Forged Piston Upgrade for Dummies?

[Chad T]

Hey guys,

Well after breaking a 2nd piston in the 86 GLHS I've decided it might be time to install some forged pistons. Thinking about getting Ross, JE or Wisecos.

Can I get any of these that will fit the stock rods? Or should I modify the rods for a floating pin?

From what I understand I can't just buy a standard set and put them in but I need to measure the bores? Then order pistons that match?

Can anybody give me the dumbed-down version of how to measure the bores for the new slugs?

Any other advice on how to best go about this would be greatly appreciated.

Thanks,

Chad

[bakes]

Get yourself some t2 rods and start there then just choose the piston for your needs.

[turbovanman²]

+2 on the new rods.

Contact TU for info on the Wiseco's, I think they are stock pin but his site has the info. As for JE's, the last set I bought were .912 pins, stock is .901. Ross, unsure, Venolia's are are also large pin.

If you have a stock bore, your kinda playing with fire as if you order stock pistons and your bores are too large, you can't do anything. Best bet is to buy some .020" and rebore, then your golden.

[Chad T]

If you have a stock bore, your kinda playing with fire as if you order stock pistons and your bores are too large, you can't do anything. Best bet is to buy some .020" and rebore, then your golden.

Is there a simple way to measure the bores? Motor only has 50k and not a lot of wear. (just likes to eat pistons.:p) Would be nice to be able to figure out where I'm at.

[cordes]

I'm not trying to be mean when I say that the motor doesn't like to eat pistons, but it requires more prudent tuning.

What is your current setup, instrumentation, and tuning method looking like? Forged pistons provide a slight margin for error, but they aren't made of Adamantium...

[turbovanman²]

Is there a simple way to measure the bores? Motor only has 50k and not a lot of wear. (just likes to eat pistons.:p) Would be nice to be able to figure out where I'm at.

You buy/rent a bore gauge and measure, then ask the vendors if they can measure a set of pistons IF they stock stock bore, then you have your answer.


I'm not trying to be mean when I say that the motor doesn't like to eat pistons, but it requires more prudent tuning.

What is your current setup, instrumentation, and tuning method looking like? Forged pistons provide a slight margin for error, but they aren't made of Adamantium...

Sure they are, heheehe, :evil:

[cordes]

You buy/rent a bore gauge and measure, then ask the vendors if they can measure a set of pistons IF they stock stock bore, then you have your answer.





You will also need a good mic to zero the bore gauge.

[Force Fed Mopar]

Best thing to do is pull the motor, strip it down, and have the machine shop check it and see where it's gonna clean up at, then order pistons. They check to see what bore it takes to make it round again all the way down.

[Chad T]

I'm not trying to be mean when I say that the motor doesn't like to eat pistons, but it requires more prudent tuning.

Very true and nicely put. :thumb:


What is your current setup, instrumentation, and tuning method looking like? Forged pistons provide a slight margin for error, but they aren't made of Adamantium...

Current setup is stock GLHS motor, 88 TBI roller cam, TU 3" Swingvalve and exhaust, Mopar Stg II Logic Module, +20% injectors MBC set to 18ish PSI.

I've got a boost gauge and an AEM wideband. I was seeing A/Fs in the high 11s low 12s. Seems to go fairly lean under part throttle sometimes too.

1st piston went when I first got the new swingvalve on and had no boost control. Blew off the FPR reference line and went way lean. Got the new piston in and things seemed OK. I knew my A/Fs were borderline at times and was planning on trying to get more fuel in there.

Not sure when this one went but I noticed oil had shot out of the oil cap and dipstick on the way to SDAC. :confused: Sure enough I've got smoke puffing out of the dipstick at idle. Haven't torn it apart but pretty sure it's a cracked piston as the car ran beautiful after I got it back together. Pulled the plugs and it looks like it's #4 again. Might have to do the cooling mod.

Since I'm going to have to tear down the motor again I thought it might be a good idea to go with forged pistons. Seems like the setup I'm running has been done before with good results but looks like I might have some sort of fueling issue.

I'm thinking I could have a bad fuel filter. I replaced the fuel filter and then had to replace the tank because rust had collapsed the strainer. I never changed the filter after that.:banghead: Just the tank and strainer. :o Car was still completely stock then except for the STG2 LM.

Installed a Walbro HP 255l pump from TU and it didn't make a difference in the A/Fs which kind of surprised me.

I thought I should be fine with the wideband but I guess the cast pistons don't give me enough time to read it. I also wasn't considering that my leanest piston could be a but leaner than the averave I'm seeing. Guess I need to get enough fuel to stay solidly in the 11s on the A/F.

