Projects KB pistons two with small chips

It has been a long time. Hello Hamb you all helped me set up a supercharged 350 and it still runs as it should.

April of 2016 this 327 was taken to the shop. .30 over the mains and rods .10 under. Installed a 142 supercharger and instantly it knocked and detonated. It got pulled back out and stuff into the corner in favor of the 350 you all helped me do correctly (Thank you all so much)


Now I’m in a better spot and I am not such a ***** (take that with a grain of salt) I got the 327 out of the corner and this is what was re-discovered.

Right under the .30 stamping two pistons have very small chips. I did the first thing I could think and pulled apart cleaned. Checked ring gaps re-torqued and now am left with it as it sets. Bearings looked new and cylinders do also. It all seems as if I don’t care about the two small chips I could run this?

I’ll wait to hear back from members but I think I know the answer already. New .30 over forged. So has anyone ran a piston like this? And did it last?

I just need an engine by the next three weeks for the mud. (Going to have fun)

 

It doesn't look like a chip to me, much too smooth. It looks like a modification for flame travel as it is right where the spark plug lines up. It is interesting that only two pistons have this. Seems like you would have noticed this when the engine was being ***embled.

If this is for a street engine, I wouldn't have any problem running it like it is.

 

Not there, on the edge next to the bore

 

In the pic # 4, it looks like it may be cracked. Right in the radius/base of where the dome/pop up starts to form. Just inboard of the OD chamfer. Maybe check that real close in person, with some magnification.

 

It looks like the sides of the dome are hitting the sides of the combustion chamber in the head.

 

Looks to me like your piston was on the edge of meltdown. If you were going to run it I'd for sure check the top ring for any pinch and radius the melted edge pretty good before using it in an engine I didnt really care much about.

 

Maybe hitting in these spots...

 

I did inspect this and it looks as if it is split on camera but once eyeballed in person it is a shelf. It had to be hitting the head and pushed material down and created a very very sharp edge shelf that was low enough not to hit the head anymore. I actually hit that spot with a file before the piston was re-installed.

This engine detonated knocked and was shutdown still banging/knocking the spark plug tip fell into the cylinder and created the chip in picture one. Only when the other pistons got pulled did I find the second piston with the same exact chip.

All rings spin free on the pistons thankfully. I have seen so many KB pistons broke right smooth off the top in other forums and even here on the hamb. so I think I’ll splurge and go forged. The machining and rods cost me enough that I guess it’s probably worth it over chunking the block.

 

The ***** in me is already showing. I saw that one shelf took a picture but did not check that spot on ANY of the other pistons.

Every single one has a shelf the same as the pictured piston. Clearly can see every spot in the head where every piston hit the head. So it did self clearance every single piston. But they are shelves not splits.

I’ll sleep on this and put every piston at top dead file in clearance then file the head. If the filed areas clean up I don’t know. On top of filing in more than needed clearance maybe a thick head gasket? I don’t even know if they make different thickness gaskets I’ll have to look.

I wrote this engine off when I pulled it out of the bay so i’m playing with stuff that I guess I stopped caring about long ago. Something wants me to care but I have a 350 at the shop going .30 over now and I’m just waiting for the call to go pick it up.

Ohhhhhh what to do maybe I’ll toss it back in the corner and still not care. Maybe it will go in a buddy’s truck and it will then be his job not to care. We just need engines to stomp on while playing in the mud.

 

The KB Hypereutectic pistons will blow into bits like gl*** if the get abused very hard. If it was detonating hard, I would be leery of putting them back in.

 

If it was detonation damage, I’d expect the top ring groove to be pounded out and have excessive side clearance.

The pictures are consistent with piston to head contact, though.

I would s**** the pistons.

 

If it were hitting the heads how in the heck did it ever get turned over while setting timing or doing lash etc. Seems like it would have had a few hard stops that would take some force to overcome?

 

i thought the same-had that happen on a kubota w/ wrong hd gasket-never could get close to firing it!--yanked it apart,quick gasket change!(tiny amt of difference!)

 

I'm curious why you chose to use pop up pistons on a blower motor? What heads are you using and have you calculated your static compression ratio? With a blower, you should have around 8 to1 compression, maybe even get by with 8.5 or 9 to 1, with the right cam and low boost. Seems obvious why that thing was detonating and knocking. You really need flat top pistons with large chamber heads, or dished pistons with small chamber heads to get your compression down to a blower freindly level.
Those pop ups could be fine in a naturally aspirated engine.

 

Maybe what you thought was detonation was actually the pistons hitting the chamber sides?

 

Exactly.

 

I think some of the generalized statements made about KB pistons are unfair. I suspect these failed pistons you mentioned are the result of misapplication and / or ***embly. Hypereitecit pistons have applications where they perform well. Blown, turbo, nitrous are not the environments for them. Those applications have specific pistons configurations for them that control material, dome shape, thickness, and top ring location to manage heat. I have used many KB pistons, mostly forged but some hypers as well, without issue. Any brand of piston that is used in an unintended application and incorrectly ***embled will fail. I am not in any way ***ociated with KB.

 

I have read the reply’s after my last comment in this thread. The simple answer is I ***embled without the heads on installed the heads and hit the key. This engine has 1000 or so miles on it naturally aspirated.

I was a very dumb kid and still am. So when it fired instantly after the build I followed cam break in procedure and bagged the snot out of it for said 1k miles. I bet I heard the tap but as a dumb kid I bet I thought it was just the lifters pumping up and I convinced myself that was any tapping I was hearing.

