lean condition. Maybe it's time to pull the carb and give it a good once over inspection and maybe even a rebuild kit while it's on the bench.
Or your timing could be out, double check your TDC mark on the harmonic balancer with actual TDC.
You could also grab some carb cleaner and have some fun spraying around all of your vacuum connections to see if you have a leak (just be careful).
Then again, it could be something like a worn out bore in the throttle plate that as you open the throttle it exposes more of the leak and causes a highly lean condition. Maybe it's time to pull the carb and give it a good once over inspection and maybe even a rebuild kit while it's on the bench.
Or your timing could be out, double check your TDC mark on the harmonic balancer with actual TDC.
You could also grab some carb cleaner and have some fun spraying around all of your vacuum connections to see if you have a leak (just be careful).
Thread Starter
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Elder User
Joined: Jun 2009
Posts: 907
Likes: 6
From: nw pa.
thank you for the input! I have rebuilt the carb and the throttle shaft is tight relatively... I have timed it using a vacuum gauge.
it runs great I guess it's something I'll have to get use too.
another thing is I have the NP 435 and 3:55 gears I can get it up to 65 and a little more... But after that its done! I like to get on the freeway with that everyone and their mother passing me like I'm standing still!
maybe I'm just running out of carburetor?
I have a autolite 2100 3:56 CFM with an adapter that I haven't used yet... The engine is all stock except for ds2 conversion with hei Module.
it runs great I guess it's something I'll have to get use too.
another thing is I have the NP 435 and 3:55 gears I can get it up to 65 and a little more... But after that its done! I like to get on the freeway with that everyone and their mother passing me like I'm standing still!
maybe I'm just running out of carburetor?
I have a autolite 2100 3:56 CFM with an adapter that I haven't used yet... The engine is all stock except for ds2 conversion with hei Module.
New User
Joined: Mar 2015
Posts: 23
Likes: 0
Something isn't right, I have the same gears and trans and can hold 75 all day if I felt the need. I usually cruise at 65-70 with only relatively little throttle.
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Moderator
Joined: Dec 2007
Posts: 7,987
Likes: 104
From: Boise, Idaho
Agreed.
Have you done things like check for dragging brakes, plugged catalytic converter, etc? Those types of things can really rob power.
Have you done things like check for dragging brakes, plugged catalytic converter, etc? Those types of things can really rob power.
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Elder User
Joined: Jun 2009
Posts: 907
Likes: 6
From: nw pa.
.holds 20 inches of vacuum, tho i did back it off a little.new exhaust all the way to the bumper.stock air cleaner.
No vacuum leaks
Heat riser not sticking...idk ?
Just covering the bases.