SB engine gurus...please step inside

[RedBarchetta]

I have some questions regarding the fuel pump eccentric.

I finally tore into the motor last night and discovered that the one piece eccentric that I have was very loose, spinning on the center bolt (which was finger tight). Avoided disaster, to say the least, and that explains why the motor quit (i.e. no fuel pressure...imagine that!).

I'm a Chevy guy by training, so please bear with me as I work through this R&R. The dowel pin that comes off the camshaft is exactly flush with the cam gear (for the timing chain). No signs of stress or duress...it may have simply worked its way forward (backward?) into the camshaft. As I see things, that little dowel needs to protrude through the cam gear by about 1/8" (certainly no more or it will interfere with the bolt washer, and any less might not provide enough "grip" to keep the eccentric from re-spinning in place).

First question. Do I have to pull out and reset that dowel pin properly (or replace it entirely)?

Second question. What's the best trick for doing that?

Third question. I've heard of "two piece eccentrics" and I've also heard of eccentrics that have a tang on the back that engages somehow with the cam gear, and it's this tang that keeps the eccentric in one spot. I've also read that it's the breaking of this tang that can result in the condition that I currently have. Do I have options here rather than resorting to #1 and #2 above?

Thanks a bunch for your combined expertise. I've been pretty comfortable with the tear down up to this point, but I'm now venturing into unchartered waters.

Oh, and one other thing. The guy who invented the Ford SB layout whereby when you pull the timing cover and get junk/fluid in the oil pan no matter what? He deserves a swift kick in the crotch. I had to pull the pan while I was at it (and I just re-did that sucker and had a nice, leak free seal).

-Dean

[Jac Mac]

You have a one piece eccentric--you have been supplied with a cam equipped with a short dowel that is intended for a two piece eccentric ( tang type ).

Remove that dowel--usually a large set of side cutter pliers will suffice, using the gear spigot of the cam for leverage.

Buy & fit the correct (longer) dowel.

Clean the gear retaining bolt threads along with those in the cam ( check the length of that bolt to ensure it is not to long along with the correct thread--- some later cams use a 7/16 thread rather than 3/8 IIRC.

The single piece eccentric also uses a thick washer that prevents the dowel moving forward once all fitted up. A drop of loctite on the bolt thread when finally fitted & torqued to 36 ft/lb is good insurance.

The gear set for a two piece eccentric usually has a raised lip in center that allows the outer ring to turn freely once fitted.

[RedBarchetta]

Originally Posted by Jac Mac

You have a one piece eccentric--you have been supplied with a cam equipped with a short dowel that is intended for a two piece eccentric ( tang type ).

Wonderful...So how come this lasted as long as it did? Was there just enough of the cam dowel showing through the gear to grab the eccentric before it receeded back into the camshaft?

Originally Posted by Jac Mac

Remove that dowel--usually a large set of side cutter pliers will suffice, using the gear spigot of the cam for leverage.).

Not sure I follow you on using the gear spigot for leverage.

Originally Posted by Jac Mac

Buy & fit the correct (longer) dowel.).

Where can I source this? Machine shops? Hardware store?

Originally Posted by Jac Mac

The gear set for a two piece eccentric usually has a raised lip in center that allows the outer ring to turn freely once fitted.

So what you're saying is that I can't just install a two piece like what should have been there to begin with?

I'm going to try to post a pic tonight.

Thanks,

-Dean

[blykins]

Now now, don't be too hard on the SBF stuff....I can think of a few SBC bright ideas that weren't so bright.

Dean, have you ever thought about switching to an electric pump?

The longer cam dowel can be bought at any engine machine shop. Sometimes, cams will come with both dowels so you can use whatever suits your requirements.

[Jac Mac]

Red,
I am too slow a typist to respond to your SBC analogy's, will wait until you post pics in case you have any other potential issues! BTW, that distributor is good to access isnt it!

[RedBarchetta]

The distributor in front is definitely a better idea. But the guy that engineered the mechanical fuel pump configuration and the non-isolated timing cover still deserves a good kick in the crotch.

Brent, this whole episode has certainly got me thinking in that direction. Might be easier to leave well enough alone, button up the front, install a cover plate on the fuel pump port and start plumbing a Holley Red (with regulator). More money overall, but might be less hassle in the long run. I just don't know right now....

[blykins]

That's the setup I had on my Cobra. Holley red pump, with a $29 Holley fuel pressure regulator. I've never ran a mechanical fuel pump before.

You could probably be electric for less than $150.

[RedBarchetta]

To heck with posting pics...I found the problem. After removing the cam gear (that took a little prying and wigglin', but it eventually worked itself loose), I was able to pull out the cam dowel with my bare fingers. This dowel is 5/16" diam x 1 3/8" long. And I was able to push it in somewhere between 1/32" and 1/16". The eccentric is 5/32" thick, so do the rough math and that little sucker is a good 1/8" too short!

