Ok having a problem with my 250. Did tune up new points plugs dist cap took carb apart cleaned good idles pretty decent starts great but held to floor won't run over about 45mph after that point wants to start sputtering any thoughts would be appreciated

Can you keep it floored over 45? What is it doing?, Will it die?
Stay @ 45 MPH? Back fire sputtering out of the carb?, Backfiring out the exhaust?

Need more info.

MBHD

once it hits the 45 mark it will start sputtering and when you let off you can hear it backfiring out the exhaust a little.

Had the same problem with a 250 cuin Camaro after a tune up. Would start, idle fine but when going up a hill it would sputter and quit, however it would start up and run fine. I found that the in carb there was a solid metallic gas filter. I removed it and it ran fine. I put a new one in and problem solved. Good luck.

i wish it were that simple i took the filter out of the carb about a year back because the old fuel tank had really clogged it up. the only filter i have on it is the sock on the end of the line in the new tank. dont know if this helps or not but i have noticed the fuel mileage has gotten really bad went from like 15-16 to around 8. does that mean i am pushing more fuel that i am using or what.

ok some new info still having issues. got out the vac gauge today and took some readings. at idle the gauge bouces very irradicaly from about 10 to 20. as you give it gas it gets very steady with a little accelerator it will start steady at about 12 as you give it more gas it gets closer to the 20 mark. any thoughts. also check all valve spring tensions they are at 180 lbs all valves seem to be moving about the same distance in travel. ????

sounds like you may have a vacuum leak somewhere. I'd double check all vacuum lines Even the one to the trans.

3speed so no vac to tranny and only 2 lines one to Pcv valve and one to vac advance, bith good. Maybe at intake exhaust manifold???

YOU DIDNT CROSS THE PLUG WIRES DID YOU ? IS DIST SHAFT TIGHT ? THERE REAL BAD TO WEAR OUT.

Plug not crossed, dist shaft good and tight, valve spring tension all good

Have a spare carb to try out?

Had another guy on here that rebuilt his carb & after rebuild it ran like crap. Took it apart several times & back together w/no luck.
Got a different carb, then it ran better.

It happens. I am pretty sure it has happened to some of us @ one point in time, incorrect float bowl adjustment, forgot a jet, etc. I have done it.
Problem is, it is hard to pinpoint your problem, you did a few things all @ the same time.

MBHD

Don't know if this is your problem or not, but I got a "rebuild kit" for my Carter YF from an online source a while back. It was sort of right. The motor would not run right after the "rebuild" I took it apart and carefully selected a few new and a few old parts and finally got it to run right. The kit came from a third world country and was marginal at best in my opinion. YMMV

Paul

To me this sounds like it is ignition related. What year and style body is it in? Earlier cars had a resistor in the ignition circuit. Sometimes this will burn out. With an HEI you need to remove the resistor. Did you replace the condenser?

it is a 66 chevy c10, no I haven't changed the condenser yet btw lookin down the carb throat when u punch the accelerator the stream of gas doesn't come out like a water gun stream, more like a slow trickle from a straw could that cause the troubles

Ok did rebuild on carb still have the same troubles, did compression check 150 lbs all cylinders what am I missing here?

What kind of rpm are we looking at when you are hitting 45mph i think we should go back to square one fuel air and spark

I have to assume nothing is blocking air passages or exhaust (although) you might check broken or plugged cat or muffler?

You just replaced most of your ignition system but how do things like your plugs look do wires pulled from the inner sockets on the plugs

Did you remove your distributor at all what kind of timing are we looking at?


And you just rebuilt the carb diuble and tripple check your work no offense just trying to help you out

hey lowboy, no offense taken at all i all ears for anyone trying to help with this. i dont have a tach on the truck so not sure of rpm at that speed it doesnt sound like it is wound out or anything though.

i have not checked to see if the muffler might be clogged will do that today and repost.

when did the compression test last night 5 of plugs had normal look to them, however plug #3 cylinder was covered in carbon build up. could be from where it has ran so rough the last week though.

didnt remove the distributor but did check the shaft, no play there, and mech advance is working fine.

timing is set at 4 deg bftd.

Have you checked your fuel pressure?

We really need to narrow it down

So what does an engine need to run
Air
Fuel
Spark
Lets start with air clean air fulter carb opens fully chokes out of the way valve lash is good exhaust is good vaccum and such is where id start with air

Also note if you make any changes change one thing at a time and always test in between another repair

Fuel i'd check the pressure check your fuel line for kinks buldging or anything else sometimes line goes bad or breaks on the inside and can glog very easy make sure the carb is functioning fully


Spark i woul check timing make sure the balancer hasn't slipped make sure all weights and such arefree in the distribotor check wires plugs for carbon tracing

Not to dull it down maybe i'll spark some old memories for aome to help with ideas

tweeked the timing a bit last night, truck now has more power. miss is still there when engine is first put under load, then seems to settle out till you start to let off the accelerator. after lots of research on the matter i am pretty sure the main trouble is in the old one barrel rochester, going to change it out to a two barrel and hopefully that will end the troubles. thanks for all the inputs!