Say, has anyone had the camshaft lobe for the fuel pump go flat on a BBC? I know there's been "issues" with cams going flat with the current oils, but the fuel pump lobe? Engine is a 454, mild performance build (@ 6 years ago), Comp Cams XE268, @ 30,000 miles on the engine. Still runs good, but needs primed with fuel to start, once running, there's enough rpm to "bump" the fuel pump so it'll pump. I have a sick feeling that the cam is going flat, and the fuel pump lobe is toast....
Never herd of it, you would have to have a very strong spring in that fuel pump. I would say it's something else making it hard to start or the wrong or faulty pump. Check your fuel pump rod also for correct length & wear...........
I've checked the pump, even swapped it out with others I know are good. And cranked engine over with no lines hooked to it. Just no "suction" from the pumps..... Rod looks fine too, even swapped in another that I welded some material on to "lengthen" it, just to try out. The lobe isn't totally "flat", as I cranked engine over with pump removed and checked, but I fear there isn't enough lobe to adequately actuate the pump at the low rpm of starting... I wouldn't think fuel pump springs are that tough either...even in HV one's like I've got...haha... I'm afraid I may just have to pull the cam and measure the lobes to see where I'm at. Was just curious if anyone has seen this problem before, as it is unusual...
Also if the rod is to long it won't let the pump arm return back for the next cycle. I understand you had the trouble before welding up the rod end but hope you didn't put that end to the cam....
kirban 2 cents worth The lack of ppm of zddp in the oil will affect not just the cam and lifters but anything that has extreme pressure points in the engine. If you are running current oil has a star burst of SM on the container by law it only has between 600-800 ppm of zddp....before government intervention (EPA) it had 1,800 ppm..... Also, cam wear will not be consistant. Issue is not just at break in anymore. We are the largest seller in the US of zddplus sell direct to major companies such as Isky-Crower-Erson....among others...good friend of mine has produced it owns the largest collection of turbo buicks in the USA..... if you send me a pm with your email I can have engineer email you info.... [email protected]
If the oil wiped the fuel pump lobe out you have bigger issues like cam lobes to the lifters that would have way more pressure applied. If the cam lobes are flat it could make it hard starting also...............
Have you tried changing the pump? At least you can run a electric until you have time for a cam change.
Yeah, that's what I'm afraid of. Starts just fine once ya get fuel in 'er.... It did die on me the other day when it was idling for a long time....now I know why, pump lost it's prime and carb just ran outta fuel. Yeah, I was going to do that, but if the fuel lobe is in fact flat to the point of not operating a pump, I have little faith in the remaining cam lobes.... I'm just frustrated, this is in my nice truck and while I have the time to tear it apart, no $$$ to put back together... I do have another cam, but it's pretty big and most likely would hit the pistons... I think my next move is to throw a dial indicator on a lifter to check actual cam lift and see what the measurement is compared to the cam card. (If I can find it...haha). Thanks fellas....
Get a dial indicator and measure the fuel pump lobe lift. It is only .25 total stroke about. Push the rod in so it will follow the eccentric. I have never seen a flat fuel eccentric in all the engines I have worked with. If the lobe is toast the push rod will be wiped also. Go with the most likely cause first. Pump.
kirban 2 cents worth Here is an interesting FACT.... My source who produces zddplus which in a 4 ounce bottle has enough ppm of the molecule zddp to treat a normal 4-6 qt oil capacity back to 1,800 ppm allowing car owners to use whatever current sm oil they want synthetic or conventional. Have you ever wondered what ppm of zddp was in the oil from the factory on a new Corvette which is one of the few high performance V8 engines made today.... we know....we convinced a local chevy dealer to save some of the oil from a customer who came in to have the original oil removed after a mere 400 miles....(way before break in).... that factory break in oil from GM in a new Corvette had 3,000 ppm of zddp in it...the oil it was replaced with Mobil One...under the SM star burst only has between 600-800 ppm........ The comments others have written are correct wear translates into metal shavings going somewhere in your engine..... The issue is real while solutions are many we have the easiest....also have Don Garlits as a user & spokesperson....Would not be able to sell to Isky and Crower and others unless it was a proven product...those companies have been in business for many many years.... Ironically, my source not only owns the largest turbo buick collection but among the companies he owns he owns a DNA lab...can't get any higher up the ladder for quality control than owning a forensic dna lab.... [email protected] even comp cam has its own oil out now.....its not just a break - in issue as originally thought.....
