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Carb size ? 68 F100

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Carb size ? 68 F100 Empty Carb size ? 68 F100

Post  whitefield April 1st 2020, 10:19 am

Good morning guys , I hope all are doing well . I have a customer with a mild street 68 F100 that has the following. .030 97 351w roller with flat top Pistons pro max heads , rpm performer air gap intake. Shorty headers , and 2.5 inch exhaust, bullet hyd roller camshaft .570 lift on intake and exhaust. Duration @ .050 is 227 intake and 232 on exhaust. Lobe seperation is 109 install 4 degrees advanced. C6 transmission 3000 stall 3.50 rear gear. Edelbrock and Holley have both recommended a 650 vacuum secondary carb . I recommend a 750 double pumper.

What are you guys recommendations? Thanks Whitefield
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Post  norm April 1st 2020, 10:50 am

I agree with you. A 750 double pumper is an awesome all around carb.
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Post  rmcomprandy April 1st 2020, 4:56 pm

whitefield wrote:Good morning guys , I hope all are doing well . I have a customer with a mild street 68 F100 that has the following. .030 97 351w roller with flat top Pistons pro max heads , rpm performer air gap intake. Shorty headers , and 2.5 inch exhaust, bullet hyd roller camshaft .570 lift on intake and exhaust. Duration @ .050 is 227 intake and 232 on exhaust. Lobe seperation is 109 install 4 degrees advanced. C6 transmission 3000 stall 3.50 rear gear. Edelbrock and Holley have both recommended a 650 vacuum secondary carb . I recommend a 750 double pumper.

What are you guys recommendations? Thanks Whitefield

I would recommend the Quick Fuel, BD-830 CFM "Black Diamond" double pumper "SS Series" with the automatic choke.
Especially on a 2 plane manifold.

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Post  whitefield May 9th 2020, 3:54 pm

Customer went with a 750 Quick Fuel . The truck runs much better now. He is however having a issue with blue gray smoke out the exhaust. I am thinking he has a valve guide issues .

He is also experiencing a random ticking noise when engine is warm along with inconsistent idle and throttle response.


What are your opinions and experience with the promaxx heads ?

Thanks Whitefield
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Post  Goldylox_fairlane May 10th 2020, 6:43 pm

Make sure you have good oil return. Sometime s oil drain back holes in heads don't line up with holes in block/ head gasket.

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Post  Goldylox_fairlane May 10th 2020, 6:51 pm

There are also some things you can do to the idle circuit.....takes some time with a micro drill index, brass set screws and a bag of aggravation to get the idle/ cruise almost perfect

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Post  rmcomprandy May 10th 2020, 9:49 pm

whitefield wrote:Customer went with a 750 Quick Fuel . The truck runs much better now. He is however having a issue with blue gray smoke out the exhaust. I am thinking he has a valve guide issues .

He is also experiencing a random ticking noise when engine is warm along with inconsistent idle and throttle response.


What are your opinions and experience with the promaxx heads ?

Thanks Whitefield

The modulator on the C6 trans may be leaking.

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Post  whitefield May 12th 2020, 11:49 am

New modulator valve , still doing the same thing !


Does anyone have any insight to tha promaxx heads? Thanks Whitefield
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Post  Goldylox_fairlane May 12th 2020, 10:50 pm

Promaxx stuff is from overseas isn't it? I heard of the blocks being rough but useable...I can only assume the same for the heads
My dart heads had oil drain back issues and the oil just found it's way down the valve guides.....I was puffing blue smoke as well.
I would also suspect an intake leak somewhere in the lifter valley area.
It could hurt to throw a vacuum gauge on it

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Post  rmcomprandy May 13th 2020, 10:26 am

whitefield wrote:New modulator valve , still doing the same thing !


Does anyone have any insight to tha promaxx heads?  Thanks Whitefield

I don't know about the Pro-Max heads themselves but, I have come across some heads which have no sealer on the intake rocker stud threads into the head and they pulled oil to the intake port under high vacuum.

Personally, I seal those stud threads with "Right Stuff" sealer.

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