Should I or Shouldn't I...pistons and cylinders?, Can of worms? Options

[computers4kids]

I pulled apart my spare 75 2ltr down to the block (didn't split the case) that I'm planning on putting in my 75 project car. I also pulled the heads. My intentions was just to clean it up, do a visual inspection on the heads and re-seal the motor. I was going to take the heads down to our local machine shop to have them cleaned and if necessary a valve job.

I'm looking for some advice on whether I should remove the pistons, have the cylinders honed and new rings installed? Is this worth doing on these type of motors...or do most just buy a cylinder and piston kit?

Looking at all the kits available make me wonder whether to go with the stock 94s or a big bore kit. I see Jake sells a stock Mahle kit for $284 and the big bore kits are between 3 and 4 hundred elsewhere. I have both stock injection and weber 40s...probably go with carbs. I don't want to split the case to replace the cam.

So what do you think? (you can tell from my questions, I'm not much of a mechanic...but I like doing things for myself)

[SGB]

I've also been evaluating P&C sets. I'm not sure the $289 "bus" ones Jake sells are for a real 914 case. I also thought about buing those, but I see through a little internet snooping that REAL Mahle 2.0 liter PC sets are $2000 and more (check Pelican) and /or are NLA. There are some other cheap sources for "Mahle" manufactured by AA prbucts. I decided to buy new KB pistons to go in my existing cylinders...but that is NEXT engine drop. This time I'm just pasting on rebuilt heads, then buttoning it back together in time for my DE on 19 April.

[Dave_Darling]

There is no difference between Bus cylinders and 914 cylinders. The 914 pistons are built to give the 914's compression ratio (7.6:1 or 8:1) when used with 914 heads, while the Bus pistons are built to give the correct (low) compression when used with Bus heads. But the cylinders are identical.

And the bit about the pistons only applies to absolutely stock motors, which AFAIK Jake has nothing to do with.

--DD

[type47]

you don't tell us how many miles are on the motor and that info would give different answers. the "best" answer is that with any disassembly it to take it down to the main bearings (all the way to "do it right the first time"). some hack mechanics (ie, me) didn't do that to their motors. it's not that much to take the p & c's off to hone and re-ring. it would be nice to know the spec's on the p & c's if they are within tolerance. my motor had low miles so i had the p & c's cleaned and honed, new rings and refreshed heads. but my car is not used that much (weekend pleasure driver) and i wanted to put it on the road to drive it (and CSOB). if the motor ever needs refreshing again, then i'll upgrade it but with the low mileage i put on it, it might outlive me.

[VaccaRabite]

Are the cylinders off the block?

Once you pull the cylinders, you pretty much have to pull the pistons, unless you have a more clever way then I do to compress the rings to get the jugs back on.

Where you getting poor leakdown from worn rings?

its a can of worms. A chain reaction. Pull the cylinder, and suddenly you find a reason to pull everything else apart too. Ask me how I know...

Zach

[Cap'n Krusty]

Are the cylinders off the block?

Once you pull the cylinders, you pretty much have to pull the pistons, unless you have a more clever way then I do to compress the rings to get the jugs back on.

Where you getting poor leakdown from worn rings?

its a can of worms. A chain reaction. Pull the cylinder, and suddenly you find a reason to pull everything else apart too. Ask me how I know...

Zach

What, you don't have a ring compressor?

BTW, if you replace the pistons, you MUST rebuild the rods and have the pins fit.

The Cap'n

[computers4kids]

A little more info...

When I bought this car (krusty's backyard...Santa Maria) it had "fuel issues" and the PO of the PO had the MPS off and didn't know alot about the condition of the engine. Anyway, I sold the car as a roller soon after buying it...put the transmission in my 74 and put the 2.0 in the corner of my gargage.

The heads appear to have no cracks, the valves look OK, and the chambers are rich with black gunk...running rich too long.

The Piston tops look good.

The cylinder walls don't have any scoring, etc..look OK.

Of course the real question, how worn is everything? I don't know. If piston/cylinder sets like the ones Jake sells (cheap ones $284) will work then that seems to be a reasonable way to refresh the motor. Are these cheap sets as good as the stock 93 pistons in there? If not, honing the cylinders, cleaning the pistons and new rings sound better.

Ah...but I didn't know the rods have to be fitted for the replacemnent pins. Doesn't that pretty much require pulling the rods and splitting the case? It's a can of worms! I don't want to dump 3-5 thousand in this motor. If I could keep the "refreshing" of this motor to $1000 I would be OK with that.

If I'm just wasting my time and $ performing a cheap refresh, then I would rather put the money towards a V-6 or V-8 conversion.

[Cap'n Krusty]

You pull the rods out through the side of the case. Just have to be careful not to drop the used rod nuts into the sum. If you do, it becomes "interesting". New nuts, new bearings, and you're back in business.

Which car was it? The copper metallic one?

The Cap'n

[computers4kids]

You pull the rods out through the side of the case. Just have to be careful not to drop the used rod nuts into the sum. If you do, it becomes "interesting". New nuts, new bearings, and you're back in business.

Which car was it? The copper metallic one?

The Cap'n

Thank you...the copper metallic one (my first parts car).

[VaccaRabite]

What, you don't have a ring compressor?

BTW, if you replace the pistons, you MUST rebuild the rods and have the pins fit.

The Cap'n

What kind of ring compressor are you using? The kinds that I have seen (and the kind that I own) get trapped between the cylinder and the block if you don't remove the pistons.

Show me where to buy something better, and i would be happy too.

Zach

[Cap'n Krusty]

What, you don't have a ring compressor?

BTW, if you replace the pistons, you MUST rebuild the rods and have the pins fit.

The Cap'n

What kind of ring compressor are you using? The kinds that I have seen (and the kind that I own) get trapped between the cylinder and the block if you don't remove the pistons.

Show me where to buy something better, and i would be happy too.

Zach

OK. Here's the one I use:

http://www.toolsource.com/piston-ring-comp...a1k5shlnebvkfg0

Here's an inexpensive one:

http://www.toolsource.com/piston-ring-comp...or-p-69800.html

The Cap'n

[TheCabinetmaker]

I removed my motor to cure a head leak problem and saw a lot of oil in the cylinders above the pistons. It also had compression aroud 110-117. new rings, rehone cyls, and back together for under 150.00. Compression now over 150 all four with very little oil usage. I'm very happy. tight top end, loose bottom end

Oh yeah, that was two years ago (IMG:style_emoticons/default/biggrin.gif)

[Brando]

I used one like the second link Cap'n posted. Just roll it out from around the cylinder and piston once you've cleared the rings.

[Jake Raby]

Are these cheap sets as good as the stock 93 pistons in there?

No, the cheap sets should be a last resort. I **really** don't like stocking or selling them, but in the 90 and 93mm bore size they are all thats available shy of a 96mm.

I'd go to 96s and not look back, our KB set works very well and with some slight head work and a 9550 cam 115 BHP is easily attainable.

[VaccaRabite]

Show me where to buy something better, and i would be happy too.

Zach

OK. Here's the one I use:

http://www.toolsource.com/piston-ring-comp...a1k5shlnebvkfg0

Here's an inexpensive one:

http://www.toolsource.com/piston-ring-comp...or-p-69800.html

The Cap'n

Ordered the cheaper one. Thanks. Its my "learned somehting new" for the day.

Zach