Ok, My 351W runs but I can't seem to get rid of the backfiring when I give it throttle, it really won't run very well at throttle but idles great, I have set timing twice, checked for arcing on the wires, changed dizzy cap, when I bought this engine the guy said it had an RV cam in it, I am just wondering, I set the firing order for a 351W, should I maybe have set another firing order? I set it at 1-3-7-2-6-5-4-8.
You're looking in the wrong direction, your carb's accellerator linkage needs to have the slop taken out of it. Too much slack in the linkage allows it to lean out when you open the throttle. With the engine dead, remove the aircleaner and move the throttle linkage, the accellerator should squirt fuel the instant you open the throttle.
I believe that man is right again. Especially considering that if the engine idles smoothly.. firing order is correct. You likely have fuel issues causing lean misfires.
Yeah it has no problems getting from idle to throttle,no hesitation at all, I can hold it at about 2000 rpm and it will pop intermittently from there on up, or can gun the throttle and it will pop. I will however check the linkage to be sure, just looking for ideas of things to check out, I like to have a few things to check when I go out and don't have my pc out there yet.
Also check the see that the advance is actually working. Remove the distributor cap, unplug the vacuum hose from it's source (not the distributor, the other end) Then while sucking on the hose, look to see if the breaker plate inside the distributor moves when you suck. The vacuum pod on the distributor can be bought separately at the parts house if the diaphram is ruptured. They do rupture occasionally from age.
If your distributor has a single diaphram pod, the vacuum needs to be connected to "ported" vacuum on the carb. If it is single and you're connected to full vacuum, then you're halfway to running it "all in" and locked down. "Ported" vacuum is when the distributor gets vacuum only when the throttle is opened.
When you change the vacuum source, reset your base timing. It should be set anywhere from 10-14* BTC, depending on your engine's octane requirements and the fuel you're running. More octane= more timing, less octane= less timing.
if your float level is too high you can get drips coming out of the carb. this usually sounds like a small pop in the exhaust. a bent valve or burnt valve can cause a pop. is your 351 freshly built or used?
Used engine, I had the carb rebuilt in the first week in November because I thought it might be the problem, but there is no change in popping after the carb rebuild, I looked the heads over and some of the valves had been replaced, I was thinking valves also but didn't want to face that possibility.
Are you sure the timing pointer matches the marks on the ballancer??? If unknown keep advancing the timing till it spark knocks under light load, set timing without any vac lines connected to dist... Also connect a vacuum gauge, if vac is low could be a timing issue(assuming this isn't a big, rumpy cam)... Unsteady vacuum would indicate a valve problem, but if it idles smooth I'm doubting that is a issue...
The pointer is lined up at TDC, not a big cam, can move the dizzy and eliminate some of the pop but not all.
the mentioned vacuum test is a good place to start. if the needle is smooth and no bounce then their is a good chance that the valves are good. if it vibrates then i would do a leak down test. it will quickly locate the exact bad valve.
