Six cylinder distributor: Points vs HEI

[68gmsee]

Been a while since I updated last.

To recap, I was trying to see if changing to an HEI distributor would make any difference on my 250 six cylinder performance or mpg. I actually went back and forth a couple of times between points and HEI to do this test.

My conlusion: There was no improvement in miles per gallon (I may need to play with adjustments a little more). BUT, I did noticed an improvement in performance!

As Longhorn man and others mentioned, throttle response, idling, etc. would be better so I paid particular attention to these and notice an improvement there. Especially when going at lower speeds in high gear and on the freeway.

I think my next move is to get a good aftermarket one and hold on to my point distributor as a backup.

[mosesburb]

Originally Posted by 68gmsee

I think my next move is to get a good aftermarket one and hold on to my point distributor as a backup.

I would recommend one thing to try prior to getting another unit. I did this same swap on my '71 Nova with a 250 and a Power Glide. With the points dist, cold starting was a test of patience. Once it got running, it was another exercise of patience to keep it running. Once I swapped over to HEI, starting was no longer a six step process. Once it was running, it was running until I shut it off. Power increase was dramatic. Drivability was improve through the entire operating range.

Anyways, the one thing that I would HIGHLY recommend trying is to get a Moroso p/n 72300 curve kit. It comes with weights and several springs. I used one light spring and one medium spring and it worked fantastic. I never put a timing light on it, I just cranked it until it pinged then took a fuzz out and locked it down. Most people who rode in it thought it was a small V-8 by how it ran. Nope, I6 Power!!

[68gmsee]

Originally Posted by mosesburb

....Anyways, the one thing that I would HIGHLY recommend trying is to get a Moroso p/n 72300 curve kit. It comes with weights and several springs. I used one light spring and one medium spring and it worked fantastic....

Thanks for the tip. Last week I went to Napa and asked them about a weight kit and they said they didn't carry them??? But I saw where O'Reilly does carry the part you recommend.

One question: I'm confused on the "one light spring and one medium spring" thing. Can you explain?

[C20-67_N_MO]

Originally Posted by 68gmsee

Thanks for the tip. Last week I went to Napa and asked them about a weight kit and they said they didn't carry them??? But I saw where O'Reilly does carry the part you recommend.

One question: I'm confused on the "one light spring and one medium spring" thing. Can you explain?

Yeah I too and interested in this, as I plan on installing a HEI unit with my Clifford 4-barrel intake and Holley 390cfm Carb.

That kit sounds like a good idea if it helps on fine tuning.

[KEL]

http://67-72chevytrucks.com/vboard/s...d.php?t=148346

[mosesburb]

Originally Posted by 68gmsee

Thanks for the tip. Last week I went to Napa and asked them about a weight kit and they said they didn't carry them??? But I saw where O'Reilly does carry the part you recommend.

Just make sure it is the Moroso kit. Of all the ones I've crossed (and been forced to tune, back in the day), it is by far the best.

Originally Posted by 68gmsee

One question: I'm confused on the "one light spring and one medium spring" thing. Can you explain?

Absolutely. The kit comes with the center cam, two fly weights, a couple pairs of bushings for the fly weights and three pairs of springs. The springs have different tensions. The copper colored ones are light tension, the silver ones are medium tension, and the greyish ones are heavy tension. The springs allow you to tune when the advance comes in. Lighter springs bring the curve in quick at low RPM, while the heavy springs hold off the advance to a much higher RPM. FWIW, of all the motors I tuned (back when HEI units were still in production vehicles) I never installed a heavy spring much less a pair of them. By using a light spring and a medium spring, you get advance a bit quicker than using a pair of the medium springs and a little slower than using a pair of light springs. It was a way to tailor the advance a bit finer than using the springs in pairs. This was actually the combination I started with in almost every re-curve I did and there was only a couple times that I deviated from it in further tuning (cars and trucks included).
Now, speaking of advance, the vacuum advance unit is set for a specific amount of advance. There are many different units available that have different total advance, so this is another avenue for more precise tuning of total advance. Once upon a time, some company made an adjustable vacuum advance unit that could be adjusted with a tiny allen wrench to set it to whatever total advance was desired. I never used one, nor do I know if they are still available, but it might be another option depending how carried away you want to get.

Well, I guess instead of telling you what time it is, I ended up telling you how to build a clock, but now you know.

Oh, one more thing--on my 250 with the HEI, it really like manifold vacuum to the vac advance while the points dist liked ported vac. If you decide to try manifold vacuum, you will need to adjust the idle speed on the carburetor down a bit because it will be at full advance at idle. The advance will drop under power (as it should) and come back in cruise conditions (High manifold vacuum). I don't know why it liked it so much, but it definitely ran better set up with manifold vac as compared to ported vac.

Ok, I'm done--I swear.

Hope it helps!!