Compression

340runner · Sunday at 8:21 PM

Cop car wagon said:
I have those pistons in several 340's. I wish they would make a factory style cast oversize in L+R and with valve pockets on one side only. At that cost, you might come in at or under budget.
A minor piston weight change probably won't hurt. As my machinist reminded me, "what does the oil, in and on the piston weigh?" Of course some people believe in underbalancing. Weigh both.
I would not add nitrous to a cast piston. But I know nothing about nitrous tuning with extra fuel.

Oh I'd be under budget, a gasket kit is 150$ and rings are another 100$

Also, summit says the wrist pins are of the press-in style for those pistons. How does that work with the rod that is bushed for a floating pin?

Only question is do I redo my main and rod bearings? I don't know, some may call Uncle Tony a nut job but he runs one of his motors with all used bearings to "rev freer"

Also, do I need to replace the wrist pins when I replace piston?

Cop car wagon · Sunday at 8:46 PM

Thats why they call this an inspection tear down. If it was all rebuilt properly, you are inspecting, and replacing the improper pistons.
Unless there is funky wear, I would not change bearings. Your peace of mind might move you differently.
But measure rod bearing clearance. Your oil weight is based on it. Tighter/ thinner- looser/ thicker.
Summit is mistaken. Those pistons show snap ring grooves in the picture.

Curiousyellow71 · Sunday at 9:12 PM

I would not buy a cast silvolite. I would get the high compression 2316 forged speed pro pistons. Unless the old bearings look exceptional.. get new.

Cam choice will depend on your budget, I'd check out the condition of the cam first. If it looks ok..you could run it, but take time to use a degree wheel to install it correctly.

340runner · Sunday at 9:20 PM

Curiousyellow71 said:
I would not buy a cast silvolite. I would get the high compression 2316 forged speed pro pistons. Unless the old bearings look exceptional.. get new.

Cam choice will depend on your budget, I'd check out the condition of the cam first. If it looks ok..you could run it, but take time to use a degree wheel to install it correctly.

Okay, looks like I can run the 2316s and be within weight to where I don't need to balance, now my other thing is I really don't have space to put a engine on a stand, much less fit both a cherry picker and get the motor out. Is it possible to do this replacement with the engine in car at all? It seems like I can do everything with r&r of the pistons in the motor, not even having to mess with timing or anything. The only thing I'm hung up on is cylinder honing, but I've seen forums of people being able to plug bottom of cyl with towels and run the ball hone? I just need new cross hatch

Curiousyellow71 · Sunday at 9:42 PM

How much room do you have to work with?
Doing it in the car is possible, but you will earn it, it will take much longer and the possibility of screwing it up are high. If you have problems with room keep with bolt external mods Instead of getting into the bowels of it. Do Nitrous or a torque storm supercharger. You could do cam swap obviously wo pulling the engine. Imo pistons swap and honing is not what you should be tackling in the car.

340runner · Sunday at 9:45 PM

Curiousyellow71 said:
How much room do you have to work with?
Doing it in the car is possible, but you will earn it, it will take much longer and the possibility of screwing it up are high. If you problems with room keep with bolt external mods Instead of getting into the bowels of it. Do Nitrous or a torque storm supercharger. You could do cam swap obviously wo pulling the engine.

I mean, I might be able to find room to do a swap, whether it being a friend or something, I don't even know if anyone is over in the Chicagoland area with a garage from here and is willing to put a car for a weekend in it. I don't want to put in a supercharger, but nitrous would be fun. I don't know though if with the cast pistons would be safe really. If I went with the 2316s I could have best of both worlds, compression and forged

Curiousyellow71 · Sunday at 9:52 PM

2385f is a forged piston made by TRW.

Cop car wagon · Sunday at 9:55 PM

Motor out, put the car back in the garage.
Piston clearance you have with existing pistons will help determine new piston choice.
Are those sealed power 2316's not hyperutectic?
They will need more clearance and careful ring gapping. Weight is listed at 745gr, which is more than cast, which is more than 72 pistons.

