B234 pistons into a B235

[MHILL8212]

just purchased a 03 saab 4cly for $800. The body and interior were almost perfect. the engine was knocking bad so he just want to get rid of it and i needed a new project to work on. Guys i wish i woulda took pictures of what i saw when i took the valvle cover off. I have never seen that much sludge in my life. it almost made me wanna vomit. I took the engine apart an began the slow process of cleaning out all the sludge. the sludge wasnt the cause of the knocking though. 3 BAD PISTONS it looked as though they got too hot and and expanded to the point of making contact with the cylinder walls. amazingly the cylinder wall were ok which is amazing considering how much damage the pistons have.

Anyway i was planning on replacing all of them regardless. i have had these pistons and rods from an old 93 9kcse for years now. the pistons look huge compared to these 9-5/gm pistons. i did some clearance measurements and turns out these pistons will be a much tighter fit than the originals. i was worried they would expand too much. But as it turns out according to the 9000 manual these pistons have a minimum clearance almost 4times less than the 9-5 pistons. they must be made of some material that expands far less at operating temps. so i went for it.

i installed the first one(9000 piston&rod) and just slowly rotated the crankshaft. BAD NEWS i knew the piston deck height was an issue and based on other post i knew the 9000/B234 head gasket would compensate for that. But it turns out the the piston skirt is too long. it actually makes contact with crankshaft right before it reaches the lowest positon in the cylinder. i was very disappointed but i still was determined to make it work.--i was surprised this wasnt mentioned in other post where guys have installed these pistons in a B235 block. im thinking maybe these pistons are a little different in this 93saab9k compared to 94 and later B234 blocks.

Anyway i decided to shaved the piston skirt down. i kept shaving and putting it back in until i could rotate the engine freely. ended up shaving off about 1.5mm. installed all the pistons after modifying them and finished putting the engine together.

AND THE VERDICT GENTLEMEN......it works at least for now. i been driving it like a grandma and will continue to do so until i let this seafoam run through for another 1k miles. hopefully dissolving all the sludge i couldnt get to. But so far i seems to run smooth

and also i think i know what happen with those other pistons. upon first starting the engine and getting it up to operating temp the oil pressure light started coming on intermittently. BIG NO-NO! it was leaking from right under the crankshaft pulley. really came pouring when it was revved up a little. the oil pump o-ring seal was split. replaced and we good to go i assume the previous owner decided to keep driving with the oil light on but seriously i thought bearings would fail before the pistons get hot and start pressing against the cylinder walls like that. but im just a man with a workshop manual and some tools.

sorry to be so long winded. just wanted to voice my experience with this project. later fellas.

[mike saunders]

wow.....I've never heard of anyone replacing just the 9-5 pistons with ones from the old 9000. That's a beer-worthy project for sure.

This probably saved a bit of time over a complete B234 swap, with stronger slugs.....

If you're using the B235 crank, is balance an issue?

Nice work all around...

[KaMiKaZi_t0M]

I hope all goes well with this, however I'm guessing the pistons expanded due to excess heat from lack of oil. Grinding pistons? That is VERY beer worthy. However, I hate to be the the negative Nancy, but I don't think this will last very long. The crank is most likely going to have some wear on it it (due to lack of oil), any other moving parts will have wear. I wish your project the best, I'm sure it took quite a bit of time, so keep us pointed! Shaving the skirt, that's a new one!

[MHILL8212]

I thought about the balance issues before i started this project. i dont know if the balance shafts are accomplishing that whole vibration damping thing based on the countering of the crankshaft rotation alone, or the pistons/rods movements, or all three of these components have to be a specific weight in order for the vibration damping to occur. But i think this function only becomes effective at higher rpm. i have not been anywhere over 3k rpm yet. i really am afraid if i push it while sludge is still roaming around in there i might mess up something.

i will give u an update after my first oil change, which is when i will really start pushing it to it limits. but for now it seems smooth up to 3k.

this is an automatic with the paddle shifters. the main reason i didnt like automatics is i just hated the premature downshifting. these motors have enough torque to remain in higher gears during freeway passing. These paddle shifters take care of that issue. i cant wait to really put them to use after this first oil change still amazed i got this for $800 even with the blown motor.

