I have a friend who has a 870 street avenger new in the box and I can get it cheap. However, this is a large carb and I was wondering if it will be okay for my 455. I have an edelbrock 750 now, leaks down after a few days and no power. Timing is now set @ 15 initial and 35 @ 3000 total without vacume. Cam is a lunati voodoo 268/276 227/233 510/522 110/106, degreed straight up, edelbrock heads, performer intake, HEI with 20 degrees advance, turbo 400 with b&m shift kit, 2400 stall, 342 gears, of course headers and 2.5 magnaflow exhaust. 5500 shift point. 9.7 compression. Car will not spin a tire at 20 miles per hour kick! Only a decent chirp when it hits second. 72 Cutlass.
Any suggestions??
Thanks

 

Maybe redo the one you have, or try the new one from your friend. See if that will get the results you are looking for.
Are you looking to burn rubber, or get down the street fast?
You have a lot of stuff I don't and mine will light them up.

I have a Holley 750 refressed.

 

BOTH! If I choose to. I am not into burning up new tires, but this thing should have no problem. I thought maybe timing, however I am at 52 degrees total with my dial back light. I thought these didn't like alot of timing.
I had an Edelbrock 750 on a cheby 396/402 and had a terrible bog. Tried everything, re-jetting etc. to no avail. I bought this one used. Maybe its also junk. I do know alot of people have very good luck with them, however, not myself included I guess.

 

I had an Edelbrock 750 on my 425. It wasn't giving me the power i knew was in the engine, so switched to a rebuilt Q-Jet and added electronic ignition. The car is now a monster!!

one thing i did notice with the 750 was the throttle arm assembly on my Delta didn't pull far enough to get WOT. I had to make mods to mine to get the plates to open fully, however it still didn't give great results.

 

Check to be sure secondaries are working and all vacuum lines are working. Also check and ensure the hotter cam didn't kill your vacuum production.

 

I have a similar build just a touch more compression 10.5.1 a full roller valve train. I run a Holly 770 street avenger with no problems what so ever with a machinical fuel pump. I would think you would need to add a electric fuel pump to get the line pressure needed to run a 870, but other then that I don't believe the carb would be to big. But I would suggest you check your vaccum as stated above to insure thats not your problem.
There are lots of opinions on carbs just wait and you will get another

 

I set the idle mixture with a vacume guage pulling off the power brake feed. I got it up to about 15 lbs. Yes, I also checked the secondaries, they are wide open. I am also running a carter muscle car fuel pump 120 gph and rated at 5.5-6.5 psi.
Thanks, the more info the better!

 

Well, I bolted on the 870 SA. Holy S******! Unbelievable difference. "Feels" like 100 more hp and 150 lbs of torque. Wow! Idles clean right out of the box, way smoother cruise. Same test, hit it at 20 miles per hour, front end came up and SMOKE! (tires). Hit 2nd and a repeat!!!! Now I am happy.

 

CONGRATS!

 

However, I don't even want to know the MPG now! Just a weekend have fun and drive!