Is my carb ok?

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Chadderbox70

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Hello,
I have a 360 LA block, J heads, mild cam, hooker headers, , A904 torqueflight with 3.91 suregrip, 2500Stall, currently 600CFM Edelbrock.

I have an edelbrock Performer RPM manifold I would like to install, in place of the performer 318/360. This manifold recomends a bigger carb, 650 cfm or more.


I have a Holley 4777 650 CFM double pumper, I am hoping I can make it work great,
I see most people talking about 750s being more ideal on an engine like this, and I also see people saying double pumpers are better suited for a manual. I hear people saying too big a car, kills response but gives more power on top end,

any takes on if this 650 DP would be great? can it be tuned well enough with my combo?
 
I like the 650 DP better than the 600 eddy for your combo. It will perform better if it's set up right.
 
You have it, use it. I've had double pumpers on automatic cars. Work well when you get them set up right.
 
Yes go with the 650 Dbl. Ball park jetting primary 66 with a 4.5 power valve. With 74-76 jets in the rear and a plug no power valve on the secondary side. try there go out pound it hard, stop pull out #1 spark plug see how it looks, jet up or down from there.
 
Fisher said:
Yes go with the 650 Dbl. Ball park jetting primary 66 with a 4.5 power valve. With 74-76 jets in the rear and a plug no power valve on the secondary side. try there go out pound it hard, stop pull out #1 spark plug see how it looks, jet up or down from there.
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I agree with this except the power valve as a 4.5 is opening too late and may give him tip in issues. Use a vacuum gauge and measure vacuum at a CRUISE and take 2-3 numbers off of that and that's your PV.

If you have 18 or more inches of vacuum at cruise you will have a hard time getting a PV that opens when you want it. So you do the best you can.

I have 15 inches at a cruise and I'm using a 10.5 and probably should be a 12.5.
 
Put vac gauge on motor put motor in gear with foot on the brake see what you have i will guess 8-10 inch of vac go down 2-3 from there? all depends on what kind of vacuum you make with your cam.
 
Picking a PV based on idle vacuum, park or in gear, will not get you the "right" PV except in the world of picking winning lottery numbers.

The DP on manual, vac sec on auto is for people that can't tune a carb. Plenty of cars with autos and DP carbs out there that run great.
 
crackedback said:
Picking a PV based on idle vacuum, park or in gear, will not get you the "right" PV except in the world of picking winning lottery numbers.

The DP on manual, vac sec on auto is for people that can't tune a carb. Plenty of cars with autos and DP carbs out there that run great.
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I have picked the power valve like this for the last 30 years, hasn't let me down yet. The power valve is really just the off idle to full throttle transition. Its all in how your car drives.
 
Fisher said:
I have picked the power valve like this for the last 30 years, hasn't let me down yet. The power valve is really just the off idle to full throttle transition. Its all in how your car drives.
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And that's the way Holley does it, BLP does it and countless other and it's still not the best way to do it. Doing it that way opens the PV so late in most cases that you get a tip in stumble and guys try to cover it with accelerator pump shot.

Why all these people are telling people to tune like that is beyond me, other than its easier to check vacuum at idle rather than get a longer hose and run it into the cab.

In the small block forum there is a video made by Mark Whitner who PROVES a power valve doesn't open at idle or affect idle. So what your idle vacuum is is rather irrelevant when it comes to setting PV opening.
 
A stock-ish 360 with a "mild cam" will likely want the PV opening a lot sooner than a 4.5 will open. That combo should be cruising in the low 20's" for vacuum. Only one way to find out though.

I'd just start with the stock set-up for a 4777 and go from there.
 
At the end of the day, you cant tune the car on the internet. Buy a tuning jet kit, some different power valves, squirters, and grab your hand tools and go get dirty and tune it in the garage and on the road.
 
If you swap out the PV for a plug and take 'er for a spin with a vacuum gauge glued to the windshield, you will know right quick, when the PV should begin opening.
And if the MJ is too small you can tailor the PV opening point to smooth it out. On a streeter,I like to run early opening PVs and small MJs, whenever possible. It's a little nicer to drive IMO.

But yeah, DP for the win.
A 600 is just way too small
 
Thanks for the replies, everyone has real good advice!
Theres a ton of snow up here in Canada so it will be a little while before I really can chime in with results!
 
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