I'm continuing to try and get my '68 GT roadworthy, and having very little success. 
When I bought it, we struggled to get it running well enough for the trip home and failed, ended up towing it. We found lots of problems right off the bat - almost every vacuum port you could find was uncapped or hooked up wrong, timing was way off. It surged, sputtered, backfired fairly regularly, and generally just sucked. Some helpful guys at an Exxon tried helped us get it running somewhat better, then it just died and wouldn't start.
We towed it home, I yanked the plugs, cleaned them off and it cranked up. It was VERY rough, stumbled if you touched the gas, seemed like perhaps it was missing, but no backfires.
The Holley 750 on a stock '68 302 (AFAIK, except for a Performer manifold) was definitely over kill, so my dad shipped me an Autolite 4100 1.08 from his stash. I threw it on yesterday, cranked it up - things seemed to have improved. It was still rough, but it didn't bog down and stumble nearly as bad as it used to when you gave it gas. I thought 'hot damn, we're halfway there, probably just needs a tune up'.
I proceeded to install my clutch fan, hopped back in, cranked it up, and it was running like crap again! I hopped out to take a look, hit the throttle with my hand, and BOOM! Huge backfire from the carb, engine dropped dead.
A few minutes later, I tried cranking it, and it just backfired 2-3 times as I cranked!
WTF?!!?!?!
I spent last night surfing the archived wisdom on here. This morning I:
1) Verified the firing order is 289/302 and not 351/5.0. I did this by yanking the valve covers and turning the engine over by hand (freakin battery died, murphy hates me) and watching the sequence of intake valves opening.
2) Verified the distributor is not 180 degrees off. When #1 is around TDC on the compression stroke (intake valve just closed), the distributor was pointing somewhere in the general direction #1 plug wire.
3) My dad thinks it's rather odd it occasionally runs well, then just goes to crap, and suggested I verify the distributor gearing. I cranked and watched the rotor, it doesn't slip or stutter. I finally yanked it and checked the gear and the camshaft gear while I turned the engine, I see nothing funky.
The carb was verified as working perfectly on another 302 before it was sent to me.
I suspect the valves may need adjustment, as the prior owner had the heads done - probably to fix all the damage done by sucking in air through countless vacuum ports. Whoever did the heads supposedly also broke the fuel pump eccentric, which also contributed to us wondering if they also botched the distributor gear on the cam.
Could poorly adjusted valves do this? I've read up on adjusting valves, is there an easy way to know if I've got hydraulic or solid lifters - since that appears to be the deciding factor on adjusting them, or am I just barking up the wrong tree here?
I have no idea what cam is in it, may be stock. Heads appear to be stock.
Anyone have any suggestions?
thanks!
When I bought it, we struggled to get it running well enough for the trip home and failed, ended up towing it. We found lots of problems right off the bat - almost every vacuum port you could find was uncapped or hooked up wrong, timing was way off. It surged, sputtered, backfired fairly regularly, and generally just sucked. Some helpful guys at an Exxon tried helped us get it running somewhat better, then it just died and wouldn't start.
We towed it home, I yanked the plugs, cleaned them off and it cranked up. It was VERY rough, stumbled if you touched the gas, seemed like perhaps it was missing, but no backfires.
The Holley 750 on a stock '68 302 (AFAIK, except for a Performer manifold) was definitely over kill, so my dad shipped me an Autolite 4100 1.08 from his stash. I threw it on yesterday, cranked it up - things seemed to have improved. It was still rough, but it didn't bog down and stumble nearly as bad as it used to when you gave it gas. I thought 'hot damn, we're halfway there, probably just needs a tune up'.
I proceeded to install my clutch fan, hopped back in, cranked it up, and it was running like crap again! I hopped out to take a look, hit the throttle with my hand, and BOOM! Huge backfire from the carb, engine dropped dead.
A few minutes later, I tried cranking it, and it just backfired 2-3 times as I cranked!
WTF?!!?!?!
I spent last night surfing the archived wisdom on here. This morning I:
1) Verified the firing order is 289/302 and not 351/5.0. I did this by yanking the valve covers and turning the engine over by hand (freakin battery died, murphy hates me) and watching the sequence of intake valves opening.
2) Verified the distributor is not 180 degrees off. When #1 is around TDC on the compression stroke (intake valve just closed), the distributor was pointing somewhere in the general direction #1 plug wire.
3) My dad thinks it's rather odd it occasionally runs well, then just goes to crap, and suggested I verify the distributor gearing. I cranked and watched the rotor, it doesn't slip or stutter. I finally yanked it and checked the gear and the camshaft gear while I turned the engine, I see nothing funky.
The carb was verified as working perfectly on another 302 before it was sent to me.
I suspect the valves may need adjustment, as the prior owner had the heads done - probably to fix all the damage done by sucking in air through countless vacuum ports. Whoever did the heads supposedly also broke the fuel pump eccentric, which also contributed to us wondering if they also botched the distributor gear on the cam.
Could poorly adjusted valves do this? I've read up on adjusting valves, is there an easy way to know if I've got hydraulic or solid lifters - since that appears to be the deciding factor on adjusting them, or am I just barking up the wrong tree here?
I have no idea what cam is in it, may be stock. Heads appear to be stock.
Anyone have any suggestions?
thanks!
