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Piston massaging #3147676
05/30/23 07:20 PM
05/30/23 07:20 PM
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Laredo, Texas
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Cudatali Offline OP
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Since we know the importance of an efficient head combustion chamber, as I see these pistons I can’t help but notice how much the air is going to bounce around due to the shape of this piston. Anyone ever smooth out the hard turns and sharp edges of this piston? Any idea how much it would affect the compression?

IMG_3511.jpeg

1970 Hemi Cuda
1971 Demon 340
1969 Road Runner 440 6bbl
2018 Demon
2021 Hellcat Durango
2023 Demon 170 soon!
Re: Piston massaging [Re: Cudatali] #3147687
05/30/23 08:02 PM
05/30/23 08:02 PM
Joined: Feb 2008
Posts: 710
Central TEXAS!!!!
sr4440 Offline
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I am not an expert, but I would be more worried about the pistons being installed with the valve pockets on the wrong side.


Joe


Without Data, you’re just another guy with an opinion.
Re: Piston massaging [Re: sr4440] #3147692
05/30/23 08:26 PM
05/30/23 08:26 PM
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Laredo, Texas
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Cudatali Offline OP
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Originally Posted by sr4440
I am not an expert, but I would be more worried about the pistons being installed with the valve pockets on the wrong side.


Joe


You know I just picked up this car and pulled the engine out to see what was all inside. I hadn’t even noticed that yet. Wow haha thanks for catching that. Lol this is getting more interesting by the minute. Decided to pull the cam out to identify and found the crank had a ridiculous amount of end play. Pulled the engine out and found the crank side journal wiped out along with cam bearings. Obviously I will now have to go through the whole engine. That situation kept me so side tracked I didn’t notice the pistons. Oh well. Thanks again 👍🏼

Still interested on piston smoothing feedback


1970 Hemi Cuda
1971 Demon 340
1969 Road Runner 440 6bbl
2018 Demon
2021 Hellcat Durango
2023 Demon 170 soon!
Re: Piston massaging [Re: sr4440] #3147694
05/30/23 08:44 PM
05/30/23 08:44 PM
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Posts: 6,130
Melbourne , Australia
LA360 Offline
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In a low compression N/A engine, it's not going to be an issue.

If it was a small chamber head, with a domed piston, I'd be wanting to remove any possible sharp edges and possible pre-ignition points. If it was an engine with several stages of nitrous, I'd be looking at enlarging the compressed area, to slow down the flame front.

A dished piston down the hole, with a factory chamber isn't going to encounter such issues.

Last edited by LA360; 05/30/23 09:20 PM.

Alan Jones
Re: Piston massaging [Re: sr4440] #3147696
05/30/23 08:55 PM
05/30/23 08:55 PM
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Kalispell Mt.
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HotRodDave Offline
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Originally Posted by sr4440
I am not an expert, but I would be more worried about the pistons being installed with the valve pockets on the wrong side.


Joe


Looks like there is 4 valve reliefs so they could be installed either way. I would have put em in the other way but it looks like they were made to go either direction.


I am not causing global warming, I am just trying to hold off a impending Ice Age!



Re: Piston massaging [Re: HotRodDave] #3147711
05/30/23 09:54 PM
05/30/23 09:54 PM
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Posts: 4,309
Prospect, PA
BSB67 Offline
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Those are 2355 pistons, correct? Someone put a “D” dish in them

Re: Piston massaging [Re: BSB67] #3147712
05/30/23 10:04 PM
05/30/23 10:04 PM
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Hot Rod Ridge
FastmOp Offline
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Softening the pistons and chambers is more for power adder combos, or very hi compression. You have neither so no need

Re: Piston massaging [Re: BSB67] #3147722
05/30/23 11:23 PM
05/30/23 11:23 PM
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Super Spudsville
Mr PotatoHead Offline
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I was just going to post that. Although I have seen TRW replacement forged pistons with two different configs from TRW. Can the OP tell a bit more of the history of that motor or what the car was used for?


Originally Posted by BSB67
Those are 2355 pistons, correct? Someone put a “D” dish in them


STOP POTATO HATE!
Re: Piston massaging [Re: LA360] #3147723
05/30/23 11:57 PM
05/30/23 11:57 PM
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Laredo, Texas
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Cudatali Offline OP
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Originally Posted by LA360
In a low compression N/A engine, it's not going to be an issue.

If it was a small chamber head, with a domed piston, I'd be wanting to remove any possible sharp edges and possible pre-ignition points. If it was an engine with several stages of nitrous, I'd be looking at enlarging the compressed area, to slow down the flame front.

A dished piston down the hole, with a factory chamber isn't going to encounter such issues.


