scooter500

iTrader: (1)

Refreshing a '91 L98 and will stay computer controlled on the timing set and want a stock depth oil pump with better flow but close to stock pressure. Goal is better upgrades over OEM parts, but without spending a ton. The engine is a daily driver.

86LG4Bird

iTrader: (1)

Are there any problems with the engine now that would prompt you to change these parts? How many miles are on it?

If you have low oil pressure, the pump is one of the last things to suspect.
1. a sender/gauge/wiring problem
2. worn bearings, cam or rod bearings most likely.
The last time I rebuilt an engine for myself, I had the 243k miles stock pump and a new Melling side by side, both opened up. The workmanship and clearances were better in the stock pump, so I re-used it and returned the Melling.

Unless you're doing something fairly outrageous with this engine, "double roller" does nothing for you. And even then, there are single rollers just as strong that will fit under the stock cover without clearancing the block. If the stock set has high miles and is worn/sloppy, get a stock replacement from Cloyes. The Cloyes part number will have a tighter fit than the GM part number.

scooter500

iTrader: (1)

Thanks, I bought the motor without details on past use so have it apart to check it out, put in new gaskets and other preventative parts. Overall the motor is in good shape. I'll keep your recommendations in mind.

AlkyIROC

Timing chains: For high mileage, an OEM style is best. Double roller reduces some friction but will stretch and wear faster than an OEM chain. If you feel you need a double roller chain, spend the extra money and buy a high end billet gear set. The cheaper sets will work but don't expect it to last. Once the chain stretches, your cam and ignition timing will change. I've given up on chains for my race engine. I now use a Milodon single fixed idler gear drive system. Quiet and timing will never change. For the cost, it's not really something you need in a daily driver.

Oil pump: I use a basic standard pressure Melling pump in my race engine. BBC is M77, SBC is M55. You don't need an HV high volume pump. The pump should come with an optional pressure spring. Installing the spring will bump up pressure slightly. That's the only modification required.

scooter500

iTrader: (1)

Okay, decided on a Cloyes 9-3545X9 after finding one a good price, so just went with it.

The M55 is available for good price too but what parts would I need to order to complete the pump?

My thought is if the new pump turns out to be sloppy then return it and reuse the stock with a new screen and spring.

Thanks --

scooter500

iTrader: (1)

Besides a new screen and spring are there any other parts needed to freshen up a stock GM oil pump?

After reading a dozen or more poor reviews I've decided not to go with a M55 pump.


Thanks --

Drac0nic

Blue print your stocker, add a bolt on pickup and arp drive. Should be overkill but not expensive. New m55s are junk as you read.

86LG4Bird

iTrader: (1)

I never saw a need to replace the screen. Is yours damaged?
Either get a "white" spring or pull the existing one out, stretch it so its free length is about 1/4" longer, re-install it, and it accomplishes the same thing.

Vader

I'll add a second vote for avoiding the roller timing chains. Alky explained why. I've replaced a bunch of failed/failing ones. They just aren't as strong or durable as an inverted link chain, and if you have a serious cam and springs, the roller chains fail/stretch/wear even sooner.

It's tough to beat a single row heavy roller like the stock LT1/LT4 type, unless you plan on installing gears.

MarineDeuce

Don't want to start a new thread so hope someone picks this up. 85 IROC runs great but I noticed a little loose chain sound when tweaking the throttle with the hood up. So pulled the timing cover and discovered a very loose and stretched OEM chain and gear set. I have used the double roller Edelbrook on Vettes previously without trouble so am installing that set on my car. The interesting part is the original cam gear from GM. This item is new to me. It is a poor quality but very lightweight aluminum hub with what appears to be a plastic gear ring pressed over it. The GM part number is 3896960. They must have put that in for a reason other than cost. The entire original system weighs about a third of the one I am installing. Are these original sets available anwhere? This one has about 170,000 on it so pretty durable.

scooter500

iTrader: (1)

Thanks everyone, appreciate the advice. The current screen is full of gasket material so it needs to be changed. I'll look around for a oem style pick-up that's bolt on and also an arp drive. Gotta love free so will stretch the spring a bit.

Too late for the double roller already bought it... next time will go stock.

AlkyIROC

Stretching a spring doesn't change it's spring rate. If you don't have a heavier spring then small shim washers between the spring and the roll pin will increase the spring rate because you've changed the install height.

MarineDeuce

Well I think that stretching a spring certainly will change the rate. The spring constant depends linearly on the material modulus G which in turn depends on hardening procedures etc. When you plasticly deform the spring you change the hardening and therefore G. Also the spring diameter changes and the spring constant goes as one over the diameter cubed. So, stretching certainly is a field expedient for changing the spring constant for a spring used in compression but generally replacing with a properly designed part would be preferred.

Confuzed1

iTrader: (4)

Both GM, Dodge and most likely Ford has installed those nylon\plastic timing chain gear sets in a lot of engines in the past. They're fairly durable, but don't seem to last as long as the other stock steel sets.

I had an old 72 Charger that had a full plastic upper timing gear, steel lower gear and chain in it. At about 65K miles on it, the chain was pretty loose....most of the looseness was due to the plastic gear wear. They also installed plastic gears on the bottom of their distributors on the old slant six engines!

They were only installed for one reason...to reduce noise. I wouldn't go looking for an original plastic set...ever. I just replaced it with a nice single Cloyes set. On my Camaro, I run a Cloyes double roller timing set and have had no issues, but all the clearancing was already done. I don't put a whole lot of miles on it either, since it's mostly a fun only car.

For the OP, 95% of all engines only need a standard volume and pressure oil pump. I've also read stuff about Melling oil pump cases being built a bit thinner in a few areas nowadays, so I opted for a Milidon standard pressure/volume pump. Not sure if they're much better, but they seem to be built a bit more "robust"...

MarineDeuce

Thanks for the reply on the timing gear thing. Had never seen that before and I am pretty sure it's original in an engine with 170,000 is miles on it. Have replaced with an edelbrock double roller. Bottom gear is about .093" thicker than the stock gear. Will probably shave that amount of the mounting collar of the harmonic balancer so belts align as stock when reassembled. Have test fit the cover and all seems fine. Thanks again.

potterc32

iTrader: (1)

How many other have had to "shave" material off their balancer? I've got the crank gear, and balancer installed all they way, and the pulleys are going to be off by about 1/8 to 3/16" . I installed a comp cams double roller chain and gear set. Is it pretty common to have to modify the balancer to fit?