kb107

-
brian6pac

brian6pac

Legandary Member
Legendary Member
Joined
Nov 15, 2016
Messages
5,668
Reaction score
4,089
Location
N.E.Ohio
Any body use KB 107 pistons in there 360, any problems with them?
 
I'm using them in a 5.9 magnum. Most people say its too much compression for an iron headed motor. But it runs great and haven't had an issue with pinging yet!
 
I have had them for a few years in my Magnum, the engine makes good power and torque.
Compression can get up there with small chamber aluminum heads, so choose your camshaft very carefully to run pump gas.
And open up the ring gap.
 
No problems here.Well not exactly true. I had to take everything apart at the end of the first season and increase the skirt clearance; .0015 was not enough.I went to .0025, which seems just right in my streeter running a minimum coolant temp of 205*F
She always ran a lil hot at the KB spec and would lock up whenever I shut it off, for up to 20 minutes or so. At .0025 that all went away. The locking up did not seem to damage the skirts.
 
Last edited:
I just went to buy a set a guy had, he said were new .030 and when I looked at them they were new but said STD on top ? The box said KB107 -.030, so I passed I didn't take a mic and he didn't have one. And life goes on.
 
AJ/FormS said:
No problems here.Well not exactly true. I had to take everything apart at the end of the first season and increase the skirt clearance; .0015 was not enough.I went to .0025, which seems just right in my streeter running a minimum coolant temp of 205*F
She always ran a lil hot at the KB spec and would lock up whenever I shut it off, for up to 20 minutes or so. At .0025 that all went away. The locking up did not seem to damage the skirts.
Click to expand...

It's been a while back but we ran a set in a 400 chevy SB and ran them at .0025 and they scuffed, so we went .004 and no problem, but the thing was a pain from the start. I think there's something wrong when you have to run the ring gap .032.
 
I'm not a builder, but .032 does sound large. I used the KB .0065 ring factor at the first build. But in late 2000 when I opened up the bore an extra thou,(now at 4.050),I put the same rings back in, so I guess they would have been around .029. I didn't keep notes cuz I never even thought it might some day come in handy. I took that engine apart every winter, 5 winters in a row, to catch trouble before it cost me big money. I figured gaskets were cheap compared to what I had in the engine. And sure enough, the first three winters I caught stuff. By the 4th time,she was A-OK,
But I took it apart one more time in 2004, and installed Plasma-Moly file fits, back at .026. Man I couldn't hardly see any LeakDown on the gauge. But it ran and it was dynomite.The one and only successful trip down the track (of 4), it posted 93MPH @3467 pounds(1/8th). I was ecstatic. The engine has not been apart since.

I don't know anything about chebbys,lol, but hypers at .004 in a streeter, I agree sounds like a lot. My whole reason for choosing the hypers in the first place was to run a tight skirt clearance. I mean the catalog said .0015 to .002 for street, up to 4.1 bore, so plunked my money down.
A long time later, I got to thinking about why the skirts had not scuffed, and I confess, the thought came to me that perhaps the skirts hadn't locked up at all, and it was the rings butted up. I never did go looking for the evidence. And the file-fits went in at .026 and the lock-up issue never returned, so I put it out of my mind.
 
Last edited:
I think we went .0075 factor and the bore on a 400 sb 4.125 + .020 so 4.145"
the .032 was off the top of my head but now that I checked it it comes out to .031. It just seems like twice as much as the old forged pistons or even stock pistons and we never had a problem with them getting hot and bottoming out the ring and breaking a ring land
 
That piston is for a closed chamber head run tight quench
if too much compression use a small dish - do not drop the piston down the hole or run a super thick gasket
If you have an open chamber head use one of the ones designed especially for those 360 heads
I like a ductile top ring
.002 .0025 should be fine except in a boat with cold water
do run gap recommended or better
run this way you should have more leeway with fuel and timing, less chance of detonation so what gas? 308 and EQ take less timing
detonation will kill anything and quench is more important than a little more compression
once you get the compression figured out and the rest of your build you can think of a cam
 
One thing that can occur to cause scuffing and forces a larger clearance is block distortion that can occur when all the bolts are put in a block and torqued. It will vary from block type to block type. I used to have to run an additional clearance in my Opel 1.9L builds because inserting the top 2 bell housing bolts and torquing them would distort the #4 cylinder out-of-round by at .003" + or -.

So without torque plates during boring and honing, the bores can go well out-of-round. IMHO, a reason to expect a gradual break-in sometimes; the rings may seal pretty well, but any high spots in bores will have to literally be worn down some.
 
Wyrmrider said:
That piston is for a closed chamber head run tight quench
if too much compression use a small dish - do not drop the piston down the hole or run a super thick gasket
If you have an open chamber head use one of the ones designed especially for those 360 heads
I like a ductile top ring
.002 .0025 should be fine except in a boat with cold water
do run gap recommended or better
run this way you should have more leeway with fuel and timing, less chance of detonation so what gas? 308 and EQ take less timing
detonation will kill anything and quench is more important than a little more compression
once you get the compression figured out and the rest of your build you can think of a cam
Click to expand...
If this is directed at me, then that applies to me and is also what I found out.
I run the closed chamber Eddies at .034Q (pistons up .005 with 1008 gaskets) and on the street, my butt-dyno could not detect power difference from 32 to 36*, and so I run 32* and burn 87E10 full-time with over 175psi, one combo at 185psi still on 87. I am at about 1000ft
The file-fits, IIRC were a ductile on the top.
If your post was not for me, then sorry to but in and thanks for the confirmation.
 
just a general post from my background AJ
thank YOU for a second opinion
something is not right if you have to run 36-38 advance in a small block good heads with a modern chamber you can be under 30
 
Mine run like a raped ape. Mine ended up well above deck with all the decking my block required to get square. I came in just above 10.5-1 with iron heads.
 
1994redram said:
I'm using them in a 5.9 magnum. Most people say its too much compression for an iron headed motor. But it runs great and haven't had an issue with pinging yet!
Click to expand...
Do you know how the weight of KBs compare to the stock 5.9 pistons? I want new slugs without a balance job
 
I had to have Mallory added to the crank to balance.
 
That's lighter than the icon forged flat tops (530/121g) which are supposedly stock weight so you shouldn't have needed mallory added?
 
macdrew77 said:
That's lighter than the icon forged flat tops (530/121g) which are supposedly stock weight so you shouldn't have needed mallory added?
Click to expand...

I used the KB 107 in a Magnum so a small about of mallory had to be added to the crank.
 
sireland67 said:
I used the KB 107 in a Magnum so a small about of mallory had to be added to the crank.
Click to expand...
Yes, the Magnum rods are a bit lighter and perhaps the pistons.

macdrew77 said:
That's lighter than the icon forged flat tops (530/121g) which are supposedly stock weight so you shouldn't have needed mallory added?
Click to expand...
Are you running an LA or Magnum? (Sorry I forgot....)

And here is a good thread to help you; I am too rushed right now to digest it all:
Magnum slug weight vs...

The KB107's look very close.

As an alternative to Mallory, you can drill some metal out of the 1st and 4th end journals, just like on the 340. You take our more than needed, then make adjustments with the holes drilled in the throws like standard.
 
Last edited:
Seal Power H116CP are a hyper piston that is the stock weight of 584 grams...
 
You must log in or register to reply here.
-

Back
Top