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Topic Review (Newest First)
12-03-2012 04:38 PM
hcompton I think you got a lemon. You covered all the bases and only got it close but always had the same issue. Normally you make wholesale changes like that you go from one side to the other and then dail it in. Since nothing removed the problem i bet they f,ed it up at the factory and a replacement will run just fine put of the box with just a few turns of the idle screws.

Only thing i can think would cause fuel to be so far off is gasket sealer or gasket covering some of the ports or air bleeds undwr the carb. Other than that im betting its just a bad carb. Most carbs will at least run smoothly on most engine they are bolted to. V8 carbs will run on a chevy or a ford a small block 302 or a big block 501 caddy. They may not make big power without tuning but it will run. You can drive it without chance of fire or damage for the most part.

Hope the new carb is the trick!
12-03-2012 02:52 PM
rusthater89
Quote:
Originally Posted by lg1969 View Post
Change the PV because it's ruptured from the backfire. That is why your eyes are watery and stinging.
Those carburetors should have a blow out protection for the power valve.
12-03-2012 02:43 PM
lg1969 Change the PV because it's ruptured from the backfire. That is why your eyes are watery and stinging.
12-03-2012 01:29 PM
350cruiser I understand the overlap and big cam. But it's on a stock 350, only mod is headers... So im lost on the whole thing. I talked to holley again and did everything that he advised with no difference. So it's boxed up and another one is on the way...
12-03-2012 11:28 AM
cobalt327
Quote:
Originally Posted by 350cruiser View Post
Well according to the guy at Holley which iv talked to twice. That carb has been tested and proven to run out of the box like that. The primary is set up different than any other carb to run at steep angles, and the secondaries are set up normal, but all he would say about the huge spacing between the primary and secondary valves is that's how it's designed and needs to be ran.... After I argued that I already put the smallest jet in my kit (64) primary, it still smokes, and makes your eyes water it runs so rich. The "puff" out the carb I believe is a little smoke and tiny gas droplets. So it's still rich. I haven't messed with the power valve because Im sure that will have nothing to do with it at idle. So he suggested upping the pump squirter from a 28 to a 35 which I did and it made it worse. He was determined it was running too lean until I told him it helped putting smaller jets. So he said put an even smaller one to see, so I went from a 65 to a 64 with no change. Under normal driving and even slamming it to the floor it only pops a few times now. But in 4 low in a muddy incline it sounds like it blowing up under the hood it pops so bad. His next best thing was to send it back and get a new one... Which is the step I'm taking now, I'll keep ya up to date on how all this goes... thanks to everyone
One way to run more secondary jet would be to use a very small power valve channel restriction and large air bleeds. But still...

Sometimes that noxious smell you get is from unburned fuel, but not necessarily from being too rich. Instead, it's because the timing isn't sufficiently advanced to burn the relatively lean air/fuel mixture that's sometimes seen w/a cam that has a lot of reversion/lot of overlap/narrow LSA/late intake closing point.

Do you know the cam specs? Does the CR of the engine match the cam?
12-03-2012 10:45 AM
350cruiser Well according to the guy at Holley which iv talked to twice. That carb has been tested and proven to run out of the box like that. The primary is set up different than any other carb to run at steep angles, and the secondaries are set up normal, but all he would say about the huge spacing between the primary and secondary valves is that's how it's designed and needs to be ran.... After I argued that I already put the smallest jet in my kit (64) primary, it still smokes, and makes your eyes water it runs so rich. The "puff" out the carb I believe is a little smoke and tiny gas droplets. So it's still rich. I haven't messed with the power valve because Im sure that will have nothing to do with it at idle. So he suggested upping the pump squirter from a 28 to a 35 which I did and it made it worse. He was determined it was running too lean until I told him it helped putting smaller jets. So he said put an even smaller one to see, so I went from a 65 to a 64 with no change. Under normal driving and even slamming it to the floor it only pops a few times now. But in 4 low in a muddy incline it sounds like it blowing up under the hood it pops so bad. His next best thing was to send it back and get a new one... Which is the step I'm taking now, I'll keep ya up to date on how all this goes... thanks to everyone
12-03-2012 10:09 AM
lg1969 It's no wonder why the carb is backfiring. You suppose to run a 6.5 PV not a 2.5 PV. Carb is leaning out you. Did you check the secondary spring. It may be opening too early. The plugs are fouling out because of the large jets.
12-03-2012 07:26 AM
cobalt327 I'm wondering the same thing. I guess they think it's going to be used on something that's WFO all the time.

