Holley 750 carb adjustment

[Wietse]

Fuel pumps has been replaced, i've re-installed and modified the fuel hoses and filters.
I put the inline K&N filter before the pump, put the filter with the vapor line after the pump.
All hoses were still in good condition, no damaged lining inside to be seen.
I screwed up a bit, as i was thinking i have new fuel hose but that is 3/8" and i need 5/16".

After that all was done and dusted i was thinking it's best to do the carb now as well so stripped it and just finished rebuilding.
Did find some black dirt/sediment inside but nothing obvious blocked or so, replaced all the gaskets and seals and installed a 5.5 power valve on the primary as i will not be able to get a higher vacuum anyway.

Tomorrow i will build it back on the car and test/adjust everything and see if i get any improvements.

 

[Wietse]

Well, things went a bit different...maybe some of you read my other thread about the mechanical fuel pump issue i ended up with.
I filled the carb float bowls with fuel and run up the engine which started fine, actually surprised after rebuilding the carb myself.
Anyway, the engine emptied the float bowl and died, turned out my fuel pump push rod was that far gone it is not operating the pump anymore.
Most likely the old one still pumped a bit but this new pump did not displace a single drop anymore.

So, as there is nothing i can do there at the moment i emptied the fuel tank and lowered it.
After removing the pick-up it was quite clear....no suction screen in place.
I did find a lot of pieces of black fiber, see picture.
There were heaps of small pieces lying about so i put a gallon of fuel in there and washed them all in 1 corner and sucked them up with a vacuum pump.
Tank is clean and new pick-up installed.

All in all, the fuel supply is fine, instead of a dying fuel pump it was the push rod that is worn out.

 

[oldbee]

Up until the last year I had never heard anyone talk about worn out pump rods. Mine has 86k on it and still works fine(?). I didn't even know there was a measurement..

 

[Wietse]

Yeah, original length should be 3.220", as seen mine "lost" 0.233" which causes a very short pump stroke (if any) on the fuel pump.
Apparently the original ones are the ones to keep.
As some others said, they are the ones properly heat treated to be hard enough to survive.
Most aftermarket push rods are not designed for survival, the manufacturers rather have it to run to destruction and take the camshaft with it so you can buy another set of them.

With that said, i think it is a good fail safe to have the push rod to wear out first rather dan eating your camshaft straight away.
When on aftermarket equipment just change them every so many miles/years and keep a good eye on the camshaft.
With a price of $20 a year for just that you can't go wrong.

I got a link for a NOS push rod which i ordered and ordered another 2 Howards from Summit racing.
Time will tell, guess i will go for the Howards first, let them polish the camshaft up and take it from there.

 

[oldbee]

I do/hope that the cam lobe is harder than the pump rod.......

 

[Wietse]

Looks like, my push rod is 0.223" shorter but the cam is still there

 

[Wietse]

Here some pictures of the camshaft lobe for the fuel pump.
It shows some small damage on surface but no deep grooves have worn in.
Think a new rod will polish it up.

 

[miller]

It shows some small damage on surface but no deep grooves have worn in.

Hard to say, long distance, but 'if' the lobe is within reason, go for it. Might wear a little smoothness into it.
Had a feeling about your pickup screen...bet it was lovely...sitting at the bottom of the tank. Exactly why I didn't put one on. Seems today's gas will eat at some of the older car's parts. Of course, old age could have done it, too.
At least your getting somewhere on it. Good show!

 

[Wietse]

Yeah, i left the screen on the new pick-up, but as most plastic material deteriorates over time when in contact with hydrocarbons.
It becomes brittle and will break, therefore i guess the new one will sit it out for some years to come.

But indeed, progress made already thanks to FBBO and it's members!
And now waiting in the sun with a cold beer until UPS stops in front of the door

 

[Wietse]

After all repairs i've finalised everything today and went for a short test drive.
Car idles and drives better then before for sure.
Set the fuel bowl levels, set the idle adjustment screws as good as i could find the sweet spot, around 8.5 Hg vacuum @ 850 rpm.
I've left the initial timing at 18*, the bushing for the max mechanical advance should be 18* (black bushing installed how i could see) but it shows 21* on the balancer.
Never double checked the timing readout is spot on, i will need a good piston stopper for that and preferably have the cooling fan removed for good acces for cranking etc.

I always had a feeling it's running on it's last strokes with a bit un-regular rpm's at cruise, poor shocking idle (engine block shakes all over the place) and hesitation especially at hard throttle.
I have not gone that far by flooring the throttle, just want to cruise around for a bit just to allow the fuel pump push rod the bead in against the cam and make sure everything is ok.
Specially after having pulled all fuel hoses around the engine, just want to make sure there are no leaks etc.

 

[Wietse]

Checked the push rod again after 40-50 miles and found only 0.002" wear, so guess that will be ok.
Did some long runs at hard throttle but all is well so far, not a single stroke is missed.

Also filled up the car today with fuel, was curious to see what the fuel gauge will show as i replaced the sending unit.
With the tank full it showed slightly over full on the gauge, weird thing was when putting the fuel back that i pumped out for the tank removal, around 30 litres, it showed empty on the gauge.
So basically i have 30 litre reserve
Total tank capacity is around 90 litres i guess?