I have a 74 w100 with a 225. I had the head cleaned up and had the valve train all replaced, but after a few months of driving i figured out that i spun a rod bearing. Im buying a new 225 that i plan on putting this head on but dont want to end up with another toasted bottom end. How do i prevent this? Just replace rod and main bearings or should i do that and get a better oil pump? Also i want to get a new cam but im not sure which numbers to choose for torque, its going in a 4x4 so i need probably about as much torque as possible. Thanks guys! ~Wesley

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Drive it like its stolen, and be glad im not YOUR son...

The slant-6 has a beefy, stout, reliable bottom end. If something failed, it was either because it was worn out, or because there was an assembly problem—not because of any deficiency in the stock components. So, preventing a premature failure boils down to quality parts, fitted and assembled correctly. You can add a high-volume oil pump if ya just gotta, but with good, precise bearing clearances, there's really no need.

One question: How many miles did the bottom end have on it when you refreshed the head? Sometimes, a nice fresh head will increase stress on the bottom end such that worn components down there that would live awhile longer with a looser head will get "finished off" sooner than later. Usually it's the rings that give up, but occasionally a bearing.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I agree with Dan. The slant six block was originally designed for an aluminum engine and was never retooled when they swapped to the cast iron blocks. The end result is a very stout bottom end (the main bearings are bigger than a 440s) that will stand lots of abuse.

I recommend a standard rebuild ont he bottom end but, as Dan said, quality components and assembly. The place you will want to spend some money and time is your exhaust, intake, and camshaft. A W100 is alot of weight for a slant six to move around, so for better mileage and performance you should have a two barrel carb, a 2 1/4 single or dual 2 inch exhaust line(s), and an "RV" type cam such as the Comp Cams 264 (I only use that as a general reference for the size you should be looking at).

High volume oil pumps arew generally not necessary and I have read many complaints that the extra tension in the pump has lead to premature camshaft wear and failure, as well as seal failure.

Just to clarify, the aluminum blocks were not made with the same "tooling" as the "Detroit Wonder Metal" (cast iron) versions most of us have. They differ in a number of areas, including details of bearing caps, cap bolts, etc. The aluminum blocks were die cast versus the sand casting used for the iron. Look at photos of the aluminum blocks, and you can quickly spot significant differences in the blocks themselves.
http://www.slantsix.org/articles/dutra- ... ck-sl6.htm

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"When you find a big kettle of crazy, it's best not to stir it." - Pointy-haired Boss

1964 Valiant V200, 225/Pushbutton 904
BBD, CAI, HEI, LBP, AC, AM/FM/USB, EIEIO

Okay, my point was that the basic design of the engine (number and sizeof main bearings, fully jacketed cylinders, etc) was intended for the aluminum block, but was carried over to the cast iron block makng the cast-iron block over-designed for strength and durability. At least that is my understanding from reading article in the Slant SIx News. I could be wrong though, I know next to nothing about how engine blocks are made.

That is true; what Reed was getting at was that the bottom end was engineered and conceived for aluminum-block implementation. This required stronger geometry, component sizing, structural rigidity, etc. than is required for cast-iron implementation. When it was decided to go ahead with the iron block, the aluminum-ready geometry/sizing/rigidity/etc. was not downgraded, so the end result is a super-strong structure.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Sorry, I didn't mean that post as criticism, Reed, just as background info. Your point about the basic geometry of the block and bottom end being derived from the earlier aluminum block designs, and being quite good, was spot on. Just wanted to clarify a small point on production.
And, in fact, with the closed deck, and (obviously) material choice, rigidity was likely improved.


I think we are all in agreement.

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"When you find a big kettle of crazy, it's best not to stir it." - Pointy-haired Boss

1964 Valiant V200, 225/Pushbutton 904
BBD, CAI, HEI, LBP, AC, AM/FM/USB, EIEIO

Hey, I didn't take it as criticism, and I am always happy when someone corrects me when I am wrong. No worries!