I could see something like a sand or mud drag racer or tractor puller w/a small displacement engine maybe needing something like a 670 cfm carb w/a 2.5 PV, but the jetting still makes no sense to me. It'll be interesting to hear what Holley has to say.
12-03-2012 06:19 AM
350cruiser I'd have bet more than a dollar that a 68/89 2.5 wasn't stock. That's outrageous to me. Especially for an off road carb, what kind of motor do they plan on putting a 670 on to do some mud and rock crawling?? I'll call holley in a couple hours and see what they recommend for fixing it. Thanks for the help.
12-02-2012 10:24 PM
cobalt327
Quote:
Originally Posted by 350cruiser View Post
Look up the instruction sheet on the holley site for pn 93670. Scroll all the way to the bottom and look at the factory specs for the 670. All that oversize non sence is factory. It was ordered brand new so it has the proper jets in it according to the paper work. Why such big jets with a 2.5 valve on an off road carb has got me wondering, but I got it where it needs to be now. But all and all it's a bad a** carb after it's been jetted and tuned properly. Almost rolled the jeep over earlier and it sat there at idle purring like a kitten like nothing was going on. Iv done everything suggested above plus some and can't seem to get rid of the last few "pops". Let me know what y'all think about it. Thanks
Thanks for correcting me- I'd have bet a dollar that was nowhere even near to stock- that's why I didn't even bother to look it up which is on me.
12-02-2012 08:37 PM
350cruiser Look up the instruction sheet on the holley site for pn 93670. Scroll all the way to the bottom and look at the factory specs for the 670. All that oversize non sence is factory. It was ordered brand new so it has the proper jets in it according to the paper work. Why such big jets with a 2.5 valve on an off road carb has got me wondering, but I got it where it needs to be now. But all and all it's a bad a** carb after it's been jetted and tuned properly. Almost rolled the jeep over earlier and it sat there at idle purring like a kitten like nothing was going on. Iv done everything suggested above plus some and can't seem to get rid of the last few "pops". Let me know what y'all think about it. Thanks
12-02-2012 07:57 PM
cobalt327
Quote:
Originally Posted by 350cruiser View Post
Alright guys, thanks to everyone for the replies. So far iv done everything possible to fix the problem. But what helped the most was rejetting, factory this carb comes with a 68 primary and an 89 secondary which seems massive to me, I cut them down to a 65/68 and now it runs 100% better. but still a pop every now and then under a hard acceleration or reving up past 1500 in the drive way. After further inspection of the carb... It also has a 2.5 power valve. According to my vac gauge I need a 6.5. Could this cause my problem??? I will indeed change it first thing in the morning, but what happened when you have too low of a power valve? Thanks
WTF 68/89 w/a 2.5 PV???

That pos would be going right back where it came from- on their dime- and a replacement that hadn't been already sold and returned demanded in return!

There's no earthly way- even w/bad QC- that the carb would have left the factory like that!

The 2.5 PV wouldn't cause it to run bad sitting in the driveway w/o a load on the engine. But God only knows what else might have been done to this carb by whoever was "tuning" it before you. If it was me I wouldn't waste any more time on it. If you do want to work on it despite all that, baseline it back to stock specs and work from there.

Holley numerical listing here.
12-02-2012 07:09 PM
350cruiser Alright guys, thanks to everyone for the replies. So far iv done everything possible to fix the problem. But what helped the most was rejetting, factory this carb comes with a 68 primary and an 89 secondary which seems massive to me, I cut them down to a 65/68 and now it runs 100% better. but still a pop every now and then under a hard acceleration or reving up past 1500 in the drive way. After further inspection of the carb... It also has a 2.5 power valve. According to my vac gauge I need a 6.5. Could this cause my problem??? I will indeed change it first thing in the morning, but what happened when you have too low of a power valve? Thanks
12-02-2012 01:29 PM
ssmonty If the fuel level and pressure(4-1/2 to 5-1/2lbs +/-1) are ok, then check for vacuum leaks, (gasket,pvc valve,vacuum hoses,ect.)
FWIW
ssmonty
12-02-2012 12:49 PM
ssmonty 350cruiser,
If I'm not mistaken, a pop out of the carb is an idication of a lean mixture or improperly adjusted valves. Since the engine was ok before the carb swap, and you think the timing is correct I'd check the float level and fuel pressure before anything else. adjust the float so that the fuel just starts to trickle out of the sight hole after removing the plug with the engine at idle.
FWIW
ssmonty
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