[Matt 69]

Can anyone tell me what the correct spec is for the amount of lift on the fuel pump cam lobe eccentric for a big block Chevy? How much of a stroke is there supposed to be to actuate the fuel pump lever?

 

[Larger Dave]

I do not know the answer to this question. If someone has a BBC on their motor stand they could put a magnetic base dial indicator on it and zero it out on the base circle. Then rotate the engine over to read the actual lift amount.

If you are having issues I would remind you that even though a SBC fuel pump will bolt up to the BBC block, the arms are different. It will not work.

SBC fuel pump arm above

Compared to the BBC fuel pump arm. Difference is the bump on the end of the SBC pump.

Big Dave

 

[Matt 69]

Dave,

I am trying to confirm the correct pump stroke. I have the Carter M4889 fuel pump which is a big block pump.

Matt.

 

[bilodeaulynn]

Is it the same stroke as a sbc?

 

[Matt 69]

I don't know.I would think so. Fuel pump stroke should be the same for both types of engines. This question has stumped all of the techs so far at Lunati, Summit, and Jegs as well as a few others that I have not heard back from yet. It's surprising that this is so hard to find the answer to. Thousands of big and small blocks built, bought, and sold every year with hundreds of custom camshaft designs out there and this eludes everyone. The quest for knowledge continues.

 

[Larger Dave]

Alternatively to what I mentioned above using an engine on a stand and using a dial indicator: If you have a cam in hand get out a caliper and measure lift and turn cam ninety degrees and subtract base circle diameter to get stroke of fuel pump.

Big Dave

 

[Matt 69]

I agree Big Dave, it is easy to figure out, but I guess no one is in the building stages of a big block right now or has a big block camshaft laying around.

 

[67econobox]

Matt,
measured installed with pump rod the travel is 0.395". That is on a brand new Crane Cam with zero wear. you will not get the correct measurement by measuring the cam lobe. It is round (approximately 1.500" measured on a new Straub cam) and offset ground like a rod journal. I happen to be putting two engines together right now and am at the perfect stage on both to measure and inspect parts.
Joe

 

[Matt 69]

Thank you Joe! You have been most helpful! That is what I came up with when I measured my rod travel on my own engine. I needed to confirm that my lobe was intact. Thank you again sir.