Using closed chamber pistons with open chamber heads - Chevelle Tech

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post #1 of 30 (permalink) Old Jan 25th, 06, 9:38 PM Thread Starter
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John
 
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Using closed chamber pistons with open chamber heads

I'm having my 454 rebuilt and would like to get the compression up to 10.5:1. Talked to my builder today about using closed chamber pistons because nobody makes an open chamber piston that gives you decent compression with a 120cc head. He advised against it saying the dome is designed for a closed chamber and the air flow/burn would hurt horsepower. So if any of you have done this I would like to hear your results.

On another note, why don't piston manfacturers make a prodcut that their customers need? We have several choices for cyl. heads which almost all have 116cc to 120cc combustion chambers and nobody makes a piston to give you 10 to 11:1 compression??? Seems to me there is a huge need here to be filled and the first company to come up the product would clean up!

'70 Malibu, 454 w/Brodix Ovals, TH400 w/10" ATI, 12 bolt with 4:11's
'98 Camaro, M6, LS6 Intake, MTI lid, TB bypass, Ported Maf & TB, Pacesetter Headers, Catted Y, Texas Rumbler Catback, B&M shifter, FRA, !EGR
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post #2 of 30 (permalink) Old Jan 25th, 06, 9:44 PM
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Re: Using closed chamber pistons with open chamber heads

No the closed pistons won't work with the open head.

The closed chamber is more squared off, where the open chamber is more rounded at the corners. The edge of the closed dome usually hits on the edge of the chamber; I think on the exhaust side, away from the spark plug, if memory serves me right.

Guess how I know that.

Problem is, it was probably 25 years ago. I don't remember. You know how they say your memory is the second thing you lose as you age; the thing is, I forget what the first one was supposed to be.
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post #3 of 30 (permalink) Old Jan 25th, 06, 9:56 PM Thread Starter
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Re: Using closed chamber pistons with open chamber heads

He did mention that the pistons would have to be cut to work correctly but doesn't want to go this route because of the dome shape.

'70 Malibu, 454 w/Brodix Ovals, TH400 w/10" ATI, 12 bolt with 4:11's
'98 Camaro, M6, LS6 Intake, MTI lid, TB bypass, Ported Maf & TB, Pacesetter Headers, Catted Y, Texas Rumbler Catback, B&M shifter, FRA, !EGR
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post #4 of 30 (permalink) Old Jan 25th, 06, 9:59 PM
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Re: Using closed chamber pistons with open chamber heads

red,
Speed Pro (TRW) L2465 is listed as 10 to 1 with 119cc head. Thats with
.025" deck hgt. If you deck the block and get "0" deck it will probably be closer to 10.5 Also, I am pretty sure that Wiseco and JE make pistons to do what you want.

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post #5 of 30 (permalink) Old Jan 25th, 06, 10:11 PM Thread Starter
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Re: Using closed chamber pistons with open chamber heads

Quote:
Originally Posted by BillK
red,
Speed Pro (TRW) L2465 is listed as 10 to 1 with 119cc head. Thats with
.025" deck hgt. If you deck the block and get "0" deck it will probably be closer to 10.5 Also, I am pretty sure that Wiseco and JE make pistons to do what you want.
In the catalog I have the L2465 shows 10.68:1 with a 106.9 combustion chamber. I don't think I can get the combustion chamber down that far. If you have any part numbers for the Wiseco or JE pistons I would be really grateful.

'70 Malibu, 454 w/Brodix Ovals, TH400 w/10" ATI, 12 bolt with 4:11's
'98 Camaro, M6, LS6 Intake, MTI lid, TB bypass, Ported Maf & TB, Pacesetter Headers, Catted Y, Texas Rumbler Catback, B&M shifter, FRA, !EGR
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post #6 of 30 (permalink) Old Jan 25th, 06, 10:36 PM
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Re: Using closed chamber pistons with open chamber heads

Beats me...I've run open chamber heads on closed chamber pistons many times with no issues. May not be perfect....but it works fine.

Basic TRW 11.0-12.5 type domes.


JIM
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post #7 of 30 (permalink) Old Jan 26th, 06, 1:32 AM
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Re: Using closed chamber pistons with open chamber heads

Quote:
Originally Posted by rednecks70
I'm having my 454 rebuilt and would like to get the compression up to 10.5:1. Talked to my builder today about using closed chamber pistons because nobody makes an open chamber piston that gives you decent compression with a 120cc head. He advised against it saying the dome is designed for a closed chamber and the air flow/burn would hurt horsepower. So if any of you have done this I would like to hear your results.

On another note, why don't piston manfacturers make a prodcut that their customers need? We have several choices for cyl. heads which almost all have 116cc to 120cc combustion chambers and nobody makes a piston to give you 10 to 11:1 compression??? Seems to me there is a huge need here to be filled and the first company to come up the product would clean up!
=
They don't make them because open chamber heads are all over the map cc wise so,,,, the question becomes what do they make??

