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-   -   holley 650dp for my 355 (http://www.hotrodders.com/forum/holley-650dp-my-355-a-230920.html)

prettyboyced 03-19-2013 01:11 PM

holley 650dp for my 355
 
i have a sbc 355 afr 190 xfi 280 cam 576.570 lift rpm intake 1 3/4 headers 3500 stall turbo 350 trans 3.73 gear 18 intial and 36 total timing i have a holley 650dp and it runs rich at wot i have to step .040 quirter to get rod of bog at take off and 64 in the primarys and 76 in the sec 6.5 power valve floats are good trickle out when i shake the car . i heard im suppose to disconnect the sec and run it lean in the primarys till it surge and go up 1 jet and tune the sec at the track for 1/ 4 time. will this cure my richness 1st time dealing with a holley

Richiehd 03-19-2013 01:39 PM

Quote:

Originally Posted by prettyboyced (Post 1658379)
. i heard im suppose to disconnect the sec and run it lean in the primarys till it surge and go up 1 jet and tune the sec at the track for 1/ 4 time. will this cure my richness 1st time dealing with a holley

Not sure about that, I will tell you I think the 64 is a way lean. I would step up to at least a 68 or 70. Make sure your throttle blades are set as per info on this site (read about transfer slot) is it 4 corner idle? Check your vacuum at idle, vacuum advance off and plug port. Take your reading divide by 2, that should be your power valve number. Start there. How do you know its rich at WOT?
Regular Holley? or Holley HP?

prettyboyced 03-19-2013 03:19 PM

Regular holley 4777-2 stock jets were 67 and at wot the car was sluggish and wasn't building rpms fast I disconnect the sec and with 67 it was ok but when I put in 64 I had more power

cobalt327 03-20-2013 01:08 AM

Quote:

Originally Posted by prettyboyced (Post 1658379)
i have a sbc 355 afr 190 xfi 280 cam 576.570 lift rpm intake 1 3/4 headers 3500 stall turbo 350 trans 3.73 gear 18 intial and 36 total timing i have a holley 650dp and it runs rich at wot i have to step .040 quirter to get rod of bog at take off and 64 in the primarys and 76 in the sec 6.5 power valve floats are good trickle out when i shake the car . i heard im suppose to disconnect the sec and run it lean in the primarys till it surge and go up 1 jet and tune the sec at the track for 1/ 4 time. will this cure my richness 1st time dealing with a holley

Which 4777? You can try 73 jets in the secondaries. 64 pri. is bit small, but if it's not showing signs of too lean it might be OK, but in my experience the stock jetting was very close (primary 67, secondary 73 for 4777-3/4).

A 65 PV might be too high, depending on the idle vacuum (in gear if AT). This wouldn't make it rich- it would be too lean, but it needs to be selected correctly, regardless. A post explaining selecting the right PV: http://www.hotrodders.com/forum/1976...ml#post1657515

F-BIRD'88 03-20-2013 07:43 AM

it runs rich at wot

Possible the air cleaner lid is too close to the top of the carb.

i have to step .040 quirter to get rod of bog at take off
Recurve the distributor for 24-26deg at idle and 34-36deg at max advance (a 10deg mech advance curve)
Be sure the idle timing does not drop off when idling in gear.
This will vastly improve the throttle response. and idle quality.

With thee 650-700 DP carbs a great upgrade is the Holley/Proform HP 750 carb body kit.
Now you got a 750HP carb with improved flow/power and throttle response for a fraction of the price.
The swappable air bleeds are a great upgrade too.

lg1969 03-20-2013 08:23 AM

Prettyboyced, The combo is good, The mistake was using Holley 650DP. DP carb do not work well in cars with automatic trannys. In some cases it will bog right off idle if you floor it. That is caused by not enough air flow going threw the secondary at low RPM. As soon the secondary are open quick you also loose air flow on the primary, resulting a bog. Too much gas and not enough air. You should of used a Holley 650 vacuum secondary. It's even worst when you are using a big cam. Hope this helps

F-BIRD'88 03-20-2013 08:54 AM

Quote:

Originally Posted by lg1969 (Post 1658625)
Prettyboyced, The combo is good, The mistake was using Holley 650DP. DP carb do not work well in cars with automatic trannys. In some cases it will bog right off idle if you floor it. That is caused by not enough air flow going threw the secondary at low RPM. As soon the secondary are open quick you also loose air flow on the primary, resulting a bog. Too much gas and not enough air. You should of used a Holley 650 vacuum secondary. It's even worst when you are using a big cam. Hope this helps

This is not true.

lg1969 03-20-2013 09:22 AM

Quote:

Originally Posted by F-BIRD'88 (Post 1658639)
This is not true.

