350 won,t spin over when hot

[grumpyvette]

I'm perplexed! I posted about it before but have made counter measures since to no avail. So I built a 350 to drop in my 84 CHevy C-10. The machine shop built the short block which is 360ci now, with an agressive cam (232 @ .050, .450 lift), and all else stock. I put on some good flowing early 70's gm iron remanned heads, Performer Intake, and went ahead and got new stock starter, water pump, oil pump, and distributor components.

I just put on a remanned Quadrajet which I'm pleased with seeing how the company sells them $211 shipped and the quality seems good. The truck runs great right now with no leaks.

My problem since I dropped in this motor, converting over from the original 305 in the truck, is the hot starts. It will not start when warmed up. It seems to slowly churg like a short pulse per second like its under a super heavy load and never turn over to build momentum.

I replaced all the electrical cables. 2 guage Positive to the starter, and the grounds, 2 guage bolted directly to the block, one to the frame, and the braid to the firewall. I even installed the remote solenoid fix and put a heat shield on the starter which is a stock rebuilt starter from AutoZ and about 1/2" away from the header.

The engine & starter get hotter quicker than the headers it seems. Especically since I recurved the distributor. I got 15 initial, 21 centerfuge, 12 vacuum. So 36 total + 48 Vacuum on manifold port. I got 16 inches of vacuum and it runs great so far since installing the new Q-Jet and recurving the dizzy.

So what the hell with these hot starts? The battery is 700 cold cranking amps and like a year old. It "churgs" when warm, even when the ignition is disconnected, even when jumpered to another battery so it must be a heat issue conducting from the block, no?

Theres only like 200 miles on this new engine so maybe it's just not broken in enough yet? Also, I remember from a year ago on the head gaskets...I vaguely remember a small passage being blocked by the head gasket. It wasn't "pre-cut out on the headgaskets". It was the same with the 305 when I replaced the headgaskets way back when, I always left the small port blocked and just installed the Fel-Pro's as was. Could this be overheating a portion of the block and heating up the starter from the inside? I never had problems with the 305 and just installing the gaskets as was.

The only thing I haven't upgraded yet is the radiator. I might just bring it to a mechanic with the right equipment and track this problem but I was wondering what everyone thought.

I feel under pressure because I'm moving across state in 6 months and have been chasing problems for the past year since I rebuilt the motor. Luckily it runs great now (even with the too big of cam that I DIDN'T tell the machine shop to put in) except for the hot starts that persist. Any insight?!?!?!?

AS almost always the correct route involves ISOLATE AND TEST, to locate the SOURCE of the problem, don,t guess!
most SBC engines are designed to operate with coolant temps in the 180F-220F range so you might want to verify the engines not over heating, and verify the oil levels correct on the dip stick, and you might want to change to a fully synthetic 10w30 oil as most synthetics have a significantly higher heat tolerance while still fully lubricating and maintaining a oil film between moving surfaces.
Id also back the ignition advance timing back 3 -4 degrees as a test as that will tend to reduce the piston surface temps a bit and look for vacuum leaks are a lean mix tends to run hotter
trying to increase the starters ability to spin the engine when its hot too over come the resistance to rotation,issue with increased force is a band aid approach !, you should be looking for the CAUSE of the increased resistance to rotation when its hot if it spins over easily when cold but locks up or acts significantly different after running awhile its most likely related to some factor that changed and the most likely factor is an increased operating temperature. attacking the issue by trying to locate whats likely binding AND reducing engine average temps seems like a logical approach here! so think it thru and find our why its running hot or whats binding due to the increased heat,etc,.
is it the valve train?, or the short block? thats heated up, causing the added resistance to rotation when its heated, from running, and some rather obvious places to look would be overly close ring end gaps and overly tight bearing clearances, or overly tight valve guides, tight rod side clearance,you might want to pull the oil pan and inspect bearings, etc. look at the spark plugs for indications of excess wear, coolant leaks or anything else out of the ordinary and do a compression test, verify the valve train clearances those factors tend to increase resistance as the parts expand with heat increases,is it running LEAN?, is the ignition timing advance curve too aggressive?
is it the valve train clearances or geometry? yeah! I know you don,t want to even think about that ! but its a rather obvious place too look, and if you take the engine out of gear, you pull the spark plugs and disconnect the accessory belts and back off the rockers , you should be able to spin the short block,engine with a torque wrench set at no more than about 35 ft lbs MAXIMUM...(USUALLY LESS). when its cold, and then you do it again when its hot, as a test!, it should never exceed 40 ft lbs, if it does theres a clearance issue that NEEDS to be addressed and changing starters is only making the issue likely worse. if the engine will spin at under 35 ft lbs under the listed conditions (after its hot) its NOT likely the rings or bearing clearances but failing to verify the likely problems just guessing at the cause, so Id suggest you look into that FIRST.
yes its a bit of work, but dealing in facts vs guessing is the smarter route to solving the problem vs throwing parts at the issue hoping to cure it