Pop goes the pistons.....................

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ProStreetCamaro

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Jul 25, 2007
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Last year I started getting a ton of blow by to the point it would push your hand off the breather hole in the valve cover. Engine ran and sounded fine but I knew something was wrong.


Whoops









Had it taken out to 4.040 and torque plate honed, decked, mains honed etc etc. It is now a 385 with 10.83:1 pump gas compression.






Here she is coming together






What do I spy cnc heads????????






The baby cam






The $1000 solid roller lifters. These have no needle bearings to go bad and drop into and wipe the engine.







Yup tons of clearance after Probe fly cut the pistons






Also sent my super comp's out to nitroplate to be coated and here she is together and ready to install.








Doing some tuning


http://youtu.be/vIQqzKXRtZw?t=48s



One of the rear oil galley plugs was leaking and we had to drop the trans to get to it. Here we are testing it to verify we fixed the leak before putting the trans back in. No exhaust here.


http://www.youtube.com/watch?v=HE27VqHn0Kk
 
Last edited:
Originally Posted By: Rhymingmechanic
Nice and lopey.

What's the reasoning behind the finish in the intake ports? I've never seen that before.


Those are cnc marks. It is just how the cnc machine carves out the runners. Many builders think it actually helps keep the fuel atomized.
 
Was the cause of the old pistons breaking above the lands caused by too small an end gap resulting in butting and lifting or was there something else going on?
 
Originally Posted By: Rhymingmechanic
Nice and lopey.

What's the reasoning behind the finish in the intake ports? I've never seen that before.


Are you referring to the rough finish. It's meant to help the fuel atomize I believe.
When I got my Harley's heads done they left the intake port finished with a rough surface. I asked why and I was told that a rougher surface helps the liquid fuel evaporate off all the extra edges.
 
Originally Posted By: OVERKILL
Was the cause of the old pistons breaking above the lands caused by too small an end gap resulting in butting and lifting or was there something else going on?


Detonation is the usual culprit on Hi-Performance stuff. Tune was off just a hair I bet.
 
Originally Posted By: OVERKILL
Was the cause of the old pistons breaking above the lands caused by too small an end gap resulting in butting and lifting or was there something else going on?



No we actually had the ring gaps set up extra wide because those were kb hyper pistons. My old brodix heads were milled down to 61cc and with those dome pistons I had 12.5:1 compression. Over the years I started putting less and less 110 leaded fuel in with the 93 premium and I ended up into detonation. That is a hyper pistons worst enemy.

I had crower sportsman rods in it before and I also changed them out to a much stronger set of scat pro comp 6" rods with upgraded arp 2000 bolts. Had the assembly rebalanced of course. The crower rods still looked like new. Sold them to a guy in Australia. He said crower stuff is real popular there.






Here is a picture of the bottom end. Had Kevco build a pan and press in / bolt on pickup. Used a melling standard pressure 10% extra volume select heavy casting pump. The crank is a Cola 4340 nitrided piece.


 
Last edited:
Originally Posted By: Clevy
Originally Posted By: Rhymingmechanic
Nice and lopey.

What's the reasoning behind the finish in the intake ports? I've never seen that before.


Are you referring to the rough finish. It's meant to help the fuel atomize I believe.
When I got my Harley's heads done they left the intake port finished with a rough surface. I asked why and I was told that a rougher surface helps the liquid fuel evaporate off all the extra edges.


Or, so Droplets of fuel do not accumulate and run down the tract. They (hopefully) break off the rough surface into the air stream.

You do not want polished intake runners!
 
Originally Posted By: WINO
Originally Posted By: OVERKILL
Was the cause of the old pistons breaking above the lands caused by too small an end gap resulting in butting and lifting or was there something else going on?


Detonation is the usual culprit on Hi-Performance stuff. Tune was off just a hair I bet.


True! I often think of forced induction applications with pictures like that and detonation, but I guess with a high enough CR (as the OP has now noted) you can do it on an N/A build too.
smile.gif


That being said, I've seen a few engines that experienced ring-butting that yielded similar failure modes which is why I asked
smile.gif
 
Originally Posted By: ProStreetCamaro
Originally Posted By: OVERKILL
Was the cause of the old pistons breaking above the lands caused by too small an end gap resulting in butting and lifting or was there something else going on?



No we actually had the ring gaps set up extra wide because those were kb hyper pistons. My old brodix heads were milled down to 61cc and with those dome pistons I had 12.5:1 compression. Over the years I started putting less and less 110 leaded fuel in with the 93 premium and I ended up into detonation. That is a hyper pistons worst enemy.


