The Stovebolt Site Forums The Shop Area Engine Shop Every mechanic for himself?

Please forgive the self-pitying dispair, but I'm gettin' a bit bummed out.

So I post a question about my 235 oil pump over at inliners. Maybe because I'm new there or something, but I got two responses and my thread died.

You guys here have done what you could, and made several good suggestions. TomL and Patrick have also lent their expertise, and been very helpful. However, even they can't tell me what happened. Since I can't find an obvious defect with their products, they infer that the problem is not with parts I bought from them. Local mechanics are worse than useless. The only local resource that may pan out is my machinist who knows what he's doing. But I never have a time to get down there during business hours.

What am I supposed to do? Just throw it back together and hope it doesn't tear up again? Here is the damning part, from a mechanical anaysis:

Has anybody had a problem with their Melling Pump? Its usually a reliabe product from a proven company.

There are a lot of Stovebolt 'mini' HEIs running around, so its not like this is a one-off crappy conversion that just flew apart.

The M4F camshaft is a proven piece, with lots of them running in 235/261s with no similar failure Im aware of.

There is no known machining problem associated with '60 235 blocks, that Im aware of. If there is a problem with my block I'm screwed, cuz there is no way to fix the oil pump mount geometery.

So am I supposed to install a new oil pump, cram a distributor in the hole, and hope I don't wipe the bearings out this time? Sounds a bit un-scientific. This can't be a good way to run a railroad???

chip

Chiphead,

Looking at the '59 parts book, I found the following entry.

1.649 WASHER, Oil Pump Thrust

37-55 ALL, CORVETTE (6 cyl.).......(1/2 I.D. x 7/8 O.D.) ..... p/n 838472

Diagram shows it between pump and distributor gear.

The oil pump listing are:

40-52 ALL,
53 ALL (exc. P.G.) ... (body cast 839159)..... p/n 839157
53 PASS., CORVETTE w/P.G.,
54 ALL, CORVETTE,
55 CORVETTE, COMM., UTIL. (1st Ser.) ... p/n 3702363
55-59 PASS. (6 cyl.),
55-59 COMM., UTIL. (6 cyl.)(2nd Ser.) ... p/n 3836203

If they redesigned the end of the oil pump housing to eliminate the thrust washer you may have found your problem.

The TRW engine parts book shows for Chevy Trucks 235 c.i. Part No 50012 (Chevy # 3702363) (unique to '54), for the later 235's it shows Part No 50019 (Chevy # 3786293) thru '62. For the older 235's it shows Part No 50001 (Chevy # 839157).

The TRW book also lists oil pump screen assemblies. What year pickup do you need? I can give you the TRW number which might help you find a NOS one.

Chiphead - Can't answer your question, but have you asked your machinist if he would meet with you after hours? Does he have a favorite beer or some other offering you can take with you?

As far as the inliners board, I haven't been there in quite some time, they seem to be a pretty tight bunch and don't favor the outsiders.

Don't make it harder than it is. Just take your time and cipher - don't take what the experts are telling you as absolute. Mock it up and measure. If you can't get a feeler gauge between the oil pump and dist gear, use modeling clay like you would to check valve - piston clearance. If the gear is bottoming on the pump before the flange hits the block measure the gap at the flange. A little gear marking paste or Prussian blue should give you a read on the gear mesh, if you can't eyeball it. Spend a little time measuring and you'll know where the problem is - if it still exists with the new parts.
Don't panic and don't give up.
If it doesn't look like this, keep modifying until it does.
http://chuckthetruck.homestead.com/chip.html

I would reassemble with a stock distributor.

Blue,
I'm looking for a '55-57 pickup assy. I'm also going to check if my NOS '60 pickup will work in my '57 pan.
The '60 pump doesn't have a thrust washer or anything, the new pump is machined flat and smooth at the top. However, in my master FelPro gasket kit, there is a white plastic washer that is roughly the dimensions you discribe. What is this plastic washer for??

FredT,
You seem to be correct about inliners. Maybe this place spoilt me, but not everybody there just piled on to help.

