Fuel lines, filter and points ???

tobluforu · tobluforu's Garage

I changed the fuel lines on my 72 mfi. Only the ones in the engine compartment. I didn't go stock. I just went to kragen and bought ones that were close and these were a tad bit bigger. Will this cause any problems? If so, I would like to upgrade to S.S. What size would they be and where can I purchase.
Thanks
Also, How often should I change my fuel filter?
And last. What would changing the gap of the points do. Say from stock to larger or smaller.
Thanks again

Superman · 02-11-2002, 03:54 PM

I doubt that fuel line diameter would make a difference, unless the hose were too big to seal properly. Increasing your point gap will make the engine run more roughly but will not improve performance.

T Bird · 02-12-2002, 04:39 AM

I would be concerned about ensuring that the replacement lines are rated for the pressures generated by the MFI system. I believe that those pressures are in the range of 1- 2 bar, or roughly 15-30 lbs. Generic fuel line is probably not rated for these pressures. Auto parts stores usually sell a high pressure fuel injection version in the same ID sizes as the regular hose.

Your point gap should be .012 and should produce 38 degrees of dwell, +/- 3 degrees. Opening or closing the points beyond these settings isn't going to do anything helpful for you, and can sure lead to a variety of problems! Get your dwell and timing spot-on if you want a good running car.

I like to change my fuel filter every 3000 miles. Of course, I only drive my car about 500-1000 miles @ year. If you drive a lot, I would replace it at every major tune up. Keep an eye on your fuel tank. After 30 years, it may be full of rust.
Good luck.

RoninLB · 02-12-2002, 05:37 AM

Points setting is directly related to initial/all ignition timing.

911pcars · 02-12-2002, 11:36 AM

Each degree of dwell changes the ignition timing one degree. Dwell is the number of dist. degrees the points remain closed.

If the point gap becomes smaller, the dwell angle increases and the ignition timing retards a like amount.

If the point gap becomes larger, the dwell angle decreases and the ignition timing advances a like amount.

Thus, adjust point gap first, then set initial timing.

Better yet, replace the points with one of the optical devices (Crane, Pertronix, etc.).

Sherwood Lee
http://members.rennlist.org/911pcars

tobluforu · tobluforu's Garage

I would love to change my points an electric version, but I have heard so many people having troubles with them. I have the crane fireball coil and would like to get the crane version. Anyone out there do this to a mfi car with cd. If so, I would live to hear the out come so i can become a true beliver.
Thanks

T Bird · 02-13-2002, 04:00 AM

Tobluforu
I need to correct something in my post above. Point gap for a 72 is .35mm, which equals .014." I noted above, incorrectly, that point gap for your car should be .012." However, dwell is 38 degrees +/- 3 degrees, as indicated in the post above.
Good luck.

Targa77 · Targa77's Garage

FYI: If you are using a Permatune box, then dwell angle is irrelevant.

RoninLB · 02-13-2002, 07:35 AM

Targa77..You are 1/2 correct

T Bird · 02-13-2002, 09:17 AM

Ron
What 1/2 is he correct on? I have a Permatune unit in place of the original Bosch CDI unit. It doesn't replace the points, so dwell is still very relevant.

RoninLB · 02-13-2002, 10:50 AM

T Bird..I agree that the points should be adjusted first then the timing. In a Permatune CDI the point setting is not important, as long as the timing is set correct. I only check the points for burning. IMO, no need to adjust points with Permatune CDI, as long as timing is set. Points should last a very long time. There is a better explanation that I can find if needed. I believe the Pertronix has a high failure rate. I believe the Crane Allison may not need a tach adapter. I have read that the XR3000 has a built in resistor and that the XR700 does not. This built in resistor may /can prevent damage to the unit, don't know. The Ignitor appears to me a much more simple/reliable unit. Don't know if it has an internal resistor. I want to replace points but have not been convinced yet which one to buy. I should just call Pelican and do what they tell me???

T Bird · 02-13-2002, 11:28 AM

Ron
The reason I say the points are relevant is that when the fiber block wears and the point gap closes thereby increasing the dwell angle, the timing retards. I notice this because the retarded timing slows idle speed- a sure indication that I need to gap/replace the points. I have never noticed burning or pitting of the points- just fiber block wear. I always set the point gap first using my Fluke 88 in duty cycle mode, as you say, then set timing at 5 degrees ATDC. Seems to work for me!