Hey guys I'm sure someone can help me. I've got a 750 dp part# 4779 I believe Anyways, I was noticing a huge bog or hesitation, strumble whatever you wanna call it right off idle when going to full throttle. A guy I know said to check what size accelerator squirters I had in there. He allmost hit the floor when I said 42 on the primary side, and 40 on the secondary side. He gave me a 32 and a 28 to try I went out for a rip and second allmost felt like neutral with my crappy street tires on. It was basically just tiresmoke everywhere! This is the first time I have even looked at my carb's jetting it's kind of a grey area for me. It is a bit harder to notice the bog with my crappy tires, it just spins them really bad and clears itself quickly. I noticed it was a huge problem when I had a set of et streets on it, and it wouldn't spin not letting it clear it's throat so to say. Heck I was even running a quicker 60foot time with my street tires than with new 12.5 et streets I was baffled, but I think im heading in the right direction. My motors in the sig, I've got a 3200ish stall. I havn't even checked my carbs jets and I know i don't wanna go any leaner with my secondary one, because aparently it's getting close to the lean area. (When I ran on the dyno and got my a/f ratio the guy said I could go up a couple jet sizes on the top end) I was wondering what people have for "squirter sizes" on there similar motors. I have a 6.5 power valve in there from the rebuild we did last winter, i'm not sure if this is about right for my cam setup (performer rpm) specs: .488 intake .51 exhaust duration is 234 @.05 intake and 244@.05 exhaust. I was also thinking if someone had a website on holley carb tuning that would be beautifull!!! If anyone has ideas on what I should have this thing set up like let me know (timing, idle speed, primary sec jets, squirter sizes... etc) Thanks alot gang sorry for the whole life story just tryin to put in as much info as possible

 

I just read holleys tuning tips I learned a fair ammount from that site. I was wondering if anyone knows the factory jet sizes, squirter sizes, cams etc. Is this a descent carb or would I be better off just getting rid of it? CArb model is a 0-4779-3

 

I just did some more tuning, I found out I had a 10.5 power valve in the primary side so i changed that to a 6.5. I also dropped 3 jet sizes to a 67 on the primary and there are 80's in the seconday side. Still not running perfect I think im heading in the right direction. Also changed the primary squirter from a 32 to a 25. I think it is a bit too small now, might put in a 30 or so later on. Someone has to have some words of wisdom on this situation.

 

Honestly the best way to know exactly what your engine likes is to do what your doing. Every engine is a little different and likes different tuning. Holleys are very tuneable, so you'll just have to keep driving and testing till you find exactly what the engine likes.

 

yea thats what I figured, I just dont wanna take my carb apart 60 times untill I get the right combo. Is there a rule of thumb as to how many jet sizes u want between the primary and secondary? Someone was telling me max 4 jet sizes, I dunno if this is true or not

 

usally 8 jet split is the min. (no less than 8 jet sizes apart).

The 0-4779-3 is the best holley carb out there IMO when looking to go fast on the cheap.

PM me on P-shop.com sometime.

 

That carb will favour a 68 to 74 primary jet and a 77 to 85secondary jet. The exact jet combo that is best for your setup can only be found by testing at the track. Look for best MPH when changing jets, with and eye on the plugs for exessive lean AFR. (overheating, detonation)
Usually its right around 70 pri and 80sec jetting at or near sea level. the pri,/sec jet spread will remain about 8 to 10 jet sizes on this carb.

Carbed motors usually want a little richer jetting to get best performance "at the track" than "on the dyno".

If you jet it for a hot muggy summer day then it will be too lean on a cool clear fall day. If you jet it for a cool clear fall day it will be too rich for a hot muggy summer scorcher day. Being a little on the rich side is much safer than being too lean. so tune for the cool days for every day driving and lean 'er out when ya go to the track on a hot muggy day. then put the rich(er) jetting back in for every day. the difference will only be a few jet sizes up or down.

Your accelerator shooter size sounds ballpark typical, now tune the pump cam for response and volume.

 

Thanks alot for the info. I noticed that the car seemed way faster on cold nights. It must have been using more of the fuel because I know when it was really hot it ran like $hit. I think the primary squirter might be too small now there is a small hesitation when I open the primarys quickly.

 

Another hour of playin around with this thing, and I think im gettin somewhere. I just bought a vacuum guage and I'm pulling about 5-6 inches of vacuum at Idle. I recently found out I had a 10.5 power valve in there so I changed it to a 6.5 I'm gonna go get a 3.5 tomorrow and see if that helps. I noticed the plugs were a little bit white so I might go back up a jet size or 2 granted I did take a large step going from 70's down to 67's. I have a fair ammount of oil on the threads of the plugs when I pull them. The ring around the plug is also pretty dark, what causes this, is it burning oil? Any input is appreciated. thanks gang.

 

The oil on the plug threads is usually from leaky valve covers. The steel threaded ring around the center porcelin will get black with soot. This is normal.