Piston question

[86Tona]

I'm rebuilding an '86 2.2 T1. My question is two actually.

First are NA pistons and Turbo pistons made of the same stuff?

Second is there a higher compression piston for the 2.2 that would work on the turbo appliaction if I need to bore it?

I'm asking because of some custom head work I'm having done. With the goals I have for the engine a slightly higher compression would be beneficial. I know that the '86 has a stock compression of 8.5:1 and later 2.2s had an 8.1:1 CR. I also know there are no oversize pistons for the '86 turbo. I have seen 2.2 oversize pistons but for the '87 and up. These have a lower compression ratio than the stock '86.

Anyone have any thoughts on this?

[speedyshelby16]

Most people don't like to go higher compression on these motors. One detnation will kill the pistons. Stock piston are weak and like to crack. Also your 86 block will have the lightwieght rods which are also weaker. If you want higher compression and your running a swirl head then look into get an 85 turbo piston and it should raise you up a little. I had this combo on my charger and it was quick. I could rev the engine in netural with the clucth pedal in and could make 11 psi of boost.

[daytonajesse]

Well stock 86 rods are LW rods and should be replaced for any performance application IMO
And I think (not positive) the bigger rods use a different style of pin, so maybe custom pistons or getting the head milled a bit would be the answer?

[turbovanman]

Stock Mahle turbo and n/a pistons are cast, there are hypers etc available. If your bumping up the compression, forged is a MUST. Yes, the 86 G-head piston is available oversize.

[86Tona]

Thanks for the input. I'm not talking about performance like I think you all are thinking. I'm only talking about taking the 141hp stock and bumping it to around 180 or so. The idea around the slightly higher compression is to keep lower RPM power with less or no boost. I understand with a higher compression ratio that more power will be made at higher boost but I plan to limit max boost to only slightly more than stock. I'm thinking in the area of 11-12 psi at most.

The light weight rods will be shot peened so I'm not concerned about them. I want the lower rotational weight for a faster spin up. My goal here is to move the power range to lower in the RPM range. Since I don't want more than 200 at the VERY most out of this engine the rods should be just fine especially if they are shot peened and balanced.

Also the head work I'm having done will help pevent or at least minimize detonation. With this custom head work it will be possible to increase the CR slightly to gain even more than what boost will offer. I'm only talking about 0.5:1 or so over the stock compression. I understand that the '86 was at 8.5:1 but if I bore it I will have to use T2 pistons which have a lower compression ratio of 8.1:1. My goal is to bore it and keep the 8.5:1 or increase compression to 8.7:1.

Turbovanman, the head I'm using is the 782 head from an '89. I don't remember if this is a G head or not but since you said '86 and this was the year they went to the fast burn head can I assume that it is a G head? In any case what is the source for oversize '86 pistons? Is the dealer the only one? Or, are they available from other sources?

If I bore it I will be installing Mahle pistons again because my goals for performance increase is not to build a killer engine. Since my head will have some port work done which will increase the size of the combustion chamber a little, the CR will drop. While this is great for really high boost I don't plan to boost really high. So I want to try and get as close to the stock 8.5:1 or perhaps 8.7:1 CR rather than have the stock CR drop.

Thanks for the input.

[turbovanman]

Fastburn is a Swirl head, the G-head has a bathtub chamber.

I am saying forged because as the compression goes up, the chance of detonation does.

All good ideas. If i was building a low boost engine, I would crank up the CR too., When I ran TBI pistons at 12 psi, it was fun but lasted a week before meltdown.

[86Tona]

TBI pistons are over 9.0:1 if not 9.5:1. That's too high. The head work I'm doing or I should say having done will permit higher than 'normal' boost while keeping detonation away. I'm even planning to run 87 octane fuel. I know this all may sound radical but the guy who's doing the work has had great luck with this. I am using an '87 T2 computer so I should get enough fuel for this to prevent leaning out.

[impuresoul2k3]

Why not pay the extra $2 or so a tank to get better performance and it's cheap insurance as well, especially if you're rebuilding?

[turbovanman]

Quote:

Originally Posted by 86Tona TBI pistons are over 9.0:1 if not 9.5:1. That's too high. The head work I'm doing or I should say having done will permit higher than 'normal' boost while keeping detonation away. I'm even planning to run 87 octane fuel. I know this all may sound radical but the guy who's doing the work has had great luck with this. I am using an '87 T2 computer so I should get enough fuel for this to prevent leaning out.

I realize that, lol, I didn't know the engine had them until it melted down. It was alot of fun in town, alot more responsive.

The T2 computer is good to 14 psi so you should be ok. I would definately be running an EGT guage. A custom cal might be in order?

