AA Slipper Skirt Pistons

[DKK Ted]

Anybody ever tried them, any problems, pro's and con's??

[Mike Lawless]

This is from a product review I had on my website a while back, (now unlinked to my main page, but still relevant)

AA Pistons....
I've been using the same set in our race motor on and off since '06. (2332, NA, 260plus HP, 8500 rpm)
After measuring the barrel and pistons right out of the box, the very first thing I did was have the barrels honed. The clearance was only .0015". Enough for a street engine perhaps, but not comfortably enough for a race motor. I had the barrels opened up to give me .006" clearance. This might have been a little much. They clatter a little when cold. Probably could have gotten away with .004"

Here's some point by point observances....
Observation # 1. Opening up the bore that far screws you up on ring selection. There are precious few ring set available that can stand an oversize that much. The standard ring that comes with the set ends up with a gap approaching .040" when the bore is honed that much. They will never seal good enough.
Solution...A total seal gapless top ringset. Made for a "file to fit" end gap. Not many other options available, and a very expensive ringset. Given those two primary problems, (cost to hone and buy a new ringset) it brings the cost up significantly for the total package. There might be other "file to fit" ring sets out there, but it will take some research.

Observation #2. Once this was done (I also drilled eight gas ports into the top to intersect with the back of the groove), the piston set out-performed anything else I tried, which included some high dollar American made custom pistons. Every time I tried some new "whizbang" piston, I ended up reinstalling the AAs.

Observation #3. I received a later set from my good friend Ron Barrett to look at. The barrels were a little larger from the factory, giving a net clearance of .0035". This only makes the bore .002" bigger than "nominal" (3.701" for a 94mm bore) and doesn't open up the ring end gaps too bad. The Barrett's chose to run that set as is without additional honing.

Observation #4. Yes, they are made in China. I find it amusing that they have outperformed high priced American made custom pistons in my application. I think overall, I might have had more peace of mind with an American made set of pistons such as Wiseco, but I didn't like the ring groove sizes in the two off the shelf version of those. 2mm top or 1mm top. The 2mm size's best place in an endurance application. The 1mm doesn't seal well enough without positive crankcase evacuation (vacuum pump). That my opinion based on my experience.

Conclusion: They are probably fine as is for a street motor, but make sure you inspect them carefully for burrs and stray metal chips. And by all means, check the clearance. Don't take anything for granted.

Funny thing happened when I called Wiseco to see about getting their piston with the standard 1.5 X 2 X 4mm ring groove package. The guy I spoke to said I was stupid for wanting that (His words) and the price for the pistons alone would be $600.

I said "OK then. I guess I won't be buying anything."

[Bruce]

.... such as Wiseco, but I didn't like the ring groove sizes in the two off the shelf version of those. 2mm top or 1mm top. The 2mm size's best place in an endurance application. The 1mm doesn't seal well enough without positive crankcase evacuation (vacuum pump). That my opinion based on my experience.

Funny thing happened when I called Wiseco to see about getting their piston with the standard 1.5 X 2 X 4mm ring groove package. The guy I spoke to said I was stupid for wanting that (His words) and the price for the pistons alone would be $600.

So by their logic, 2mm is good, 1mm is good, but 1.5mm is stupid?

[Mike Lawless]

.... such as Wiseco, but I didn't like the ring groove sizes in the two off the shelf version of those. 2mm top or 1mm top. The 2mm size's best place in an endurance application. The 1mm doesn't seal well enough without positive crankcase evacuation (vacuum pump). That my opinion based on my experience.

Funny thing happened when I called Wiseco to see about getting their piston with the standard 1.5 X 2 X 4mm ring groove package. The guy I spoke to said I was stupid for wanting that (His words) and the price for the pistons alone would be $600.

So by their logic, 2mm is good, 1mm is good, but 1.5mm is stupid?

Wiseco logic. Who knows. I figured that I was the customer and I knew what I wanted. All he had to do was give me a simple yes or no. But he had to be insulting and as a result Wiseco will never get my business, and I will continue to spread the word of their superb customer service.
Anyway, AAs are still in there running good.

[DKK Ted]

 Mike, I heard that the wrist pin part of the piston is weak and they break. Hear anything like that? The reason why I'm asking is because I'm rebuilding my other 2303cc with a E125 on 106LC W/1.25 rocker's for the street. Using JD 42X37 heads with IDA's.