Blower installed after 1k miles and hit the key. Went off down the road about a half mile commence broken spark plug knocking and banging. Key off tow home. Ripped it out in favor of the beautiful running 350 you all helped me with so long ago. (Still an animal of a 350)

Every single piston was just pulled out (again) (haven’t slept in two days) Every piston was filed to clear the heads. ARP moly lube and the 8740 bolts torqued (again) to arp spec. All torqued correctly and I felt nothing scary when torquing the bolts.

While every piston was out I verified ring end gaps all measured a what seems like an excessive .38 I seem to now remember the piston supplier (a great man) doing the end gaps with me at his shop and telling me the gaps were safe for the street.

All rings spin on the piston very free. It’s my buddy’s problem now it’s going into a truck to bash on at the pit. (Oddly I have this feeling it could live a happy naturally aspirated life)

I stomp the life out of the 350 with the blower and the darn thing won’t blow up. (Return spring was temporary and changed to a bracket setup I know that return spring was junk)

 

Hyper 1 step up from cast .What octane was you running ?
Plug # ?
Those piston on 64-68 chamber
10 3/4 to around 11:5
10:1 you can get away with pump 91-93
with 4- psi max I would say with Hyper
kinda pushing it .
& you would want to take timing away under boost to 30-33 , each engine differs .
Put / set head on No gasket
Maybe some clay & cellophane
No plugs , rotate engine .

Take scotch bright / rollocks
Light buff those
Marks

 

The 327 I’m working on now with the eagle rods/kb hypers will not see boost.

The 350 in the Jeep with the supercharger has an xe262h camshaft but other than that is a bone stock 350 with 74cc chambers. Has been problem free for 3k+ miles and I will not tear that setup down unless it fails. It runs 97 from the pump. And is locked to 28 degrees all before 3,200 rpm just as I was taught by members on here long ago. (You all did me right)

The 327 with the kb hypers will get a set of 62cc chamber power packs. The same exact heads that that the pistons self cleared against long ago. An XE268H camshaft and a general dress up kit for the pit.

I am going to pour Sunoco 118 from the pump into the 327 I want to ask about that fuel on here as I know low octane with high compression could be a problem. But I do not know if 118 is too much octane and would cause any trouble with the kb hypers and small chambers.
(Please advise if possible)


I will polish every piston where filed. I will grind away a slight bit of material from each chamber in the heads to ensure expansion won’t allow re-contact with the pistons.

Is (snow) still on this forum? (May not have his username right) but he was always recognized as snow to me whether he likes that or not. I’ll look back through my posts and recognize him or whatever his real username was eventually. (He was one of the greats)

 

Jim Snow?
Signs his post with “Snowman”?

 

There are chart's for Octane verse compression.

118 yr wasting yr $$
Even 116 ..
100 or 105 would be fine compression ratio under boost 14 :1 ish (6 ish boost )

with 118 u could probably lock the timing at 36-38 .

 

If you are buying new pistons I would buy flat top pistons and set them at 0 deck. Get a head gasket with a crush around .040 or a little less.

 

I’m not buying new pistons for the .30 over 327 engine. Said in my above post the kb pistons were filed to clear the heads the heads will be filed to make sure they cannot hit and I will polish the filed spots.

Everything torqued down fine and all ring gaps were checked and rings all spin very free on the on pistons.

Bearings/bores looked great and I found nothing that really scared me past two very very small piston chips in the very first photo in this thread I posted post #1 photo #1

(Snowman) that’s gotta be him! I looked back and I can’t even find the posts. He helped me setup the the distributor for the supercharged stock 350 in the jeep that was put into the Jeep after the 327 was pulled for the broken plug and knocking/banging. He told me what bushing springs and lockout was needed for the small cap distributor and even recommended what carb was ideal for the supercharged 350.

Been 6 years and I specifically remembered him because he helped me do things right for once. Again (one of the greats) Are posts talking back and fourth are just gone? He needs to know I’m only having fun with that 350 in the Jeep because he helped me set it up. 3k miles and the Jeep has stock 1940’s 4wd and drivetrain behind the Lakewood bell housing. 5.38 gears and I bangshift that ****er it’s hard to let off the loud pedal but extremely dangerous to stay in it.

 

Let’s ask him…

@jim snow

 

It’s not me. Must be someone else. Sorry I couldn’t help.Snowman ⛄️

 

Ain’t no women gonna hold my hand won’t be there to lie makes me a happy man

 

I have timed engines without the flywheel key for Cdi systems to upgrade from magneto to Cdi. I put the piston at the top of the bore on the compression stroke rocked it back tightened the flywheel and let the Cdi do the rest of the advancing.

On this Chevy 327 I’m going to 12 btdc static on the compression stroke then allowing the va***m advance and mechanical weights do the rest correct?

I cannot set it to 30 degrees btdc compression stroke and point the rotor at #1 because with static at 30 degrees the weights and vacuum advance would then take the timing way to far advanced?

Can I set it compression stroke 30 degrees btdc rotor pointed at #1 and lock it out there? I’m thinking that would cause hard starting issues?

 

More likely 12 deg of initial not enough.
Even stock cam chevy likes around 16.
Me 18-28 with Advance. Each set up differs ,
If using a non lock you will need to set Avance limiter in distributor,
Nothing in stone says rotor has to point
to # 1 cy on block just need to verify
Tdc 1 & any poll on cap / rotor .
Mine any where I feel .

If you where to lock @ 30 , you would have a remote ****on, get engine spinning b4 flipping power to ignition on because of so much BTDC .

 

^^^^^ WTH?