283 missing/loses power

[dstarrett]

283 new rebuild,old three speed with granny on floor, HEI, new plugs gapped to
.045, timing set(4 degees advanced I think, mech friend set for me) Starts runs well until it warms up. (on road 50 mph) Miss and carb backfire in 4th around 2100-2500 rpms. Power loss. shift up to 3rd r's come up to 4-4200 and it smooths out a power is better. Ideas? You guys have been great and my 8 year project is getting real close. Pics soon.

[Rich 5150 69]

4 degrees you think....maybe recheck your mechanical advance and check your vacuum advance too as well.

[Blue Heeler]

I had the same issue check fuel pump pressure. mine was low so i replaced it problem solved.

[soxplayer]

Did you check and or replace the valve springs? Sometimes old springs work until your engine warms and then they hang open and let exhaust back into the intake manifold causing the exact symptoms you posted. If you changed a worn cam to a newer aggressive cam, this is an even more likely cause.

[crazy longhorn]

Try 10-12 initial on the timing, see how that goes... crazyL