Piston discussion

[CammedS197]

I'd be more concerned with bore taper and size.

Size as in overall diameter? and taper?

 

[msvela448]

Size as in overall diameter? and taper?

Your machinist should be able to measure this and tell you whether a bore is necessary, or just a hone. Like what has been said before you want to take out as little material as possible. Since you are going to be boosted, spend the money to get the deck squared and heads milled flat. You really want to make sure you have a good seal.

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[Juice]

Size as in overall diameter? and taper?

Yes, bore diameter determines piston diameter needed. Cylinder bores taper with wear, so depending on how much taper is there (if any) will mean the difference between over boring or just honing. This is why you should NEVER buy pistons BEFORE the block is checked/machined.

Also, if the block does need boring, a good machinist will NOT start the work on the block until the pistons are in his hands. And then fit each piston to a specific cylinder individually.

Note: Personally, I prefer piston clearances on the "loose" side of the specs for an engine that will be run hard/raced. Also, ring gapping is an area where attention to detail can be beneficial.

 

[CammedS197]

Your machinist should be able to measure this and tell you whether a bore is necessary, or just a hone. Like what has been said before you want to take out as little material as possible. Since you are going to be boosted, spend the money to get the deck squared and heads milled flat. You really want to make sure you have a good seal.

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Thanks and I did actually plan on doing this lol. I want it to be perfect. Which is also why I'm going to take it very slow. Hoping I can find a wrecked 3v and pull the motor at a junk yard so I can really take it slow and do it right and have time to have questions answered on here lol.

Yes, bore diameter determines piston diameter needed. Cylinder bores taper with wear, so depending on how much taper is there (if any) will mean the difference between over boring or just honing. This is why you should NEVER buy pistons BEFORE the block is checked/machined.

Also, if the block does need boring, a good machinist will NOT start the work on the block until the pistons are in his hands. And then fit each piston to a specific cylinder individually.

Note: Personally, I prefer piston clearances on the "loose" side of the specs for an engine that will be run hard/raced. Also, ring gapping is an area where attention to detail can be beneficial.

Ahh okay thanks. I will remember this when I do that. Well it won't be built for that which is also why my eyes are set for 4032 forged to have a tighter clearance.

 

[Pentalab]

Lito has recommended several times in the past, to leave the CR stock 9.8:1
Dunno why, unless perhaps if you were using crazy amounts of boost?
Meanwhile the 11-17 coyotes are 11:1 and the 2018 is 12:1
Back in 2010, Roush used 8.5:1 on it's all forged 540 H and stage 3 cars... + 14.5 psi boost.

For DD use, most of the time you are not in boost, so the higher CR is worthwhile. 10.5:1 doesn't seem unreasonable for a built 3V.

 

[Juice]

Compression ratio used to be more critical in the past, but advances in combustion chamber design and engine management systems have dropped octane requirements quite a bit. Look at the coyote for example, 11:1 and runs on 87. Heck, a buddy of mine has a mazda suv. It has 14:1 CR and runs regular gas.

 

[msvela448]

Compression ratio used to be more critical in the past, but advances in combustion chamber design and engine management systems have dropped octane requirements quite a bit. Look at the coyote for example, 11:1 and runs on 87. Heck, a buddy of mine has a mazda suv. It has 14:1 CR and runs regular gas.

Agreed.. Somewhere between 10:1 and 11:1 will make it very responsive even when not in boost, and you can run regular gas. It's all about the tune.

Higher CR, and adding boost, will mean that head sealing will be very important. Have everything milled flat, get some Cometic MLS gaskets, ARP studs... Let it rip.

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[CammedS197]

Okay thanks guys. I really appreciate the help and never thought of that with the coyote. But I swear I did hear that on the coyote they "bleed" some compression. But Shoot I'll shoot for some flat tops and a 10.5-11:1. 1 whole point of compression would be roughly 20 crank hp I believe or more not sure lol.

 

[46addict]

100% not the point, you don't need them for any reason on a sub 600 HP build when a shelf piston will do. Why are we even discussing custom pistons...

I'm pretty sure the point of Gibtec being brought up is because they're a local business in America. But then so is DSS, Modmax, and MHS, etc. You don't have to get all defensive and argumentative. There's more than one way to skin a cat here.

 

[msvela448]

I'm pretty sure the point of Gibtec being brought up is because they're a local business in America. But then so is DSS, Modmax, and MHS, etc. You don't have to get all defensive and argumentative. There's more than one way to skin a cat here.

Gibtec also offers thicker skirts and a bunch of options for no extra price.. Move ring packages up or down, change ring groove thickness, wrist pin offset, any size, etc.

They were great to work with (Nick is who helped me) . Scanned my cylinder heads with some laser computer thing to get the valve locations and then cut valve reliefs specifically for my heads and cam profile, while keeping the compression ratio where I wanted, and kept my piston to wall clearances tight.

I was just very happy with the process, the product, and the price, so I am confident in recommending them.

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[RocketcarX]

I'm pretty sure the point of Gibtec being brought up is because they're a local business in America. But then so is DSS, Modmax, and MHS, etc. You don't have to get all defensive and argumentative. There's more than one way to skin a cat here.

I'm not being shitty, I'm trying to understand the logic that gets us to custom pistons when they have no place this particular discussion. It's just chasing rabbits, distracting.
You have dozens of shelf piston options good to 700-1000 horsepower and zero need to have custom parts created at this and most power levels.