Oh Really... I had similar problem years ago. Using DP with an automatic. It was a mistake. I have been playing around hotrodding for over 35 years.

lg1969 03-20-2013 11:23 AM

BTW: DP will cause rich condition when accel pump dumping raw gas then a lean condition when accel pump has used up the shot. VS carb will only give lean bog condition because the secondary has open early.

F-BIRD'88 03-20-2013 11:24 AM

Quote:

Originally Posted by lg1969 (Post 1658650)
Oh Really... I had similar problem years ago. Using DP with an automatic. It was a mistake. I have been playing around hotrodding for over 35 years.

It only proves you are not very good at tuning the carb and the rest of the engine correctly.
And have not improved your tuning method in 35 years.

A 650 DP is easy to dial in, especially with the stated 3500 stall converter.
Once you know how....
Once correctly tuned this combo will fly and with very clean crisp throttle response right from idle.

It is a matter of setup.

Getting the idle circuit right is where you start. Starting with the right amount of timing at idle. Which is more than what the OP is using now.
Get it up around 24 to 26deg. (a short 10deg mech advance curve)
you won;t need that .040" acel shooter any more either .

The 650 carb on this motor is actually a bit too small for max perf.
That is easy to fix too.

Timing should be 24 to 26deg at idle base timing
max timing @WOT should be 34-36deg.

Then: vac advance should be about 10-12deg at max ( high vacuum part throttle)
but adjusted for correct rate by drive testing. (not all pegged in at idle)
Use ported vacuum on the carb. (in this specific application it is just better)

Go back to a stock carb jets and a .031" pri and sec shooter,
The acel cam and linkage arm will need adjustment. Often these get bent.
Make sure the shot starts right when the throttle moves from idle.
Probabily needs new fresh spark plugs now too.

Use a 4.5' rated pri power valve. Get some sec jet extensions.

Remove the carb flip it over and reset the pri and sec throttles at idle.
T slot exposure at idle....

Thebest oer jetting will be very close to this.
The HP 750 carb body upgrade is a great way to make this carb even better.

And the 72 and 84 jets that are included in the 750HP body KIT are just about right.
(sometimes the idle air bleeds need some fine tuning...not that hard)
When you do do this upgrade look at the idle air bleeds size of what ever carb was your donor carb.
that is your default idle air bleed size to start with. it will be very very close to optimum.
From that point you find the optimum idle/off idle tune using a AFR gauge. A simple narrow band type is fine.

Often with a choke and a low profile air cleaner the air cleaner lid is just too close to the choke, resulting in richnesss when @ WOT.
The HP carb body fixes this too.
You kill may birds with one stone.

F-BIRD'88 03-20-2013 11:39 AM

If you have a auto transmission with a stock low stall converter and espdcially combined with a hiway gear
like 2.73 or 3.08.....THEN..... a vacuum secondary carb is often your better choice...
Especially on mild low power near stock like engines.
That is where a Vacuum secondary carb has an advantage.

But:

This engine/car needs a double pumper carb for maximum performance.

It will GLH once dialed in.

(a good 750 vac sec carb can be made to work very well on this car too.
BUT: It will require as much or more actual work and mods and tuning to make it just right for
maximum performance on this specific car too.) The work required is a bit different in a few areas....but just as much effort and more cost} It will not be better.or faster ...just different.

And there is a cool HP body upgrade kit for the vac sec carbs too.

Again it is a matter of knowing how and doing it.

lg1969 03-20-2013 11:44 AM

You can get max performance using vacuum secondary carbs, also. It's not just for a stock setup.

F-BIRD'88 03-20-2013 11:51 AM

Many many carb tuning problems are actually ignition system issues.

lg1969 03-20-2013 11:55 AM

In that area yes I agree.

Richiehd 03-21-2013 05:46 AM

There is always something to learn here.


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