750 Holley jetting questions

[fishy68]

A buddy of mine bought a 750 Holley double pumper HP series list #82751 from a guy used but like new and the guy was pretty car dumb because he bought it for his stock 75 Monte Carlo 350. Well needless to say it was way too much. So my bud got it at a decent price. Well it got here and looks nice. Terry don't have his engine together yet and asked me to put it on my engine and see how it runs. I put it on and set the floats and fired it up and warmed it up and set the idle. All went fine up to this point. Well when I accellerate it falls flat on it's face Under light, med., or full throttle. So I checked the accellerator pumps. Their real lazy. WTH. I pull the front squirter out and see there's no check ball/needle under it. Pull the rear squirter. Same thing. Either the original owner took it apart and lost the needles or Holley forgot to put them in. I pulled the bowls to see what jets are in it and what PV is in it. Has a 5.5 inch valve and 75 jets in front and 82's in the rear. Can't find any info on Holley's sight on this perticular carb. Anyone here run one that knows what the stock jets are? I'd like to know a baseline since this one may have been altered. Seems the seller won't answer Terry back to tell us if he changed the jets and if so what the originals were. Probably cause he knew the carb. was screwed up.

Thanks and sorry about the novel. Tracy

 

[rumblefish360]

Fishy, I think the OE jets are 76's. Don't quote me on that as for surely a fact.
You should be able to get the small parts at a local speed shop or JEgs/Summitt racing easy.

 

[fishy68]

Thanks for the info Rob. I thought he may have jetted it down. I have a set of 76 jets so I think I'll put them in and I found a set of the needle/check valves that go under the pump squirters that were missing and put them in and give it a try. It seemed a little lean before and of course the pumps mot working right made it bog bad. Hopefully this fixes it.

 

[2shelbys]

Actually, those probably ARE the original jets. My 750 had 75's and 82's out-of-the-box. The secondary jets are always 6-9 sizes larger than the primaries because the primaries also get fuel flow through the power valve. DO NOT put the same jets in both ends and if you change one change the other by the same amount. Jetting is the one really hit and miss aspect of tuning because the only way to know for sure you are running the right ones is to spend a test and tune day (or 2 or 3) at the track swapping them out and recording the results in ET's and MPH. If you give me the model number off of the air horn I can tell you which jets it had stock. 82751 does not show up on any of my reference sheets.

 

[fishy68]

Actually, those probably ARE the original jets. My 750 had 75's and 82's out-of-the-box. The secondary jets are always 6-9 sizes larger than the primaries because the primaries also get fuel flow through the power valve. DO NOT put the same jets in both ends and if you change one change the other by the same amount. Jetting is the one really hit and miss aspect of tuning because the only way to know for sure you are running the right ones is to spend a test and tune day (or 2 or 3) at the track swapping them out and recording the results in ET's and MPH. If you give me the model number off of the air horn I can tell you which jets it had stock. 82751 does not show up on any of my reference sheets.

Hi Shelby. There isn't any list number on the air horn like normal Holley's have because it doesn't have a air horn. The number 82751 is the only number on it and it's stamped on the side of the main body. I also looked on Holley's site and couldn't find that number listed in the reference sheets but it is shown as a good number for a carb. It also is listed in Summit's catalog. It's the HP series carb. with changeable air bleed jets. The jets it has may be stock but I wasn't sure since it's been messed with and the guy that did it won't answer our e-mails. I'm also familiar with not jetting the same on both ends because of the PV. Just trying to get a baseline of what jets these things came with. Thanks alot for the info. Tracy

BTW: here's the carb. http://www.holley.com/0-82751.asp

Ha! If I wasn't blind I'd have seen the instruction link on Holley's sight that shows the jet sizes for this carb. Their supposed to be 75's in front and 80's in the back.