 

[raredesign]

Lito has recommended several times in the past, to leave the CR stock 9.8:1
Dunno why, unless perhaps if you were using crazy amounts of boost?
Meanwhile the 11-17 coyotes are 11:1 and the 2018 is 12:1
Back in 2010, Roush used 8.5:1 on it's all forged 540 H and stage 3 cars... + 14.5 psi boost.

For DD use, most of the time you are not in boost, so the higher CR is worthwhile. 10.5:1 doesn't seem unreasonable for a built 3V.

I’m having mine built with 9:1 to see how high of psi I can hit on 93 octane.
From what Lito and Jeremy have said, e85 is a miracle worker, so you can boost to the moon on higher than stock compression.


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[tjm73]

Any forged off the shelf piston that maintains the stock C/R will get the job done at the stated power level goal. In fact, I am sure the factory hypereutectic pistons would get the job done with a tune that doesn't make the engine run too lean and detonate.

Guys are making 700+ whp in Coyotes with hyper pistons. GT500's have hyper pistons. The piston is not the problem. It's the tune and/or the gas used. Get bad gas on a tune that's too close to the edge and.....BOOM.

 

[raredesign]

My goal: 450-550rwhp daily not really raced but some spirited driving with a v3 blower.

MMR sells Manley, and if you’re set on using the stock crank, perhaps this is worth a look.

http://www.modularmotorsportsracing.com/cart/index.php?main_page=product_info&products_id=765

They are building my 1500se billet rod motor with all the bells and whistles.

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[raredesign]

Any forged off the shelf piston that maintains the stock C/R will get the job done at the stated power level goal. In fact, I am sure the factory hypereutectic pistons would get the job done with a tune that doesn't make the engine run too lean and detonate.

Guys are making 700+ whp in Coyotes with hyper pistons. GT500's have hyper pistons. The piston is not the problem. It's the tune and/or the gas used. Get bad gas on a tune that's too close to the edge and.....BOOM.

You're in Rush?! I'm next door in Henrietta...hold on you're getting a PM...

 

[01yellerCobra]

MMR sells Manley, and if you’re set on using the stock crank, perhaps this is worth a look.

http://www.modularmotorsportsracing.com/cart/index.php?main_page=product_info&products_id=765

They are building my 1500se billet rod motor with all the bells and whistles.

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Start saving for a replacement. It will blow up. And MMR won't back up their work.

 

[raredesign]

Start saving for a replacement. It will blow up. And MMR won't back up their work.

Facts please, because I have read all the posts and negative info and most is regurgitation of 10 years ago. Aside from the known issues now rectified, many of the people named didn't even have an MMR block, and instead bought a rotating assembly, and after blowing it from a fault of the builder, tuner, or pushing the motor beyond the initial intended specs, decided to blame MMR. I've seen multiple replies on forums from Mark offering to make it right. If I have a problem, we'll take care of it then, but Mark and Greg have been great to deal with. Aside from that, out of the many people I now know with built motors, some have been running an MMR motor for years without issue.
There was even a long drawn-out post that used a member as an example customer with a poor experience, but the member chimed in to clarify that it was a different motor that blew and his MMR motor had been running strong for years. "Misinformation strikes yet again."

They are also building Mo Makki's motor to take Trump to another record. I'm happy to give them a chance, and as I said, if there is a problem, I'll deal with it then.
Also, consider this: In Upstate NY, we have a phenomenal motor builder that told me he is done doing any more boosted applications, because after a solid record of 30+ years in the industry, he has had repeated tuners blow his motors on a dyno resulting in furious customers that blame him.

Hope this info helps.

 

[Juice]

I will never run boost on hypers. One bad tank of gas, or getting a little aggressive on the tune, and BOOM. I got a 7 cylinder pushrod 5.0 to prove my point.
About half the piston material is all I found in the pan, the rest is on the track somewhere or went out the tailpipes. Hypers are brittle, and won't tolerate much detonation. You want to play with dynamite, be my guest. Can it be done safely? That is up to you how you define "safe".

Now that said, I've got well over 10,000 track miles of boosted HPDE events on my current pushrod FI engine (340 hp GT 40 crate + Vortec Strim) with hypers in it with a conservative tune.

Bottom line, you have less of a safety margin with hypers on boost.

Yes, this is kind of comparing apples to oranges with pushrod vs mod, but detonation does not know the difference between them.

 

[eighty6gt]

302's don't have fast ecu's and knock sensors. Also I don't get what was just said.

 

[RocketcarX]

I will never run boost on hypers. One bad tank of gas, or getting a little aggressive on the tune, and BOOM. I got a 7 cylinder pushrod 5.0 to prove my point.
About half the piston material is all I found in the pan, the rest is on the track somewhere or went out the tailpipes. Hypers are brittle, and won't tolerate much detonation. You want to play with dynamite, be my guest. Can it be done safely? That is up to you how you define "safe".

Now that said, I've got well over 10,000 track miles of boosted HPDE events on my current pushrod FI engine (340 hp GT 40 crate + Vortec Strim) with hypers in it with a conservative tune.

Bottom line, you have less of a safety margin with hypers on boost.

Yes, this is kind of comparing apples to oranges with pushrod vs mod, but detonation does not know the difference between them.

You sure you don't have TRW forged pistons? What year was the original 5.0 that let go, it also likely had TRW forged pistons...