a Ouestion about a 400 SB
Thread Starter
Cruising
Joined: Jul 2004
Posts: 13
Likes: 0
From: Munic Bavaria
a Ouestion about a 400 SB
Hey Guys,
maybe you have some Answers to me ?
I´m here with my Car ( a 59 Corvette) in Munic Germany.
I bought that Car with a 400 Sb in it. This Engine get putted in by the Owner bevor me. My Problem is that the Engine is a High Horse Power - Maschine and i really don´t know what kind of Staff the Owner put´s in.
The Idle is about 900 Upm and a little shaky - it means the Engine don´t shut off but it isnt smooth at all. Until 2000 Upm it defenetly not Fun to drive but after that it´s vroooam.
So my Question:
Ilike to have a smoother Idle and i dont want to have that Hole to 2000 UPM´s.
are there some Tricks that i can do - to manage that without changing the Cam?
I heard about Rhoads Lifters? Or do you have some Tricks about Timing, Carb-Adjusting, or,or,or???
What i know about the Engine is:
600 Cfm Edelbrock Carb. Edelbrock Performer Inntake, Headers, TRW - Pistons, Standard Ingiton(with Point´s) Cylinder Heads with bigger Valve´s - no sorryi don´t have the size. 2,5 inch Exhaust System without Crossover, 4 Speed Manual Tranny.
Thamks for the Help
Sorry for my English
Greetings from Germany
Michael
maybe you have some Answers to me ?
I´m here with my Car ( a 59 Corvette) in Munic Germany.
I bought that Car with a 400 Sb in it. This Engine get putted in by the Owner bevor me. My Problem is that the Engine is a High Horse Power - Maschine and i really don´t know what kind of Staff the Owner put´s in.
The Idle is about 900 Upm and a little shaky - it means the Engine don´t shut off but it isnt smooth at all. Until 2000 Upm it defenetly not Fun to drive but after that it´s vroooam.
So my Question:
Ilike to have a smoother Idle and i dont want to have that Hole to 2000 UPM´s.
are there some Tricks that i can do - to manage that without changing the Cam?
I heard about Rhoads Lifters? Or do you have some Tricks about Timing, Carb-Adjusting, or,or,or???
What i know about the Engine is:
600 Cfm Edelbrock Carb. Edelbrock Performer Inntake, Headers, TRW - Pistons, Standard Ingiton(with Point´s) Cylinder Heads with bigger Valve´s - no sorryi don´t have the size. 2,5 inch Exhaust System without Crossover, 4 Speed Manual Tranny.
Thamks for the Help
Sorry for my English
Greetings from Germany
Michael
One gear at a time
Joined: Aug 2003
Posts: 5,231
Likes: 24
CI 8-9-10 Veteran
St. Jude Donor '07-'08-'09
Michael, does your car hesitate when you first press the gas pedal, then rev quickly? The carb may be leaning out on initial acceleration? If so, adjusting the pump shot could help; Edelbrock has tuning tips posted on their website. If it is surging while cruising, the carb could be lean, and jetting up (making the carb richer) could help.
Depending how your timing is set, advancing your initial timing, then backing down the idle speed may help your idle quality. Your 400 will probably like total timing between 34 and 36 degrees.
Assuming there are no tuning issues or vacuum leaks contributing to your rough idle/driveability problem, a milder cam may improve driveablity. We need to know your static compression ratio before recomending a cam. If your static compression is too high for the new cam, you may have detonation problems.
Are your pistons dished or flat top? Do you know the casting number of your cylinder heads, or if aftermarket heads, which ones?
If you could provide any additional information, I'm sure others can help with a cam recommendation. BTW, I also have a '59. Good luck, Wes
Depending how your timing is set, advancing your initial timing, then backing down the idle speed may help your idle quality. Your 400 will probably like total timing between 34 and 36 degrees.
Assuming there are no tuning issues or vacuum leaks contributing to your rough idle/driveability problem, a milder cam may improve driveablity. We need to know your static compression ratio before recomending a cam. If your static compression is too high for the new cam, you may have detonation problems.
Are your pistons dished or flat top? Do you know the casting number of your cylinder heads, or if aftermarket heads, which ones?
If you could provide any additional information, I'm sure others can help with a cam recommendation. BTW, I also have a '59. Good luck, Wes
Safety Car
Joined: Feb 1999
Posts: 3,631
Likes: 14
From: Fountain Hills AZ
One way to improve the idle on engines with a big cam is to hook the vacuum advance to manifold vacuum and to use a vacuum canister that fully deploys at idle vacuum. I would also make sure that the engine is tuned correctly and that all of it's ignition components are in good condition. Something simple like a bad plug wire, incorrect dwell, etc., can mimic the low rpm effects of a radical cam. Flat tappet cams and lifters should be changed as a set so to properly install new lifters you'll be doing the cam also.
Thread Starter
Cruising
Joined: Jul 2004
Posts: 13
Likes: 0
From: Munic Bavaria
New Information
I played a little with the Parts.
What happend was -
I disonected the vacuum cannister - since them the idle is still shaky but not so much any more and to rev over 2000 upm is a lot better ?
Did anybody know on witch Side i have to search?
Thanks
Michael
What happend was -
I disonected the vacuum cannister - since them the idle is still shaky but not so much any more and to rev over 2000 upm is a lot better ?
Did anybody know on witch Side i have to search?
Thanks
Michael
Race Director
Joined: Nov 1999
Posts: 10,643
Likes: 8
From: Foxfield CO 1970 Convertible
Hi Michael -
The combination of your carburetor and intake is a good one. A couple of suggestions (chime in everyone if you think I'm wrong), to smooth out the idle and lower rpms:
- start with the basics, check the plugs, plug wires, and distributor for cracks and looseness; replace them if necessary
- run the car in the dark and look for stray sparks jumping from the wires to the engine or to other wires which cause mis-firing
- check the intake, gaskets, carb and all hoses for any signs of vacuum leaks into the intake - these can cause uneven idle and surging
- I think a good RPM for idle is around 750-800, the engine is pretty smooth at this speed
- make sure any gas filters are clean, replace them if necessary
Good luck
The combination of your carburetor and intake is a good one. A couple of suggestions (chime in everyone if you think I'm wrong), to smooth out the idle and lower rpms:
- start with the basics, check the plugs, plug wires, and distributor for cracks and looseness; replace them if necessary
- run the car in the dark and look for stray sparks jumping from the wires to the engine or to other wires which cause mis-firing
- check the intake, gaskets, carb and all hoses for any signs of vacuum leaks into the intake - these can cause uneven idle and surging
- I think a good RPM for idle is around 750-800, the engine is pretty smooth at this speed
- make sure any gas filters are clean, replace them if necessary
Good luck