Gotcha. Yeah, I've heard some mixed opinions on the KB hypers in the SBF world, so I imagine it is similar in SBC land
smile.gif
Was it rattling like crazy? I would expect it to in order to yield that much damage (hence my thought on ring-butting) but you could surprise me and say it wasn't!
grin.gif


Quote:
I had crower sportsman rods in it before and I also changed them out to a much stronger set of scat pro comp 6" rods with upgraded arp 2000 bolts. Had the assembly rebalanced of course. The crower rods still looked like new. Sold them to a guy in Australia. He said crower stuff is real popular there.


The machinist I know swears by Crower stuff, says it is top-notch. So it doesn't surprise me that there is a following for it in Aus.


Great looking piece of equipment BTW
thumbsup2.gif
 
Originally Posted By: expat


You do not want polished intake runners!
x2. The rough surface may also help with reversion with the big lumpy cam. You do want a smooth exhaust port though.
 
What type of main bearing bolts are those and any reason not to stud the mains (cost obviously, but just curious)?
 
The rough surface allows the wave of pressure caused by the piston to effectively spread out killing the dead spaces in the intake manifold over a wider range of speeds and vacuum/pressures. That helps to prevent wet spotting which can lean out the mixture. At idle you get lumps. At speed you get detonation and pistons sometimes give up and make a mess in the engine. This also makes tuning easier and helps to eliminate confusing responses to mixture changes. In small block Chevys the area that needs the work is valve size and combustion chamber shape. The above pictures show a burn pattern that needs to be corrected both for temperature and pattern. Flame propagation is the likely culprit. Modern ignition systems can fire a rusty nail in a bucket of mud but after that the flame has to grow and travel on it's own and in this case an improved environment and better shape would be worth looking into.
 
Originally Posted By: OVERKILL
Originally Posted By: ProStreetCamaro
Originally Posted By: OVERKILL
Was the cause of the old pistons breaking above the lands caused by too small an end gap resulting in butting and lifting or was there something else going on?



No we actually had the ring gaps set up extra wide because those were kb hyper pistons. My old brodix heads were milled down to 61cc and with those dome pistons I had 12.5:1 compression. Over the years I started putting less and less 110 leaded fuel in with the 93 premium and I ended up into detonation. That is a hyper pistons worst enemy.


Gotcha. Yeah, I've heard some mixed opinions on the KB hypers in the SBF world, so I imagine it is similar in SBC land
smile.gif
Was it rattling like crazy? I would expect it to in order to yield that much damage (hence my thought on ring-butting) but you could surprise me and say it wasn't!
grin.gif


Quote:
I had crower sportsman rods in it before and I also changed them out to a much stronger set of scat pro comp 6" rods with upgraded arp 2000 bolts. Had the assembly rebalanced of course. The crower rods still looked like new. Sold them to a guy in Australia. He said crower stuff is real popular there.


The machinist I know swears by Crower stuff, says it is top-notch. So it doesn't surprise me that there is a following for it in Aus.


Great looking piece of equipment BTW
thumbsup2.gif




Actually the car at that time was so loud with 4" bullets right off the headers and couple that with my 50% hearing loss I would have never heard it pinging. The darn thing still ran good is what blew my mind.

Video of it running with the two broken pistons.

http://youtu.be/umR7ONaVOEw?t=1m19s


I love most of crowers stuff except for the lifters. Tolerances are all over the place on the lifters body causing some loose fitting lifters. My machinist looked at the rods and said no way they are not strong enough and they only had the small 3/8 arp bolts with no upgrade bolts available. He is one of the best builders on the east coast and built a shop at his house and retired. Now he only does work for a few select race teams but my cousin is very good personal friends with him. He built my cousins 496 for his 8.50 index nova and he just built a 555 with a procharger that made 2,200hp for my cousins 10.5 outlaw pro street camaro. I trust anything this guy tells me. He told me for the money the scat pro comp rods are exceptionally strong. They are a carbon copy of the Callies Ultra I beam rod.

ultra-rod-header-v3.jpg
 
Originally Posted By: 2010_FX4
What type of main bearing bolts are those and any reason not to stud the mains (cost obviously, but just curious)?



They are actually the stock bolts. I asked the machinist about upgrading and he told me if it needed to be line bored it wouldn't hurt to upgrade them but if it only needed a line hone to not bother with it. He only had to line hone my block to open up the main clearance a little. Some guys like them at .002 but he likes the mains at .003 and .002 on the rods so thats how he set it up. I am making right at 600hp and turning 7000rpm so its nothing super crazy. I was actually thinking about going with a Dart shp block but he talked me out of it. He said I would make around 600hp with my new combo and I would still be safe to spray another 250 shot on top of it. Anymore than that and he would suggest a better block.
 
On my small block Chevys, I ran main studs and a windage tray and that was only with an LT-1 in my Vette and a 302 in my Z/28. I ran solid lifters and never rev'd past 7,000 rpm. I always wondered if the windage tray affected power. Your cam must peak in the super high rpm range. I bet you have a wicked idle!!!!
 
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