Cop car wagon · Sunday at 9:59 PM

Maybe you got lucky with the heavy 72's being forged.
They match the weight of the 2316's.

340runner · Sunday at 10:37 PM

Curiousyellow71 said:
How much room do you have to work with?
Doing it in the car is possible, but you will earn it, it will take much longer and the possibility of screwing it up are high. If you have problems with room keep with bolt external mods Instead of getting into the bowels of it. Do Nitrous or a torque storm supercharger. You could do cam swap obviously wo pulling the engine. Imo pistons swap and honing is not what you should be tackling in the car.

Knowing what you know about the internals, would you run a 200shot of nitrous and not be worried about it exploding? I'm thinking that should get me to at least 520hp, which is hopefully enough to push me faster

Curiousyellow71 · Sunday at 10:40 PM

I would not run 200 unless you verified what the ring gap was and had a fuel system that would keep up with the demands of a 200 shot.

340runner · Sunday at 10:49 PM

Curiousyellow71 said:
I would not run 200 unless you verified what the ring gap was and had a fuel system that would keep up with the demands of a 200 shot.

To do that though, I would need to remove the pistons, which would mean i might as well put in the higher comp pistons, and then not even have to run a higher nitrous shot

The fuel system side i can keep up with, I was thinking of a nx safe system. Knowing that, what would you shoot max?

RemCharger · Sunday at 10:54 PM

There's only 3 things you have to worry about when dropping a 200horse bomb on an unknown smallblock 4 gear build
1 everything in front of the clutch
2 everything behind the clutch
3 and of course the clutch itself.

Some successful people have ironed out the NA program first. And then done their research and start with a 100 shot.
Then slowly advance their tune upwards

340runner · Sunday at 11:00 PM

RemCharger said:
There's only 3 things you have to worry about when dropping a 200horse bomb on an unknown smallblock 4 gear build
1 everything in front of the clutch
2 everything behind the clutch
3 and of course the clutch itself.

Some successful people have ironed out the NA program first. And then done their research and start with a 100 shot.
Then slowly advance their tune upwards

Well, I know the clutch and behind the clutch. I'm worried more about in front of it, as it also happens to be a lot harder to replace if it kills itself. I know the clutch and trans have it to stand it, and if the clutch or trans doesn't for some reason I've done both myself before on jack stands, I'll do it again. Rear end is the same way, I just shattered a pinion yoke for my 3.55s so I swapped in center that'll be even harder on my stuff, 4.56s. I haven't done engine yet, but I assume time will tell as it's the only thing that hasn't committed suicide

Have the book ordered that you posted, supposed to come in a couple days hopefully it gives me good insight.

weedburner · Monday at 6:07 PM

I say embrace the low compression you have and use it to your advantage!

Back in 2012 I had a stock block 355 sbc with hyper .055" in the hole "rebuilder" pistons. With .093" quench and 251/261/114lsa solid roller, it only cranked about 100psi on the starter! To wake it up, I bought a used 150hp plate system for $150. Took out the n20 jet, then bored/ported the nitrous solenoid and let the solenoid itself be the jet. Ended up spraying that engine to about 700hp on 87oct pump gas, ran 5.73 1/8th in a manual trans 2525lb car.

I liked that low-compression/cheap-gas engine so much that I built a proper version with forged pistons, aluminum rods, and 345cfm sprint car heads.

Grant

340runner · Monday at 6:45 PM

weedburner said:
I say embrace the low compression you have and use it to your advantage!

Back in 2012 I had a stock block 355 sbc with hyper .055" in the hole "rebuilder" pistons. With .093" quench and 251/261/114lsa solid roller, it only cranked about 100psi on the starter! To wake it up, I bought a used 150hp plate system for $150. Took out the n20 jet, then bored/ported the nitrous solenoid and let the solenoid itself be the jet. Ended up spraying that engine to about 700hp on 87oct pump gas, ran 5.73 1/8th in a manual trans 2525lb car.