[4 L-bodies]

Quote:

Originally Posted by 86Tona Thanks for the input. I'm not talking about performance like I think you all are thinking. I'm only talking about taking the 141hp stock and bumping it to around 180 or so. The idea around the slightly higher compression is to keep lower RPM power with less or no boost. I understand with a higher compression ratio that more power will be made at higher boost but I plan to limit max boost to only slightly more than stock. I'm thinking in the area of 11-12 psi at most. The light weight rods will be shot peened so I'm not concerned about them. I want the lower rotational weight for a faster spin up. My goal here is to move the power range to lower in the RPM range. Since I don't want more than 200 at the VERY most out of this engine the rods should be just fine especially if they are shot peened and balanced. Also the head work I'm having done will help pevent or at least minimize detonation. With this custom head work it will be possible to increase the CR slightly to gain even more than what boost will offer. I'm only talking about 0.5:1 or so over the stock compression. I understand that the '86 was at 8.5:1 but if I bore it I will have to use T2 pistons which have a lower compression ratio of 8.1:1. My goal is to bore it and keep the 8.5:1 or increase compression to 8.7:1. Turbovanman, the head I'm using is the 782 head from an '89. I don't remember if this is a G head or not but since you said '86 and this was the year they went to the fast burn head can I assume that it is a G head? In any case what is the source for oversize '86 pistons? Is the dealer the only one? Or, are they available from other sources? If I bore it I will be installing Mahle pistons again because my goals for performance increase is not to build a killer engine. Since my head will have some port work done which will increase the size of the combustion chamber a little, the CR will drop. While this is great for really high boost I don't plan to boost really high. So I want to try and get as close to the stock 8.5:1 or perhaps 8.7:1 CR rather than have the stock CR drop. Thanks for the input.

Advance the camshaft 4-5 degrees. That will wake up the bottom end.

Your spending money on someone porting your head. That isn't cheap. Spend another few bucks on some ARP rod bolts. Most important fastener in the motor. They're like $30 bucks. Magnaflux the rods too.

The 2.2 TI and TII both used a 14.5cc dish. Swirl chamber volume is 49-50cc. Only difference in piston, is one is a press pin, the other a floating pin. The g-head piston used a 9cc dish, with a 55-56cc chamber. Same compression ratio.

The factory rated the 86 TI and TII at 8.1:1 not 8.5. Most factory compression ratios were more optimistic than reality. Bore increase, milling the head, milling the deck will all increase compression. The MP head gaskets are a few thousands thinner than the original gasket too, which will also increase your compression by a smidge. All those smidges add up.

Most porters of swirl heads will unshroud the valves which will increase combustion chamber volume and decrease compression. Depending on valve type selection, this will be a factor too. CC the combustion chamber so your not just guessing. If I were you, just mill the head and deck a bit to get where you want to be.

Rebuilding a motor by decking, cylinder head rebuilding, overboring, using current MP head gaskets, will increase compression not drop it. If your worried about the cylinder head, give it another .005-.010 cut, but measure it first! You probably don't know how many times that cylinder head has been in the shop already. That will make up for your unshrouding of the valves. FWD also stocks thinner Cometic MLS head gaskets, which will help your quest for slighty more compression.

Hope you can get good pump fuel where you live. Been my experience that a lot of rebuilds are more prone to detonation due to things mentioned above. Then they throw in a inexpensive set of high silicone pistons, and a few months later they have broken ring lands from detonation. Fuel is not gettiing any better either. IMO, I might re-think what you are trying to do.
Todd Nelson

[86Tona]

Quote:

Originally Posted by 4 L-bodies Advance the camshaft 4-5 degrees. That will wake up the bottom end. Your spending money on someone porting your head. That isn't cheap. Spend another few bucks on some ARP rod bolts. Most important fastener in the motor. They're like $30 bucks. Magnaflux the rods too.

My brother owns a shop where they rebuild aircraft components like wheels and propellers. He has an NDT shop which does Non Distructive Testing including Magnaflux, eddy current and mag particle. I plan to do the block especially around the journals and the rods. Then the rods will be shot peened after they are balanced. I will be getting new bolts for the head and rods. If the ARP rod bolts are only about $30 then that's a no brainer.

Quote:

Originally Posted by 4 L-bodies The 2.2 TI and TII both used a 14.5cc dish. Swirl chamber volume is 49-50cc. Only difference in piston, is one is a press pin, the other a floating pin. The g-head piston used a 9cc dish, with a 55-56cc chamber. Same compression ratio.

I'm planning to use the '89 782 head and if I need to bore I will get the T2 pistons. The fact that one is press and the other is floating isn't a concern since the pin diameter is the same either way. So the 'new' pistons will work with the existing rods.