Ted

[TexasTom]

rebuilding my other 2303cc with a E125 on 106LC W/1.25 rocker's for the street. Using JD 42X37 heads with IDA's.

Ted,
Sorry, I have no info for you on the AAs ...
But, your OTHER engine sounds Sweet for the Street!
TxT

[DKK Ted]

Thanks Tom, but I need to pull it to freshen IT up and install the new heads that are coming from Fred Simpson (Performance Tech.). But with the other motor will have a bit more street fun.   

Ted

[Mike Lawless]

Mike, I heard that the wrist pin part of the piston is weak and they break. Hear anything like that? The reason why I'm asking is because I'm rebuilding my other 2303cc with a E125 on 106LC W/1.25 rocker's for the street. Using JD 42X37 heads with IDA's.

Ted

Ted, I Know people have said that, but I don't know if that's an accurate assessment. When the they came from the supplier, there was only .0015" clearance at the skirt. One might get away with that for a lightly loaded street motor, but not a highly loaded race motor. I'd have to imagine that some of those that had trouble with the pistons installed 'em straight out of the box, assuming they were good to go. Motor is then  driven aggressively. Piston heats up, expands more than the clearance given, seizes in the bore, yanks the pin out.

Some my disagree, but that' the way I see it.

I've ran two sets. Muffler Mike has ran 'em. We both clearanced 'em first. We both run the snot out of our motors.

[Neil Davies]

.... such as Wiseco, but I didn't like the ring groove sizes in the two off the shelf version of those. 2mm top or 1mm top. The 2mm size's best place in an endurance application. The 1mm doesn't seal well enough without positive crankcase evacuation (vacuum pump). That my opinion based on my experience.

Funny thing happened when I called Wiseco to see about getting their piston with the standard 1.5 X 2 X 4mm ring groove package. The guy I spoke to said I was stupid for wanting that (His words) and the price for the pistons alone would be $600.

So by their logic, 2mm is good, 1mm is good, but 1.5mm is stupid?

Wiseco logic. Who knows. I figured that I was the customer and I knew what I wanted. All he had to do was give me a simple yes or no. But he had to be insulting and as a result Wiseco will never get my business, and I will continue to spread the word of their superb customer service.
Anyway, AAs are still in there running good.

Could you buy the 1mm pistons and machine them yourself for 1.5mm?

[DKK Ted]

Mike, I heard that the wrist pin part of the piston is weak and they break. Hear anything like that? The reason why I'm asking is because I'm rebuilding my other 2303cc with a E125 on 106LC W/1.25 rocker's for the street. Using JD 42X37 heads with IDA's.

Ted

Ted, I Know people have said that, but I don't know if that's an accurate assessment. When the they came from the supplier, there was only .0015" clearance at the skirt. One might get away with that for a lightly loaded street motor, but not a highly loaded race motor. I'd have to imagine that some of those that had trouble with the pistons installed 'em straight out of the box, assuming they were good to go. Motor is then  driven aggressively. Piston heats up, expands more than the clearance given, seizes in the bore, yanks the pin out.

Some my disagree, but that' the way I see it.

I've ran two sets. Muffler Mike has ran 'em. We both clearanced 'em first. We both run the snot out of our motors.

I kinda figured, what do suggest clearance should be on a 83X94 with E125 cam with JD 42X37.5 heads CR at about 9.1? Thanks for the info. Mike.

Ted

[Mike Lawless]

If it were mine, I'd shoot for between .003 and .004". Based on the pistons I've measured, this would mean a bore size of 3.7025 to 3.7035" or about .001 to .002 over. That shouldn't cause you any grief with excessive ring gaps.

It seems that newer sets are now coming this way with the barrels already honed a littl oversize with about that clearance already there. Otherwise, it's an added expense to get the right size bore that needs to be figured into the total cost, making them not such a great deal.

[Mike Lawless]

.... such as Wiseco, but I didn't like the ring groove sizes in the two off the shelf version of those. 2mm top or 1mm top. The 2mm size's best place in an endurance application. The 1mm doesn't seal well enough without positive crankcase evacuation (vacuum pump). That my opinion based on my experience.

Funny thing happened when I called Wiseco to see about getting their piston with the standard 1.5 X 2 X 4mm ring groove package. The guy I spoke to said I was stupid for wanting that (His words) and the price for the pistons alone would be $600.

So by their logic, 2mm is good, 1mm is good, but 1.5mm is stupid?

