273 Commando Slugs

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tmcdowell1

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Where can I find some new flat-top pistons for my 273 HiPo? Oversize (+.030) would be great. Suggestions? Thanks!​
 
Kanter has flat tops listed. Egge has domed pistons available although I can't seem to find them in their new online catalog. I e-mailed them a couple min. ago for an answer. I will talk to my machinist on the 30th and find out what I need for my rebuild. I will be ordering pistons soon. toolman

(scroll down to the bottom of the page)

http://www.kanter.com///productdeta...0&Vdr=&Itm=&MDv=1&MDpt=0&MSb=0&Cat=32&Prc=362

Here's a link for Hughes Engines that sells the Egge pistons.
http://www.hughesengines.com/Index/...dpbmVz&searchmode=keyword&page=2&partid=24544
 
Got a call from the machine shop and it's time to order pistons. Time to call
Egge tomorrow. Wish me luck. Mike
 
I called Egge today and ordered my pistons and rings. I talked to Sam. Nice guy!
I also let him know we've been name dropping Egge Machine here on FABO for quite some time now. He said the HP 273 and the poly 318 parts have been flying off the shelves. Apparently a lot of people rebuilding/restoring them.
I also stopped buy the machine shop today who is a customer of mine on my tool route. My block has been cleaned and crack checked. A +.030 will clean things up nicely. The crank needs a .010/.010 turn and he will recondition the rods with new bolts. Here's a shot of the block all cleaned up and waiting for some machining and a set of pistons. In the next couple weeks I need to send the heads off to get done. This is getting exciting! toolman

Block at D Machine.jpg
 
Hey Mike, It would be great if you kept us up to date on your build. Are the pistons forged or cast, thats what I had issues with. I lost sleep at night when I was going to build up my 273 in my 67 barracuda. I wanted to keep it #'s matching Sooo Badd. I wimped out at the last second and found a bad *** 340, in Iowa and drove from KC to Des Moines to pick it up, it has been a blast, but I still second guess my choice. I pretty much just swapped out blocks and my 340 has all my 273 externals( alt. tranny, exhaust,headers,dist.etc) and I bought a nice engine cradle and cleaned up the 273 and it sits next to my barracuda in the garage. May put it another project down the road. But a report as the build goes would be real cool. Thanks!
 
I'll keep you'all informed if you don't mind me rambling on. LOL The factory pistons were cast pop-up's. The Egge replacements are also cast pop-up's. They are 10.5:1 just like the factory ones. I ordered cast rings. Steve at the machine shop said the cast rings are more forgiving and seal better for engines that don't get driven much and sit over the winter. They deal with surface rust in the bores better than Moly rings do. Race engines that have moly rings seal better but usually get rebuilt every season. Makes sense to me. I'll keep you posted. Toolman
 
Great!, Look forward to hearing all about it! Keep all your shop info and prices to. It's hard to find good Mopar work and I would drive 200 or 300 hundred miles for good work!
 
toolmanmike said:
I'll keep you'all informed if you don't mind me rambling on. LOL The factory pistons were cast pop-up's. The Egge replacements are also cast pop-up's. They are 10.5:1 just like the factory ones. I ordered cast rings. Steve at the machine shop said the cast rings are more forgiving and seal better for engines that don't get driven much and sit over the winter. They deal with surface rust in the bores better than Moly rings do. Race engines that have moly rings seal better but usually get rebuilt every season. Makes sense to me. I'll keep you posted. Toolman
Click to expand...

Will you be having the heads cc'd and the true compression determined? I'm curious to see what the actual compression is with those pistons. Since the 8.4 listed in the books for the flat tops is more like 7.9, or 8 as mine was.
Also if the compression is an actual 10.5, you could mill the top of the domes a little to get a little less for our gas.

What heads are you using, and did you decide on a cam?

Sorry about the hi-jack.
 
Looking at the 273 Commando pistons on the engine I just took apart the 10.5:1 pistons appear to be quench pistons. They actually come above the deck and match quite well into the heads.

