Hi guys -

Working on a Holley 4778-2, 700 CFM double pumper. Somewhere in its previous life a 50cc secondary pump was installed. I'm assuming this won't fit my intake without a carb spacer, which I don't have hood clearance for, so am converting back to a 30cc pump and lever. Question: Which color pump cam to use and in which hole? Thanks.

PS Scoured the web and couldn't find that spec.

Probably no exact answer unless someone has your exact combo... I'd start by matching the primarys and go from there. You could also look at the Holley web site as they have a pdf file with the breakdown of how all their carbs come from the factory by list number...

Thanks, Dennis - I looked there, and they list most everything EXCEPT pump cams -

Most of the Holley double pumpers on combos similar to yours work well with the orange pump cam in hole # 1 and # 31 squirters front and back. That should get you in the ball park for your ZZ430 :D

Thanks, Eric. There's a pink on the front side right now. I'll see if I have a couple of oranges laying around.

Pink in position #1 should be close too . . . just a little less fuel then the orange.

4778 Holley 700 DP comes stock with a 50cc rear accel pump.

4778 Holley 700 DP comes stock with a 50cc rear accel pump.


Interesting. Where did you find that info? and does the list 0-4778-2 come with the 50cc rear pump?

Either way - there's no room for it on my intake - my current 0-4777-2 650 DP has 30cc pumps front and rear and I don't see the need for the 50cc pump. Thanks.

Interesting. Where did you find that info? and does the list 0-4778-2 come with the 50cc rear pump?

Either way - there's no room for it on my intake - my current 0-4777-2 650 DP has 30cc pumps front and rear and I don't see the need for the 50cc pump. Thanks.
Swap base plates and rear bowl
or rear bowl and accelerator linkage

Swap base plates and rear bowl
or rear bowl and accelerator linkage

I found the correct secondary pump lever (same as the primary) and 30cc pump housing cover on e-bay for $11 - already installed. Had the correct spring from an old parts carb. Thanks for the info.

The old 700 DP I had back in about 1990 came with a 30cc pump . . . there must be different versions of this carb.

Thanks, Eric - that's what I was thinking, too. I remember having one way back when and I don't recall the big pump on the rear. Bit I was running a single plane Victor Jr. so clearance wouldn't have been a problem (I don't think). Anyway, FYI, here's what I'm working on, to be installed in the spring. A Holley HP main body conversion on a 4778-2, supposedly flows around 830 CFM. As I posted in an earlier thread, I'm a bit concerned if I'll have to mod the metering blocks to get this tuned right. Do you think this is too much carb for my 383? Replacing a 4777-2 650 DP, factory jetting. Thanks again.

http://img.photobucket.com/albums/v61/gort69/DSCN3521.jpg

Looks nice Al. :)

I think it should work fine on your 383, but I forgot exactly what cam, heads, and compression you were running so cannot be 100% certain.

Keep in mind that if the old carb body flows 830 cfm you will need jets that fit for an 830 cfm carb with the same kind of boosters (downleg in your case). If you use 750 jet sizes the carb will be lean. Also, if the carb is a hair on the big side for your combo it will probably want more jet then it would if the carb were under-sized.

Thanks, Eric. The combo, in short:

383, 9.5:1, mildly worked GMPP Fastburns, 230 236 .515 .515 110 HR, 1 3/4 Supercomps, 2 1/2 X pipe system, 3.73's and 2400 stall.

The new main body came with baseline jetting of 72 84 assuming front PV only. I'm fairly certain stock for the 4778-2 was 66 76. Thanks again.

72-84 is about right for a 750 cfm carb. You might want to start about 76-84 and lean it out if needed.

Good luck :)

Eric,

Al is a butthead and I for one would offer him no advice.
His Camaro is nice but it's a garage queen.
It will never see the track. In fact it rarely comes out of the garage.
I expect next he will get hooked on chassis dyno numbers and join the import crowd.

Of course his brother whom I know pretty well has a wide variety of Holley pump cams and also knows how to use a die grinder to clearance the manifold for the big rear pump.....but his phone never rings.

Oh well...........

OK....I am his brother and I'm giving him crap.:hurray: :waving: :beers:
That's what brothers are for.
I need to get him to go drag racing....with a different car!

Ron

Who let HIM in here???

http://www.novas.net/forums/

:D You guys crack me up . . .

My 700DP came with 30cc rear as well as front, too.

:D You guys crack me up . . .

Yeah, I was a bit hard on Al in that one.
It is a very nice Camaro and runs very well.
Being a convert, we well never get an ET though.....

Ron

...Being a convert, we well never get an ET though.....

Ron
You should be able to get a few ask to run clocks off. Then make a couple shake down passes letting off early. Then let 'er rip. :thumbsup:
It works around here anyway. At least a few times a year. A buddy of mine run 10's on spray with his t-top T/A. (no cage):clonk: