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Hey Engine Guys


Lance B. Johnson

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What piston rings will my 05 monsoon take?

My guess would be same rings as the 5.7HO with the upper two at 5/64ths and the oil at 3/16s.

I am a little unsure on this as the HO has 9.1CR and the monsoon 9.4CR. A difference in CR would indicate a difference in Pistons and "maybe" the rings if you follow my train of thought.

The Indmar part is 315.00. Crazy.gif A good set of automotive rings much, much less and probably no different.

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Like John said, I don't think you'll see a difference in CR from the ring selection. Just from the distance from the top of the piston to the top ring groove. I don't think you'll get .3 points just from that anyway. It's a very small part that most overlook. I'd look at head gasket thickness and the heads themselves as possible sources for CR differences also. Some pistons will have valve reliefs, others won't. Again, very small change to CR. Also make sure those are static CR numbers (most likely). The cam will affect dynamic CR and I know the cams are different. I don't have the answer to your question at my fingertips. But my gut feel is that besides the cam, the base short block shouldn't be any different than the GM crate motor other than brass freeze plugs. I can't see there being any special need for "marine" (Indmar) rings. So I wouldn't worry about it.

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Like John said, I don't think you'll see a difference in CR from the ring selection. Just from the distance from the top of the piston to the top ring groove. I don't think you'll get .3 points just from that anyway. It's a very small part that most overlook. I'd look at head gasket thickness and the heads themselves as possible sources for CR differences also. Some pistons will have valve reliefs, others won't. Again, very small change to CR. Also make sure those are static CR numbers (most likely). The cam will affect dynamic CR and I know the cams are different. I don't have the answer to your question at my fingertips. But my gut feel is that besides the cam, the base short block shouldn't be any different than the GM crate motor other than brass freeze plugs. I can't see there being any special need for "marine" (Indmar) rings. So I wouldn't worry about it.

Ahhhh! You guys are killen' me. ;) I know very well about CR. What I am saying is that the 5.7HO and 5.7 ZZ4 DO have different pistons and different ring thickness. Our monsoons have a different CR and therefore POSSIBLY use an entirely different piston.

Using this logic, leads me to believe that the monsoon could be 5/64 or 1/16th.

The monsoon shares the same block as the Truck and ZZ4. There is NO marine block. I agree with you totally that one should be able to run a standard moly ring but 5/64 or 1/16th?

Probably best to open her up and see.

Edited by Ruffdog
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I re-read my first post and I see where you guys are comming from. Just for clarity I never suggested that rings or ring thickness affect CR. I was saying that the engines HO, ZZ4, Monsoon, use different pistons and therefore could use different ring thickness. The example- HO is 5/64th and the zz4 is 1/16th.

Some specialty pistons even use 1.5MM

I teach automotives and have been a tech 16 plus years.

So back to the basic question:

05 Monsoon 5/64th or 1/16th?

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If you can't wait until you tear it apart, order one piston set from Indmar and see what you get. I bet you could call SkiDim and they could tell you too.

Good thought. I hadn't called SkiDim. I called Indmar directly and the guy did not know either, and had no reference. I suppose he could have pulled the part and measured....

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I re-read my first post and I see where you guys are comming from. Just for clarity I never suggested that rings or ring thickness affect CR. I was saying that the engines HO, ZZ4, Monsoon, use different pistons and therefore could use different ring thickness. The example- HO is 5/64th and the zz4 is 1/16th.

Some specialty pistons even use 1.5MM

I teach automotives and have been a tech 16 plus years.

So back to the basic question:

05 Monsoon 5/64th or 1/16th?

My gut feeling is a 5/6th ring package. There is a .786% power gain when going from 9 and 9.3 CR...I wouldn't worry about it. I would just tear it apart and measure a ring. Summit will have rings in stock and to you in 3-4 days. Winter is basically here soooo you have some time Whistling.gif .

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The marine upfitters actually just purchase a marine crate engine from GM and add the externals. The long block is all standard production hardware, there is a specific GM P/N marine cam. The ZZ4 cam works really well though.

It looks to me as though the ring set you will want is the 5/64th set P/N 88894219 if standard size bore. I would follow up with Indmar to confirm that as I am using the Performance Parts Catalog as reference.

Compression ratio is controlled by head chamber size, 9.1:1 is 64 cc heads, 9.6:1 is 62 cc heads

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The marine upfitters actually just purchase a marine crate engine from GM and add the externals. The long block is all standard production hardware, there is a specific GM P/N marine cam. The ZZ4 cam works really well though.

It looks to me as though the ring set you will want is the 5/64th set P/N 88894219 if standard size bore. I would follow up with Indmar to confirm that as I am using the Performance Parts Catalog as reference.

Compression ratio is controlled by head chamber size, 9.1:1 is 64 cc heads, 9.6:1 is 62 cc heads

Funny, I just found the spec for the ZZ4 and it is showing a 58 cc head.......so I just figured that one out.

I was eyeing the ZZ4 replacement engine Drool.gif

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ZZ4 would make a good replacement engine. If you are ordering new rings for you engine I suggest the total seal rings. They seal much better and stop blowby. We have used them in many race angines and had good luck with them. Not really much more money for the gain either.

If it was my boat I would go with the ZZ4 and marinize it. What are you doing with your old engine?? I am trying to find the cam specs on one so I can replace mine. If you dont have a use for it I might be interested in the heads and cam, or you could measure the cam for me. I want to install the zz4 cam, but dont know if I would gain much.

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I was just kidding about the ZZ4, I will be needing the parts. Thanks for the inquiry though. I agree, the ZZ4 would be a great replacement. The HO also would work well, but not quite as fun.....

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The ZZ4 cam is really good, I coupled that with a set of Fast Burn 385 heads and the boat runs great. Lots of mid range torque, great hole shot and idle, plenty on the top end.

Marine cam specs: P/N: 14093638

Cam lift: .287"/.300", Valve lift (1.5 rockers): .431"/.451", Duration (@.050" lift): 196/205 deg

ZZ4 cam specs: P/N: 10185071

Cam lift: .316"/.340", Valve lift (1.5 rockers): .474"/510", Duration (@.050" lift): 210/221 deg

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