New HEI

[JerryIndy2112]

I have a 402, 1971, in a 1 ton truck. A couple months ago I bought a cheap hei distributor on Ebay. It did not run very well. I could either idle good or rev up good. Set timing over and over. Engine was not happy with a 40 dollar distributor. So I got a new Petronix distributor. Ready to put it in. It came with several springs and also has adjustable vacuum advance. This should work much better. My question is, what is best spring and vacuum adjustment? I took a picture of instructions so the people here came inform me of best option.

[aerotest]

Mine is fixed vacuum advance but I run 12 degrees base with 36 total and all in at 3000 rpm on a stock 396. It runs great and really woke the engine up. Make sure you are on pure vacuum and not ported vacuum for the advance to work at idle. You can use an adjustable timing gun to measure the idle advance and adjust it to your liking. Normally it’s +14 over total timing.

[JerryIndy2112]

Thanks Aero,
I have an adjustable timing light. But what do you mean by port vacuum? Vacuum line ties into carb. Is there something wrong with that?

[68 P.O.S.]

^^^ That's great advice by aerotest there. Adjust the total timing to 36 degrees and let the initial sit where it's at. You want the springs that allow the engine to fully advance to 36 degrees between 2500-3000 rpm. Basically your cruise rpm. You'll have to test different combos of springs and recheck total timing after each change until you find the combo that gets you as close as possible. For the vacuum advance, aerotest is talking about manifold vacuum. Your vacuum advance hose must be connected to the port on the carb that has manifold vacuum. Manifold vacuum is the port on the carb that has suction at idle. Next, leave the vac advance set to 16 degrees. The magic number for your cruise timing is 52 degrees (total timing of 36 + vac adv of 16 = 52). After connecting to manifold vac, your idle should jump up so you'll have lower it. You'll also have to adjust the carb to the new settings.

[aerotest]

Originally Posted by JerryIndy2112

Thanks Aero,
I have an adjustable timing light. But what do you mean by port vacuum? Vacuum line ties into carb. Is there something wrong with that?

Quadrajets have a port vacuum signal and manifold vacuum. Port won’t provide vacuum at idle....it only provide vacuum off idle. This won’t let your advance work at idle which is less than desirable.

[aerotest]

Yes spot on ....thank you for clarifying.

Originally Posted by 68 P.O.S.

^^^ That's great advice by aerotest there. Adjust the total timing to 36 degrees and let the initial sit where it's at. You want the springs that allow the engine to fully advance to 36 degrees between 2500-3000 rpm. Basically your cruise rpm. You'll have to test different combos of springs and recheck total timing after each change until you find the combo that gets you as close as possible. For the vacuum advance, aerotest is talking about manifold vacuum. You're vacuum advance hose must be connected to the port on the carb that has manifold vacuum. Manifold vacuum is the port on the carb that has suction at idle. Next, leave the vac advance set to 16 degrees. The magic number for your cruise timing is 52 degrees (total timing of 36 + vac adv of 16 = 52). After connecting to manifold vac, you're idle should jump up so you'll have lower it. You'll also have to adjust the carb to the new settings.

[JerryIndy2112]

So, I got my new HEI distributor from Summit Racing. It was a nice one with 3 sets of springs and an adjustable vacuum advance. Cost was $228.00.
The one that came had a cracked cap. Ordered new cap under warranty. Got new cap and changed it out. Put it in. Spent hours trying to get it to run. Got it to start once for a few minutes. Then no more, no matter what I did. Then started looking close, the cap was crooked. Tried taking it back apart and reassembled. Still crooked. So called them. They sent another one. Put it in. Fired right up. Set timing as was suggested. Wow! The 402 is a monster again. I still need to try different springs and make some adjustments. But truck now has big block throaty roar. The points distributor and the cheap hei, did not sound or run like this. Left rubber on road without even trying. Feel good the truck is running again.

Thanks for the help, Jerry

[68 P.O.S.]

Awesome, glad you got it running well. Once you finish it you'll love the difference.

[HO455]

I suggest that you find someone local who has a distributor machine and knows how to use it and have them curve your distributor. It is difficult to get a good curve by doing it on the vehicle. To many variables uncontrolled. The person who curves the distributor will want to know your rear end ratio and tire size, manual or automatic transmission, compression ratio, camshaft specs and manifold vacuum. If they don't want this information then they don't know, or don't care, so go somewhere else.
As much difference as you have found in the engine between the old distributor and the new one can be found just by having a properly curved distributor in your engine. In other words you still have horsepower on the table. Just need to pick it up.
Years ago (about 1988) after having recurved my distributor on the car I happy with the improved elapsed times and though I was done. Long story short pulled the distributor had it curved. Nothing was terribly wrong with it but once I dropped it in and set the timing the very next pass down the strip was 2 tenths faster in the eighth mile. Now it was a 12 second daily driver. and it got better MPG too!

[slikside]

Sub'd. Great info...