440 Carburator Jetting Advice

[Schober Motorsports]

Hey guys,

Brought the Coronet back out and getting it ready for racing season... Got it fired up and all that, but I'm having the same issues as last year. Car bogs down and sometimes backfires a bit when you slam on the gas. Figured out that it was running real rich (Spark Plug Carbon Deposit) I was looking to get some incite on what # jets to run in it?

Its the 4779-2 DP Holley -4150- Pumps are turned down quite a bit and I know its not timing.

440
TM7 Intake
Hughes "Whiplash" Cam .518 Lift
2500 Stall Converter
Balanced internals
8.5 to 1 Compression
452 Heads
440 Source Roller Rockers
MSD 6T
4.11's out back

Any more info that you guys might need just ask...

What set of wires and spark plugs would you guys suggest w/ my combo?

Would the car running too rich cause it to have starting problems also???

Thanks
-Craig

 

[Moparmatt72]

Id check timing, then look at plugs and see how they are reading

 

[HEMI-ITIS]

Does it backfire up [carb] or down [exhaust]?
up is lean or too much advance,down is most likely misfire due to ignition issue.

 

[fiorock]

If it backfires through the carb when you whack the throttle, it could be momentarily leaning out as Hemi says. You might try increasing squirter size, changing the accelerator pump cam setting to increase stroke, and/or upgrade to larger accelerator pump. When the throttle is opened quickly, the vacuum signal to the main metering drops off, so increasing jet size won't really help. Sounds from your description that this could be the case since you said the plugs look black.

Does it backfire/bog from a standing start, or if you're already moving? If its the later, could also be power valve selection. Holley power valves are stamped (at least they used to be) with the vacuum value below which the valve opens. I guess the idea is if you're cruising along at part throttle & you nail it to pass somebody, the power valve responds to the vacuum drop by opening & adding fuel when there isn't enough throttle travel left to use the full stroke of the accelerator pump.

 

[Schober Motorsports]

First start up of the day it fires up no issues. Runs great, still has the issue when you slam the gas it'll bog down... Then if I'd go n' start it up after that it'll have a HELL of a time starting, it'll just turn over and have a pop or two... It really backfires only coming out of the exhaust side when it really gets up there in the RPM's revving it in park. Also when I'm starting it [If it doesn't start and stumbles], the carb will just light right up...

I got the 6T MSD Box and when I take off the boot for the coil I can see the 6 sparks jumping out of it... Maybe the wires are crap??

I've had nothing but issues with this damn engine, and I just can't get it dialed in to be reliable...

I'll try and make a video tomorrow of what it's doing see if that'll help

Now I do have an electric fuel pump, it is regulated to about 8psi right now, could that be a possible issue?

Also as for being able to drive it??? Good luck, car doesn't run well at all. It'll kinda stumble out, have no power and if you slam on it, it'll either just bog down then GO or else just have a holy load of misfires and stumbles...

Please help me fix my mopar lol

 

[fiorock]

Your headers don't get real hot by any chance, do they? Now that I'm reading your second description it does sound timing related, & reminds me of a similar problem I had years back. I had built my 440 around a BDS blower setup & they recommended very conservative timing settings to prevent detonation (don't remember exactly the numbers), & as it turned out, the ignition was firing late. I experienced a lot of similar symtoms: running rich (my eyes would tear up if I would walk around the back of the car while it was idling), backfiring, hard starting, & the headers would get extremely hot. In a fit of disgust I pulled the blower off & stuck a single 4bbl manifold on it & tuned as I normally would - I cranked the distributor up, since I basically had an 8:1 smog motor at that point - & it ran great.
Ran it that way for years, & it turned mid-12's. Anyway, maybe try bumping up the base timing a couple of degrees at a time. Not sure how adjustable your distributor is (I have an old Accel that's mechanical advance only), but you may have to get the advance in quicker or limit total advance.

 

[WileE]

I'd start with the basics. As a prior poster stated,for a bog condition check the accelerator pumps (lever/adjustment, & you may want to take it off to check if the bellows is good inside). 8psi should be ok, but I'd check the float level & needle/seat for sticking. Afterward, check inside the dist cap.

 

[Schober Motorsports]

Your headers don't get real hot by any chance, do they? Now that I'm reading your second description it does sound timing related, & reminds me of a similar problem I had years back. I had built my 440 around a BDS blower setup & they recommended very conservative timing settings to prevent detonation (don't remember exactly the numbers), & as it turned out, the ignition was firing late. I experienced a lot of similar symtoms: running rich (my eyes would tear up if I would walk around the back of the car while it was idling), backfiring, hard starting, & the headers would get extremely hot. In a fit of disgust I pulled the blower off & stuck a single 4bbl manifold on it & tuned as I normally would - I cranked the distributor up, since I basically had an 8:1 smog motor at that point - & it ran great.
Ran it that way for years, & it turned mid-12's. Anyway, maybe try bumping up the base timing a couple of degrees at a time. Not sure how adjustable your distributor is (I have an old Accel that's mechanical advance only), but you may have to get the advance in quicker or limit total advance.

