Smoked a piston, need casting info.

[binderbird]

I smoked a piston in the Binderbird over Memorial weekend. When I called for another one the parts guy said the flat top piston was the emission piston and had scuff gaurd stuff on the side. The non emission piston was domed and didn't have the scuff gaurd. When I rebuilt the engine about 9 years ago he sold me the flattop piston with scuff gaurd for the emission head. I didn't know there was differance and always thought I had the non emmision engine/heads. Today I found what I think is the casting ### and need to know what heads these are. I looked in the FAQs and found nothing that helps. One set is out of a 79 scout ###432089-C2. The old set that is in the port shop is 359489-C3. The second set has cost me a fortune to get right and is the set I plan to reinstall next week.
I also would like to know about these so called scuff gaurd pistons that scarred my #6 cylinder on Memorial week end. Are they any good. This set only had 10,000 miles on them. Yea, I know,,, I turned it too tight.
Any help with the casting ###s would really help.
http://videos.streetfire.net/video/d...a0b3c069ac.htm

[Bill usn-1]

All my stuff is in storage so I can't get you the numbers.
These pics may help others understand the difference.

This is the flat top piston head.



This is the contour piston head. Notice the large chamber. This will kill your compression with flat top pistons.





Flat top piston. Stock



Contour piston

[Will Marsh]

Brian,

Bill's got it nailed.

Per our Phone Con earlier, check out Dan Phariss' posts in this thread about the differences between a 345E and 345A.

http://www.binderplanet.com/forums/s...ad.php?t=43198

HTH,

[71 Scout 2]

The 359489-C3 is an "E" casting for flattop pistons, it just isn't drilled for the air-injection tubes. I have four of them, the chambers look like Bill's first pic, decent cylinder head overall for an SV.

[jeff campbell]

#432089-C2,is w/out air tubes.,jeff

[ScoutmanSV]

Let's not forget that most of the aftermarket pistons are destroked .020" & if you use a newer head gasket > it's also thicker than stock by ~ .015". Prolly wouldn't hurt with a blower/turbo, but w/o: it'll kill your CR. Silvo-Lite is the only company I know of that doesn't destroke IH SV pistons.

Scuff guard? I dunno that these high nickel blocks need it esp when ppl say they pull apart a stock 200K+ engine & still find the cyl cross-hatching evident.

HTH,

[binderbird]

Let's not forget that most of the aftermarket pistons are destroked .020" & if you use a newer head gasket > it's also thicker than stock by ~ .015". Prolly wouldn't hurt with a blower/turbo, but w/o: it'll kill your CR. Silvo-Lite is the only company I know of that doesn't destroke IH SV pistons.

AAAARRRRGGGGHHHHH, I didn't know when I biult this engine they destroked the pistons. I looked today and thanks to your reply, saw the piston is WAY below the deck.AAARRRGGGGHHHH. I just didn't understand why the performance dropped off so much. Iv'e blamed it on everything. Here's another one for the fire.
How much did it hurt the compression?
What is estimated compression?

Stock deck.
Aftermarket flattop pistons.
E-heads shaved .030.
.047 head gasket.
bored .030.

Should I?
Buy a whole new set of pistons?
Shave the deck?
Shave the deck AND buy new pistons?
AAARRRGGGHHH!!!

[ScoutmanSV]

Originally Posted by binderbird

Stock deck.
Aftermarket flattop pistons.
E-heads shaved .030.
.047 head gasket.
bored .030.

Should I?
Buy a whole new set of pistons?
Shave the deck?
Shave the deck AND buy new pistons?
AAARRRGGGHHH!!!

Pistons .020 - .030 (heads shaved) = -.010 (increase in CR)
New head gasket .047 - .025 (old) = + .022 (decrease in CR)
.022 - .010 = .012 (added to the comp chamber vs stock for a decrease in CR)

You sure that new HG is .047 seems awful thick? IIRC stock steel is .022 ~ .025ish.

New, not destroked, pistons will alleviate the need for .020 taken off to compensate & if you use the same .030 shaved heads w/a .047 vs .025 HG > you'll net a .008 gain (less overall CC volume) over stock instead of a .012 loss (more overall CC volume than stock) like now. Adjust accordingly for different HG thicknesses.

CR is bore x stroke / CC volume .... IIRC. Someone correct me if I'm wrong.

HTH,

[71 Scout 2]

I'd say that you're roughly around a CR of 7.92:1. Other things can sway this figure slightly, but I'd say that's pretty close.
What do you mean by smoked? Does it have a hole in the top? Or did you score it? Break a ring? If one piston is damaged, what about the others? I'd place money that you either run it lean, or cranked too much timing in it verses spinning it too tight.
My personal opinion, if more than one piston is damaged, I'd look into getting a set of Silvo-lites. If only one piston is damaged maybe look into getting one replacement and drop it in. The .020" destroke will only bump you to about 8.2:1, not really something to get too excited over. I wouldn't recommend shaving the heads anymore than you have to. Taking material off most "E" cylinder heads only nets about 75% gain in CR verses decking, it also hampers flow on the exhaust port (but can help on the intake).

[Bill usn-1]

Something else to remember, The stock piston is below the deck.
I had to deck my block .070 just to get it to a .007 deck hieght.
Thats .77 below the deck.

If you figure a compression hieght difference of .020 for pistons.


so .077-.020=.057 below the deck before I even start.

But you have to keep in mind the gasket surface angles wether you shave heads or deck the block. The intake will not just bolt back on after shaving that much.

I preassembled the crank and 2 pistons on opposite corners to check deck measurements prior to cutting. And left it preassembled for the machine shop to verify.