I hoping you guys can shed some light on this…

A little background:
This past weekend I picked up a 1989 F150 LB 4x4 with a 300 4 speed and 3.55 gears to use to tow my 2500# boat a few times during the season. I got it for a song because it doesn’t run. The current engine had just been replaced 3 days before it failed, I’m guessing from the condition that it was just a junk yard engine, the old engine is still in the bed of the truck. The guy I got the truck from said the engine just died quickly and didn’t sound good as it died.

So I started checking it out, the engine cranks over fine, as smooth as you could expect..
No spark…
Pulled cap, rotor not turning…
Removed distributor, the cam is not turning…
Oil pump turns freely and generates pressure when spun with drill…(pump not seized)
Watched 1st cylinder valve train through the oil fill cap, no movement, (cam not broken)

I haven’t pulled the front cover yet but feel that the cam gear is definitely shot!?

This is where I really get confused. Because I still have the old engine in the bed of the truck and its much easier to get at, I decided to pull the front cover of that motor to get an idea of what I will be looking for on the real engine,. To my surprise, this cam gear is wasted too, missing a half dozen teeth in one section. I remove the gear, its only plastic (phenolic?) and I’m able to turn the cam, so its not seized. What could be causing these failures?? Is this a common problem? Is the 300 an interference engine ie. can the cylinders contact the valves? What are the chances that I’ll be able to get away with just replacing the gear set?

Thanks in advance
Kevin

 

I know those cam gears can strip the teeth off ,But Ive personally never seen one do it . Im not 100% sure , But I dont think the 4.9L is an interference engine , If Im wrong you will see a post correcting me . If you turn the engine over by hand , just so you can watch to see if the cam moves & it doesnt move then the cam gear is dead . Id say both engines were likely driven hard with little maintenance . Infrequent oil changes , hot running engines will kill parts like the cam gear a lot sooner than if the owner took better care of the truck . They arent hard to replace , You simply take a chisel to the old gear to split it & use an installation tool to press the new gear on the camshaft . They are kinda pricey , About $90 from Ford . Another thing too is shredded cam gear teeth can end up down in the oil pan , the front cover bolts to the front part of the oil pan .

 

You said that the cam gear is plastic ?????? there is the problem. I went to Napa and bought a set of steel timing gears for about $40.

Plastic gears?? We are talking about the gears on the front between the crank and cam right??

 

Are you sure it's a 300? I thought only the 240's came with the phenolic gear. That's what my 240 had, I've never seen one on a 300.

 

I'm 99.9% certain its a 300, the one in the bed was the original engine, and I don't think 240's were available in 1989.

From what little research I have done, it seems that only the HD 300's had steel gears from the factory, the regular ones had phenolic, but all the aftermarket/replacement gears are aluminum. Is this because they know they wouldn't hold up?

Kevin

 

I don't think that only HD's came with the steel cam gear. I'm positive mine has a steel gear, but it's not a HD from what I've looked at so far. I believe the switch from steel was an attempt to quite the "timing train". Mine whines like crazy, typical 300... on second thought the "only on HD's" may have been a dated policy of Ford - at least after '79.

 

My 300 has steel gears from the factory?!?!?!? I thought all 300s had the steel until the EFI models came out? Does that mean my could possible be a HD with the forged steel crankshaft? Is there anyway to tell? Hopefully it is!

 

Talked to a Ford Service Mech. today. He said that the "Plastic" gears is the only reason that he knows od a crank going south by cloging the oil screen.

 

Sounds like the classic teeth gone/engine dead syndrome on the 240/300 I6's. I'd give good odds that you can replace the timing gear set, line up the timing and probably get the engine to fire up. The question is which enigine is in better shape overall? Obviously you should go for the better of the two but you'll probably have to get both running to determine that (outside of any obvious damage from a visual inspection). One suggestion that I have is to remove the pan and clean it out along with the pickup (replacing the main seals of course!) and to remove the cam from the engine before replacing the cam gear. Believe me, you are far less likely to damage anything when you do this and you're more likely to get the gear fully seated. Heat gear/freeze cam/use anti seize. Plus, you'll get to inspect more of the engine this way. If you're gonna go for an 8 yard gain, you might as well go for 10 and the first down! -Restoman
PS Don't let the lifters fall into the pan and get mixed up if you pull the cam! They need to stay in their original bores or you risk quick failure!!!

 

Could you please elaborate on the process of installing the cam- Before installing my new BlueRacer camshaft, I have to freeze the cam and heat the gear (for obvious reasons) and install out of the engine? Using an install tool? Then sliding the assy into the block and align with crank gear? I was under the assumption that the cam gear simply bolted directly to the camshaft with four bolts. Please help, I don't want to screw up the new install of camshaft.
Thanks.

 

same thing happened to my boss's truck(89' F-250 inline six). he just replaced the gears and cleaned out the oil pan put it back together and its been running fine ever since. how many miles were on it when the first engine was replaced? chances are you may get the same miles out of the engine with new gears and proper maintenance if the rest of it is ok. if it were me(of coarse i overkill on everything) i'd rebuild the engine completely if the rest of the truck is in good shape. then you know what you've got.

 

speaking of cams, i changed mine recently, and i can't get a bolt back into the front. i put one in, tightened it, and then the head of the bolt prevented me from putting the timing cover on. what's the deal with that? is there some special thin-headed bolt or something? i knew i should have kept better track of the one i pulled out.... is that bolt even neccessary since the gear is pressed on? this is the only straight six i've ever worked on, so this is all new to me.

 

No, it's not necessary, the 300 doesn't run a bolt in the cam, that's exactly why you can't get the front cover back on.
1982 F100 SWB
300 HD, 9.5:1 compression 1.94/1.60 valves
Clifford 270H, Hedman Hedder
2½" duals
NP 435/2.75 geared 9"
1985 F150 HD, 300 HD/needs a NP 435/4.10 geared 8.8
70,000 miles
1980 F100 Custom, 300/Np 435/2.75 geared 9"
60,000 miles

 

cool, thanks. just seems odd that there's a threaded hole that doesn't need a bolt in it.