lag on acceleration
Thread Starter
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Joined: Apr 2006
Posts: 75
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From: Ridge NY
lag on acceleration
My 76 L-48 has a noticable lag when accelerating, then will take off and go. Im happy with the "go" part, but it takes a long second to get there.
Im thinking accelerator pump in the carb? Ideas please... Car is a 76 L48 w/ Edelbrock Performer RPM manifold, Edelbrock Performer 1407 750 cfm carb. Previous owner was told it has "mild cam". True dual exhaust w/ Flowmaster super 44's. Replaced the typical "tuneup" parts and set to stock timing last year.
Thanks in advance for your help.
Im thinking accelerator pump in the carb? Ideas please... Car is a 76 L48 w/ Edelbrock Performer RPM manifold, Edelbrock Performer 1407 750 cfm carb. Previous owner was told it has "mild cam". True dual exhaust w/ Flowmaster super 44's. Replaced the typical "tuneup" parts and set to stock timing last year.
Thanks in advance for your help.
Burning Brakes
Joined: Jun 2010
Posts: 1,165
Likes: 93
From: Bellmore NY
Is the car an automatic? How mild is the cam? Has the car always been this way? If the answer to the first and third questions are yes, Im going to speculate that you have too much cam for your torque converter.
Thread Starter
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Joined: Apr 2006
Posts: 75
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From: Ridge NY
Thanks for the reply. Car is a 4 speed. I don't know the cam manufacturer or any specification other than it is not stock. And yes it has always been this way since Ive owned it (6yrs). It also has the stock "rams horn" manifolds, but I've heard they aren't restrictive enough to be worth changing over to headers.
Burning Brakes
Joined: Jun 2010
Posts: 1,165
Likes: 93
From: Bellmore NY
Well then the converter theory is out, but you still need to know what cam is in there. When does it seem like the car "comes alive"?
What gear is in the car, and please describe when the car does what you describe.
Is it that you are leaving off idle, punching it and the car lags, or is it that you are cruising at speed in a specific gear, punching it and then it lags?
The more info the better
What gear is in the car, and please describe when the car does what you describe.
Is it that you are leaving off idle, punching it and the car lags, or is it that you are cruising at speed in a specific gear, punching it and then it lags?
The more info the better
Drifting
Joined: Jul 2002
Posts: 1,944
Likes: 20
From: The only Corvettes in Highett Victoria
Overcarbed!
There is your problem, the carb is too big for a low compression, low horsepower L48. If you MUST use a Holley, then go to a vacuum secondary 600 cfm and it will make a huge difference.
Best of all, fit an original Qjet that is in good condition or has been reco'd by someone like Cliff Ruggles, even if you have to use an adapter. Ideally, swap the manifold for one with a spreadbore pattern and you won't need an adapter.
No matter what you do to an L48, you won't make too much horsepower to overcome the flow capacities of a Qjet, or even a 600 Holley.
Good luck.
Regards from Down Under.
aussiejohn
Thread Starter
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Joined: Apr 2006
Posts: 75
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From: Ridge NY
BB Dave: either off idle, or cruising and punching it gives the lag. Any RPM, any speed. Car has stock rear and trans. Didn't notice you were from LI, but the mild winter is getting me out early!
Aussiejohn: I had a feeling I would be hearing that from someone...It seems the carb/manifold is better suited for a different setup than I have, but I didn't think it would cause the lag I'm experiencing?
Thanks.
Aussiejohn: I had a feeling I would be hearing that from someone...It seems the carb/manifold is better suited for a different setup than I have, but I didn't think it would cause the lag I'm experiencing?
Thanks.
Drifting
Joined: Sep 2006
Posts: 1,986
Likes: 21
From: Columbus MN
My 76 L-48 has a noticable lag when accelerating, then will take off and go. Im happy with the "go" part, but it takes a long second to get there.
Im thinking accelerator pump in the carb? Ideas please... Car is a 76 L48 w/ Edelbrock Performer RPM manifold, Edelbrock Performer 1407 750 cfm carb. Previous owner was told it has "mild cam". True dual exhaust w/ Flowmaster super 44's. Replaced the typical "tuneup" parts and set to stock timing last year.
Thanks in advance for your help.
Im thinking accelerator pump in the carb? Ideas please... Car is a 76 L48 w/ Edelbrock Performer RPM manifold, Edelbrock Performer 1407 750 cfm carb. Previous owner was told it has "mild cam". True dual exhaust w/ Flowmaster super 44's. Replaced the typical "tuneup" parts and set to stock timing last year.
Thanks in advance for your help.
I was able to SEE the evidence of the problem when my car was on a dyno a couple of years ago (before I got all the tuning figured out). I could see the car go extreme lean on the AF meter when I punched it.
I fixed the problem by 1) replacing the accelerator pump diaphram, 2) increasing the size of the squirters, and 3) replacing the original accelerator pump cam with a more aggressive and longer squirter cam.
Make sure your timing is adjusted correctly first. I had to replace the springs in my distributor with the lightest in the kit to get the advance to come in sooner.
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Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
To check condition of accel pump, just pop off the air cleaner, open the choke plate, exercise the throttle linkage to WOT, and see how much of a 'squirt' gets dumped into the primaries. If none...or it's weak...there's your problem. Otherwise, it's probably a timing issue.
Le Mans Master
Joined: Oct 2000
Posts: 8,897
Likes: 1,357
From: Santa Ana CA
I had a serious lag when accelerating too. I have a Holley carb on a GM Performance 350 HO crate, but I the problem/solution may be similar.
I was able to SEE the evidence of the problem when my car was on a dyno a couple of years ago (before I got all the tuning figured out). I could see the car go extreme lean on the AF meter when I punched it.
I fixed the problem by 1) replacing the accelerator pump diaphram, 2) increasing the size of the squirters, and 3) replacing the original accelerator pump cam with a more aggressive and longer squirter cam.
Make sure your timing is adjusted correctly first. I had to replace the springs in my distributor with the lightest in the kit to get the advance to come in sooner.
I was able to SEE the evidence of the problem when my car was on a dyno a couple of years ago (before I got all the tuning figured out). I could see the car go extreme lean on the AF meter when I punched it.
I fixed the problem by 1) replacing the accelerator pump diaphram, 2) increasing the size of the squirters, and 3) replacing the original accelerator pump cam with a more aggressive and longer squirter cam.
Make sure your timing is adjusted correctly first. I had to replace the springs in my distributor with the lightest in the kit to get the advance to come in sooner.
