Piston Part Numbers??????

[DAVEZ84SVO]

I have been tearing my motor down over the last few days.. I now have the head off & have found that the pistons have some #'s stamped into them.. I'm looking for a little assistance in making sure that I will not have an issue reusing them.. The #'s that are stamped into the top are 5435P, then under that is a .040.. I'm assuming that the .040 means that it has a .040" over bore.. I know that the motor is a rebuild unit that was installed back in May of 1991.. P/O tossed a rod through the original motor.. It has only 6,000 miles on it since then.. The cylinder bores still have very clear hash marks & are smooth to the touch.. They look very nice & fresh..

1. How do I know that these pistons are of the Forged nature?? I thought that the turbo motors had dished pistons to keep the compression lower than the N/A ones.. They look like flat-top ones to me.. They have 2 valve reliefs, one on each side (see attached pic)..

2. Is the 5435P the manufacturers part #?? If so does it look familiar to anybody??

3. Will I have anything to worry about if the cylinders are bored .040" bigger?? The reason that I ask is that my cleveland had a max of going .030" over.. I'm hoping to reuse most of the short block items, cause they look to be in very good condition..

4. When removing my dipstick tube from the block, I noticed that fron the last ring that seals to the block, the tube only goes into the block about 1/2".. Does this seem correct?? There also was NO rubber seal on it like I was expecting..


P.S. I'm not going crazy on this rebuild, Just a little port & polishing along with some port matching.. I just want to do it right the first time!!

Thanks for any comments & suggestions!!

Dave

[Pat_in_L.A.]

Nope, those are not turbo pistons (no dish).
Yup, they're +.040".
If the rebuilder's invoice is available, call them and ask if they're forged or cast.
I think that 5435P is an old Perfect Circle part number.
Most piston manufacturers only go up to +.030. There are exceptions.
Don't worry about the dipstick tube till reassembly.

You could reuse the pistons but they're likely 9.0/1 CR. It would be nice to have a machinist take a look at them and maybe shave a .050 to .070 dish into them if you reuse them. Original dish is ~.090 deep. Go shopping for pistons and determine what your budget will allow. You have several SVOCA members in your area who could probably give good advice as well.

[Jim W]

I did a quick check, and I believe that is the standard 2.3 replacement piston and it is not a forged piston. The 2.3 block can normally handle a + .040 bore job. The Speed Pro (Formerly TRW), forged 2.3 turbo piston part number is L2500F. They are available again, but I don't know if they make +.040.

Jim

[Pat_in_L.A.]

The Speed Pro (Formerly TRW), forged 2.3 turbo piston part number is L2500F. They are available again, but I don't know if they make +.040.

Jim

I looked at Speed Pro too . L2500F is available up to .75mm (+.030").

Dave, you really got off cheap finding this out now rather than later.

[GAboySVO]

Looking at the pistons on this page for the 2.3 it looks like you have the Hypereutectic Pistons style pistons too.

http://store.summitracing.com/egnsearch.asp?N=700+4294908331+4294908282+4294925022+4294869676+4294925232+115+4294839001&NeXID=5

Racer Walsh carries a Weisco 0.040 over turbo piston.

[Jim W]

Just be careful and check what your actual bore size is. Different types of pistons require different piston to wall clearance. The hypers normally require less clearance than forged.

Jim

[DAVEZ84SVO]

Well guys, that explains why I was having big timing issues under higher boost.. The EEC was pulling a ton of timing at 4500 rpms.. It actualy made the car fall almost flat on its face.. When I unplugged the K/S it would pull real hard intill about 4K when it started to detionate REALLY BAD!!

I think that I will be looking at getting new pistons.. There is a guy local that has a ton of NOS & new SVO parts.. I just put a call into him also.. I know that he had a NOS long block still in the crate.. I think that he also had a new block.. That might not be a bad idea, to just start fresh..

So much for a quick rebuild!!

Dave

[DAVEZ84SVO]

If you have the $$, I'd suggest talking to Race Engineering and pick up a set of pistons and rods: http://www.raceeng.com/p-7862-turbo-piston2300040.aspx

Mike, do I really need to get rods also?? I thought that the factory rods were good enough fo a basic srteet build.. (please remember that I'm not building a motor like you have, I just can't afford that kind of stuff or I would be)

Why do you say "ouch" about having the pistons installed on my rods?? Are they that weak that they could fail..

Thanks Dave

[DAVEZ84SVO]

If you *do* decide to do both, get a longer rod (5.5) with a shorter piston. More better, same price.

Is the longer rod/shorter piston has to do with the rpm range of the engine?? The longer rods make more TQ??


Dave

[boostedbruiser]

Hey Dave,
Check and make sure the engine really is .040 I know when i pulled my engine out of the SVO it had several stamps on the blocks stating .030 over, but come to find out the cylinders were only .010-.015 and it had stock size pistons. I also had Hyper you cracked flat top pistons, but mine were at 9.5 /1 even 8 psi of boost the car would detonate.

I wish i had known about the rods. I did put ARP bolts in the old rods so that should be better than stock, but i really don't plan on spinning the engine crazy RPM's. Oh well we'll see what happens since Jim Whelan has my car right now.

[boostedbruiser]

The Speed Pro (Formerly TRW), forged 2.3 turbo piston part number is L2500F. They are available again, but I don't know if they make +.040.
Jim

I have these pistons but in .030 Summit had them cheap. 50.00 ea, but if you talk to the guys at summit make sure they clearly understand that you only have 4 cylinders. the guy i talk to tried to tellme i needed 8 since a SVO came with a race bred 302. that was the special engine.

[Jim W]

It is great that Mike has the time to fill in all the important details. Keep up the good work.

Jim

[under pressure]

I disagree Mike. The longer rods limit the high rpm's. The shoter stroke allows for high rpm's. You know that formula about piston speed.

[under pressure]

Ok I'll concede a little, but not much. As long as you do change piston & wrist pin location you can compensate some. That's what Honda did when they increased the bore on my 929 to 954 displacement. Same stroke bigger piston. Longer rod more torque. Torque is what the R.W. used when he was battling 007 going out of turn 1 at Barber! Here's a pic of the piston difference.

[under pressure]

To be more concise: Undersquare engine configuration- high rpms hp ,; square engine config.- good combination hp & tq ,; oversquare config. increase tq. & decrease higher rpm due to p/s. They have been able to make comprimises with piston design, valve, crank, etc. Post some pics of your stock piston & the pistons you're using with the longer rods. Did the shorten the piston skirt? Rick