dieseling problem

[yody]

i checked the stock jetting for you it is;
71 primary
80 secondary
so you are a little lean in the primary, What are the specs on the motor? i have a feeling the carb is too big for the engine, and someone tried to de-jet it to run better, but the carb is still flowing X amount of air and needs the gas to match. Does it bog at all? I would put the 71's in the primay back in.

[ChevyIIMan]

Yeah 71's were stock in front and I will swap those out. Unsure how I got 69's in there but they have been there for years from what I recall. 71's will go back in and well see how she does. When I tok the front bowl off today and saw the 69's I knew something wasnt right.

No bogging, I bought the carb new and jetted it a while back. Specs on the motor is...

355ci
GM L31 Vortecs
Comp 274 xe cam
RPM air gap manifold

Orginally ran a TH-400 w/ 3600 stall
Now has a 200-4r w/ a 1800 stall

Thank the tranny change could have anything to do with it? I swapped trannys maybe 1600 miles ago.

[yody]

well that is borderline for a 750, I wouldnt' rule it out, but it might be too big, however it is probably fine. you might put the 71's in and find out they are too big, . I don' tthink the tranny would do anything if anythhing it has better gearing

[LowBuckX]

You went from a 3600RPM stall to a 1800rpm stall? How well did the motor take that? 3600 sounds too big 1800 sounds to small.... sorry off topic

[ChevyIIMan]

The motor was doing fine with the intital swap, 1800 may be a hair low for the cam. But it loved the 3600 stall... Ill eventually goto a 2500 or so.

[ChevyIIMan]

Although since im not drag racing it like I used to I have comtemplated seling my 750 off and buying a Edelbrock 650cfm Thunder Series AVS carb instead. The 750 DP was great for drag racing but maybe not so much for a cruiser/road car now.

[ChevyIIMan]

Well ran the new plugs. While I was attempting to set the idle mixture I check the plug they all had a light black coating on them from the idling. I took it out on the highway for maybe 5-10 miles or so and came home shut it off without any idling and they are all WHITE as can be.

See the pictures here http://www.odiesgarage.com/Nova/imag...reak/newplugs/ , the black dusting on them after idling covered the entire plug, once they were run the black was either totally gone or gone from the tips of the porcelain. Just white porcelain, the picture may be deceiving but they are bright white. And you can see the discoloration in the ground strap also.

Oh and shutting it off today she deisled again. Now I checked the plugs shortly before heading out for my trip and they were all a nice tan color, even on the dark side a bit but she did run rich. Why all the sudden does EVERY cylinder run super hot? What in the world changed in the course of 1400 miles?

[paul67]

Would the timing do that, maybe its advancing to much on open throtle see if it pings under heavy load, it might be a vac pipe does 1 go to the carb . just a guess
paul67

[ChevyIIMan]

No pinging under load that I can tell. Timing is at 12 initial and 28 iirc total. Ive checked all the vac ports on the carb, none of them leak and they are all sealed up, the carb gasket doesnt leak, the flange is flat also. Im going to check both my fuel filters and make sure they are not clogged, check my fuel lines for bends or kinks that may have happen on the trip. Either way its not getting enough fuel or too much air. Now I just gotta figure out which one and why.

[paul67]

Are you running elect or mech fuel pumps, on when I had a elect fuel pump it would run ok but would run lean found that the pump gears were worn got flow but very little pressure, found this because the fuel filters were only showing 1/2 full changed to mech pump no probs.
paul67

[ChevyIIMan]

Electric Pump but the fuel pressure guage at the carb shows fine pressure.

[paul67]

what pressure are you running

[ChevyIIMan]

what pressure are you running

5~5 1/2 psi if I remember correctly.

[paul67]

Also the presurre when the engine at open throttle

[yody]

No pinging under load that I can tell. Timing is at 12 initial and 28 iirc total. Ive checked all the vac ports on the carb, none of them leak and they are all sealed up, the carb gasket doesnt leak, the flange is flat also. Im going to check both my fuel filters and make sure they are not clogged, check my fuel lines for bends or kinks that may have happen on the trip. Either way its not getting enough fuel or too much air. Now I just gotta figure out which one and why.

hey, you were supposed to advance the timing to 15, your timing is too low, you need to advance you timing, that raises your idle, and lets you turn down the idle on the carb reducing the transfer slot, and lets less air in. Okay grasshopper? also 5 1/2 PSI is too liitle for a holley they like 7psi, however thats probably not your problem, oh yeah also check the springs and weights under your cap like paul mentioned make sure they aren't sticking

[ChevyIIMan]

I did advance it to 15, turned the idel down ect... no diffrence everything stayed the same. Tonight I will pull the distributor and check those weights, its a pain to get to on my distributor honestly (Mallory Magnetic Breakerless Distributor). I can try and bump the pressure up a bit, paul not sure of the WOT pressure dont have a guage to try on the road. Can I just rev it up in neutral and see if it drops?

[yody]

just bump the pressure up, revving it in neutral will do nothign. Also make sure your floats are low

[ChevyIIMan]

just bump the pressure up, revving it in neutral will do nothign. Also make sure your floats are low

Make sure they are low? or arnt? Ive got them set so with the engine running if I slightly rock the car fuel runs out.

[yody]

perfect

[ChevyIIMan]

Fuel system checked out ok, I pushed the PSI up to 6.5 and still the same.