84noname

I THINK this is around a 79 gmc 25 seirra grande. it has a holly street avenger carb on it and some bbk oops they are headman headers. intake is stock. wondering if this carb will fit my stock 305 intake on my 84?? theres some adapter plate on this for the carb as far as i can see. is this motor a 454? i cant tell what it is and dont know if its stock or not to this truck

Apeiron

It's a big block chevy of some sort. The carb won't fit your stock manifold without an adapter.

84noname

cool, so whats the last size sbc? and whats the first bbc size? i wonder if the adapter on this motor works with mine? can i just buy an adapter at auto zone>? or some place to make it fit. arent all holleys the same size as far as where they bolt up?

Apeiron

Gen I SBCs came from the factory as 262, 265, 267, 283, 302, 305, 307, 327, 350, and 400. Mk IV BBCs were 366, 396, 402, 427, and 454.

84noname

would any of those bbc fit in my 3rd gen without custome mounts?
what about the adapter plate for the carb? this motor has one i want to switch the carbs around, mostly to lose the vacum line mess on my car

Apeiron

Anything except maybe a tall-deck block could be made to fit, they're all the same externally. Changing the manifold would be better than using an adapter plate.

AlkyIROC

That isn't a tall deck block. They also didn't install tall deck blocks into pickup trucks and the intake is wrong. The only factory tall deck blocks are 366T and 427T. (6 liter and 7 liter)

Being in a 79 and a C25, that's probably a 454. Chances are it will have 781 casting heads but not guaranteed. If the engine runs, it should be worth a minimum of $500.

As for the carb fitting, it probably will. Stock intakes use the spreadbore Q-jet bolt pattern. Doesn't matter if it's on a BBC or a SBC. It looks like the carb already has a Holley squarebore to Q-jet spreadbore adapter under it.

84noname

yes theres an adapter under it:P it does run too, my friend bought it from some chick and shes in jail, and he needs the title from here still, he has no license now so he is talking about getting rid of it. he said he thought it was a 454 too. how easy is it to put in a 3rd gen? and what about the tranny? its a 2wheel truck, will its tranny work or would that not be good to use anyways due to gearing?
so i can just slap that carb on my 305?since it does have an adapter. where do i look to find out what size the carb is?? any gains over my stocker? besides ,looks and no more vac crap? any issues to be concerned when swapping onto my stock intake? im going to put it on tonight or tomorrow and put mine on his motor, will mine work on his? we just need it to run and drive if we need to move the truck

Supervisor42

Your carb will bolt on where the adapter was and will run the truck engine just fine.
The problem is the carb (+adapter) will be "too much carb" for your 305. It'll idle fine, but it'll be bog city when you floorboard it.
So the fact that it'll interchange becomes a moot point...

AlkyIROC

How well the carb will work depends on what size it is. A 454 can use a lot more carb that a street 305 will ever need. A 750 is small for a 454 but big on a 305. It's a Holley so get the list number off the choke horn. That will tell you exactly what the carb is.

As for dropping in the BBC, read the sticky at the top of the engine swap forum.

84noname

ok ill check it tomorrow and ill read the sticky. thanks
so if its a 750 will it make my motor bog at wot

ploegi

The carb is going to be jetted for the 454. Also, the accelerator pump is going to be set up for the 454. It will dump way too much fuel when you step on the gas, and will run extremely rich all the time. You will be carbon fouling plugs on a daily basis. As stated before, while this carb may bolt onto your 305, but, it is WAY to much carb for that motor.

84noname

well this is assuming its the right carb for the 454 to start with, but usually when someone puts a carb on a OE intake mani its usually whatever they had laying around to probably replace a old messed up stock one...but anyways ill pull the number off the carb here in a second and then we can have a better idea

84noname

im not sure if i got the right numbers off the right place, but stamped on the front of the carb where that thing sticks up into the aircleaner on the first 2 barrels its says
80670-1
2062

looks like its this one
http://www.holley.com/applications/C...lector/0-80670
so i think thats it, 670cfm, wonder how that would be on my 305 then?

AlkyIROC

A 670 CFM vacuum secondary with electric choke. 4150 style with center hung float bowls. Looks like a basic no hassle replacement carb. That should work fine on a 305. It was probably way to small for the 454.

84noname

i was kinda figuring it was just slapped on there with no real regard to the size of the motor. so is a 670 better than my stock one? on my stock mani? is it worth using it over my stock one?

five7kid

iTrader: (14)

No, for a bunch of different reasons.

For one thing, a stock q-jet has more flow capability than that Avenger.

84noname

thanks five7. i will leave it on the truck motor then. what would be a good carb to look for that i can get used for my 305 that would be good later on down the road if i switch to a 350? or 400

Apeiron

A quadrajet.

five7kid

iTrader: (14)

Want to guess what I had to do to my stock cc q-jet when I went from 305 to 350?




Zero.


Zilch.


Nada.