I can't go back to stock boost..I really can't. :p

[Chad T]

You buy/rent a bore gauge and measure, then ask the vendors if they can measure a set of pistons IF they stock stock bore, then you have your answer.


I was talking to 4lbodies at SDAC and he said he usually measures and orders custom pistons from Ross to fit the bores. He also has access to a machine shop though.


Best thing to do is pull the motor, strip it down, and have the machine shop check it and see where it's gonna clean up at, then order pistons. They check to see what bore it takes to make it round again all the way down.

Arrg..This is sounding like a lot of work. Might have to call my machine shop and see what they say.

[cordes]

You need to ride the brakes and take readings of your gauges every 500RPM. I will hold it at WOT while riding the brakes at whatever RPM I am tuning for and watch my AFR and EGT. If you do that and take your time while adjusting things you will be met with much success.

Also, if you are constantly popping #4, I would get the injectors flowed. There was a thread the other day in which someone posted a link to a place which flows them for $6 each. That's hard to beat.

If the injectors are fairly close, then I think it is probably just a situation of too much timing since your AFR doesn't seem that bad. 18PSI with the exhaust done is probably pushing the injector DC on +20s through that motor though.

[1FastCSX289]

Check out my for sale thread.....ive got a nice set of practically new forged Venolias already set up on shot peened T2 rods with ARP hardware. They are .020", so you will need to get the block bored.

[johnl]

On similar set up running CA 91, I can't run over 15 lbs. The Stage II logic module has too much advance and/or too little fuel, especially at 3/4 or 7/8 throttle just before WOT. That's where the damage is done - under load, maybe third gear, time in detonation. You can see adequate A/F at WOT but not realize you are lean/detonating at 3/4 - 7/8. Take some base timing out. I know it's going backwards but try 8* or better yet get a different cal or start injecting alky.

[Force Fed Mopar]

Installed a Walbro HP 255l pump from TU and it didn't make a difference in the A/Fs which kind of surprised me.

A hi-volume pump does not change anything by itself, it merely gives you the capability to provide more fuel when/if needed.

My machine shop won't bore a block unless they have the pistons, as they fit each bore to the actual piston size.

[bakes]

You might want to go over you timing maps i bet you your detonating and taking out the ring lands if you dont fix it now when you get your forged pistons you start to lifting the head and over time take out you pistons again.

[Juggy]

you could probably get away with stock size bore and forged pistons.

forged usually require a little more clearance then cast, so a quick honing job will bring the bore up to size and snuff. especially if they are JE or venolia. wiseco holds the tightest clearances.

measure your bores and go from there.

PS i thought pins were as follows
901 wiseco
912 JE
927 venolia

[Force Fed Mopar]

You might want to go over you timing maps i bet you your detonating and taking out the ring lands if you dont fix it now when you get your forged pistons you start to lifting the head and over time take out you pistons again.

Also, could be the teeth on the intermediate shaft are getting worn and causing the timing to jump around a bit uncontrolled. DodgeZ lost at least one, maybe 2 pistons to this issue.

[bradp]

Had Wiseco's in the wagon and always before used J&E's. Absolutely loved the Wiseco's (very quiet). Had good luck with the J&E's too but they weren't always the same size and were a little noisy.

[Chad T]

You need to ride the brakes and take readings of your gauges every 500RPM. I will hold it at WOT while riding the brakes at whatever RPM I am tuning for and watch my AFR and EGT. If you do that and take your time while adjusting things you will be met with much success.

If the injectors are fairly close, then I think it is probably just a situation of too much timing since your AFR doesn't seem that bad. 18PSI with the exhaust done is probably pushing the injector DC on +20s through that motor though.

Ah of course! Just ride the brake to get the reading. So simple. I was thinking a bit more injector couldn't hurt. I've got the AFPR back to stock 55psi base and it's still borderline on the A/Fs.


Check out my for sale thread.....ive got a nice set of practically new forged Venolias already set up on shot peened T2 rods with ARP hardware. They are .020", so you will need to get the block bored.

Thank you. I'll keep that in mind if I decide to bore it. Hoping to get by with a hone if I can and get the proper sized pistons. Or just find a nice already built shortblock. :eyebrows:


On similar set up running CA 91, I can't run over 15 lbs. The Stage II logic module has too much advance and/or too little fuel, especially at 3/4 or 7/8 throttle just before WOT. That's where the damage is done - under load, maybe third gear, time in detonation. You can see adequate A/F at WOT but not realize you are lean/detonating at 3/4 - 7/8. Take some base timing out. I know it's going backwards but try 8* or better yet get a different cal or start injecting alky.

That's exactly what I was seeing on the way to SDAC. You can breathe on the gas pedal in 5th gear and it will build boost instantly but the A/Fs will not always increase.


