sbc issues??

[seanv]

ok im up and running and, well i cant find the culprit. i figured ask here before i do a teardown. 350 chev 10:5 comp roller rockers with girdles comp cams mech cam. i set it to .22 like the card said to. awesome idle very snappy and crisp. under a load it pops out the carb over 2k. timing is at 10 with 35 total. re adjust the valves and set to .26 and it went away. well, only for a short time. it's now doing it again. im at a loss any ideas??? thx

[jasonsnova]

sounds like a carb or ignition problem, start by checking out the ignition system ,then see if anyone you know has a spare carb you can try to see if it goes away

[zbugger]

What cam, and what's the head setup?

[HILROD]

It sounds like the start of a wiped cam lobe. Does the lash open up on one or more cylinders?

[justanova]

what kind of heads are you running, I knew a guy that put short reach plugs into and head that required the long reach style plugs and had a very similar issue to what you are describing.

just though I'd throw that out there because he tried everything before he found that.

[seanv]

the valve train does not change adjustment. i did this on the builders advice.
heads are the world? iron angle plug heads? pn unknown at this time.
someone suggested i check the exhaust gaskets on the headers at the head. he said that some shops use a mr gasket item that has a small round opening creating alot of back preasure right at the port.
the timing is right on the money and, i even pulled the advance to a more tame advance rate with no change.
im also going to check valve stem height to see if a valve or seat may be going away.

[seanv]

ok got her warm and did a comp check.1-7 are 175 185 185 175.
and cyl 2-8 are 165 165 180 180.
so, put new plugs in her and fired it up. yup as soon as i open it up from an easy throttle position it pops thru the carb. darrrr this here be drivin me nutz.
boats are so much easier

[red67camaro]

Is this a single pop or a multiple pop-pop-pop-pop when throttle is applied?

A single pop is usually caused by a lean condition or accelerator pump shot being inadequate.

Multiple popping when the throttle is opened indicates a flat cam lobe. Since valve clearance is measured on the base circle, it may not change much if at all. To check for wiped lobes, remove the valve covers and crank the engine. Look for a rocker that doesn't move as much as the rest.

[MonzaRacer]

Well now another thing is to double check it. Is the cam a hot lash or cold lash spec.
Also you may have sticky valve guides. My buddies very first pro ported heads on his drag car kept sticking the guides so since then every set of world heads we have installed bronze K-line guide liners and we used a worn crank polishing belt on our valves to smooth them up.
The sticky valves would act better upon loosing the valves and these things had the strongest K-Motion valve springs he could fit on them.
Most people could never believe his car had a 355 in it cause it was set on kill. We scratched out heads for a week after the second one stated sticking and after the 4 th valve, third head removal we decided to line all the guides and polish the valves and it was done. That engine lived for 4 yrs and then after the bottom end got trashed from a bad crank sensor he freshened them and built another block and kept same heads and didnt even have any problems.
But before you start ripping give those rockers a check while cranking the engine over with the plugs out.
ALSO do a running compression check, also called a dynamic compression check. and then hook up a vacuum guage and watch that if the popping corespondes to a jumping vac guage then you may have cam problems.
Good luck

[Davezz28]

Might want to check the distributor/cap/wires/firing order. Might be cross firing

[seanv]

well, i have all new msd ignition and no issues there. i spoke with the engine builder and he's going to check it out next weekend. i guess we'll see....
after cutting a coil off the back it sits alot nicer though

[seanv]

update.....well, HILROD you were dead on. cyl#8 exh lobe is non existant. i ended up pulling the intake and the lifter wasnt even coming up above the lifter bore
sux big time after that thing made cool power in another car, got new rings n bearings then slid in my car. ohhh wellll. summers close so car goes on back burner and the boat comes out