[MHILL8212]

also fellas i wanted to note that i heat wrap the part of the exhaust that goes under the oil pan. i do this for all my 9-5s and suggest it to all my friends who own one. All the saab 9ks had heat sheilds to protect the oil pan from excessive heat but for some reason GM decided that wasnt necessary for the 9-5s. and they wonder why they have a sludge problem

i wish i could believe the pcv mod fixed the problem but there are too many reports of people with the pcv mod and regular oil changes but still somehow ended up with sludge. Hmmmm!

[Mike Brennan]

Nice job. As an afterthought I would recommend you pull out the oil pump and housing and replace it with the new part which was upgraded and much more robust. I believe it is the same pump used in the pre 1998 models. The early 9 5 pumps were quite bad.
Read this from Andrews starting at the top of page 2 regarding oil pumps:
http://www.saabpros.com/saab/nines/a.../nines_290.pdf

[jwwells]

You got brass ones! Personally I would never actually modify pistons to make them fit, but way to go fella! Hope it runs great for years. Keep us updated. If you do anymore projects please take a bunch of pictures. Would love to see you're project.

[Jssaab]

Very MacGyver of you. You need to use both the rods and pistons ( they have a lower mounting point on the 234) but modifying the skirt is one way around that, very beer worthy indeed

[MHILL8212]

hello Jssaab. i did use the rods and pistons from the 9000. i tried to use the 9-5 rods at first but when i rotated the crankshaft the piston came so far above the the block that no headgasket could ever compensate for that. (it did however cross my mind to use about 4 or 5 headgaskets though)

but seriously im sure i have read post of owners putting b234 pistons and rods in a B235 and they didnt mention a skirt problem. thats why i figured these 93 9000 pistons must be slightly different from the 94 and later 9000. according to the manual the compression ratio changed starting with the 94 9k.

think im still kinda lucky though. these 9k pistons are class AB and the 9-5 block is stamped class A for all 4 cylinders. thats for those of u who are familiar with piston classification. But im happy with the result and hopefully it will last awhile.(fingers crossed)

[Jssaab]

Gotcha, you are right, I used a pre-odbII block for my hybrid engine..

wish I new someone wnated pistons I have a set of Wossner forged I am oking to get rid of, wodl be good for an upgrade

[MHILL8212]

here are the 3 bad pistons i removed. not pretty

[N.E. Swede]

I'm not sure if this borders on insanity or genius, but I like. Out of curiosity, were the oil sprayers for the cylinders all gunked up?

[bob3000]

Originally Posted by MHILL8212

here are the 3 bad pistons i removed. not pretty

And in a moment of irony...are they pictured on a beer cooler?

[MHILL8212]

Nice one bob3000

N.E.Swede- i removed the oil sprayers during disassembly and they were good and clear of sludge. surprisingly!

Mike Brennan- thank for the link about the oil pump study. after reading it i decided to just go pull a pump assembly off a 95 9000(blown motor) in a nearby salvage yard. i was curious to know if it would be a direct fit to the 9-5. be nice if it fits but if not no biggy. i will let u know how it goes. later fellas.

[Jssaab]

9000 oil pump wil not fit the 9-5 timing cover sorry

[Green9kAERO]

I "Know someone" who put b234 NA pistons into their 02 9-5 Aero, and rough calculations say that the Cylinder head compensated for the added compression, leaving it boost friendly....

The setup has 2000 miles on it so far with no troubles:P

[D_Boy]

I've been tossing around the idea of doing the same thing. Has this worked out okay so far? Notice any differences in performance, mpg, oil consumption, or otherwise?

I need to put new pistons in a B235, but I'm having trouble locating some, so I thought putting B234 pistons and rods in the B235 block might work. Any thoughts?

[jwwells]

Originally Posted by D_Boy

I've been tossing around the idea of doing the same thing. Has this worked out okay so far? Notice any differences in performance, mpg, oil consumption, or otherwise?

I need to put new pistons in a B235, but I'm having trouble locating some, so I thought putting B234 pistons and rods in the B235 block might work. Any thoughts?

I decided against using the B235 pistons and just purchased a new one. I'd stick with stock.