Quote:

Originally Posted by 4 L-bodies The factory rated the 86 TI and TII at 8.1:1 not 8.5. Most factory compression ratios were more optimistic than reality. Bore increase, milling the head, milling the deck will all increase compression. The MP head gaskets are a few thousands thinner than the original gasket too, which will also increase your compression by a smidge. All those smidges add up.

I was getting the CR for the '86 from several sites like Allpar and my FSM. I guess they could be wrong but I'm really thinking about doing a cc on the chambers and calculating the actual CR before I install the head. It will be fun and I'd get an accurate CR.

Quote:

Originally Posted by 4 L-bodies Most porters of swirl heads will unshroud the valves which will increase combustion chamber volume and decrease compression. Depending on valve type selection, this will be a factor too. CC the combustion chamber so your not just guessing. If I were you, just mill the head and deck a bit to get where you want to be.

I don't want to mill too much. Only enough to clean up and flatten the decks. My concern here is the length of the belt. I really don't want the cam timing to be thrown off just because the distance from the cam to the crank is less. I could get a degree wheel for the cam or some offset cam keys but if I don't have to do this I can save that expense.

Quote:

Originally Posted by 4 L-bodies Rebuilding a motor by decking, cylinder head rebuilding, overboring, using current MP head gaskets, will increase compression not drop it. If your worried about the cylinder head, give it another .005-.010 cut, but measure it first! You probably don't know how many times that cylinder head has been in the shop already. That will make up for your unshrouding of the valves. FWD also stocks thinner Cometic MLS head gaskets, which will help your quest for slighty more compression.

I will be using the MP head gasket. I had to think about why overboring will increase CR till I realized that it adds to the cylinder volume which is then compressed into the same combustion chamber. I understand how decking can increase compression.

But I think this may be offset by the custom chamber work I'm having done. In fact there will be a groove cut in the flat area farthest from the spark plug to help with flame disperment during combustion. This helps the flame expand across the piston faster and while the piston is high in the cylinder. This custom combustion chamber work is designed to help increase fuel burning efficiency. This also helps allow lower octane to be safely used while keeping boost less than 12psi.

As far as the head and not knowing how many times it's been in the shop, I'm lucky. I pulled it from a car that had a fire. It was the fuel hose and not enough damage to harm the head. So it was installed by the factory and hasn't been off till I pulled it. I'm lucky there. We'll measure the centerline of the cam to the deck just to be sure.

Quote:

Originally Posted by 4 L-bodies Hope you can get good pump fuel where you live. Been my experience that a lot of rebuilds are more prone to detonation due to things mentioned above. Then they throw in a inexpensive set of high silicone pistons, and a few months later they have broken ring lands from detonation. Fuel is not gettiing any better either. IMO, I might re-think what you are trying to do. Todd Nelson

No high silicone pistons at all. I'll get some Mahle pistons like the ones offered by FWD. In my standard Daytona I've run Shell or other brands for the past 250,000 miles. In the Turbo Z I will run only name brand fuels. While I hope to be able to run 87 octane I am not totally opposed to running something else. For example if I'm on the road crusing from Florida to Carlisle I may run '87 since I'll be doing mostly highway driving. However when I get there I'll tank up with a higher octane. This also applies to local shows and cruise-ins. You also mention an EGT gauge. I'm building some circuits that limit boost but have a few settings. For example when the switch is set to 'normal' the stock boost limiter controls boost. When the switch is in the other position the adjustment that you set controls boost level. While I won't need one for my application since I won't want to boost more than 12psi and I think I can make the necessary mechanical adjustments to limit to 12psi with the '87 T2 computer. The other circuit I'm building is an A/F gauge. As you know this will tell me when and if I start to lean out. I'll be monitoring this carefully.

[John B]

I know it's hard to justify parting with more hard earned money but you'll be glad if you spend a bit more for forged pistons.

[86Tona]

Quote:

Originally Posted by John B I know it's hard to justify parting with more hard earned money but you'll be glad if you spend a bit more for forged pistons.

I agree that they would be better but if a T2 which puts out 174 HP with cast pistons from the factory then I can strive for 180 with the same. This car will be used as a show car mostly. The ONLY reason I'm going through this mess in the first place is because the engine was blown when I bought it (cracked head) and I don't like the look of the log intake. If I can get 160 I'll be happy but I'm setting my sights on 180ish. This will be a pampered car not a racer.

[genghis05]

I've heard that the camshaft out of a NA '88 2.5L engine will bump up your low end torque on the turbo 2.5Ls.
alternative fuels help a little too. at the uhaul center where I work we like to spike the gas tank of a certain 14 footer with a little model fuel from time to time. helps the old 454 twist the frame a little better.