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Dead Parrot · 04-09-2024, 03:22 PM

The nice thing about SBC motors is parts interchangeability. Don't worry too much about a older 283 manifold on a 350 motor with HEI in a 67 truck that originally had a points distributor. As long as the assembler did a good job on sealing things up, it should work.

Do your checks for vacuum leaks. If equipped with vacuum boosted power brakes, the booster can be a source for a leak.

Quick distributor checks:
Vacuum pot - with your timing light in place and motor running at idle, remove the vacuum hose from the ported outlet. Timing should stay the same. Connect hose to manifold vacuum. Timing should advance 8~12 degrees(depending on vacuum pot, they come with various advance numbers). If timing doesn't change, replace the vacuum pot.
Mechanical advance - as above remove the vacuum hose and leave off. Rev the motor. Somewhere around 1200 to 2000, timing should start to advance. It will keep advancing as you speed up the motor until it reaches a maximum. If it doesn't advance or sticks when you let off throttle, repair mechanical advance.

If it passes the above checks, try moving the vacuum advance to manifold vacuum and readjust idle speed. Manifold vs ported can be a debate but try both. Pick the one that works best for your motor.

If your truck is emission exempt, try advancing base/initial timing to 10 or 12 BTC. Stock or mostly stock SBCs usually respond well to initial timing in the 10~14 range. If it begins having hard to crank while hot issues, back off a couple of degrees. Adjust idle speed after adjusting timing.

Once you get the timing dialed in, redo the idle mix and idle speed adjustments.

As long as you are using 10w-30(or 40), 'thick oil' shouldn't be a cold start issue unless you are well below 0 when starting.

04-09-2024, 03:22 PM	#7
Dead Parrot Registered User Join Date: Aug 2012 Location: Oklahoma City, OK Posts: 2,495	Re: Hard starting conundrum The nice thing about SBC motors is parts interchangeability. Don't worry too much about a older 283 manifold on a 350 motor with HEI in a 67 truck that originally had a points distributor. As long as the assembler did a good job on sealing things up, it should work. Do your checks for vacuum leaks. If equipped with vacuum boosted power brakes, the booster can be a source for a leak. Quick distributor checks: Vacuum pot - with your timing light in place and motor running at idle, remove the vacuum hose from the ported outlet. Timing should stay the same. Connect hose to manifold vacuum. Timing should advance 8~12 degrees(depending on vacuum pot, they come with various advance numbers). If timing doesn't change, replace the vacuum pot. Mechanical advance - as above remove the vacuum hose and leave off. Rev the motor. Somewhere around 1200 to 2000, timing should start to advance. It will keep advancing as you speed up the motor until it reaches a maximum. If it doesn't advance or sticks when you let off throttle, repair mechanical advance. If it passes the above checks, try moving the vacuum advance to manifold vacuum and readjust idle speed. Manifold vs ported can be a debate but try both. Pick the one that works best for your motor. If your truck is emission exempt, try advancing base/initial timing to 10 or 12 BTC. Stock or mostly stock SBCs usually respond well to initial timing in the 10~14 range. If it begins having hard to crank while hot issues, back off a couple of degrees. Adjust idle speed after adjusting timing. Once you get the timing dialed in, redo the idle mix and idle speed adjustments. As long as you are using 10w-30(or 40), 'thick oil' shouldn't be a cold start issue unless you are well below 0 when starting.