Whats the deal with the KB 243's, good or not?

-
340doc

340doc

Well-Known Member
Joined
May 8, 2010
Messages
2,716
Reaction score
993
Location
Hollywood Fl
I'm banging my head trying to figure this out. I want a piston with the factory compression height of 1.840 which is 10.5 to 1 factory spec. I've found two after staring at the internet for two days. One is the old reliable Speed pro/TRW slug and the other is the KB 243. I've ran the old TRW piston years ago and I know there bullet proof, but know very little real world about the KB's, just what I've read. I might add I'm not looking at anything custom or high dollar. So they're not good if your using a power adder and prone to detonation failure I've read. So to those who are running them what say you?! Good?
 
I was on summits web site last week and the trws were at over $600.00. Almost doubled in price. For that price i'll go for srp or something. I've heard nothing bad about the 243s. Sorry that's for the .060 pistons only. 320.00 for other sizes.
 
Last edited:
It's like anything, pick the right part for the application. They are excellent street performance pistons with proper ring gaps. I have ran them to 7000 rpm for thousands of laps in a oval track engine with zero failure. But for forced induction or nitrous, I'd be looking into a forged piston.
 
Hypereutectic's don't have the 'toughness' of a forged piston but that does not mean you cannot use power adders. I raced hypers for some time in a 14-15 psi turbo rally engine producing around 1.75 HP per cubic inch... never a single issue. And I have destroyed forged pistons in an N/A engine when the timing got all whacked out. So neither is 'proof' against detonation, just that the forged will more likely survive it than hypers.

So, IMHO, nothing wrong with the KB's. The weight is a lot less (like around 145 grams for piston + pin) so the engine has to be rebalanced, and there is that cost. But that much lighter weight that takes some stress off the rotating assembly. My son and I put a set in his 340..... not a bit worried for hard street use.

BTW.... actual stock 340 compression ratio was around 9.75, not the advertised 10.5; that was only achieved with 'ideal' parts, not the typical factory parts.
 
I don't have a 340 so I can not comment on KB 243's, I do have a 360 with KB 107's, I like them. I think they are a good product, pay attention to KB's installation instructions you will be OK. They will take power adders, I have stated in another post, survival is due more to tune-up, not piston. If the engine detonates hard enough to break a piston, you already had broken rings, maybe collapsed ring lands, again goes back to tune-up.

I'll say this, I kinda like the looks of the KB's.......at 184 grams (piston, pin ) less mass from stock, that translates into just over 3 lbs removed from rotating assembly, it would rev like mutant chain saw engine.
 
aaronk785 said:
I was on summits web site last week and the trws were at over $600.00. Almost doubled in price. For that price i'll go for srp or something. I've heard nothing bad about the 243s. Sorry that's for the .060 pistons only. 320.00 for other sizes.
Click to expand...
I looked hard at the SRP's, there compression height is lower than stock requiring a smaller CC chamber. I was bummed as its a nice piece. Appreciate your input 785
 
replicaracer43 said:
It's like anything, pick the right part for the application. They are excellent street performance pistons with proper ring gaps. I have ran them to 7000 rpm for thousands of laps in a oval track engine with zero failure. But for forced induction or nitrous, I'd be looking into a forged piston.
Click to expand...
Good to hear they hold up to that punishment, thanks.
 
nm9stheham said:
Hypereutectic's don't have the 'toughness' of a forged piston but that does not mean you cannot use power adders. I raced hypers for some time in a 14-15 psi turbo rally engine producing around 1.75 HP per cubic inch... never a single issue. And I have destroyed forged pistons in an N/A engine when the timing got all whacked out. So neither is 'proof' against detonation, just that the forged will more likely survive it than hypers.

So, IMHO, nothing wrong with the KB's. The weight is a lot less (like around 145 grams for piston + pin) so the engine has to be rebalanced, and there is that cost. But that much lighter weight that takes some stress off the rotating assembly. My son and I put a set in his 340..... not a bit worried for hard street use.

BTW.... actual stock 340 compression ratio was around 9.75, not the advertised 10.5; that was only achieved with 'ideal' parts, not the typical factory parts.
Click to expand...
Thanks for the info, I'm feeling better about them.
 
JBurch said:
I don't have a 340 so I can not comment on KB 243's, I do have a 360 with KB 107's, I like them. I think they are a good product, pay attention to KB's installation instructions you will be OK. They will take power adders, I have stated in another post, survival is due more to tune-up, not piston. If the engine detonates hard enough to break a piston, you already had broken rings, maybe collapsed ring lands, again goes back to tune-up.

I'll say this, I kinda like the looks of the KB's.......at 184 grams (piston, pin ) less mass from stock, that translates into just over 3 lbs removed from rotating assembly, it would rev like mutant chain saw engine.
Click to expand...
That's a plus, thanks.
 