I never had pinging problems even with 87 Octane gas.

If paying for new pistons and concerned about the compression ratio, I wouldnt go and bugger them up. Just order a lower compression piston and reduce your HP.


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Edit: Not really Quench Pistons by definition, but have a small distance between the piston and the head. And matches to the head chamber. Because they come above the deck and fit into the chamber without matching flat areas to flat areas on the head, they arent quench.
 
I got my box from Egge today. (just pistons and rings and a few catalogs)
The pistons look good. They are marked for left and right banks with offset pins
for a quieter engine. They look just like the factory slugs. I'm getting excited! The photos are off my phone and not the best quality but you can get the idea of the shape and dome. I got my transmission back yesterday (wednesday) and it looks good. Nothing inside was broke or excessively worn. It was disassembled, cleaned, reassembled and adjusted with new seals and gaskets. I think Mike glass beaded the case too. it looks good. Sorry about the poor photos. toolman

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010700_1802[00].jpg


010700_1940[00].jpg
 
Babyblue66 said:
Will you be having the heads cc'd and the true compression determined? I'm curious to see what the actual compression is with those pistons. Since the 8.4 listed in the books for the flat tops is more like 7.9, or 8 as mine was.
Also if the compression is an actual 10.5, you could mill the top of the domes a little to get a little less for our gas.

What heads are you using, and did you decide on a cam?

Sorry about the hi-jack.
Click to expand...

I probably wont cc the heads. The replacement pistons are 10.25-10.5/1 and with composite head gaskets instead of the factory steel shims the final compression should be around 10:1. 93 pump premium should run fine with that.
I got a Isky E-4 cam. (#390144) It's a solid lifter cam with .425 lift, 216 deg.@ .050 with a 108 deg. lobe center. Its a bit bigger than the stocker but has a slight lope to it which the stock cam doesn't. Mike
 
A little trivia from about 40 years ago. With the factory formula S 273 10.5 pistons, they had offset pins. The trick was to swap banks, and turn the piston and rod assemblies backwards. In other words, take 1, 3, 5 and 7 and put them in the 2, 4, 6 and 8 holes, but notch to the rear, not the front. It was suppose to be worth more horsepower and up to 1000 more rpm's, but you might hear piston slap until the motor warmed up, but didn't hurt any parts.

I did this to a couple of motors, and although I didn't quite get 1000 more revs, it definitely up'd the power and never had a problem. The TRW forged replacement pistons (I think they were L2222F) had a centered wrist pink, so the above wouldn't make any difference.

Like I said, just trivia I remembered when I read your post.

Russ.
 
I remember reading that. The offset is noticeable and I might have to try it as long as it doesn't hurt anything. Thanks for the reminder.
Mike
 
toolmanmike said:
I probably wont cc the heads. The replacement pistons are 10.25-10.5/1 and with composite head gaskets instead of the factory steel shims the final compression should be around 10:1. 93 pump premium should run fine with that.
I got a Isky E-4 cam. (#390144) It's a solid lifter cam with .425 lift, 216 deg.@ .050 with a 108 deg. lobe center. Its a bit bigger than the stocker but has a slight lope to it which the stock cam doesn't. Mike
Click to expand...

All you need is a piece of plexi glass and something to measure the cc's, like a big syringe.
I think its nice to know to get actual compression. Just for my own knowledge I'd like to know what those pistons actually have for compression.
Its most likely less than the advertised 10.5.
Since mine was under 8 with the flat tops.
Just curious.
 
I used a CD Blank from my computer, put a thin coat of vaseline around the outer ring, pressed it to the head, then a syring with oil in it to CC the heads on my 440.

I plan todo the same for my 273 as I get into the build of it.

I found the #6 had spun a rod bearing. Looking at re-conditioning, and seeing IF the slight grooves in #5 and #6 holes can be honed out without having to bore it. Else, I'll be looking for some of these pistons at .010 over as well. Already looking at turning the rod bearings on the crank because of the grooves in it on #6.

