Proform Metering Blocks

[BBKNARF]

Has any one experience Proform billet metering blocks ? I just installed a set on my Proform 950 cfm body, jet size 79 front 84 rear, 4.5 power valves, so far I have all 4 mixture screws set at 1 1/4 turn out and its blowing out grey smoke out of the exhaust at idle, I set everything the same as it was on my orginal metering blocks and had no problems.

[firefighter3931]

Has any one experience Proform billet metering blocks ? I just installed a set on my Proform 950 cfm body, jet size 79 front 84 rear, 4.5 power valves, so far I have all 4 mixture screws set at 1 1/4 turn out and its blowing out grey smoke out of the exhaust at idle, I set everything the same as it was on my orginal metering blocks and had no problems.

How fast is the engine idle speed ? You're not idling on the main curcuit are you ?

It's obviously rich at idle so you need to lean it out. Too much engine vacuum can pull excessive fuel from the boosters at low engine speed....what's your idle vacuum reading ?

Make sure the ide air bleeds are clear and there are no obstructions. A quick blast with carb cleaner might help. You might also need to play with the bleeds to dial in the idle mixture. 


Ron

[BBKNARF]

Thanks for the tips Ron, I only know the basics on carb tuning, my engine idle is 1000 and the last time I checked idle vacuum it was in the spring it was @ 7, and I don't know anything about air bleeds, even though you can change them on my carb. When I bought the main body I did not touch the air bleeds. Tomorrow I will try to blast a little carb cleaner, do I blast the cleaner down the air bleeds or do I remove the metering blocks ? Thanks, Frank.

[firefighter3931]

Frank, just blast some carb cleaner down the air bleeds and see how it responds. 


Ron

[BBKNARF]

Amazing what a blast of carb cleaner will do, thanks Ron  I took it for a little drive I noticed a little hasitation like it almost wanted to backfire from a set of lights but as soon as I gave it more gas it was fine, I guess it needs a little more tuning and also I will check the timing.

[firefighter3931]

Amazing what a blast of carb cleaner will do, thanks Ron  I took it for a little drive I noticed a little hasitation like it almost wanted to backfire from a set of lights but as soon as I gave it more gas it was fine, I guess it needs a little more tuning and also I will check the timing.

That's better !  It might need a larger squirter or it may just be a matter of tuning the accelerator pump circuit.

Where do you have the timing set at currently ?



Ron

[BBKNARF]

I have #40 squirters front and back, 50cc pumps, im not sure what my inition timing is but my total advance timing is set at 36, Im running a MSD distriuter and a 6AL box. Thanks Ron.

[firefighter3931]

I have #40 squirters front and back, 50cc pumps, im not sure what my inition timing is but my total advance timing is set at 36, Im running a MSD distriuter and a 6AL box. Thanks Ron.

Frank, try installing the black bushing in the MSD distributor....this will give you 18* of mechanical advance so when you set the total at 36* you will have 18* at idle. Most aftermarket cam profiles like lots of base timing to improve vacuum and throttle response. I bet it runs better with the black bushing 


Ron

[BBKNARF]

I will try that, thanks alot Ron !  I know the camshaft im using is not producing alot of vacuum, its a Comp Cam part #23-702-9 with the duration of 248/254 @ 50

[firefighter3931]

I will try that, thanks alot Ron !  I know the camshaft im using is not producing alot of vacuum, its a Comp Cam part #23-702-9 with the duration of 248/254 @ 50

The 286XR street roller is an excellent grind  ....should be perfect in a hot street/strip type build. That cam will definately respond well to increased base timing, guaranteed ! The "stock" bushing in the MSD distributor is designed for cam profiles that produce more idle vacuum than your's does....you need to swap it out. 

Take an idle vacuum reading before and after just to compare....let us know what you come up with. 



