Ignition Issue????

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thanson_mopar

thanson_mopar

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Ok, ive had this problem for a while and i think im getting it narrowed down. ive got a 360 with 800 Double Pumper, comp cam, J heads with 2.02 valves, ect....let me know if you need more on my engine. My car takes off great, up untill about 4k to 4500 RPM. then it revs slowly, spits and sputters, sometimes you can make it to 6k rpm(very slowly) and sometimes you can only make it to 5k rpm??? Its NOT the carburator, (ivehad 3 different carbs on it that were tuned/adjusted while on the running motor and always still had the same problem). Its not the fuel pump (thanks Rumblefish360). When you shift into the next gear it starts to rev insantly(no waiting for fuel to come) util 4k rpm of course. I just tried another ignition box with no luck. It could be the distributer but ive got brand new rotating cup, cap, vacum advance on it. So what do i have left as an option? Coil? Im pretty sure its an ignition problem somewhere but i just cant figure it out. any help?
 
Coil or a weak charging system can do that.
 
800 DP? That is a big carb for that engine. I run a 650 DP on my built 340 and it works great.
 
also could timing not advanced far enough be an issue? I had the local carburator guy tune my first carb and timed my car. He said he set the timing at Stock specs for a 74 360....I believe 8 degrees adv
 
66340SEDAN said:
800 DP? That is a big carb for that engine. I run a 650 DP on my built 340 and it works great.
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lol thats what i thought at first. it sounded too big to me but a local guy that races AMC javelins and has been through a few chryslers, builds holley carbs and told me an 800 would be good on my engine, he jetted it to my engine , then adjusted floats ect. i think it is better than i thought it would be
 
Damn, that's a lot of carb! I know you said it's now the carb and you have tried 3 others, but that can't be helping. maybe you should step down to a 650 or so.
 
He just stepped up in cfm and his engine has the gumps to take on the 800 fine. It is alot of cfm, however, it can be tuned for the cars engine. (I ran a 800 on a otherwise stock 318 for a month till I grabbed a 600 cfm. It really wasn't a problem.)
It's not the cfm that kills, it's the poor tune of a carb that kills. Wacking the throttle to WOT can kill low end with the supper sudden drop in velocity. Not the problem here.
 
I'm thinking that you need a new distributor. It seems that once the vacuum advance is pulling the plate it's throwing the pickup out of phase. You can send your distrib to FBO and have them set it up ($70 iirc) or buy a new aftermarket one. You'll most likely have the same problem if you change out to a auto parts store rebuilt. Those vacuum advance plates get super wobbly with age. They weren't all that hot new either, lol!

Yeah, it's seems to be a big carb, but by your description of the problem, it sure doesn't seem carb related. I've a got a 650 DP on a 5200+ lb truck with a super tight converter 3.55 gears and 33" tall tires and seems to want even more.
 
ramcharger said:
I'm thinking that you need a new distributor. It seems that once the vacuum advance is pulling the plate it's throwing the pickup out of phase. You can send your distrib to FBO and have them set it up ($70 iirc) or buy a new aftermarket one. You'll most likely have the same problem if you change out to a auto parts store rebuilt. Those vacuum advance plates get super wobbly with age. They weren't all that hot new either, lol!

Yeah, it's seems to be a big carb, but by your description of the problem, it sure doesn't seem carb related. I've a got a 650 DP on a 5200+ lb truck with a super tight converter 3.55 gears and 33" tall tires and seems to want even more.
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yes, i was wondering if someone would chime in with distributer, im thingking unless its a simple problem of the coil being junk/defective new (accel superstock) it must be distributer. Although i do have new parts in it, Its still a pieced together old one. Ill think i will put an old coil on it first to see if it makes a difference, if not i will have to get an aftermarket distributer. By the way who is FBO?
 
thanson_mopar said:
also could timing not advanced far enough be an issue? I had the local carburator guy tune my first carb and timed my car. He said he set the timing at Stock specs for a 74 360....I believe 8 degrees adv
Click to expand...

You need a lot more intial timing (maybe as much as 15-20 degrees) if you have anything but a stock cam.

What does the timing do over the rpm range? At what rpm does it stop advancing? You should see approximately 34-36 degrees total in the 2500 +/- 200 rpm range. If its a stock distributor it may not stop advancing until 4000 rpm or so.

I agree with the others on the carb. Once you get the igntion sorted out and it runs well through the rpm range you should try the smaller carb again, especially if the car is primary street driven. The throttle response in the 1000-3000 rpm range where you will spend most of your time will be much improved.
 
thanson_mopar said:
yes, i was wondering if someone would chime in with distributer, im thingking unless its a simple problem of the coil being junk/defective new (accel superstock) it must be distributer. Although i do have new parts in it, Its still a pieced together old one. Ill think i will put an old coil on it first to see if it makes a difference, if not i will have to get an aftermarket distributer. By the way who is FBO?
Click to expand...

Sorry, meant to say 4 Seconds Flat.
 
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