Chuck,
Good point about the prussian blue, its something tomL had suggested. I plan on doing it to check type/quality of contact between gear and pump.

How do I use the prussian/layout red to check gear tooth contact?

TonyM, I would use the stock type dist, but I've had problems with them too. One new reman dist chucked its roll pin in my '54 motor, and I hate trying to tune with that dist. However if this problem tries to happen again, I may be stuck with a stock-type dist with petronix ign.

Does the gear on a stock dist ride on the oil pump case? Or does a washer in the dist take the end-thrust?

thanks
chip

OlBlue, I have several original GM parts books , printed in the early 70's. None show any sort of thrust washer or list the part number you mentioned.It may have been deleted by the time my books were printed.I 've had a few 235/261's apart and never seen a thrust washer between the gear and pump, and the 3 I have rebuilt and running over the last 7 years don't have them so...who knows?
Chiphead ,your email is out to lunch,send me an email, I have some info on the mini HEI. Here's my email ,no one else can look at it ,lol. [email protected]

Tony,

My book is a '59 Chevy Parts and Accessories Catalog. I also have a Corvette only P&A from 1971 and the 6 cyl. oil pump illustration doesn't show the washer and there isn't a listing for it either.

My one and only experience with a 235 was when I built one for my '49 using a Speed-O-Motive kit. Had a performance cam, Mallory dual point conversion, headers, Clifford intake with a Carter 390 CFM four barrel. After about a thousand miles, I ended up with 'gold' metalflake oil. I had used one of those bronze aftermarket distributor drive gears and the teeth had worn away on the cam gear. I replaced the distributor gear with a stock one and changed the oil. About a year later the cam started to go flat. Not to long after that, I pulled it out and put a 350 in it. All this was after the machine shop ruined the original 235 block for me. (They were kind enough to replace it though.)

That was in 1978 and I finally sold the 235 a few years ago. I don't have a clue whether it had the thrust washer in it or not.

I feel Chipheads pain though...

Chiphead,

I checked the 1942 Master Parts Price List and it shows the thrust washer.

838472 $.02 (7/8" O.D. - 1/2"I.D x 3/64") 1937-1942

That would make it a pretty common piece (i.e. all 216 c.i.). Per Tonys reply, it seems it wasn't used very long on the 235.

Paint the dist gear evenly with the marking compound, install the distributor (without the oil pump installed if you haven't verified that clearance first), clamp as you would normally, and turn the engine by hand in the correct direction at least two full crank rotations. If you can eyeball it in place do so. The compound will have a "wear pattern" that should be centered on the dist gear. If it is high or low, you'll have to cipher out the best means to correct it. If you have to remove the dist to see the pattern, you'll smear a couple teeth but should still get a good read on the remainder. If the mini-hei is off, just repeat the exercise with stock dist for comparison.

This may be going somewhere...

Blue, what cam were you running? One difference with this motor VS the old 235 is the cam. This HEI worked fine with the Clifford 260M cam in the old motor, but has showed this failure mode with the M4F in my new motor.

Could the cam drive gear be ground wrong on the M4F cam?

What takes the end-play with the stock distributor? Is it the distributor body, or is the gear supposed to contact the oil pump at all??

What is that plastic washer in my Fel-Pro kit for???

thanks

chip

Chiphead,

This picture is from the 1961 Chevrolet shop manual.

Oil Pump - Distributor drive cutaway

Notice the thrust washer between the bottom of the distributor drive gear and the machined end of the oil pump shaft housing. The cam rotates counter clockwise as viewed which means the distibutor gear is forced down against the thrust washer and hence the oil pump.

Look closely at the distributor hold down. It appears to be flanged downward around the distributor housing and would then only put downward force on the gasket setting in the block. Appears, that the distributor has little if any downward force applied from the hold down assembly.

I would expect there to be a small amount of end play in the distributor shaft when installed in the engine. i.e. clearance between the distributor drive gear and the distributor body. If the distribtuor body was pushing down on the gear, then I would expect to see what happened in your engine.

