Hi Hambers, I just changed a cam in a 350 and it just won't run right / also gets hot on #7 exhaust. I've tried timing to #6 with no results. Did I get the cam timing a tooth off??
Whenever you install a new cam you should degree it. Given all of the tolerances of crank sprocket, cam sprocket, cam bolt holes, drive pin, and the actual grinding of the cam, they can be off even when installed with the marks lined up, especially if all of the tolerances are additive.
X2. Add timming 12 -15 , set RPMs around 850 to 1,000 . If you are retarding the timming to hear cam , install a biger One, Use a Vacuum Gauge , avance untill vac falls off , see where you are @ with light , then back off a few degrees , Cam specs ? Manual or Auto? Stalll /converter Cam type. H -S -HR--SR or ?? What oil are you using, if not Race oil you need ZINC befor yr new cam goes SOUTH,
Lota guys have gotten #5 and 7 crossed for a shitty running 350. If #7 is getting hot I'd look for crossed wires first and then a vacuum leak on #7. I've also seen chrysler 4 barrel carb/carb mounting gasket used on a GM intake that can cause a vacuum leak under the carb. Some guys have experienced a vacuum leak under the intake in the valley when an intake gasket slips on assembly. All things to check. Someone here mentioned a tight valve...another thing to check. Tight exhaust valve will cause lotsa heat going into the header/exhaust manifold.
It's kinda frustrating, well - really disappointing.. Using the same timing set and dampener that ran before. Cam and lifters is the only real change. I really hate rolling a brand new cam around with spring pressure on it trying to figure where the timing is wrong. I took the cover off and see no error in mark alignment - just mystified & not pleased. Something is really wrong, it seems unlikely that I suddenly have an ignition failure. I'm thinking on taking the cam out. Cam is a 370 hp. lashed at an approx. .024 hmmmmmmmmmmmmmmmmmmmm
Also something that I remembered on your carburetor you might be past the transferor slot with new cam ,pull cab without doing any adjustments and see where the butterfly is to the transfer slot you might have to drill a couple holes in the butterflies. Another thing are you losing your adjustment on number seven cylinder is a possible that your stud is coming out unless you have a screw in studs
Check cap, rotor and plug wires. Make SURE you don't have a wire crossed, EASY to do! Recheck STATIC timing - rotor at #1 terminal of cap, timing mark at 8-10 degrees BTDC. Better to have the valves set too loose than too tight, I think that could be another problem. I add .004" to the hot-lash spec to allow for heat expansion, AND set lash at TDC for both valves on each cylinder COLD. Bump the starter over with a remote starter switch, finger over the spark plug hole - when compression blows your finger out, you're close 'nuff to set the valves for that hole. When the engine is at temp, hot-lash one pair of valves and check that pair again stone-cold - set the remainder at the same clearance COLD... no mess or burnt hands from hot oil! Get the engine running the BEST you can to break the cam and lifters in - 2,000 rpm for 30 minutes AT LEAST, then maybe go back to find a vacuum leak if need be. Break-in need not be all at once, just watch the water temp. Use Valvoline VR-1 racing oil (NAPA) from now till forever to keep everything happy - old levels of zink/zddp in that oil. Let us know what you find... Good Luck, Tim
The Jalopy Journal
