13 replies to this topic

[StephenSLR]

I'm in a predicament.

My Mustang is at my sister's place in the Illawarra NSW (near Dapto).

It sounded quite rough warming it up and when I looked under the bonnet I noticed a fuel leak near the front bowl of the Holley (double pumper).

Not sure if it's a gasket leak at the bowl or from that arm attached to the spring/nut for throttle calibration.

I'm weighing up my options, would this be an easy fix I could do, i.e. a gasket replacement?

I just need to get to Sydney before I get a mechanic to look recondition it, I don't want to risk driving while leaking fuel (it's not a slow leak either).

My other option is to have a mobile mechanic to remove it while I get it serviced in Sydney at a couple of places I know... or can anyone recommend a mobile mechanic in the Illawarra that could do it all?

I'm back in Sydney so this will involve to and fro trips

Regards,

Stephen

Yes it's been a while since I've posted here.

[claysummers]

If it’s running rough and leaking, chances are it is just an ineffective needle and seat overfilling the bowl. Pull the needle and flush. Chances are it will come good.


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[yel327]

Would it be easier to pull it off and drop it to Hume or Xtreme to give the carb a service? Would save a bit of screwing around other than the trip to get the carb to and from.

[StephenSLR]

Pull the needle and flush. Chances are it will come good.

I imagine I'll have to remove the bowl to do this?

 

Excuse my ignorance, have never pulled apart a carb.

 

s

[StephenSLR]

Would it be easier to pull it off and drop it to Hume or Xtreme to give the carb a service?

 

That's what I'm thinking too.

 

Would it be a simple bolt off/bolt on or is there further tuning, etc. to be done once on?

 

s
 

[claysummers]

I imagine I'll have to remove the bowl to do this?

Excuse my ignorance, have never pulled apart a carb.

s

I’m not familiar with these specific carbs, but here is a video. https://www.google.c...BX8r4oeFOg,st:0 Couldn’t be much easier, and surely worth a shot prior to removing the carb and sending it off. I’m not saying it wouldn’t benefit from a refurb if it has been laying around unused for a while.


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[yel327]

That's what I'm thinking too.

 

Would it be a simple bolt off/bolt on or is there further tuning, etc. to be done once on?

 

s
 

 

They will put it back together as they found it and ask them to put the mixture screws as close as they can to where they are. Although you'd probably have to setup the idle adjustment once back on. It will be good enough to drive, will need a proper tune when you get it back. It may just be a stuck needle and seat as Clay says, but they always run better after an overhaul. Every Quadrajet I've had done by Hume or Extreme runs like clockwork out of the box and they are more complicated than a Holley.

[StephenSLR]

surely worth a shot prior to removing the carb and sending it off. I’m not saying it wouldn’t benefit from a refurb if it has been laying around unused for a while.

 

Will absolutely give it a reco, if not exchange it for something else. It's had a pulsing idle for a while now and it was next on the list but after sitting at my sisters for over a month it seems to have gotten worse, not sure if it was leaking all this time.

It's on a 302 so may be a bit big? I think it's a 650.

 

will need a proper tune when you get it back. It may just be a stuck needle and seat as Clay says, but they always run better after an overhaul. Every Quadrajet I've had done by Hume or Extreme runs like clockwork out of the box and they are more complicated than a Holley.

 

Yeah, I purchased a Quadrajet from Carburettor Service Co (Burwood) and have it on the SL/R, it's been running fine for over 20 years now. Hasn't skipped a beat.

 

s

[yel327]

Will absolutely give it a reco, if not exchange it for something else. It's had a pulsing idle for a while now and it was next on the list but after sitting at my sisters for over a month it seems to have gotten worse, not sure if it was leaking all this time.

It's on a 302 so may be a bit big? I think it's a 650.

 

 

Yeah, I purchased a Quadrajet from Carburettor Service Co (Burwood) and have it on the SL/R, it's been running fine for over 20 years now. Hasn't skipped a beat.

 

s

 

650cfm is probably overkill on a 302 unless its a Boss. But if it's a vacuum secondary spread bore it'll run fine.

[StephenSLR]

650cfm is probably overkill on a 302 unless its a Boss. But if it's a vacuum secondary spread bore it'll run fine.

 

It's actually what they've nicknamed a 'Clevor' - Cleveland heads on a Windsor engine. An imitation Boss.

 

Mechanical secondaries.

 

s

[yel327]

It's actually what they've nicknamed a 'Clevor' - Cleveland heads on a Windsor engine. An imitation Boss.

 

Mechanical secondaries.

 

s

 

That is what a 302 Boss essentially is, Cleveland heads on a 302 Windsor. Still a big carby for a street driven 5.0L car, would go nice at peak revs. That engine is what Moffat used to run in Group C in that Kar Kraft Mustang although those original Boss 302 had a vacuum secondary 780cfm 4150, I think the same basic carby as the XY GT-HO and L34 HO-kit. The L88 427 BBC and Z28 302's ran these too.

 

A 650 mech secondaries (assume square bore double pumper?) is a pretty simple carby to overhaul. I'd give Nigel at Xtreme a call and see if he can give it a birthday for you. I still reckon you'd be better off with a vacuum secondary carb though for street use.

[StephenSLR]

Looks like I have a 650

 

https://imgur.com/a/vJPZw3W

 

Removed the bowl and the acc. pump screws were loose. I removed it to inspect the diaphragm, couldn't see any splits or holes, even tried sealing my lips around and blew to see if I could notice any leak, nothing.

 

Put it back together, definitely leaking from the acc. pump.

 

I guess my lungs don't have anywhere near as much psi as a fuel pump, lol.

 

https://imgur.com/a/gdnG6cK

 

Have ordered a new diaphragm.

 

s

[yel327]

Yes, 4777 is definitely a 650cfm double pumper. It's a later revision (-7). Here is a listing showing what it was setup as originally.

 

 techlibrary_carb_numerical_listing.pdf   611.91K   1 downloads

Edited by yel327, 29 July 2024 - 08:18 AM.

[StephenSLR]

The acc. pump diaphragm arrived from an eBay seller this week, a very easy job to replace it myself.

 

No leaks, engine runs smoother and I drove home without problem.

 

Just in time to book a pink slip inspection and I'll have my mechanic overhaul the carb and give it the usual service while it's in the shop.

 

s