SRP/JE makes a piston that is 10.0 @ 118 advertised. This piston will give you anywhere from about 9.4 to 10.6 without much issue. by simply adjusting the deck & chamber volume.
You need zero deck (9.78 with this piston) & 112 for 10.5

All the aftermarket heads will normally go to 110 flat milled.

The 2465's will give you 10.5 with the block decked to 9.,78 (.005 down) & a 115cc head

The Brodix RR head is available in 119 or 115 for the same price & 110 for an additional charge

Or you can have a piston made any way you wish for a "nominal" fee

Mike (Wolfplace)
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post #8 of 30 (permalink) Old Jan 26th, 06, 5:46 AM
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Re: Using closed chamber pistons with open chamber heads

Closed chamber pistons will work with open chamber heads.

I'm running the TRW L2349 closed chamber piston with a set of 049 open chamber oval ports; no problems at all.

Darren
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post #9 of 30 (permalink) Old Jan 26th, 06, 6:23 AM
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Re: Using closed chamber pistons with open chamber heads

I built my .030 over 454 motor with H693CP -22cc dome pistons. Equivalent in a TRW forged is L2465's (fairly sure that's right). The open chamber design have a land around the circumference of the piston, whereas the true closed chamber pistons, the dome goes all the way to the edge of the piston. Aftermarket open chamber heads have a slightly wider combustion chamber to accomodate valves up to 2.30/1.90 combinations, this also alows the fitment of the CC pistons.
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post #10 of 30 (permalink) Old Jan 26th, 06, 10:00 AM
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Re: Using closed chamber pistons with open chamber heads

I ran Ross 13:1 (big .700" dome)closed chambered pistons with 781 open chamber heads with no problems. Ran great. 6.29@108 in a 3150lb Camaro. I would be leary of any machine shop that says it won't work. As far as I know it's pretty common knowlege that it will.

Jay Campbell
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post #11 of 30 (permalink) Old Jan 26th, 06, 12:38 PM
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Re: Using closed chamber pistons with open chamber heads

I'll add to that also, I have 3993820 oval port open chamber heads on top of my 454 LS-6 (late casting date) with the stock pistons and it works fine for me.

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post #12 of 30 (permalink) Old Jan 26th, 06, 1:03 PM Thread Starter
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Re: Using closed chamber pistons with open chamber heads

Quote:
Originally Posted by Wolfplace
=
SRP/JE makes a piston that is 10.0 @ 118 advertised. This piston will give you anywhere from about 9.4 to 10.6 without much issue. by simply adjusting the deck & chamber volume.
You need zero deck (9.78 with this piston) & 112 for 10.5

All the aftermarket heads will normally go to 110 flat milled.

The 2465's will give you 10.5 with the block decked to 9.,78 (.005 down) & a 115cc head

The Brodix RR head is available in 119 or 115 for the same price & 110 for an additional charge
Hey Wolfeplace, if I use the 2465's and get the heads milled down to 110cc will the intake manifold have to be cut as well?

Also do you have the part number for the SRP/JE pistons that makes 10:1 with a 118cc chamber?

Thanks!

'70 Malibu, 454 w/Brodix Ovals, TH400 w/10" ATI, 12 bolt with 4:11's
'98 Camaro, M6, LS6 Intake, MTI lid, TB bypass, Ported Maf & TB, Pacesetter Headers, Catted Y, Texas Rumbler Catback, B&M shifter, FRA, !EGR
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post #13 of 30 (permalink) Old Jan 26th, 06, 2:54 PM
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Re: Using closed chamber pistons with open chamber heads

i believe if you use a open chamber piston on a closed chamber is where you run into problems.
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post #14 of 30 (permalink) Old Jan 26th, 06, 2:58 PM
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Re: Using closed chamber pistons with open chamber heads

I have closed chamber pistons with 781 heads on a 396. I did have a clearance problem with the sides of the dome hitting the head. I gasket matched the combustion chamber to the head gasket and this solved all problems. I would go with a SRP or JE piston They market specifically a 10.25-1 piston for big block chevys, check their catalog.

Ray

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post #15 of 30 (permalink) Old Jan 26th, 06, 4:24 PM
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Re: Using closed chamber pistons with open chamber heads

Quote:
Originally Posted by rednecks70
Hey Wolfeplace, if I use the 2465's and get the heads milled down to 110cc will the intake manifold have to be cut as well?

Also do you have the part number for the SRP/JE pistons that makes 10:1 with a 118cc chamber?

Thanks!
=
Not if the heads are done properly.
The intake side of the heads should be cut the same amount as the face.
You may need to cut the bottom of the intake or top of the block depending on how much is removed though.
Best to have the block cut if possible.
This is not normally necessary unless you cut the crap out of the heads & or heads & block.

The SRP is a 212135 or 136 depending on bore for a stock rod 454
Again, this piston won't make 10.0 if you don't deck the block as above.

And, closed chamber pistons will not always fit.
Most do, some hit so just because someone say's I did it & it worked is not the best recommendation.
They usually work but you will not know for sure until you bolt your heads on your engine,,,

Mike (Wolfplace)
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