Header's do get a bit hot... They love to melt all my spark plug wires constantly

 

[midnightrider1818]

is it when you launch. i might be able to help you out. pull your jets and get some copper tubing the same size as the jet. solder that onto the jet. then take a pair of pliers and bend the top of it down a little for the float to clear. when you launch all the fuel gets shoved to the back of the bowl. with this fuel tube soldered onto the jet the jet will still be able to suck fuel

 

[Schober Motorsports]

Wow, now thats a trick!!!

But nah it bogs down when it's not even moving...
Right now I'm having a heck of time just trying to get it started to see what my timing is at...

 

[70rr-brian]

Maybe a compression check is in order as well.

 

[Schober Motorsports]

Forgot to add this too... All the plugs have this hazy coating on the top of the spark plugs, Does anyone know what this is? Maybe does this have something to do with my issue w/ the timing? I am using the original distributor and coil w/ my MSD box, could that be causing issues?

 

[fiorock]

Can you static time it to get it running? At least you'll know where you're at.

 

[Meep-Meep]

8.5:1 compression with what appears to be a radical cam is a red flag in my opinion. What is you vacuum at idle? I suspect less than 10 in-hg and even less in gear. Also what is your cranking compression pressure? You need to either put in a smaller cam (earlier intake valve closing point) or raise the compression.

 

[Schober Motorsports]

http://www.hughesengines.com/Index/...V2hpcGxhc2ggTXVzY2xlIENhciBjYW1z&partid=25116

I understand your concern. Its actually is ment for low compression engines, its the whole reason why I bought it... If ya look at the bottom of the page you'll see my car

Now as for measuring vacuum, how do I do it? What kinda readings should I go for?

 

[sstocker31]

By the looks of those plugs maybe you got a bad batch and they are leaking through the insulator??? How about the headers are they nice and tight? You also mentioned burned plug wires.....
-Plugs are cheap....i'd change them.
-Pull off the plug wires inspect & test them.
-Ensure the headers are tight.
-How about the gas....is it fresh?
- 8 PSI is a bit high for fuel pressure, i'd cut it back to 5-6 psi
-If your car has been sitting, it's possible a float is stuck or powervalve stuck open, or some other gremlin allowing too much fuel into the idle circuit. I've had it happen to me on a Holley....
-Those plugs look like it's a really rich idle circuit....

Just some things to look at.....

 

[Schober Motorsports]

I'm pretty sure it's the plugs... Did a test today with a fouled plug, gonna buy a new set and see where it goes.

Also got the carb apart, one of the jets were clogged with crap... Now I got 66 in the front and 76 in the back (Bought it used already in there). Was thinking on doing 74's all around... Thoughts?

 

[coloradodave]

At this point jetting is not your problem. I'll bet if you can get it running at night and put a load on the motor it'll light up like a Christmas tree. The MSD units put out serious power and everything else needs to be up to snuff. After blowing Chemtool through all the orifices in the carb and metering blocks, set float levels with bowls inverted to 1/4" from the inside of the top of bowl (1/4" drill bit works as a gauge). Make sure to check inlets and needle and seats for debris. Replace wires (8MM MSD, Accel, Taylor are all good) and route away from headers. Replace distributer cap and rotor with ACCEL quality units. If necessary, use heatproof protectors near plugs. Replace plugs with correct ones for your motor. Remove vacuum line from metering block and plug nipple with a rubber cap. Order a timing tape to fit your harmonic balancer and install it. If you can get the motor running, set initial timing about 12-14*BTDC and then rev engine and watch to see what total timing is on the tape. It should end up being about 34-36*. If not, adjust until it is. After setting timing, reconnect hose to nipple on the Holley baseplate. I would preface all this with asking if you used a product like Sta-bil in your fuel before the car sat. If not, I'd drain the tank and lines and refill with fresh fuel. Trouble shooting has to start with all the basics being right. Good luck. BTW all this stuff is available from Summit, Jegs, etc.

 

[Schober Motorsports]

Alright, rebuilt the carburator today, found a good amount wrong with that... Put a new coil n plugs in it and BAM

It fired up, soo much better than before, GREAT throttle response... Finally I've been fighting these problems for so damn long I forgot what all the work was actually for haha

Thanks for all the help guys, as for a moral of this whole story???

Don't buy AC Delco haha

 

[coloradodave]

Glad you got it fixed. Mind sharing what you found wrong in the carb? Also, I saw the video at Hughes and copied this from their site as it is good info:

"Whiplash Series Flat Tappet Hydraulic Camshaft Drop in Muscle Car Cams. Want that mean 60's & 70's muscle car lope without doing a complete rebuild? You need one of our muscle car cams.
No machine work, leave the heads on, raises cylinder pressure. Ground on true .904" cam lobes. This gives you max area under the curve. Has low lift to clear guides.
SHAKE, RATTLE & RUN!!!!

Anyway, good for you for hanging in there..................