I liked that low-compression/cheap-gas engine so much that I built a proper version with forged pistons, aluminum rods, and 345cfm sprint car heads.

Grant

Well, it's got aluminum heads and forged pistons so it's kinda like your proper ish version. How much gas do you think you were spraying hp wise after you bored out the solenoid?

Did you gap the piston rings also for nitrous, or did you just ball with it?

weedburner · Tuesday at 12:22 AM

340runner said:
Well, it's got aluminum heads and forged pistons so it's kinda like your proper ish version. How much gas do you think you were spraying hp wise after you bored out the solenoid?

Did you gap the piston rings also for nitrous, or did you just ball with it?

Stock small body solenoid only flows about 175hp? I bored the solenoid orifice to .078" which added about 20% more area, so 220+ with the porting. Didn't try more as I was afraid the solenoid might have trouble with a warm bottle. The solenoids were mounted directly to the Powershot plate with a short brass pipe, only nitrous orifice was the solenoid itself which was near the point of discharge to minimize phase change. On the fuel side, an .065" Holley jet was pressed into the 1" long pipe between the solenoid and plate. Adjusted the tune with fuel pressure.

4.040 bore, 1st/2nd gaps were .032". I had a retard box that automatically retarded timing when the n2o came on. Ended up using 14* of retard on 87oct after cracking a few pistons with 8 and 10 degrees. On my sbc, #5 and #6 were the ones to watch.

Grant

weedburner · Tuesday at 12:44 AM

Here's a pic of the crossbar plate that I currently use on the more proper version of the low compression engine, it's set up similar to the Powershot plate mentioned above with bored/ported direct mounted solenoids...

Grant

340runner · Tuesday at 6:14 AM

weedburner said:
Stock small body solenoid only flows about 175hp? I bored the solenoid orifice to .078" which added about 20% more area, so 220+ with the porting. Didn't try more as I was afraid the solenoid might have trouble with a warm bottle. The solenoids were mounted directly to the Powershot plate with a short brass pipe, only nitrous orifice was the solenoid itself which was near the point of discharge to minimize phase change. On the fuel side, an .065" Holley jet was pressed into the 1" long pipe between the solenoid and plate. Adjusted the tune with fuel pressure.

4.040 bore, 1st/2nd gaps were .032". I had a retard box that automatically retarded timing when the n2o came on. Ended up using 14* of retard on 87oct after cracking a few pistons with 8 and 10 degrees. On my sbc, #5 and #6 were the ones to watch.

Grant

Okay, that's the thing that scares me, you had from the get go double the ring gap on the piston if this PO didn't gap the rings for boost. Would I if I ran such godly low compression in a original high compression motor? Yeah because who would run it NA?

I don't know if running 93 in tank and in the dedicated nitrous fuel cell race gas will help keep it cooler

weedburner · Tuesday at 10:54 AM

340runner said:
Okay, that's the thing that scares me, you had from the get go double the ring gap on the piston if this PO didn't gap the rings for boost. Would I if I ran such godly low compression in a original high compression motor? Yeah because who would run it NA?

I don't know if running 93 in tank and in the dedicated nitrous fuel cell race gas will help keep it cooler

I doubt you would have much trouble with stock-ish ring gaps as long as you didn't give it too much timing. Overly rich nitrous tunes want more timing for best power, problem with rich is that you will then get into trouble with too much timing if for some reason the fuel system doesn't keep up. Contrary to popular opinion, a "lean and mean" nitrous tune is safer than a rich one.

I used an early warning system to detect damaged hyper pistons and compromised ring seal, a sealed crankcase with a pcv valve drawing crankcase vacuum. If the pcv valve drew less crankcase vacuum at idle after making a pass, I drove it home and leaked it down. Caught many cracked hyper pistons before they took out the entire engine...

A similar system could give you some peace of mind if you wanted to incrementally sneak up on spraying 200hp with unknown ring gaps.

Grant

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