blu69sting

i got a 69 350-350, when i take off i can only rev to about 4200 and it starts to break up.. and need to shift. Anybody have any clue what could be the prob? ive replaced the carb, coil, points, condencer, i dont know what else it would be.. the engine has had a total rebuild and it did it before that to.. HELP!!!!!!!

...Roger...

check dist shaft bushings if their bad it will cause point bounce--are you running out of fuel--usually just flattens

MWieczorek

Maybe upgrade to an HEI ignition? Your points distributor could be worn out... Mine does something similar, I'm just going to dump an HEI distributor in the car and be done with it...

Mwieczorek

blu69sting

Not sure if im running out of fuel.. it just kinda pops and wont go any more till i lower the rpm's i had a 850 holly on when i got the car.. it was dumping to much gas in it and got in the oil.. solved that.. (engine rebuild and new carb* but the edle is a 650 i think.. and it does the same thing. HOw much is the hei distributor?? im guessin alot?

big_G

The points distributor is a good unit. Make sure the upper and lower bushings are not worn out, and the coil is giving a hot spark. If anything, you may convert it to electronic ignition, (I like the Crane unit). If not the distributor, look for a fuel flow/pressure problem, like pinched fuel line or clogged filter/sock in the tank.

73, Dark Blue 454

If the problem occured before and after an engine rebuild, and the same distributor was used, I'd look there first. Then fuel delivery (fuel filter?), then I'd look for a broken valve spring(s).

Jclgodale3

Interesting thread. Mine was already converted to HEI with a recurve kit and different springs. Engine has 385 miles on it and just the last couple times, right around 45-4800 rpms it breaks up like that. Sounds like a back fire, popping. Not flattening out. Its a new issue.

Driftwood

My '69 350/350 does a similar thing. I can slowly accelerate through the entire RPM range, but at WOT it starts cutting out around 3500-4500 RPM, depending on the starting speed, what gear, etc. If it's in the garage under no load-- it can rev high no problem. So that makes me think I'm maybe running out of gas at WOT under load. I'm going to hook up a fuel pressure gauge and duct tape it to my windshield to see what happens at WOT under load.

Unfortunately I have a Holley 4165 so it's not easy to direct connect a fuel pressure gauge to only the secondary feed, since it's fed through a tube from the primary bowl.

So maybe you should try removing your fuel filter and monitoring your fuel pressure. It could be your fuel pump just can't quite keep up when your foot's to the floor. Also you could try keeping your secondaries closed and running on primaries only. If it doesn't cut out-- it's probably your secondaries are too lean-- maybe increase the jets, or the fuel pressure is too low when the secondaries are also sucking gas.

blnvette

Mine did the same thing, it was the coil. Get a Msd Blaster coil.
blnvette

sdonnelly

I was having the same problem and found a kinked gas line at the fuel pump. Have not driven the car since finding that but I'm hoping...

7t6vette

I had the same problem with my 383 stroker. Bushings were gone in the distributor. Replaced with a Summit 50v distributor and it is running great. Night and day difference.

Ed Blue 03

Could be your Timing Chain Gear on the camshaft. GM used those BS fiber coated gears to quiet engines. The fiber wears out and the timing is off. Good luck.

jackson

68 thru 74 C3 needs mechanical tach drive ... new HEI w/ tach drive $163 http://forums.corvetteforum.com/show...46806&posted=1

Mr.Gearhead

Similar issue here... it was my cam. Exhaust lobe was rounded badly. Right around 4000rpm... starting backfiring and sputtering. Had a slightly rough idle as well. That is what I got for thinking I knew how to adjust rockers... NOW I know... but it cost me... live and learn. Good luck with your toubleshooting...