I'll plead ignorance on what the plastic washer is for.

I think the cam in my 235 was a Howard's. It's been 25 years since I did that project and I'm getting a littly hazy on some of the details.

End-Play is one thing I'm going to check with the new pump and the HEI. With parts installed, there should be some endplay of distributor shaft. TomL said anything from about .010"-.050" is fine as long as gear geometery with cam is maintained. IE, gears meshing correctly with above mentioned endplay. I assume that if I have any installed endplay, the distributor is not jamming the gear into the oil pump all by itself.

Now looking at your pic, I see the thrust washer. Is it part of the oil pump? Or does it just sit between the pump and gear? My new pumps didn't have this. Sadly, all my old pumps got tossed before this happened, so I don't have them to look at. Also the pic shows a gap between the drive tang and slot in oil pump. So shaft is not bottoming out there. Thrust must go to top of oil pump.

So is it dist or oil pump problem? Im going to measure old vs new pumps and post the results.

Chip, I was measuring my stock dist with a dial gauge last night for entertainment- it has about 10,000 miles on it. It had 0.007 of end play and 0.001 runout at the oil pump drive tang.

The things some people do for fun!

Chiphead,

From my research yesterday, the thrust washer appears to have been used on 216's and 235's from 1937 thru mid-1955. It doesn't appear to have been used after that. It looks like it sets on the top of the oil pump drive housing.

Since the distributor drive gear runs directly on the end of the oil pump drive housing, I'd be checking how they fit together. The oil pump appears to have a recess machined into it to hold the thrust washer in the picture. Does your pump have the recess and does the gear fit down into it? The late '55 thru '62 pumps (that didn't use the thrust washer) may not have had the recess.

I assume that GM doesn't redo cutaway drawings unless that have to so the picture is probably of an earlier 235 even though it's in the '61 manual.

The new pump I have does not have any recess cut into the top. TomL was measuring some sort of recess on a pump he had during one of our conversations, but he didn't say what brand or how old it was.

Has anybody else had a distributor drive gear wear/failure problem? What gear is used on the "mini" HEI? The shaft diameter is different from a stock dist shaft vs a HEI shaft, so its not just a 235 gear on a HEI distributor. I have a stock 2.8 dist out of a V6. Its gear is totally different from the other two distributors.

Also, I was looking at the leading and trailing edges of the dist drive gear teeth on my old Clifford Cam. They are asymmetrical. Is it possible for one or just a few new cams to have a distributor drive gear manufacturing problem? Or would a huge batch of cams be defective? I can only guess if my cam is OK or if it has a problem.

I never thought I could discover a whole universe in a distributor shaft.

chip

Say there Chiphead, I recently rebuilt my 57' 6 cyl. with a fel pro gasket set and the plastic washer you are talking about I used for my oil pan plug.My engine runs good with no leaks so far.Check to see if that drill start in your oil pump for your lockdown bolt and nut is in the correct location from the top(BASE).Thats my only guess the rest of the bolters have really tried to determine your probem GOOD LUCK. OL'55

Any more progress Chip?

Hi JYF,

Refer to the thread on oil pump measurements. After bangin my head & getting oil in my eyes under the car for several hours lookin' at stuff, and measuring oil pumps, distributors, cam gears, distributor gears, distributor shaft diameters & lengths, distributor gear tooth wear patterns and relative angles, I decided to drink heavily and listen to late '70s punk to relax.

Seriously, I'm still searching for what happened. What is jumping out at me is that nothing obvious is jumping out at me.

My current theory is that my '60 235 engine block's dimension between oil pump and distributor mount is smaller than normal, crashing distributor into cam gear and oil pump. Still taking measurements to prove or disprove this. Like I said, refer to the newer thread for the current debate.

thanks man,
chip

Just a follow up on this thread, I can't imagine a thrust washer in the top of the oil pump that is not captive, otherwise pulling the distributor would be a risky thing to do. The oil pump on my 216 shows drive tang wear that would go along with the diagram.