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GT40 Tech - Engines/Induction/ExhaustMotors and engine related - right here!
I'm coverting my motor over to drive a mechanical fuel pump. However, my two piece fuel pump cam has a locating tab that my cam gear does not have a provision for. I vaguely remember there was another another type of fuel pump cam, a single piece, but did it have a tab?
The round hole in the fuel pump cam goes allow the cam sporket retaining gear to be bolted to the cam. That square notch (bad angle) is a punch out that is actually a tab, the tab is just facing you so you can't see it.
Looking for a solution around this issue. Any you fellows encounter anything similar?
Its been awhile, but as I remember its a matter of early (289, etc) and late (302) timing gears. I am running a one piece eccentric with the FMS 302 in my '65 Mustang (mech. fuel pump) which I had to swap the gears out on. The GT has the stock (later) gear set that came with the FMS 302 in that car, of course timing covers are different as well.
The locating tab goes in the dowel hole of the cam gear. To make that setup work you will have to put a large dia fender washer suitably notched for the tab between the eccentric and the gear. The washer should be just thick enough to allow the outer ring to spin freely. Check clearance with Timing cover before final install.
The other option is the early one piece eccentric which require's a longer dowel for the cam .
What if I took the inner piece I have now and installed it without the outer piece, AND drilled a hole into the cam gear and tapped it for like a 10-32 screw. Then put the screw through the eccentric and the cam gear? What is the deal with the outer piece?
The one piece eccentric was made/formed out of 0.200"( approx) steel & hardened for wear protection where the fuel pump arm runs against it. The cam dowel was longer and extends thru the cam sprocket by approx 0.150" to locate it,& the washer that you have now prevents the dowel from coming out.
There would be no need for the 10/32 screw, The outer ring by spinning on the inner reduces wear on the fuel pump arm, If you dont use the outer ring you may reduce the fuel pump stroke to a low enough level that supply may be inadequate at high rpm.
The early eccentric can be found on any small block up to around 1968 I think. To fit it to your motor without changing the dowel get a short piece of 3/8"dia x about 3/8"long round bar turned down to the dowel dia, but leave a small ridge in the middle that prevents it moving fwd thru the eccentric, a small chamfer ground/machined either on the back of the eccentric or front of the sprocket dowel hole will accomodate this.
Okay, sounds like I need an early eccentric, then, I'll get Jac Mac to draw me a picture!
I've got a lathe, I think what you are saying is to make a T. The T will push through the eccentric hole, while some relief on the can gear with a die grinder will allow a place for the top part of the tee to index and stay put.
I used to build a lot of early 289 and 302's. The eccentric for the early motors had a round hold for the dowel pin. You may consider trying to locate an eccentric from an early motor, 64 thru 73 should work.
I would assume the dowel pin hole in the camshaft sprocket isn't drilled all the way through to the front?? If it is why are you not locating the tab in it?? That's where they locate.
Jac is right about the outer ring it acts like a bearing. I'd keep this setup if you can. If the dowel pin from the cam is limiting the tab on the fuel pump cam from going in far enough for it to set flat on the front of the sprocket, just shorten the stamped tab alittle.
The possibility exists that your engine builder shortened the original long (early) dowel slightly so that the retaining washer would not sit proud of the sprocket. Or and this is a concern is that a later (short) dowel that has not been pressed fully into the front of the cam. ( DO NOT try to turn the motor over with the cam retainer bolt loose, you will shear the dowel if the valve train is still in place)
The timing set you have is meant to be used with the early one piece eccentric & longer dowel. The little piece I suggested you turn up was simply a piece of dowel that would have a raised ridge halfway along its length which would hold it captive between the eccentric& sprocket when fitted in the dowel hole. However in light of what you have now told us I recommend checking out just what is really going on regards the dowel position. The Mechanical Mayhem that will result if its wrong does not bear thinking about!
Well, here is another picture. The cam looks like it used a late model shorter pin from the start as it doesn't look to be ground off. The cam and pin either came that way or the pin was put into a lathe and turned down correctly.