Since the pin is not in there very tight to begin with (let's assume it's been spinning and dancing in there for its 10,000 mile life), I also have to assume that it may have ever so slightly opened up the hole in the camshaft where it's inserted. Said another way, another dowel of the same diameter will only work if it's the correct length (meaning it will just barely butt up to the inside edge of the eccentric, where the washer backing up the hold down bolt will keep it from dancing around. Throw in some heavy duty Loctite and that may keep the dancing to a minimum. But even if the Loctite does nothing, the dowel won't have anywhere to go.

Anyway, I suppose I need to visit a machine shop and ask for 5/16" x 1 1/2" dowel.

FWIW, the timing chain/gear is a Cloyes double roller set and the motor was assembled by RDI in North Carolina. Oh yeah...the crank bearings wore out prematurely, too (that was last year's R&R).

I would still like to understand why a two-piece eccentric wouldn't work on this set-up (just so I know).

Thanks,

-Dean

[Jac Mac]

Dean,
Not uncommon for that dowel to only be a very light push fit--varies from cam to cam in my experience ( coming up to 40 years now ). Find an old 289/302/351W cam and steal the dowel out of it.

I would just get the new longer dowel or even just cut an 1/8" long piece off a 5/16" bolt to stick in the hole before fitting the existing dowel, though given that its had a bit of pain recently your probably best to bin it!

Two Piece eccentric- assuming the cam gear does not have the raised lip on its front face you will have to make up a washer to fit between the inner part & the front of the cam gear that is slightly thicker than the outer ring in order that it can rotate as designed when its all bolted up. This washer will also require provision for the tang that fits into the dowel hole.

[PANAVIA]

Jac Mac has the right idea here, I have been messing with SBFs for 25 years and agree with his dowel pin assessment(s). I am embarrassed to say , that one time I used a ball bearing to shove down in the dowel pin hole to space the dowel out. --Steve

[RedBarchetta]

Thanks, guys. I will try to source the new dowel pin locally. If I'm not successful with that, I suppose I could hijack my kid's skateboard for the ball bearing.

[RedBarchetta]

Found the correct dowel length at a local metals supply house this morning...cost me all of $1.02 with tax.

Yeah, think about that for a moment. A $1.02. By the time I add up the gaskets, oil, distilled water/Water Wetter, replacing the water pump (might as well...it's all apart), AND ALL MY LOST TIME AND LABOR, a little more care and measuring during the manufacturing process (at RDI) would have prevented this little mishap and saved me a LOT of $$$.

That motor was built some 8 years ago. I still may send them an invoice/bill just to clear my mind.

-Dean

[madmaxx]

Is there anyway the a loose dowel could change the timing. In other words does the dowel ensure the camshaft sprocket stays where it is supposed to. The reason I ask is I hated, loathed, my electric fuel pump and wanted to go mechanical but the dowel was to short. I called eddlebrock and they told me to send the cam to them and they would install the longer dowel, if I were to do it I would mess up the timing. Who is correct, non issue as of now for me since i have a mechanical fuel pump but always wondered.

[RedBarchetta]

Before I pulled the timing gears, I realigned the dots on both (this put the dowel in approximately the 6 o'clock position). So long as I don't move the cam during reassembly it should align correctly because of the dowel. Just have to be careful not to be off one tooth, but again as long as the cam doesn't move I'm okay. With the complete valvetrain in place there is already much friction/pressure being exerted on various cam lobes, so it's not going anywhere. I also have the battery disconnected and the ignition keys on the seat so nothing stupid happens.

EDIT: To answer your question, so long as the dowel (loose or not) was engaged with the cam gear properly, there would be no loss in timing. It would have to be very sloppy loose (i.e. a 1/4" dowel vs the 5/16" that's in there) for a timing change to occur.

[Rick Parker]

The dowel should be a VERY snug fit in the cam. If for some reason when you install yours and it is a slip fit, you might want to put a couple of "pricks" (sorry) on it with a sharp punch, then use red locktite on it. It must not wobble in the bore, or stick out above the surface of the installed eccentric. If it is necessary to tap or drive it with a hammer, be careful to not drive out the cup plug that covers the cam bore behind the flywheel.

[RedBarchetta]

Thanks Rick. Someone else told me the same thing...take a good quality punch and put a couple nubs around the circumference. I'm also going to stop by a machine shop during lunch and scope out other hardened pin sources...way too much effort on this job to have to go in there, again.

[Jac Mac]

Man, some of you guy's are a worry & then some of you worry too much!

[RedBarchetta]

Yeah, these aren't Swiss watches we're repairing, but attention to details is important to many (including myself). I visited an actual engine rebuilding & supply shop during lunch and the foreman gave me the correct dowel.

Junior's skateboard has been sparred.