What's new
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.

670 or 770 truck avenger...?

rob h

rob h

1/2 ton status
 Premium
Joined
Sep 13, 2008
Posts
2,311
Reaction score
429
Location
frackville,pa
My .040 over 350 , 450 hp, 12:1 comp, 515 lift sollid cam, and ive been wanting to change the carb,but it also has low vacuum, now i have a jetted down 750 double pumper that i dislike. i was thinking of buying a 770 or 670 truck avenger with electric choke....but not sure what to do..any ideas..? i would like either the holley offroad carb or the edelbrock...........anyone with a lil help..?
 
I have a stout 400sbc with approx 400HP and have the 670. Works real well. I thought I read somewhere on Holley's site that the 670CFM was good to about 300-400hp and the 770CFM was for more HP's. I could be wrong but that's what I recall.
 
I had pretty much the same set up and I went with the Holley Truck Avenger 670cfm. I bolted it on, adjusted the idle and never had a problem with it. a 750 is a lot of carb. Also, you can get boosters to increase your vacume but... I think if you went to the 670 you would be happier and have better throttle response.
 
Last edited:
That's a pretty hot engine. You may have to get a wideband and tune the AFR due to the cam profile. Also, the TA series carbs have no emulsion on the mains so tuning through the RPM range can be very challenging.

Also, agreed on the CFM - go smaller than larger unless you'll spend most of your time >5000 RPM. I'm running a 780CFM on my 402BBC and frankly I'd rather have a 670 or 650. The primaries are too big for slow speed trail work.
 
Last edited:
i also read that the edelbrock offroad carbs are much easier to tune, work just as good and are cheaper.........anyone know about that one...?
 
I used the Edelbrock 750 quadrajet on a 454+.030 with a 6500rpm cam. When running higher (5800+)rpm, I was running it out of gas. Had it tuned/adjusted by a quadrajet specialist(the son of one of the original designers). Then no problem up to 6600rpm's. On a small block, a 650 should be plenty unless running screaming R's often, then maybe bigger and have it tuned for your motor.
 
rob h said:
i also read that the edelbrock offroad carbs are much easier to tune, work just as good and are cheaper.........anyone know about that one...?
Click to expand...

Not sure how its easier than the holley. The adjustments on the holley are

1) choke - simple turn the dial to have it come off early or stay longer

2) curb idle - 99% of the time factory set

3) A/F mix - very simple, hook up vacuum gauge and turn the screws 1/8 of a turn either way to acheive the highest vacuum

4) Idle - simple enuff.

:D
 
Agree... Holley all the way. Also, I read a test recently (online one of the 4x magazines) between the Edelbrock and the Holley off-road models the the Edelbrock had stalling issues while it was at an 30 degree incline both front to back and side to side. God forbid you dump the 4x into 3 wheel motion! LOL We talkin about low riders or trucks? HA HA
 
i have a 400hp 350 with .525lift and 1.6 rockers etc....and i bought a 770 truck avenger because thats what a really well respected hot rod shop said to get...but never ran right even after re-jetting and everything. i bought the 670 and it runs A LOT better now....my secondaries would barely open with the 770 also. if u search im sure u can find a couple threads on my battle with the 770.;)
 
i guess ill try the 670 and see what happens, ill keep my 750 dp for now....if it doesnt work out i can then put it back on..
 
rob h said:
i guess ill try the 670 and see what happens, ill keep my 750 dp for now....if it doesnt work out i can then put it back on..
Click to expand...

BTW, a DP can be made to work on a truck application but it requires a hell of a lot of tuning on the accelerator pump circuits and the CFM has to be matched to the application. 750DP sounds too big for this application. And of course the DP will still be susceptible to off camber fuel flow out the vents and main boosters.

Good choice going to the TA.
 
the dp works well for me and its tuned, i did the jets, power valve, nozzles etc to make it work.....i just wana go to an offroad carb, so it works all the way around and i was thinking that the 670 would make it a lil better on fuel.
 
bought a 670 truck avenger today, i bolted it on, set it all up and i have a dead spot under load( more so on hills) i bought the pack of springs for the secondaries, helped some but not enough. i tried changing the nozzle to a larger onr and its almost out but faintly there.....any ideas...?
 
Last edited:
also tried today the 2nd hole on the accel pump cam, worked better but not perfect still a lil hesitation when under a load and stood on, im thinking as i searched here to try the other cams such as the blue one, i have the orange now...ill mess with the cam kit and changing the secondary springs and see what i get...........anyone.......???????
 
i've seen the dirt track guys take all the vacuum advance stuff out of the dizzy,..then they fully advance the dizzy(where the bars that held the springs and stuff) are in a ''X'' instead of flush w/ each other...then mig tack it on both sides of the >X< to lock it fully advanced, then tune for highest vacuum ....they swear it is quicker out of the corners,..

so last october at the tri-county fair demo derby, i helped build 3 or 4 cars and started out doing the pinned dizzy on 1 car,..and it was such a noticeable difference,...the other car owner/drivers wanted me to ''do'' their car like the 1st one...i had used a screw to lock it, incase it didn't help off the line as anticipated, i could go back stock,...i wound up welding it & doing that little trick to every car i came across that was a friend...needless to say i did alot of dizzys in the pit area

i also have a locked dizzy, for the mud truck & it does do away w/ the vehical's lack of throttle response, it bleeps when you pin the throttle, not BbOooooGggggg..rrreeeevvvvvvvv
 
i have a mallory unilite in my 358, it always worked perfect b4, thanks for the suggestions, if i cant get it i might try the screw in thel inkage so it has to open just like mechanical, but i didnt wana go that route..
 
what i'm talking about, isn't a screw in the linkage, its a screw inside the dizzy, that holds the vacuum advance...fully advanced,....not exactly sure what it does, but it gets rid of the hesitation when you pin the throttle, but prolly not good for a truck that see's any road...or street time
 
You must log in or register to reply here.

Latest Posts

Top Bottom