I have a long association with the KB's helping design the reverse deflector pistons for the open chamber heads
lots of good advice above
with any piston detail your heads and make sure there are no spark plug threads on the plug or head showing,
round any sharp edges
dial in your timing and tune tune tune
detonation will kill anything and as said forged will give you a little margin- but not much
do get the ring gaps right
I like ductile top rings
weight does make a big difference
I only now use TRW style for low rpm Trucks
hone with a torqueplate
do the oil mods
clean
enough
 
Wyrmrider said:
I have a long association with the KB's helping design the reverse deflector pistons for the open chamber heads
lots of good advice above
with any piston detail your heads and make sure there are no spark plug threads on the plug or head showing,
round any sharp edges
dial in your timing and tune tune tune
detonation will kill anything and as said forged will give you a little margin- but not much
do get the ring gaps right
I like ductile top rings
weight does make a big difference
I only now use TRW style for low rpm Trucks
hone with a torqueplate
do the oil mods
clean
enough
Click to expand...
Thank you, good advice. From what I've read they call for a large top ring gap.
 
Yes, that is due to the top ring being higher up on the piston than a lot of piston designs and getting more heat exposure. (Plus them being hammered on regularly puts even more heat in the top ring).

This higher ring location seems to have become more and more common in modern engine design.
 
nm9stheham said:
Yes, that is due to the top ring being higher up on the piston than a lot of piston designs and getting more heat exposure. (Plus them being hammered on regularly puts even more heat in the top ring).

This higher ring location seems to have become more and more common in modern engine design.
Click to expand...
I see. So I can only assume they provide a formula for their recommended ring gap based on bore size. Thanks
 
Not sure what you mean.... I'd assume that their numbers account for both bore size and ring position.

I was just noting that this is not an unusual ring position anymore; I am looking at a Chevy Lumina piston and a Ford HSC engine piston, where the higher top ring position is the same as on these KB's. So IMHO nothing to be concerned about.
 
nm9stheham said:
Not sure what you mean.... I'd assume that their numbers account for both bore size and ring position.

I was just noting that this is not an unusual ring position anymore; I am looking at a Chevy Lumina piston and a Ford HSC engine piston, where the higher top ring position is the same as on these KB's. So IMHO nothing to be concerned about.
Click to expand...
Thanks, appreciate your time.
 
340doc said:
I see. So I can only assume they provide a formula for their recommended ring gap based on bore size. Thanks
Click to expand...
Yes, the KB slugs will have a guide in/on the box as to what to tap the rings at and for there useage. That being said, they also have a gap size for N02 useage. You can go to the Kb web site and get a heads up on what is needed.

I myself am almost ready to assemble a 340 with those pistons. I’m waiting on a little warmer weather.
 
rumblefish360 said:
Yes, the KB slugs will have a guide in/on the box as to what to tap the rings at and for there useage. That being said, they also have a gap size for N02 useage. You can go to the Kb web site and get a heads up on what is needed.

I myself am almost ready to assemble a 340 with those pistons. I’m waiting on a little warmer weather.
Click to expand...
Excellent
 
340doc said:
Thank you, good advice. From what I've read they call for a large top ring gap.
Click to expand...
Yes you have to increase Top ring gap per instructions. I read a thread where they recommended increasing 2nd ring as well just not as much. They did a test and found this did not make piston use oil as well. I did this with mine but can't comment on results as of yet as I'm waiting for my crank balancing to get done.
 
Kendog 170 said:
Yes you have to increase Top ring gap per instructions. I read a thread where they recommended increasing 2nd ring as well just not as much. They did a test and found this did not make piston use oil as well. I did this with mine but can't comment on results as of yet as I'm waiting for my crank balancing to get done.
Click to expand...
Ok. What's the theory behind this? Is the heat from the high ring placement going to close the large gap? I don't want to worry about lost compression.
 
340doc said:
Ok. What's the theory behind this? Is the heat from the high ring placement going to close the large gap? I don't want to worry about lost compression.
Click to expand...


You hit the nail on the head..............
 
340doc said:
Ok. What's the theory behind this? Is the heat from the high ring placement going to close the large gap? I don't want to worry about lost compression.
Click to expand...
Because of the extreme heat increase with a N02, the rings expand even more than during normal use. The extra gap is needed to insure they do not collide and pop the top of the piston off.
 
The higher ring is to minimize the dead space between the top of the ring and the deck of the piston, think unburned hydrocarbons- polution

The high silicon hyperutectic alloy does not transfer heat as well as the other alloys, therefore the rings run hotter and expand more
simple as that
which is why the bore prep and plateau finish works
you want a coarse hone to hold oil and a fine finish to minimize oil usage and hold hP
Pleateau hone with a torque plate then a super fine bottle brush just before final assembly and clean clean clean works for me (ductile moly rings)
more important the narrower the ring
I rotate the bottle brush the opposite way from the CK-10
 
Wyrmrider said:
The higher ring is to minimize the dead space between the top of the ring and the deck of the piston, think unburned hydrocarbons- polution

The high silicon hyperutectic alloy does not transfer heat as well as the other alloys, therefore the rings run hotter and expand more
simple as that
which is why the bore prep and plateau finish works
you want a coarse hone to hold oil and a fine finish to minimize oil usage and hold hP
Pleateau hone with a torque plate then a super fine bottle brush just before final assembly and clean clean clean works for me (ductile moly rings)
more important the narrower the ring
I rotate the bottle brush the opposite way from the CK-10
Click to expand...
Good info, thanks. Feeling better about them.
 
You must log in or register to reply here.
-

Back
Top