Proform 67101c install and write up.

[Canadian1968]

I purchased a the proform 67101c main body to install on my holley 3310 750 Vac secondary carburetor. This main body gives you down leg booster , adjustable air bleeds, and no choke horn. It is basically a holley HP series main body at fraction of the cost. Best of all I keep the efficiency and driving manners of the vacuum activated secondaries.

When I opened the box I was surprised to see all brand new non stick re usable gaskets. A new metering plate , new fuel bowl screw gaskets and a pair of 72 and 84 fuel jets . The body itself us also aluminum and considerably lighter than the original main body

In my case I have already modified my carb by removing the rear metering plate and installing a meter block so that I can easy change the jetting . The proform comes with gaskets for front and rear meter blocks and fuel bowls which is a total bonus!

I got started on disassembling my carb, pretty straight forward process . With the bowls and blocks removed you can see some slight differences in the two main bodies. Mainly the well where the power valve sits. The holley main body has a considerably larger area, as well the hole in center is actually a threaded mounting hole for one of the 6 screws thar hold the throttle plate to the main body. On the proform this hole is completely blocked off from PV well. I see this having 0 affect on anything performance wise.

From the top the difference is obvious. Most notable is the different boosters and adjustable air bleeds .

The proform main body comes with 31 pump nozzle. I had installed a 35 in my original body. I swapped this over. In the process found another surprise. The proform comes with the hollowed out screw that holds the pump nozzle in place. This allows for maximum fuel flow for an unrestricted pump shot !

I am going to install the same jetting I was running before ( 72 front , 72 rear) . Will see how this performs .

Over all very happy with this product. The added surprises in the kit really make this a great " bang for buck " purchase as far as I am concerned.

Unfortunately I'm in Ontario Canada, aside from a start up and idel setup in won't be able to do much else until spring time!

 

[WileE]

A fan of the 3310 from 50+ years ago, thank you for a well written take on your modification.Looking forward to your results !

 

[RemCharger]

All good news. I would use the 84 jets as a starting point. It may like an 81-82, but that's all in the ballpark of where it should be

 

[Canadian1968]

Have 3 more points to add.

The main threaded hole for the air cleaner stud is a different size and shallower than the factory holley 1/4". For the proform you will need a 5/16 rod or you can buy adaptors . For the price of an adaptor your honestly better off buying a piece of 5/16 threaded rod.

Also something I thought worth mentioning is the different style orfice the Proform main body has for the signal to activate the vacuum secondaries. The proform has a small brass tube that protrudes into the venturi just shy of 1/8". The end is cut on an angle, which increases the surface area of the opening. My thoughts are this will provide a much stronger signal for the vacuum diaphragm? Possibly changing the required spring to get the secondaries to open correctly ?


Last point is , the proform body does not support the ported vacuum fitting on the primary fuel bowl.

 

[Geoff 2]

Ported vac has to work off the primaries. My guess is that you have the pri & sec met blocks reversed.

 

[Canadian1968]

Ported vac has to work off the primaries. My guess is that you have the pri & sec met blocks reversed.

Huh? The picture IS of the front primary block.

The proform mainbody does not support ported vacuum

 

[Jonas Nordstrom]

Cool thread.
The proform bases does have the ported vac.

 

[Canadian1968]

I have a small update to add.

I had set of 71 jets laying around, that I knew I was never going to use again. Knowing that I had 84 jets that came with kit ( but think they will be to big ) I decided to experiment drilling out the 71 jets . I went smaller than 84 but bigger then a 74.

I have had the car out a few times this summer. And have to say with nothing else changed the car idles better. There is definitely crisper throttle response . Over all power level is hard to judge until I make it to the track .

At cruise the car runs a bit richer 13.8 vs the original that running at 14.7 . I.m thinking the adjustable air bleeds may account for that as the primary jets are still the same 72.

A few WOT pulls show 12.4 on my wideband which seems to be right where it likes to be based on readings with the original mainbody that gave me my fastest ET. So I actually May have got lucky drilling out the jets !

