440 hesitation and backfire

Hemimad · Post by **Hemimad** » Tue Sep 01, 15 8:58 pm

Car has been running fine for the last 600 miles, but on Sat it it showed the first sign of a problem when turning the car around. As I changed from D to R it almost stalled, same again going from R to D, then behaved all day. Tonight I fired it up selected R, stalled out. Fired up again ok, select R almost stalled but recovered enough to back out the drive. Off down the road a mile or so then really started hesitating time to turn back me thinks! Pulled into a road to do a U turn and it kangarooed in D and R chirping the tyres, what a show! Off back down the road major hesitation, tried to drive through it massive backfire managed to kangaroo it back home😢 no obvious signs of any fuel leaks, cables disconnected. In N it's fine revs ok idles ok, just when loaded. Carb, fuel or transmission, any ideas??

440 HP motor (just rebuilt)
750 CFM Holley (rebuilt)
Mopar elec ignition (orange box)
727 torqueflite (pink fluids to level)

morgan · Post by **morgan** » Tue Sep 01, 15 9:24 pm

Sounds like mine does when the vacuum advance is connected. Are you running vacuum adv ? I'd plug the vac can and see if problem persists.

Bangs, pops, hesitation sounds timing to me. Dizzy jumped ?

latil · Post by **latil** » Wed Sep 02, 15 11:06 am

Sounds like fuel or a severe lack of it. But just check all your timing first before jumping in.

Dave999 · Post by **Dave999** » Wed Sep 02, 15 11:46 am

blocked idle jets or circuit???

Hemimad · Post by **Hemimad** » Wed Sep 02, 15 8:14 pm

Timing a fraction out, checked the bowl levels, primary ok, secondary pouring out. Time to revisit the carb....

John · Post by **John** » Wed Sep 02, 15 8:43 pm

Hemimad wrote:Timing a fraction out, checked the bowl levels, primary ok, secondary pouring out. Time to revisit the carb....

Strange,

A backfire if carb related usually means its lean.

ANTON · Post by **ANTON** » Thu Sep 03, 15 7:22 am

Backfire through the exhaust is over fuelling. My carb did this when the secondary float needle failed and pored fuel in.

RobTwin · Post by **RobTwin** » Thu Sep 03, 15 8:33 am

Hemimad wrote:Timing a fraction out, checked the bowl levels, primary ok, secondary pouring out. Time to revisit the carb....

Maybe time to get that 6 BBL on there

ANTON · Post by **ANTON** » Thu Sep 03, 15 10:32 am

What fuel are you using and where did you get it from

Hemimad · Post by **Hemimad** » Thu Sep 03, 15 1:31 pm

6BBL a serious contender, got the correct intake, just need everything else $$$$. The petrol is BP super with Miller octane booster, purchased locally, it sat for two weeks while on hols, I bombed over after getting back and put 34 Ltrs in to top up tank. The carb has the problem on the secondaries over filling, so pulling carb to investigate today.

Scooby · Post by **Scooby** » Thu Sep 03, 15 6:45 pm

Octane booster will clog up the jets is this a race engine or high compression engine just wondering you use this stuff ...

RobTwin · Post by **RobTwin** » Fri Sep 04, 15 1:03 am

I'm presuming it's this one that Dave B put together...

http://www.moparuk.com/forums/viewtopic ... ht=#570626

Hemimad · Post by **Hemimad** » Fri Sep 04, 15 8:58 pm

Yes, but the carb was not his responsibility, it was rebuilt by a member of the family as a favour!

Carl · Post by **Carl** » Mon Sep 07, 15 11:40 am

Hemimad wrote:6BBL a serious contender, got the correct intake, just need everything else $$$$. The petrol is BP super with Miller octane booster, purchased locally, it sat for two weeks while on hols, I bombed over after getting back and put 34 Ltrs in to top up tank. The carb has the problem on the secondaries over filling, so pulling carb to investigate today.

Needle valve stuck open, a tap on the adjustment screw can sort that out.

Hemimad · Post by **Hemimad** » Sat Sep 12, 15 12:10 pm

Carb repaired with new needles. Fired up but still with hesitation, pull off the vacuum and it settles down, put it back on and it starts acting up and won't Rev without fluffing and mostly cutting out, similar to the way Morgan describes. It has a new MP electronic ignition fitted only a few hundred miles ago, is it a simple fix, other than blocking the vacuum off?