Anyone running a 2 piece rms block?

[KeyserGogo]

I want to purchase a MK IV kit at the end of the summer and have been planning like a mad man. Because I live in NJ, my emmissions requirements are based on the year of the block. My engine builder said he would build on a 69 block and use a roller conversion kit so that we can run a roller cam. However, he said that the 2 piece rear main seal is notorious for leaking on these things. Also, if the seal does leak and needs to be replaced it requires dropping all of the main caps to loosen the crank aka a pain in the butt. Add to that the extra cost of the roller conversion parts and it seems less like a good idea.

Looking to see if these old blocks are actually that prone to leaking. I'm building the car to be a fun cruiser, it will never see a drag strip or road race course. My other option is to run cats and smog pump etc which I'm trying to avoid. Looking for a simple carbed motor and clean engine bay. Will be a no frills car with manual brakes/steering, nothing fancy.

[Olli]

You need to deal with an engine builder that really knows Fords. Not just in how to build one but proper machining. Yes, the 2 piece seals can be leakers (been there) but a good Ford engine builder will machine the block for a 1 piece rear main seal. Problem solved. It sounds like your engine builder doesn't know this, be cautious. My HR has a '72 302 based 349 with a 1 piece seal and my Mark IV has a '69 351W based 416 with a 1 piece seal.

My engine builder is not in NJ.

Olli

[KeyserGogo]

Thanks for the quick reply. Sounds like machining the block for a 1 piece seal would be the easiest way to go since nothing has been built yet. I'm guessing this would also allow us to run a crank without the oil slinger on it. I spent some time on the old mustang forums digging around and it seems like alot of guys that have leaks switch to a red fel pro high vacuum 2 piece seal and never have a leak again. I guess I am going to have to talk to the builder and go from there. I know that 1 piece seals leak on people too, but they are alot easier to replace.

[Avalanche325]

.....a good Ford engine builder will machine the block for a 1 piece rear main seal. Problem solved. It sounds like your engine builder doesn't know this, be cautious. .....

There is the answer.

As stated, if you engine builder doesn't know this, I would be concerned.

[Bob Cowan]

A two piece seal doesn't really leak any more than a one piece. The difference is that he one piece requires a very meticulous assembly procedure. Ford made the change because it's easier to install on the assembly line.

Also, to change a one piece requires transmission, clutch, and flywheel removal. If you have the special tool, you can change the seal without removing the oil pan. Otherwise you need to remove the pan and the rear cap, too.

To change a two piece seal, you drop the pan and the rear cap only. No special tools are required.

[tirod]

I've replaced rear main seals by just dropping the one main, with no special tools. Modern two piece units are steel lined and drive in with a pin punch. It's the old rope seals that didn't cut it. The new seals use the same polymers that the one piece use. Done right, I haven't heard of either being more prone to leaking. I wouldn't pay extra to convert a block, run two piece and assemble per instructions. And plan for adequate crankcase ventilation.

Hydraulic clutch cylinders inside the bell housing are much more prone to failure, and they are a lot of work to change out, too. I'd rate that much higher on the list of things to avoid.

[KeyserGogo]

Thanks for all of the opinions and experience guys, was just what I was looking for.

[mike forte]

Hi KeyserGogo,
Jesse always machines the rear of the block for a 1 piece rear seal. This makes any year small block useable. Jesse only builds hydraulic roller cam engines these days. The cam/lifter failure is so high I can't sell them with any confidence it will last.


I want to purchase a MK IV kit at the end of the summer and have been planning like a mad man. Because I live in NJ, my emmissions requirements are based on the year of the block. My engine builder said he would build on a 69 block and use a roller conversion kit so that we can run a roller cam. However, he said that the 2 piece rear main seal is notorious for leaking on these things. Also, if the seal does leak and needs to be replaced it requires dropping all of the main caps to loosen the crank aka a pain in the butt. Add to that the extra cost of the roller conversion parts and it seems less like a good idea.

Looking to see if these old blocks are actually that prone to leaking. I'm building the car to be a fun cruiser, it will never see a drag strip or road race course. My other option is to run cats and smog pump etc which I'm trying to avoid. Looking for a simple carbed motor and clean engine bay. Will be a no frills car with manual brakes/steering, nothing fancy.

[KeyserGogo]

Thanks for continuing to provide experiences/wisdom guys. The topic of machining the block hadn't come up, he just said the 2 piece blocks are notorious for leaking. I've been reading about this all week and feel better about the whole thing. I will talk to builder about the machining/1 piece seal option and see what he says. I've owned a bunch of Jeeps over the years and they were 2 piece rear seals - they didnt give me trouble... while my 1990 5.0 mustang on the other hand had a leaky rear main at about 100k miles.

He did say, like you mentioned Mike, that he won't put a solid cam in it. He said they are nothing but problems. To convert to full roller it costs $$$ but it's the only way. I contemplated just chucking a stock late 60s 302 in for the initial inspection but the hassle of playing musical engines is not worth it. I just want to do it "right" from the start. I'll stop by the shop this Friday and see what happens.

[CraigS]

I have hydraulic non roller lifters in my 351. 26000 miles w/ 6 seasons of autocross and no lifter problems. I am looking at going stroker and plan to stay w/ non roller lifters since I never turn over about 5700 so I don't see the value in the extra $ to convert to rollers.