In any event, the pin completely fills up the hole in the cam sproket and it doesn't protrude outward so that I can use a early model eccentric.
Dammit.
What to do now?
Got too many parts setup for the conversion to mechanical pump to toss it all - cover, water pump, fuel pump, etc.
Looks like the best option is to simply drill a hole in the gear opposite the one that is already there. Should be able to do this without removal by being extremely careful with a vacuum, and plently of masking tape/papers around to deflect and catch filings.
What you mentioned should work fine you don't have to drill very deep. Shorten the tab to fit the depth of you new hole.
Are you positive that the pin is pressed in all the way??
If you take a washer and grind it off where the pin hole is in the cam sprocket, you could tighten the bolt back up with the pin showing. This would keep the cam from moving back and you could try tapping it in further with a punch and hammer.
In all reality it's not that hard to loosen the valve train up until the poly locks are fairly loose then turn the motor upside down and then carefully roll the motor over which will push the lifters out far enough so you can pull the cam and shorten the dowel pin slightly. The push rods will hold the lifters from falling out and Gravity will keep them out of the way.
Seems like a lot of work for using the mechanical pump, just get a fuel plate block off for a big-block chevy and bolt it to the cover and be done The mech pumps always seemed dinosaurish (sp), especially when running a high rpm motor, the SB ford single cam bolt thing was always suspect too but I guess both work pretty well over the years...
Just out of curiosity why the drive for the mech vs. electric pump (might have missed it earlier in the thread).
Sandy
__________________ RCR GT40 #11 348" Alloy SBF, 930 Box, Gulf 1075 Trim Now in the Garage, still under construction...
Try Jim's idea to check that the dowel is fully home. If that works , then you can fit using the existing hole. If not , drill another as you have suggested & either make up the Small Dummy Dowel for the early eccentric or fit up the two piece unit you already have. I will warn you now that even when you have that two piece one correctly mounted you will wriggle it and start to doubt its durability. But they seem to work, the only one,s I have seen fail were mounted in such a manner that the outer ring could not spin.
Jac Mac-----( ps. Grind the C*** p/n's off any parts you use, make's them more reliable! )
Thanks for all the help, forum really works for this sort of stuff!
Jim I checked that dowel, but it was not going in any further. So, it must be a dowel for late model cars that have no need for a eccentric.
Sandy, on the why - simplicity, less is more and all that jazz. Seriously though, I didn't think it would be such a PITA to swap to a mechanical. I figured it'd be a new cover (got it from Oliver/John, who's been very helpful in this), bolt on eccentric, and go. I wanted the mechanical to make the Lola very "simple" and sort of true to origin. I even didn't use Fran's nice electric gauges and went all SW mechanical gauges to really make it basic.
Jac Mac, I drilled the new hole a little while ago and it'll fit on there now with no trouble. If I get some time this evening I'll put the front of the motor back together and be done with it.
If I mount the two piece cam the outer ring will not spin - it can't. The inner, when the cam bolt is tight, will hold down one side of the thing and trap it against the cam gear.
If I put a washer under the inner piece, to space it up like 0.100" (optimal would be less, just mock up here) then it will spin, but it seems like a flimsy POS.
I think I'll use the early model one piece and tap that hole I drilled, and afix it that way. I think I'd feel better about all that.
I knew this would happen!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Quote:
Originally Posted by Ron Earp
Jac Mac,
That thing is a POS. (WONT ARGUE WITH THAT)
If I mount the two piece cam the outer ring will not spin - it can't. The inner, when the cam bolt is tight, will hold down one side of the thing and trap it against the cam gear.( & now you have re-read post#3)
If I put a washer under the inner piece, to space it up like 0.100" (optimal would be less, just mock up here) then it will spin, but it seems like a flimsy POS.( DITTO- but the washer needs to be thinner)
I think I'll use the early model one piece and tap that hole I drilled, and afix it that way. I think I'd feel better about all that. ( Good Idea)
Fuel Pump Eccentric - How to secure? 
I knew this would happen!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! 