That's the thing......there isn't any "metal" anywhere.... And yes, I've cut open the oil filter.... Maybe it's as simple as the two, new "replacement" pumps are as weak as my HV one that's was on it...stranger things have happened.
I'd swap out the pump first. I think that if the pump had a return spring in it strong enough to flat-lobe a cam, it would have snapped the pump body when you first started it up, and like you said, no metal. I'd check the filter, and float level too, just for ha-ha's.
I'd just stick my finger on the pump pushrod and rotate the crank by hand to see what kind of lift you have on that lobe. Measure it and then measure what the fuel pump arm needs to move to pump. I would check everything else before I went at the cam. And there's alot of other thing's to check in a fuel system. Just like if you don't get the pushrod on the low part of the lobe to install the pump in the first place it would be a bitch to even line up your bolts. If your pump bolt's will fall in where they belong at any rotation of the cam, then I'd start wondering for sure what the heck is going on.
I think you have a bad pump if you were having issues with oil screwing lobs up the pan would have grey paste all in it! At least this is what I would think. Good luck with your problem
kirban 2 cents worth I would at the very least install a magnetic drain plug that will capture any "grit" floating by......or they sell magnets that attach to the end of oil filters.... Otherwise metal shavings may be so obscure to detect? Just my thoughts... Good luck may be just a bad fuel pump set up....still if you are running of the shelf oil look at the starburst symbol on the back...its kinda like a date code...runs in alphabetical order...example back in 1988 or so it was sf, then sg, sh sl they did not do a si and sm came out maybe 2 years ago....sm is when the ppm really took a dump from sf which had 1,800 ppm before the reduction of zddp...everything happens gradually...
They do have a lot of cam Issues with the BBC. Never heard of that on but is is very possible. If you have changed the pump and the rod with the same issues then I would say the cam is bad. W
I've got a few wore out BBC cams I could cut the pump lobe off for you..... Seriously, put an indicator on the pushrod and see how far it moves.
fuel line may be have a very small hole (fuel line top of tank), then sucks in air like a hole in a drinking straw. When you manually prime it it can overcome a very small hole. When it sits it looses its prime, especially if you have leaking carb.
When I worked at a chevy dealer a carbed celebrity (1982) came in with the fuel pump lobe gone on a 2.5 so it can happen.
Just an observation from an 87 bbc motorhome I had a while back.The factory fix for earlier chassis that had supposed vapor lock issues.Electric pusher pump in the tank running forward in 1/2" hardline to the mechanical pump. There was a short molded hose from the hardline to the mechanical pump that even at idle and even with the electric pump pushing fuel to it you could see the pulse of the mechanical pump in that molded hose on the suction side trying to pull that hose closed.
Thanks for all the feedback and ideas fellas... I'm thinkin' it's as simple as the fuel pump (usually is the easy stuff right? haha) I'll be returning the one I have for another. When pumped on the bench and the inlet blocked, the pump lever moves to easy....whereas a pump I have here for a SBC get's tight immediately and can't be pumped with the inlet capped. The stroke on the fuel pump rod is @ 3/4"...so the cam is fine. While I'm at it I'm replacing the fuel line on the tank valve, as they look swelled.
I wasd told that if you have a billet core cam and a standard steel fuel pump push rod it will flatten out the lobe. I'm not exactley sure what a billet core cam is but I researched by engine to make sure I didn't have one. At least you can always go with a electrical pump.
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