Posted By: Boise Chall
Fuel and timing question - 07/21/09 03:17 AM
First I have to say thanks to all of you that helped me with my 72 Challenger project. The car is pretty much complete at least I can drive it. Well I am up to the tuning phase of the project when I'm driving the car at a cruise speed about 2000 rpm the car will kind of sputter kind of like mmmmmm puh puh puh mmmmmmmmmmmmmmmmm puh puh is that from a lean condition or is it not enough timing? the motor runs fine at idle and at full throttle. The motor is a 512 with stealth alum heads Holley 950 HP, MSD pro billet dist ( still with the facory setup) and MSD 6al
Posted By: RapidRobert
Re: Fuel and timing question - 07/21/09 03:26 AM
what is your timing @ 2000rpm & might drill a hole in the cap & check rotor phasing also @2000rpm. Might up the pri jets 4 sizes just for a test
Posted By: Boise Chall
Re: Fuel and timing question - 07/21/09 05:48 AM
Can you give me more information on rotor phasing? what is it and how do I check it. My msd cap has a hole in it near #1 plug wire. I can't check my timing until morning my neighbor accross the street says my car rattles the back windows of his house I think he just needs new windows
he's cool about it but I would still rather be nice
Posted By: RapidRobert
Re: Fuel and timing question - 07/21/09 12:34 PM
You would drill a ~1/2" hole on the flat top of the cap between the center post and the #1 post & set the throttle screw at 2000 rpm & connect your timing light to #1 plug wire & point it straight down onto the rotor & see how far away from the underside of the #1 terminal the rotor blade is. If between a stackup of tolerances, your curve(initial & mech) at 2000 plus the vac adv amt the rotor could end up being)at that point) just far enough away that the spark has trouble jumping that distance each & every time & hence the misfire. You could use an old cap if you did not want to drill your MSD cap though the hole is good for letting the ionized air out(which also contributes to misfire for the opposite reason) & a faster check might be to adv your initial 5-7.5 degrees & try it then retard it 5-7.5 degrees & try it one of which will swing the rotor closer to the terminal & help you if rotor phasing(the distance) is the problem here.
Posted By: Boise Chall
Re: Fuel and timing question - 07/21/09 02:37 PM
I don't have vac adv. I will pick up a cap and drill it out like you suggested I will also pick up a jet kit. I will try the 4 sizes bigger as you suggested. I have an inovate motorsports LM-1 AFR meter but the communication cable is in my other car I will get that today and install it.
Posted By: Boise Chall
Re: Fuel and timing question - 07/22/09 01:33 AM
OK I checked my timing at idle 1,000 rpm (9" of Vacuum) I have 12 deg. At 2000 rpm I have 22-24 with a max of 38 at about 3,500 - 4,000 Rpm. I turned the dist about 10 deg back and forth and it made no difference with the sputter I was getting ready to change my primary jets from 79's - 84's so I pulled my fuel pump fuse to run the bowls dry while the fuse was pulled and the engine running in neutral I ran the motor up to get rid of fuel faster and the sputter was gone so I think I have my fuel pressure too high. I have it set at 7-lbs Holley says it should be between 7 and 7 1/2 lbs But I am running a Russel gauge ( a schucks screaming cheapy) so I don't trust it I will let you know what happens. does my timing sound about right?
Posted By: Boise Chall
Re: Fuel and timing question - 07/22/09 01:59 AM
I turned the fuel pressure down to 3 lbs on the gauge. I don't know what the actual pressure is but the sputter is pretty much gone if I turn it up about a 1/2 pound more the sputter comes back.I will try to drive it tonight and see if I run out of fuel at wot
Posted By: Boise Chall
Re: Fuel and timing question - 07/22/09 03:48 AM
I don't think it's 3 or 4 psi when I first fired the car up the pressure kept dropping I would adjust it up then the next day it would drop again this went on a couple of times until it finally stayed at 7 psi I think the gauge was screwing up and I kept adjusting the regulator up thinking it was the regulator until i had it turned up to the pumps max which I think is 9 or 11 psi ( it's a Holley black top pump) I just drove the car and it was much much better but it still had a little sputter I dropped the fuel pressure about another 1/2 pound and the sputter is gone and I can pull 2 gears at full throttle and it's not running out of fuel. I do have to say it's nice to feel mopar power again man this 512 rips
Posted By: RapidRobert
Re: Fuel and timing question - 07/22/09 03:54 AM
That's good news & I thought 3 or 4 psi sounded strange that maybe the needle was damaged but we're good now.
Posted By: Boise Chall
Re: Fuel and timing question - 07/22/09 04:18 AM
When I pulled the plugs out to check color the had wet fuel on them I should have known something was up then I think the wet fuel was from me having the key on and the pump running while I was working on my front marker light. I'm sure I shortened the life of this motor with all of the fuel draining into the cylinders. By the way RapidRobert the info you gave me about the push rod in the vac booster was dead on I set it an 1/8" from touching the master cyl piston and brakes work perfect thank you. I just have a few thing left to do I need to have the new vinyl top replaced ( the guy that installed it slashed the top with a roller tool he said) it should be in tomorrow, get it cut and buffed, side markers and emblems on it's been a long 7 months getting this car done from looking like this
Posted By: Boise Chall
Re: Fuel and timing question - 07/23/09 04:10 AM
I hope I didn't offend you RapidRobert I was just joking with my last comment. The last thing I want to do is offend you you have been a great help on this project.
Posted By: Boise Chall
Re: Fuel and timing question - 07/23/09 04:58 AM
Sorry about that it was just my careless sense of humor
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