Also, could be the teeth on the intermediate shaft are getting worn and causing the timing to jump around a bit uncontrolled. DodgeZ lost at least one, maybe 2 pistons to this issue.

Wow great info guys! Starting to learn a few things. :thumb: Never even considered the intermediate shaft but that makes sense. I do get a weird slapping noise when the motor is cold sometimes. Goes away pretty quick depending on how warm it is outside.

[Chad T]

Finaly did a compression check and it looks like it's the #3 cyl this time(150-150-60-150). Might have to put in one of the used pistons I have, throw some more fuel at it, back off the timing a tad and let 'er rip.

Maybe do the forged pistons over the winter. Is there a good way to check that intermediate shaft?

[DodgeZ]

Hey guys,

Well after breaking a 2nd piston in the 86 GLHS I've decided it might be time to install some forged pistons. Thinking about getting Ross, JE or Wisecos.

Can I get any of these that will fit the stock rods? Or should I modify the rods for a floating pin?

From what I understand I can't just buy a standard set and put them in but I need to measure the bores? Then order pistons that match?

Can anybody give me the dumbed-down version of how to measure the bores for the new slugs?

Any other advice on how to best go about this would be greatly appreciated.

Thanks,

Chad


I dont' have time to read all the thread so this may have been said already, but you have a bad tune or a problem with the car. Forged pistons wont crack like the cast ones but the side effect is blown head gaskets and extreme wear on the rod bearing until you get your real issue fixed. Figure out why you are having the problem, trust me, I have a stack of cracked pistons to prove it ;) I got my tune right and I am at 369wtq on used cast pistons and rings on a pump gas tune....

[Chad T]

Figure out why you are having the problem, trust me, I have a stack of cracked pistons to prove it ;) I got my tune right and I am at 369wtq on used cast pistons and rings on a pump gas tune....

Yeah I'm seriously thinking about putting in the used cast piston I have and trying to get the issue sorted out. Looking like forged pistons will be a big expense. Will probably get some +40 injectors.

Care to share any of the issues you were having? Trying to rule out as much as I can.

[Mike_Shepard]

Chad have you pulled the head to look at the walls? You may have scored them up and you may need a honing or a new block. I bet me best looking piston is still better than your worst piston haha and mine were Forged too

[Chad T]

Haven't pulled the head yet Mike but last time it was off everything looked beautiful.

http://www.motorgeek.com/phpBB2/gallery2/d/84352-1/nospiston3.JPG

This time I caught it before the piston could melt and get stuck to the bore. Might be able to just swap out the one piston but I'll see when I get it apart.

[bfarroo]

You need to look into getting a computer to control boost at that level. The mopar stage II is a 2 bar cal and can only support 14.7 psi. above that it's just guessing. If your running a drag race car and are all full throttle or idle you can adjust fuel pressure to compensate, it's when you get into part throttle situations and it's trying to work off the O2 feedback but doesn't know that the boost is above 15psi it will go lean. The vendor cals and 3bar map sensors are a bargain compared to tearing down a motor all the time to replace pistons. What are you using to eliminate overboost?

[Chad T]

You need to look into getting a computer to control boost at that level. The mopar stage II is a 2 bar cal and can only support 14.7 psi. above that it's just guessing. If your running a drag race car and are all full throttle or idle you can adjust fuel pressure to compensate, it's when you get into part throttle situations and it's trying to work off the O2 feedback but doesn't know that the boost is above 15psi it will go lean. The vendor cals and 3bar map sensors are a bargain compared to tearing down a motor all the time to replace pistons. What are you using to eliminate overboost?

I didn't have to use anything to eliminate the cutout. I've read the Stage 2 has a 13 sec delay? Doesn't seem to care about the extra boost.

It does seem like the issue is at part throttle but it doesn't really go much above 15 PSI until it's at WOT. Bad thing is it will shoot to 15 psi real quick without much change in the A/F from cruising.

I really love the way it runs with this setup and would like to figure out a way to make it work. Would be nice to have a 3bar cal but don't want to wait forever or do a lot of sending back and forth etc.

[cordes]

Holly mackerel! I didn't realize that you were boosting that high in part throttle on the stage II cal. The part throttle tables have much less fuel and much more timing than the WOT tables in all the cals. This certainly could be your problem.

If you don't want to send computers back and forth, you may want to give it a go yourself. It's not that hard to do. I knew pretty much nothing about cals when I first started and had better drivability, gas mileage, and performance with my first shot at it than with +40s on the GLHS stg. II cal.

[bakes]

I didn't have to use anything to eliminate the cutout. I've read the Stage 2 has a 13 sec delay? Doesn't seem to care about the extra boost.

