I have a newly put together 350..mildly built (about 320hp) also have a 400 t trans...ok, there is no rattle when I start it, no rattles when I warm it up, and no rattle when I take my foot off the accelerator. And there is no rattle when I give it a good amount of throttle, but when I am bareley pressing the gas to keep up with 55-65 mph traffic, there is a distinct but low rattle coming from (seems like the meet with the trans and engine) I dunno what it is and its driving me nuts! Any input would be appreciated
Noise.....
Racer613
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I have a newly put together 350..mildly built (about 320hp) also have a 400 t trans...ok, there is no rattle when I start it, no rattles when I warm it up, and no rattle when I take my foot off the accelerator. And there is no rattle when I give it a good amount of throttle, but when I am bareley pressing the gas to keep up with 55-65 mph traffic, there is a distinct but low rattle coming from (seems like the meet with the trans and engine) I dunno what it is and its driving me nuts! Any input would be appreciated
Sounds like it could be detonation. If it is, it could be your timimg is too far advanced. A simple test for this would be to disconnect your vacuum advance and plug off the port on the carb or manifold where it was connected.
Now take it for a drive and see if the problem is gone or less pronounced. If so, check your initial timing and back it down some. If you have a way to check your timing curve see where your are at 2000, 2500 and 3000 RPM. You should max out at about 34º or 36º total by 3000 or so. If you are above that, adjust your initial timing down some and check again.
You may have to adjust your idle as you change your timing. Once you have made a change take a test drive and see if that improves the situation.
If none of this helps, you need to get with someone who knows performance engines and have them give you some help figuring this out. Whatever you do, don't ignore it if it's detonation because you could slowly destroy that engine.
BTW - very slight detonation is sometimes exceptable under very light throttle to maximize gas mileage. I prefer not to have any on a performance motor.
Anyone got other ideas?
Troy.
Now take it for a drive and see if the problem is gone or less pronounced. If so, check your initial timing and back it down some. If you have a way to check your timing curve see where your are at 2000, 2500 and 3000 RPM. You should max out at about 34º or 36º total by 3000 or so. If you are above that, adjust your initial timing down some and check again.
You may have to adjust your idle as you change your timing. Once you have made a change take a test drive and see if that improves the situation.
If none of this helps, you need to get with someone who knows performance engines and have them give you some help figuring this out. Whatever you do, don't ignore it if it's detonation because you could slowly destroy that engine.
BTW - very slight detonation is sometimes exceptable under very light throttle to maximize gas mileage. I prefer not to have any on a performance motor.
Anyone got other ideas?
Troy.
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If it's comeing from the transmission, engine area, it could be loose tourqe convertor bolts.
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795 Posts
Racer,
Where in Az are you perhaps I could listen to it and see if I could help you figure it out.
Where in Az are you perhaps I could listen to it and see if I could help you figure it out.
I don't know agreat deal about pinion angle, but i know it can cause vibration sif it's off some. The name refers to the angle of the transmission and rearend. Say the trans is 5* down, the rear should be 5*up so it keeps the drive shaft straight and good. Someone else can explain better but a mismatch can cause vibrations at higher speeds.
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