The plan is to install some aluminum heads, get compression between 9.5-10.0. Install a 22X-23Xish cam and a 6bbl setup. With that being said, Would CR close to 10:1 warrant the need for removal of sharp edges? Honestly it’s something I’ve always done even if it’s just the very sharp edges but the face of this piston really surprised me. Terrible design IMO.



To answer the question of history of the engine, it is all unknown to me, I bought the car a few months ago and I felt it was overcammed, Removed cam to identify and pick something more to my liking and began to find multiple issues.


1970 Hemi Cuda
1971 Demon 340
1969 Road Runner 440 6bbl
2018 Demon
2021 Hellcat Durango
2023 Demon 170 soon!
Re: Piston massaging [Re: Cudatali] #3147726
05/31/23 12:02 AM
05/31/23 12:02 AM
Joined: Jan 2003
Posts: 6,130
Melbourne , Australia
LA360 Offline
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Do it if it makes you feel better, it's your time.

Is it going to make a noticable difference? No...

If you had 15 or 16:1, then it would be a must


Alan Jones
Re: Piston massaging [Re: Cudatali] #3147728
05/31/23 12:12 AM
05/31/23 12:12 AM
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Bend,OR USA
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Cab_Burge Offline
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Originally Posted by Cudatali
[quote=LA360] The plan is to install some aluminum heads, get compression between 9.5-10.0. Install a 22X-23Xish cam and a 6bbl setup. With that being said, Would CR close to 10:1 .
I shoot for between 10.530 to 10.80 to 1 compression ratio on my non ethanol 91/93 octane pump gas BB builds with aluminum heads, that has work very well for me and my customers up work twocents

Last edited by Cab_Burge; 05/31/23 12:12 AM.

Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: Piston massaging [Re: Cab_Burge] #3147730
05/31/23 01:13 AM
05/31/23 01:13 AM
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Laredo, Texas
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Cudatali Offline OP
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Originally Posted by Cab_Burge
Originally Posted by Cudatali
[quote=LA360] The plan is to install some aluminum heads, get compression between 9.5-10.0. Install a 22X-23Xish cam and a 6bbl setup. With that being said, Would CR close to 10:1 .
I shoot for between 10.530 to 10.80 to 1 compression ratio on my non ethanol 91/93 octane pump gas BB builds with aluminum heads, that has work very well for me and my customers up work twocents


Thanks for the advice unfortunately I have no access to non ethanol in my area.


1970 Hemi Cuda
1971 Demon 340
1969 Road Runner 440 6bbl
2018 Demon
2021 Hellcat Durango
2023 Demon 170 soon!
Re: Piston massaging [Re: Cudatali] #3147766
05/31/23 09:09 AM
05/31/23 09:09 AM
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usa
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lewtot184 Offline
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they might work a lot better if they weren't installed upside down,.... whistling. piston/rod assembly as a unit may be in backwards. i'd check for possible bearing/crank damage.

Last edited by lewtot184; 05/31/23 10:12 AM.
Re: Piston massaging [Re: sr4440] #3147774
05/31/23 10:16 AM
05/31/23 10:16 AM
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Mt Morris Michigan
mopar dave Offline
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I think that was an old Dick Landy technique? It was said to make a little bit more power. I would be worried about bending valves/pushrods.

Re: Piston massaging [Re: mopar dave] #3147776
05/31/23 10:34 AM
05/31/23 10:34 AM
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Posts: 13,319
Marion, South Carolina [><]
an8sec70cuda Offline
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The pistons may actually be installed "correctly". The arrow pointing "front" does appear to be pointing to the front of the engine, if that's the engine stand I see on the right side of the pic.
Someone modified those L2355 "six pack" pistons by milling a dish in them...they are normally a 4 valve relief design. I've never seen a dish like that on the "top" side of the piston before, that would ruin any quench you may have had. It's possible whoever machined the pistons put the dish on the wrong side of 4 of them.
It really won't hurt anything, just not the normal way of doing it. grin


CHIP
'70 hemicuda, 575" Hemi, 727, Dana 60
'69 road runner, 440-6, 18 spline 4 speed, Dana 60
'71 Demon, 340, low gear 904, 8.75
'73 Chrysler New Yorker, 440, 727, 8.75
'90 Chevy 454SS Silverado, 476" BBC, TH400, 14 bolt
'06 GMC 2500HD LBZ Duramax
Re: Piston massaging [Re: an8sec70cuda] #3147780
05/31/23 11:07 AM
05/31/23 11:07 AM
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Laredo, Texas
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Cudatali Offline OP
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Originally Posted by an8sec70cuda
The pistons may actually be installed "correctly". The arrow pointing "front" does appear to be pointing to the front of the engine, if that's the engine stand I see on the right side of the pic.
Someone modified those L2355 "six pack" pistons by milling a dish in them...they are normally a 4 valve relief design. I've never seen a dish like that on the "top" side of the piston before, that would ruin any quench you may have had. It's possible whoever machined the pistons put the dish on the wrong side of 4 of them.
It really won't hurt anything, just not the normal way of doing it. grin