Looking forward to trip the track for some real world numbers and to test out the new calvert mono leaf springs !

 

[oldkimmer]

Well, what’s the verdict? Kim

 

[RemCharger]

Well, what’s the verdict? Kim

Thread 'Port work payed off ? NEW PB' Port work payed off ? NEW PB

 

[Canadian1968]

Well, what’s the verdict? Kim

Over all performance is great. But I am still struggling to get the around town drivabiliy dialed in.

Before I did thr port work this last winter the car had extremely slight almost un noticeable stumble at very light throttle . After the head porting the problem got much worse.

My understanding or at least theory is that that the main body is basically a race design now, ment for max flow and rpm. Where it seems to struggle is the low rpm low air velocity.

You can feel the motor " searching " in the transition circuit. First attempt was to lower IAB size which did not seem to help. I seem to have more success with smaller Highspeed air bleeds. Trying to get the mains to kick in a bit earlier and remedy the stumble I get cruising around town. It's close but not perfect yet !

 

[oldkimmer]

Over all performance is great. But I am still struggling to get the around town drivabiliy dialed in.

Before I did thr port work this last winter the car had extremely slight almost un noticeable stumble at very light throttle . After the head porting the problem got much worse.

My understanding or at least theory is that that the main body is basically a race design now, ment for max flow and rpm. Where it seems to struggle is the low rpm low air velocity.

You can feel the motor " searching " in the transition circuit. First attempt was to lower IAB size which did not seem to help. I seem to have more success with smaller Highspeed air bleeds. Trying to get the mains to kick in a bit earlier and remedy the stumble I get cruising around town. It's close but not perfect yet !

Well good luck 2 ya. I know u will get it perfect. Just a pita. Kim

 

[Canadian1968]

Thanks I'll keep playing with it and give the details when I get to where I'm happy with it. Overall I would recommend it if your looking to get every little bit you can out of setup without having to go buy entire new HP holley carb for 3 times the price

 

[RemCharger]

What was the end result with the PV? Is the vacuum hole drilled? Can you see it kick in on the AFR ?

 

[Canadian1968]

What was the end result with the PV? Is the vacuum hole drilled? Can you see it kick in on the AFR ?

I did bump up to an 8.5 PV from my 6.5 It helped richen up my roll in AFR. But the stumble happens at much higher vacuum, the PV is not in play at this time. The problem is all in the transition , i have slots adjusted correctly, pump shot is good, pump cam is good, its just that 5 -15% throttle where i get the stumbling. I can watch / feel it clear itself as I either keep steady throttle position and RPM/ speed increases or let off throttle and RPM/ decreases . ITs that knife edge transition point that seem to struggle with.

Are you asking about the ported vacuum port? in the main body? If so no that is not drilled in the Proform main body.

 

[RemCharger]

I did bump up to an 8.5 PV from my 6.5 It helped richen up my roll in AFR. But the stumble happens at much higher vacuum, the PV is not in play at this time. The problem is all in the transition , i have slots adjusted correctly, pump shot is good, pump cam is good, its just that 5 -15% throttle where i get the stumbling. I can watch / feel it clear itself as I either keep steady throttle position and RPM/ speed increases or let off throttle and RPM/ decreases . ITs that knife edge transition point that seem to struggle with.

Are you asking about the ported vacuum port? in the main body? If so no that is not drilled in the Proform main body.

Sorry you had mentioned a hole completely blocked off in the PV well. But I see it must have a vacuum port or the valve wouldn't operate.
Do you still have the tiny jets in the secondaries?

 

[Canadian1968]

Running about 78 jet in the rear. I say "about" becuase I drilled out an extra pair of 72 I had laying around. AT WOT at the track the other day I was getting 12.4 AFR so seems to be right in the ball park

 

[Geoff 2]

What is the timing at idle?

 

[Canadian1968]

What is the timing at idle?

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