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If the pistons only come at .030 over, I guess that will have todo.
 
hi, I couldn't let the comment about cast rings versus moly rings slide. a cast ring is all metal it will rust to a bore, moly will not!! plus a moly ring is self lubricated, it will seal under wide open throttle, a cast ring will not!! thats why a moly ring seals better. and race motors with moly rings do not need to be rebuilt every season. I have done a motor that had cast rings in it, the guy raced it, ran at the middle of the pack, , rerung with moly rings, now runs at the front easily, and picked up 400 RPM down the back stretch. way faster. the rings lasted way longer too, without loosing seal and power. just food for thought!!
 
Your points are valid. I'm sure moly rings would seal more effectively and make more power. The cast rings lasted for 40+ years and should work ok in my basic
rebuild. I read a couple of piston/ring articles and I came to the conclusion that
for a race or high performance street engine, forged pistons and moly rings should be used. Especially if you're going to rpm the motor to get horsepower. For my basically stock rebuild, cast pistons and cast rings will do just fine. The last paragraph sums it up for me.
http://www.carcraft.com/techarticles/piston_ring_technology/index.html
 
I suspect I will be looking for some 10.5:1's very soon. Do they wait to batch the pistons, or manufacture them on order? How much did your egge's run you (PM if you dont want to post public).

I have a few grooves in #5 and #6 cylinder from metal thrown by the #6 spun rod. Too shallow to catch a fingernail, but can feel them. The block will be at the machine shop this weekend, and will find out if they can hone it out, or whether It'll have to be bored.

--Tom
 
Pistons, pins , lock rings, and a set of rings cost me just over $400. Talk to Sam
and they had them on the shelf.....they shipped that same day. toolmanmike
 
Double M said:
A little trivia from about 40 years ago. With the factory formula S 273 10.5 pistons, they had offset pins. The trick was to swap banks, and turn the piston and rod assemblies backwards. In other words, take 1, 3, 5 and 7 and put them in the 2, 4, 6 and 8 holes, but notch to the rear, not the front. It was suppose to be worth more horsepower and up to 1000 more rpm's, but you might hear piston slap until the motor warmed up, but didn't hurt any parts.

I did this to a couple of motors, and although I didn't quite get 1000 more revs, it definitely up'd the power and never had a problem. The TRW forged replacement pistons (I think they were L2222F) had a centered wrist pink, so the above wouldn't make any difference.

Like I said, just trivia I remembered when I read your post.

Russ.
Click to expand...

I read that in a couple of small block books. Mopar motor builders have been reversing pistons for years. It would be interesting to find out who came up with the idea first. Tom Hoover I would bet. I measured the pistons and all came out within .0005 of each other. It will be an easy job for Steve (the machinist). He can bore and hone the cylinders all the same size and I can install the pistons in any bore I need. He was impressed with the quality of the pistons and the machining. It was fun, the piston pins seemed stuck when I took them out of the box but after they warmed up the pins slid back and forth in the pin bores like butter. (very precision machining) This is fun!
Mike

011200_1914[00].jpg
 
Have your machine shop weigh the pistons. They are lighter than the originals.
My machine shop called today and said the originals weighed 753 grams and the new +.030 slugs weighed 685 grams. He will balance it! Light is good!!!!!! Mike
 
Did you attempt to reverse your pistons, or just install them straight up? Where these are above-deck I'd always worry about hitting a head.

I've made some headway on my 273 rebuild. No longer a refresh. Gonna have to be bored. Cant order the pistons till I know whether its 20 or 30 over.

Ordered a Racer Brown Mechanical ST-1 today. Jim says it'll give me just what I want with my setup. Its a little hotter than the 273 Hipo cam, but not as hot as the D-Dart Race cam. Those ran really lumpy. Not as streetable as I want.

My total budget is around $1500 if income taxes come out right and based on the machinist I talked to today, I will probably come in just under the wire even with buying pistons. Cant wait. Block and everything to be dropped at the machinist tomorrow.
 
Sounds good! What's the specs on that Racer Brown cam? Keep us posted and don't forget to take lots of photos. Mike
 
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