Wiseco logic. Who knows. I figured that I was the customer and I knew what I wanted. All he had to do was give me a simple yes or no. But he had to be insulting and as a result Wiseco will never get my business, and I will continue to spread the word of their superb customer service.
Anyway, AAs are still in there running good.

Could you buy the 1mm pistons and machine them yourself for 1.5mm?

I'd imagine one could do that. However size and finish needs to be very precise. Besides, if I'm paying over 500 bucks for a set of custom pistons, I'd expect to dealer to say "Yes sir Mr Lawless. What you want!"

[DKK Ted]

Thanks Mike, who sell the AA pistons??

Ted

[Mike Lawless]

Get hold of Ron Barrett. If he can't help you, he can point you in the right direction

[DKK Ted]

Will do Mike, thanks.         Ted

[Lids]

There were quality issues with these pistons, that I hope were sorted.  I have one of the first batch ever made sat waiting to be used.  I remember a few yeasr ago the QA guy from AA trying to explain the issues they had and the fact that someone was flogging failed QA samples via the samba.  I recieved a personal email reassuring me etc.  My engine builder is also the offical importer into the UK, and he doesn't liek to be messed around.  If there good enough for him....well there good enough for me.

I also have a set of long AA barrels which means no spacers.

http://cal-look.no/lounge/index.php/topic,6803.0.html

[brian e]

I just got a new set of AA 94mm strokers from Brothers for $169.  I went over them with our fancy measuring tools in our machine shop and I would have to say they are closer then the last set of Mahle 94's I measured.  I spoke with the guy at brothers and Greg Tims and both have been using them on the engines they build with good results.  Both mentioned no turbos and no real high compression. 

-Piston weights were within .005oz. on all 4
-Pin to piston crown was within .0005 on all 4
-Skirt Diameter within .0005 on all 4
-Cylinder bore diam. within .0005 on all 4
-zero bore taper all 4
-Bore to skirt clearance .0025 on all 4
-Cylinder top sealing surface to bottom sealing surface within .0005 all 4

I still need to measure the ring gaps.  The piston casting looks as good or better then Mahle, and the cylinders don't have that annoying bump at the case end of the head studs that needs to be clearanced on the Mahle's. I think they will be a pretty good inexpensive setup for street engines.

These will be going on a 2276 for a baja.
-Brothers 82mm crank
-Brothers 5.4 Chevy H-beams
-Steve Tims Stage 2's
-125 cam, 9.5 CR
-44 webers
-Stock AH case completely worked over at Brothers.  (I sent it off, they worked it over, and and I will have it back in less then 2 weeks!!)

Brian

[DKK Ted]

Hi Brian, are these the race slipper skirt pistons/barrel sets?? And does Brothers sell just pistons only? ssounds pretty good! Thanks!

Ted

[brian e]

Hi Brian, are these the race slipper skirt pistons/barrel sets?? And does Brothers sell just pistons only? ssounds pretty good! Thanks!

Ted

They are not the race version, just the cheap $169 set.

http://aapistons.com/index.php?main_page=product_info&cPath=15_1_6&products_id=46



I also forgot to add the pin clips that come with the kit seem to be a little flimsy.  They are not the stock style wire circles, but a real internal snap ring.  I was going to junk them and get some tru-arcs.  The pins also don't come matched and slid into each cyl. like Mahle, but I measured all the pins and they are all dead on.

Brian

[DKK Ted]

Thanks Brian for the reply. I e-mailed Brothers, see what info I get. You say the pins mic all the same and fit all the pistons? Then you say they don't come matched, a little confusing. Good call on the Tru-Arcs.

Ted

[brian e]

Thanks Brian for the reply. I e-mailed Brothers, see what info I get. You say the pins mic all the same and fit all the pistons? Then you say they don't come matched, a little confusing. Good call on the Tru-Arcs.

Ted

Sorry.  They didn't come install in each piston like the Mahle's do.  They are individually wrapped in standard Chinese cheap sealed clear wrap and in the box.  No real problem since they all measured good.  Just thought it was a little different.

Brian

[DKK Ted]

Got it, well let see what Brothers say, my motor I'll be using them on is my 2303cc back up motor. Almost like yours, Jeff Denham 42X37 heads, E125 cam with 1.25's. Well be going in my street car. Yours sounds good! Brothers really do good work. They did some work on my case also, was very pleased. Thanks again.

Ted