Thanks for the insight as far as why they may be that way. I agree, the surface shape totally messed with the quench, You are correct the pistons are facing the correct way in the engine. No idea what the thinking was behind this but what began as a quick cam correction is snowballing into a full blown overhaul.

I got way too many projects to add to my list LOL oh well, here we go!


1970 Hemi Cuda
1971 Demon 340
1969 Road Runner 440 6bbl
2018 Demon
2021 Hellcat Durango
2023 Demon 170 soon!
Re: Piston massaging [Re: Cudatali] #3147805
05/31/23 12:34 PM
05/31/23 12:34 PM
Joined: Jan 2003
Posts: 4,707
Moved to N.E. Tennessee
GomangoCuda Offline
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Originally Posted by Cudatali
Originally Posted by Cab_Burge
Originally Posted by Cudatali
[quote=LA360] The plan is to install some aluminum heads, get compression between 9.5-10.0. Install a 22X-23Xish cam and a 6bbl setup. With that being said, Would CR close to 10:1 .
I shoot for between 10.530 to 10.80 to 1 compression ratio on my non ethanol 91/93 octane pump gas BB builds with aluminum heads, that has work very well for me and my customers up work twocents


Thanks for the advice unfortunately I have no access to non ethanol in my area.

If there are any boating areas around you check gas stations in that area for non ethanol gas.


In theory, there is no difference between theory and practice. In practice, there is.
Re: Piston massaging [Re: Cudatali] #3147809
05/31/23 12:46 PM
05/31/23 12:46 PM
Joined: Oct 2005
Posts: 265
Anchorage, Alaska
metallicareload Offline
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Anchorage, Alaska
Originally Posted by Cudatali
Originally Posted by LA360
In a low compression N/A engine, it's not going to be an issue.

If it was a small chamber head, with a domed piston, I'd be wanting to remove any possible sharp edges and possible pre-ignition points. If it was an engine with several stages of nitrous, I'd be looking at enlarging the compressed area, to slow down the flame front.

A dished piston down the hole, with a factory chamber isn't going to encounter such issues.


The plan is to install some aluminum heads, get compression between 9.5-10.0. Install a 22X-23Xish cam and a 6bbl setup. With that being said, Would CR close to 10:1 warrant the need for removal of sharp edges? Honestly it’s something I’ve always done even if it’s just the very sharp edges but the face of this piston really surprised me. Terrible design IMO.



To answer the question of history of the engine, it is all unknown to me, I bought the car a few months ago and I felt it was overcammed, Removed cam to identify and pick something more to my liking and began to find multiple issues.


Depending on the size of the dish, getting a lot of compression might be “difficult”…. Wouldn’t it be “better” if the dish was underneath the spark plug and the quench pad matched up with the chamber?


440, 4-Speed, 3.54
1968, when Dinosaurs ruled the Earth
Re: Piston massaging [Re: metallicareload] #3147813
05/31/23 12:54 PM
05/31/23 12:54 PM
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lewtot184 Offline
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the pistons are just plain in upside down, peroid! i use a icon 836 with the same basic configuration, but installed correctly, and combined with an edelbrock rpm head is the best burning big block i've ever had. just a case of someone messing with something that has no business messing.

Re: Piston massaging [Re: an8sec70cuda] #3147815
05/31/23 12:57 PM
05/31/23 12:57 PM
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So. Burlington, Vt.
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Originally Posted by an8sec70cuda
The pistons may actually be installed "correctly". The arrow pointing "front" does appear to be pointing to the front of the engine, if that's the engine stand I see on the right side of the pic.
Someone modified those L2355 "six pack" pistons by milling a dish in them...they are normally a 4 valve relief design. I've never seen a dish like that on the "top" side of the piston before, that would ruin any quench you may have had. It's possible whoever machined the pistons put the dish on the wrong side of 4 of them.
It really won't hurt anything, just not the normal way of doing it. grin


The pistons can be swapped side to side, which will properly orient the dish and quench areas so there could actually be some benefit when swapping to closed chamber heads.
The arrow would then be pointing towards the rear........ which some claim is beneficial as well.


68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123
Dealer for Comp Cams/Indy Heads
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