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SBC 350 rpms drop off at 5k rpm

E

Edub

Active member
Looking for some insight on this. Having an issue with a 350 dropping off at 5000 rpm. It will get up to 5000 and stay for a second and then drop down to around 4500 and have a bit of a surge if I keep it floored. Total timing is set to 32. Edelbrock 750 carb. New mechanical fuel pump. And hei distributor. Everything else is stock.


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Rich Andrews said:
fuel delivery problem, or maybe an advance issue w the new HEI ? Easy checks if U have a timing light
Click to expand...
Ya timing checks out at 32 total at around 4000 rpm


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May want to degree the camshaft up 2 degrees and to move the powerband up in rpm's. Just from an engine builder point of view.
 
Rich Andrews said:
check it at 5000
Click to expand...
Gets to 32 at around 3800 and holds it all the way through 5000 where it starts to drop off. No spring kit yet and vacuum advanced plugged.


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Rich Andrews said:
Did this just pop up or is it a new build that never ran right yet?
Click to expand...
engine was pulled from a truck and just pieced it together and trying to get it going right. Faulty tach had me running at only 4k so once the prop was adjusted for more rpm I ran into this issue. No fuel pressure gauge. And haven’t gone into the carb yet. Another thing I was looking at is the distributor. How big should the wire feeding the distributor be? The one that was wired with the rigging I got seems very small. Could this be an issue at the higher rpm or does it sound like more of a fuel starvation issue?


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Could be a bevy of issues since it was a pulled motor pieced together. You may want to conduct a compression test and have someone tell you how well it it, valve ajustments and all. The simple things are what has been mentioned but you could just have a worn out motor? Id definitley make sure the distributor has a good kit in it not some cheap parts..seen it happen on cheap coils and modules but im no expert at all
Lubricate the distributor deep creep works good and wont harm any parts and good luck wait till U build an LS motor the first time and learn all the things that can or will go wrong :)
 
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