Thread: Webber/Edelbrock 500 bogging down on revs

I would say that it is leaning out. Try some bigger secondary jets. Pay little attention to a book that recommends a certain jet size, as everyones vehicle/ application is different. They are only useful as a guide.

JC

Originally Posted by justinc

I would say that it is leaning out. Try some bigger secondary jets. Pay little attention to a book that recommends a certain jet size, as everyones vehicle/ application is different. They are only useful as a guide.

JC

Thats what we have decided. I'll have to go online and order a couple of sets jets of varying degrees richer.

Originally Posted by coops71

Ive had this carb for 18 months now from new. Has been really good so far. Ive just moved it from my 3.5 to my 3.9 which has had a bit of work done to it. Problem is that it starts fine and goes well from idle through to WOT until it gets to around 3500-4000rpm. Then it starts to bog down and sounds lean when the secondaries open. Back off about 5% throttle and it comes back again. Cleaned out all jets with a compressed air and put the normal size richer primary jets back in. No difference. I really don't think it has too smaller secondaries in it seeing as this carb is apparently too rich for rovers to start with from stock jetting. Any ideas ? By the way - LPG runs very sweet through this carb so electrics are fine.

I have no knowledge of the type carby you are talking about, But most carbs have a "Power Valve", usually operated by Vacuum (or sometimes rods/levers), this valve is designed to supply fuel during the trasition between Accelerator Pump circuit and Main Jet circuit. when working properly this "valve" elimenates stumble or "bogging down". For instance in a Holley carb the Power Valve is in the metering block and is operated by Vacuum, each Holley valve has some numbers stamped on the valve, these numbers indicate, in inches of Mercury when the valve begins to open, so if you can get a parts manual it should show you where the power valve is, replace the old with a new one and see if this helps, Regards Frank.

I have one of these on my 4.6 and it's great.You can buy an Edlebrock jetting kit which includes a host of springs, jets, needles etc and just swap them around until you hit the right combination using the Edelbrock tuning guide.You can swap jets in a few minutes on these.

I ordered the kit online from Summit Racing in the US - here in a week. That was five years ago and I've never had to touch it since - fit and forget.

Originally Posted by Traco

I have one of these on my 4.6 and it's great.You can buy an Edlebrock jetting kit which includes a host of springs, jets, needles etc and just swap them around until you hit the right combination using the Edelbrock tuning guide.You can swap jets in a few minutes on these.

I ordered the kit online from Summit Racing in the US - here in a week. That was five years ago and I've never had to touch it since - fit and forget.

Ive ordered a rod with one stage richer power mode and two jets which are one and two stages richer than stock. Got these from JEGS online. The carb was great on the 3.5 but the 3.9 with the work Ive done is a bit of a nutter and really likes a drink at 4000rpm on WOT. I pulled the choke a tad at WOT and it fixed the problem. Floats are at the right level and there are no air leaks or fuel blockages.

Pulling the choke at WOT to improve means that it's running lean. You need larger secondaries.

Originally Posted by jakeslouw

Pulling the choke at WOT to improve means that it's running lean. You need larger secondaries.

Yes Im thinking of trying one stage richer secondaries and richer rods for the primaries on power stage. Im wondering if having only richer secondaries will let the front cylinders go to lean seeing as the secondary jets sit rear of the primaries on the carb/manifold and get there charge from mainly the primaries?