jensenracing77

I am undecided what I will do with my 4 speed Jetfire engine during the restoration. The engine has 44,300 miles on it and runs really good. It sit from 1974 till I got it in 2015 and still never started it till 2016. There are enough issues from it sitting that I am going to rebuild it. I am undecided if I will reuse the original 57 year old Jetfire only pistons or if I should go with the Egge pistons. Egge makes the Jetfire replacement piston but not sure of its quality for a turbo application. The original pistons were beefed up from the factory for the turbo.

I am also concerned with the height of the egge pistons compared to stock. I really want this engine to run exactly like original and keep the 10.25 compression. I even have an NOS cam I will run. I also know that I will have a heavy foot and spool the turbo at least one time every drive.

Any thoughts on Egge pistons?

68442

I would check everything(spec's) upon disassembly. If all is within spec , re ring/etc. and stick with OEM. With 44K on it unless it was under water i bet you will be fine reusing all the factory parts including the cam! You cannot beat the factory GM USA made parts in that car. Just my opinion

jensenracing77

These cams went flat around 80,000 to 90,000 miles even with regular oil changes. I plan to replace it but have an NOS Oldsmobile cam to put in it. It does not smoke but I have only driven it around 300 miles.

Olds64

I used Egge parts when I rebuilt the 394 in my 64 98 years ago. As I recall, the parts were high quality and they had good customer service,

Be wary if you intend to reuse old parts. When I disassembled my 394 I found 2 pistons with broken piston skirts and 1 with a broken ring land. This has happened to others on our site too.

BillK

Jr,
I have sold a few sets of the Egge pistons and they look ok for a stock type application. Not sure if your original turbo pistons were cast or forged but for the price of the Egge pistons I think I would rather have a set of custom ones made by Diamond etc. The price probably would not be that much more and you would absolutely get a piston that would take whatever abuse you could give it.

Also almost all of the basic rebuilder type pistons will be "compression modified" so the Egge piston will probably be less compression than stock. Might not be much but they are usually shorter. With someone like Diamond, Ross etc you can specify exactly what you want. I have sent them oem pistons to duplicate.

Run to Rund

I would not use any cast piston for a high performance gas engine, especially a rare one.

Fun71

This is what I found a few years ago when asking about the Egge pistons specs (not for a JetFire engine, though). I had called Egge and they would not give me the piston height, so I had to ask on ROP and got a few responses that confirmed they were shorter than factory pistons.

Charlie Jones

X2 on this When I did my 394 , I went this route .
One thing I would add though . If you go this route , the engine will probably have to be balanced .
The forged pistons are considerably lighter .
The difference between forged and cast for me was less than $200 .

jensenracing77

I will have the rotating assembly balanced no mater what I use. How much is a custom set of pistons? I am not opposed to having a set made if need be. How long does it take?

This is really a stock rebuild but I also know I will have my foot in it to spool the turbo every drive.

bigrbandit

I would go look at a buick or rover site. These engines only had about 3-4psi boost because of the high static compression. If you put a more modern lower compression piston in it, you could crank up the boost and have a more satisfying ride, with less reliance on the Water injection.

jensenracing77

They had 5 to 6.5 PSI of boost with 10.25 compression. I like to get them closer to 7 psi. much higher than that and you start having injection problems. My bypass valve was stuck and was boosting to 10 psi a couple times. I had no knock at all but never boosted with that system again. I am rebuilding that one now.

jensenracing77

I talked to D&D aluminum V8 today. He knows these engines very well and builds them all the time. He is saying he would not use the old original pistons and go with the Egge pistons. He is saying that he has guys using nitrous on them on a regular basis with no problems. He said I can beat on them pretty hard and not hurt them in this engine.
Still undecided and need to think about it more. I am very temped to just re-ring it as is and live with it. Obviously I still need to pull it apart and measure everything before final decision.

83hurstguy

Custom pistons with rings and pins can run around $1100, depending on what forging they start with and how much work they have to do. You might be able to find them for less if you shop around. IIRC, 215 pistons are your typical old school piston with a high compression distance, so most modern forgings won't work without a longer rod.

Once you use custom pistons, you're kinda hooked. They are nice and do everything you want... and you end up with a modern ring pack that preserves the cylinder wall, generates less friction/heat, makes more power...

jensenracing77

I just checked the Egge site and the compression height for them are 1.875 and then I measured a couple stock Jetfire pistons I have and come up with 1.877 so that looks like a non issue. I also called them and the tech was not comfortable with more than 6 psi of boost. I told him I was shooting for 7 and he did not really like that.

I have no desire to increase HP for the sake of more power. My goal with the engine is to have NO less than stock HP but also have something I am not worried about boosting with. If a quality item ups the HP than I am ok with that but that is not the reason I want it.

With custom pistons they will be lighter and I would assume it would rev faster also after being balanced. This may be a dumb question but how would that affect taking off from a stop in casual driving with a manual transmission. I would think it would not affect it. I know I may be over thinking things but want all the information I can before making decisions.

70-442-W30

Hard to believe 1 psi would make that much difference. Why can't you just build your twin-turbo JTS-V and let us all see it? 500 HP like the car's designers really wanted to put in there.

Olds64

If you aren't looking to drastically bump up the HP have you considered spending money on head studs instead of pistons? They would prevent you from blowing a head gasket if you happen to boost to 7 or 8 psi.

jensenracing77

These engines don't have any problem with head gaskets luckily. Oldsmobile used 18 head bolts per head (or 6 bolts per cylinder) so they hold up well.

83hurstguy

With custom pistons, it would rev faster but with most weight being in a steel flywheel, you probably won't notice a huge difference. Typical rod bearing failures occur when the rod is thrown over TDC and the bolts have to keep the rod halves together and the bearing parting lines off the crank journal. Less piston weight helps reduce the rod stress a ton when it has to change direction.

jensenracing77

With a custom piston, would I just send them my piston and tell them I want the same thing? It is a 3.5 bore and if I get custom pistons made I wonder if a modern ring would be available for it? I don't think it needs it but if I replace the pistons I will bore it just to be sure I have a fresh true wall. Every day I am back and forth on this. One day I say heck with it and run the original pistons and the next day I think I want to replace them. I am somewhat liking the idea of custom pistons but boy will the cost to rebuild go way up.

Oldskeeper

Hi Eric,
I rebuilt the 215 in my 61 and used the Egge pistons, bored the block and fitted the rods to the pistons. We bought the rings from a jobber supply shop here and fitted them. I have no reservations about buying pistons from them for my next project. As far as getting custom pistons from them I wouldn't hesitate calling and discussing this with them, they are very well informed and know what you are talking about.
Steve

83hurstguy

Typically you surface the block (deck if needed to true everything), measure stroke and rod length, then set your pin height to finalize your deck clearance. Then you figure out your bore size. When you don't need valve reliefs it's relatively easy after that (pin diameter, ring grooves). The total seal catalog lists a 3.524 metric ring pack. The bore size seems to be near a 2.8L Ford and an S&S Harley engine, so something should be out there... I'm not a ring catalog expert so I don't want to mislead you.

Another risk I didn't think of is the rings not sealing if you aren't honing the cylinders with a deck plate, and if thick vs thin rings will make a difference there.

Your best bet is to talk to your machinist, determine if he has a preferred piston company they work with, and then have the discussion. You could always call CP / Wiseco / JE / Racetec / UEM and see what they have...

The economical option is definitely the stock pistons or the Egge option...