Ron

[BBKNARF]

I took a vacuum reading at idle it read 8 in. hg. @ normal running temp. Changred the bushing from silver to black took another reading, it did not change   took it for a drive it seemed ok but as soon as I steped on it it started to sputer, I checked timing still @ 36 @ 3000 rpm. I dont know if the advance springs have anything to do with it but right now im using 1 silver (light) and 1 blue (light) spring.

Frank.

[firefighter3931]

Frank, swapping in the black bushing should have increased the idle vacuum somewhat....did you check to see how much timing you had at idle with both bushings ? Try mapping out the timing curve in 500rpm increments so we can see what the timing curve looks like. I'd like to see what it's doing for advance and where it stops.


Ron

[BBKNARF]

Sorry Ron, I did not check the timing @ idle with both bushings  I did the 500rpm increments like you said, this is what I got :

1000rpm = timing 17, vacuum @  8 (idle)
1500rpm = timing 27, vacuum @ 16
2000rpm = timing 29, vacuum @ 17
2500rpm = timing 35, vacuum @ 19
3000rpm = timing 36, vacuum @ 20

This was done with the large black bushing, I also noticed as I was timing, the rpms were going up and down by 200rpm is this normal 
Before I turned off the motor I gave it a couple of hits of gas it sputered a little out of the carb. I'm sure my neighbours love me this morning.
Thanks for helping me out on this Ron, I cant beleave this is happening just from changing the metering blocks.

[firefighter3931]

The timing is good, no need to mess with that anymore ! 

It sounds like the carb is flooding from what you're describing. Look down the throat and see if you can see fuel dripping out of the boosters with the engine at idle. If so, you have an issue with the float level...either it's set too high or it's sticking from debris in the needle and seat.

The correct float fuel level : the fuel should be even with the bottom of the site plug....no higher.

Lemme know what you come up with 



Ron

[BBKNARF]

Back to the drawing board, I looked down the carb everything looked good, rechecked the float level, good  so I decided to order an overhaul kit, it took almost a week to come in 
After rebuilding the carb I took it for a little drive and so far so good I'll wait until the weather gets a little better and I will take it for a longer ride, thanks again Ron  maybe some day I will meet you at the track.

Frank

[firefighter3931]

Good work....the main body probably had some varnish in it that was affecting the idle mixture adjustment. 

Glad to hear it's running better 



Ron

[greenpigs]

So it sounds like I should spray my proform main body down with card cleaner before assemble. Any other issues with the metering blocks? I might as well upgrade that also.

[RECHRGD]

Sorry Ron, I did not check the timing @ idle with both bushings  I did the 500rpm increments like you said, this is what I got :

1000rpm = timing 17, vacuum @  8 (idle)
1500rpm = timing 27, vacuum @ 16
2000rpm = timing 29, vacuum @ 17
2500rpm = timing 35, vacuum @ 19
3000rpm = timing 36, vacuum @ 20

This was done with the large black bushing, I also noticed as I was timing, the rpms were going up and down by 200rpm is this normal 
Before I turned off the motor I gave it a couple of hits of gas it sputered a little out of the carb. I'm sure my neighbours love me this morning.
Thanks for helping me out on this Ron, I cant beleave this is happening just from changing the metering blocks.

That 200 rpm deal is the exact same thing that my car is doing!  Did you resolve that issue?  I've got a proform main body on a holley 750dp.  See my (what would cause this thread).  Thanks Bob

[firefighter3931]

So it sounds like I should spray my proform main body down with card cleaner before assemble. Any other issues with the metering blocks? I might as well upgrade that also.

Yep, hose it down good before assembly 


Ron

[firefighter3931]

That 200 rpm deal is the exact same thing that my car is doing!  Did you resolve that issue?  I've got a proform main body on a holley 750dp.  See my (what would cause this thread).  Thanks Bob

Bob, it sounds like the rebuild of his carb fixed the problem. Try squirting some carb cleaner into the idle air bleeds to see if that clears it up. 


Ron