It does seem like the issue is at part throttle but it doesn't really go much above 15 PSI until it's at WOT. Bad thing is it will shoot to 15 psi real quick without much change in the A/F from cruising.

I really love the way it runs with this setup and would like to figure out a way to make it work. Would be nice to have a 3bar cal but don't want to wait forever or do a lot of sending back and forth etc.

Just what i suspected to much timing at part and at over 15psi

Buy a moates burn2 or ostrich and jump into d cal and start tuning to you engines need it not that hard.

[Chad T]

. I knew pretty much nothing about cals when I first started and had better drivability, gas mileage, and performance with my first shot at it than with +40s on the GLHS stg. II cal.

Did your car run OK with the STG II and +40s? Thinking about adding those and cutting back the timing a bit. I do have an AFPR already but I had to crank it to get enough out of the +20s.


Just what i suspected to much timing at part and at over 15psi

Buy a moates burn2 or ostrich and jump into d cal and start tuning to you engines need it not that hard.

Never even considered doing a cal myself. Will have to look in to that. Thanks for another great idea guys!

[cordes]

My car ran OK with the +40s. I could never get the FP down low enough for it to be really good though. If the car would idle for extended periods of time I would get fuel in the oil. :(

[OmniLuvr]

i never had a problem with my stage II with a map clamp, 18psi of boost, 1 piece intake, flex fuel injectors(+21s), 255, 3" sw and dp, with a stock 180k long block at 47 psi of fuel pressure i was still running rich at around 10.2 a/f ratio. if your running lean with those injectors at stock fuel pressure, and no head or intake mods then your having a fuel delivery problem for sure.

change out that fuel filter and blow through it, that sounds like your problem. 12 a/f is scary at 18ish psi with no spark control above 14.7. Part throttle was a little scary for me sometimes (15ish psi), but im usaully in it to win it, foot to the floor.

[mo' parts]

Ouch!! that sucks, been there done that. Just got internet back at the new place, you should have called.
i have a common block in the shop that just had the int. shaft bearings re-done, line bore on the crank journals,and has been decked just waiting for pistons. you could slap some forged pistons in there. i also have t2 rods, and a forged 2.2 crank for it. it will be a few till i have use for it, still un-employed.:( and no car.
in the meantime, just pop another piston in yours, you can prob. do it in half the time now, lol.
or you could gather the stuff you need for your orig. block and swap to forged rods and pistons over the winter. i personally would leave the number matching 50k block alone....
i also have an early block that needs to go to the shop, just a few ideas for ya.

you can get the wiseco in the stock pin size. thats what i did on Mikes motor, along with stock bore. the block had 89k on it and it checked out good, the shop just honed to fit. Too bad Mike tried to fuse them to the cylinder walls.
i have a decent bore gauge if ya need it, just dont have a good mic to zero it. lmk

[Chad T]

i never had a problem with my stage II with a map clamp, 18psi of boost, 1 piece intake, flex fuel injectors(+21s), 255, 3" sw and dp, with a stock 180k long block at 47 psi of fuel pressure i was still running rich at around 10.2 a/f ratio. if your running lean with those injectors at stock fuel pressure, and no head or intake mods then your having a fuel delivery problem for sure.

change out that fuel filter and blow through it, that sounds like your problem. 12 a/f is scary at 18ish psi with no spark control above 14.7. Part throttle was a little scary for me sometimes (15ish psi), but im usaully in it to win it, foot to the floor.

Thanks. That's good to know. I thought there were some more people out there with similar setups. I've got a new fuel filter ready to go on, slightly bigger injectors on the way, I'm going to put in some colder spark plugs and pull a bit of timing as well. Should be able to keep the A/Fs in a safer range.


Ouch!! that sucks, been there done that. Just got internet back at the new place, you should have called.
i have a common block in the shop that just had the int. shaft bearings re-done, line bore on the crank journals,and has been decked just waiting for pistons. you could slap some forged pistons in there. i also have t2 rods, and a forged 2.2 crank for it. it will be a few till i have use for it, still un-employed.:( and no car.
in the meantime, just pop another piston in yours, you can prob. do it in half the time now, lol.
or you could gather the stuff you need for your orig. block and swap to forged rods and pistons over the winter. i personally would leave the number matching 50k block alone....
i also have an early block that needs to go to the shop, just a few ideas for ya.

you can get the wiseco in the stock pin size. thats what i did on Mikes motor, along with stock bore. the block had 89k on it and it checked out good, the shop just honed to fit. Too bad Mike tried to fuse them to the cylinder walls.
i have a decent bore gauge if ya need it, just dont have a good mic to zero it. lmk

Hey Adam! Those are some good ideas. Just going to use one of those spares I have for now and see if I can get a better tune going. Maybe build something over the winter.