JBradley500

I'm trying to get the most out of my current fuel setup. Its mainly stock besides the LP Piston pump, drilled banjo bolts and a fs1221 fuel filter.I was wondering about the spacer between the pump and the block.

I guess im wondering if its too thick will it shorten stroke of the piston? That seems logical and then it return it would be limiting how much fuel the pump would move.

Has anyone thought about/messed with that shim or am i just thinking craziness?

BC847

The lobe on the cam is what drives the mess. That being said, that's the limit to the total stroke length. Is your lobe worn beyond spec?

Perhaps you could check the total stroke that the piston itself can make in it's bore, and compare that to that afforded by the cam to see if there's an "adjustment" that could be made to the LP's push-rod, so as to position the piston in it's bore for optimum pumping.

JBradley500

Well i was hoping you had already done that lol. I figured someone had already figured out how much total stroke the pump could handle and how much spacer exactly would give you full stoke without pushing the piston through the pump lol

BC847

The spacer plate has no effect on the stroke of the pump. It just holds the pump far enough away from the block that the push-rod doesn't jamb the piston through the pump's head. It seems they could just shorten the push-rod and do away with the spacer. (Most likely because that same pump body is used on a number of engine blocks).

JBradley500

ok that's what i was wondering. i didnt know if there was stroke to be gained or not but i guess if the rod is always riding on the cam lobe then you dont have anything to gain.

thanks.

ZSkibo

JBradley, you could always go to the HP spring and regulate it down for max volume all the time...

JBradley500

I could but im scraping the barrel of funds now. I like the mechanical pumps though so if i need to, i will be doing that. How much does it cost to do that?

i guess i have another question (3 actually). how come regulators dont work like on a gas engine? how come you cant just put an inline one in with no return line? is it because it limits volume too?

ZSkibo

Well, you have the LP pump already right?

All you'd need to add is the regulator between the pump and filter head and a return line back to the tank. Figure $100 for the regulator (or cheaper used on ebay), a couple bucks for line and fittings, and a bulkhead fitting for the spare tank bung. I bet if you shopped around on ebay you could do it for less than $100. Find yourself a junk HPLP and pull the spring out of it.

This is the regulator I used:
http://cgi.ebay.com/ebaymotors/Mallo...#ht_2091wt_941

JBradley500

Yeah i have the pump installed. Thanks for the info. I will make sure once i get my 30 psi (dont install a 15 psi lol) ill know where my WOT pressure is then ill go from there.

Thanks for the link. Theres guys out here that probably have a piston pump laying in the garage that i can sneak parts off of.

dodgetrucker75

you need the spacer because the piston LP engines also had a fuel heater and it bolts up between the block and LP, with out the spacer, it will stroke too far and probably blow the LP right off the block, the regulator with return is nessary because with out a return, the regulator will limit the pressure to the IP but basically dead head the LP and again blow it up

BC847

That's not accurate. The spring within the LP is what pushes the piston to send the fuel out and to the IP. The cam operated push-rod simply pushes the LP piston back against the spring. If one were to dead-head the output the the piston lift-pump, it would simply stop pumping fuel as the piston/spring can't move the fuel. The push-rod would flop back and forth in it's bore I suppose.