650 DP Help

B

black_bullit

Club Member
I need to rebuild the carb on my junk and need some input.

The bitch is running pig rich, I think I popped a PV during a N20 back (Carter pumps are fucking junk).

I have a stock 94 F150 long block (E7 heads, shitty roller cam), RPM intake, shory headers, and a cheater kit. It ran a 12.5 with a low pressure 100 shot.

I'm thinking a 9.5 PV would work with such a high vacuum setup. Err are there 2 PVs? I was going to drop the jets down also. I have some 66s, any ideas on jets and power valves(s)?
 
How much vacuum at idle in gear? That should tell you what pv to use. As for jets let me know what you need or want to try. I have a bunch you can try then you can just buy whatever you end up using. If it has a rear power valve just plug it??
 
I guess I'll have to put some gas in it (it's been sitting for 2 years) and see what the vac gauge reads. I have some jets but may take you up on the offer. Thanks.
 
WOH WOH WOH...need more input here ..You dont just start popping in new jets on the main circuit...
When did it start running rich??? Has it always ran this way???
Where is it running rich??? Idle??? Top End??
How do you know its running rich???
Your leaving too many varibles open...How do you know its a power valve??
Air Cleaner dirty???
Is it pulling over on the boosters??? If so might be power valve. What is the Inches Hg at idle??
Need more input...
Holleys are not rocket science...they are very easy to dial in.
 
The Big Cheese said:
WOH WOH WOH...need more input here ..You dont just start popping in new jets on the main circuit...
When did it start running rich??? Has it always ran this way???
Where is it running rich??? Idle??? Top End??
How do you know its running rich???
Your leaving too many varibles open...How do you know its a power valve??
Air Cleaner dirty???
Is it pulling over on the boosters??? If so might be power valve. What is the Inches Hg at idle??
Need more input...
Holleys are not rocket science...they are very easy to dial in.
Click to expand...

It always ran a bit rich but the times I had it at the track it was late in the year and cold. After a back fire it started blowing black smoke out of the tail pipes (it would do it before when I drove it during warm weather). Black smoke at idle too. I put a 600 VS on it and no black smoke.

Remember, stock F150 long block, I think it's jetted too rich from the get. I drained the gas so I don't know idle vacume but I'm sure it's damn high with the tiny stock truck cam.

Air cleaner has 200 miles on it if that. I drove out to the dirtway 4 or 5 times and ran some laps.
 
Ok this could be a number of things not related to the main circuit or jets.
First you need to check float levels at idle..then check Hg at idle. While your checking HG you can trim the idle mix a bit with the idle mix screws. All this considering timing is on. Pull the most hg & RPM you can out of the mixers.
If that doesnt cure your black smoking at idle then we need to look at the boosters see if there are pulling over from the backfire may have plugged something up in metering block. Also check that the thottle plates in the back are closing and not pulling fuel in. Look for a carbon build up ring under the plate. make sure this is not making plates stick.
As for the power valve..sounds like your want top performance so go by a plug kit and plug it like suggested.
After everything on idle checks out then it is time to main jet it.
For main jetting you must be able to read plugs effectively. This is not a easy task if you are running an MSD. You have to do what is called a power jetting run with new plugs. This is performed as you run the vehicle up thur the gear full tilt till you get into high gear and pull for a moment then turn key off coast over to a stop and pull a plug..
Again plug reading is really a science but if you look deep inside the plug you will be able to see the fuel or mix ring size deep inside the plug on the insulator. Color will tell if you need to jet or not. You are looking for a 2-5mm ring color light brown or grey.
If you get this you are on the money for main jets.

How to read a plughttp://www.dragstuff.com/techarticles/reading-spark-plugs.html
This is a good read...

Try this stuff and repost on how you did..
Always here to help
~Cheese~:_slide_:
 
Don't plug the front PV if you're gonna drive it on the street at all. Plenty easy enough to get the primaries tuned w/ a PV in the front. Having it in there when you're making heavy part throttle acceleration increases and allows you to jet for better cruise a/f.

No point in running one out back though but a 650 likely has a plug out back anyway. If it's track only, plug 'em both and square jet the bitch.


Main jetting....agree plug reads are hard. Once you have idle squared away jet down on the primaries till you get a lean surge at cruise. Come back up 3. Re-evaluate. Should be damn close. Jet sec's at track for high mph.

Your starting points sounded good. Very good chance the backfire killed that PV.
 
I can;t find one in the holley catalog. It should be a rochester Q-jet replacement carb.

two versions. square bore and spread bore. the spread bore single feed is an old bastard.
http://www.holley.com/0-4777C.asp

http://www.holley.com/0-4777S.asp

there is an even older spread bore that has a single feed inlet like the 600cfm carbs. they are all good units. If i was building a street car the spread bore Holley 650 DP is a good choice and you can run it without power valve up front for good economy.


motorcitymustang said:
standard 650 dp is a squarebore
Click to expand...
 
http://www.holley.com/0-6210.asp is a spreadbore. Both listed above are square. Just one w/ the new fancy finish. There's http://www.holley.com/BrowseCatalogs.asp?Catalog=Reman&Page=282 but they're rebuilds from the looks of it.

If you're gonna go that far just go to an Edelbrock carb IMO. Easier to work on (once you grasp the metering rods thing), cheaper, and better street throttle response.

I thought about it after that "past cars" thread. Except for '97 and half of '98, until Nov. of '04 I drove nothing but carbed stuff for daily drivers (since '86). I held out as long as I could. :)
 
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I agree that the edelbrock carter AFB clone might be a better choice. Honestly I really like the Q-jet when it's modded up properly its a great working and power producing carb. Not so good with a single plane though. Its a much better dual plane carb becuase of the split barrel size on a single plnae it will create distrobution issues.

motorcitymustang said:
http://www.holley.com/0-6210.asp is a spreadbore. Both listed above are square. Just one w/ the new fancy finish. There's http://www.holley.com/BrowseCatalogs.asp?Catalog=Reman&Page=282 but they're rebuilds from the looks of it.

If you're gonna go that far just go to an Edelbrock carb IMO. Easier to work on (once you grasp the metering rods thing), cheaper, and better street throttle response.

I thought about it after that "past cars" thread. Except for '97 and half of '98, until Nov. of '04 I drove nothing but carbed stuff for daily drivers (since '86). I held out as long as I could. :)
Click to expand...
 
I haven't had a Quadrajet since the Chevelle I had in H.S. and I quickly swapped it for a Holley vac sec. Should have tried to mess with it. I had the Edelbrock 750 on a Vic Jr. sitting on a big cammed 302 (24? duration at .050). The Holley probably would have done better on the top end but that AFB was GREAT on the street once dialed in. After messing w/ that Edelbrock I had wished I had tried to mess w/ that Q a bit more.
 
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