KB pistons and a possible 360 build.
07-10-2009, 02:20 PM
#1
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KB pistons and a possible 360 build.
i just read the thread about the guy who wants to build a 360 for his car using KB pistons. Ive always wanted to know why you guys are dead set against them, since everywhere else i read kb pistons are recommended by mopar guys.
and another thing. Id like to rebuild my 360 someday. i want it to be a midrange motor that will still make good low end torque since its for my truck.
i want to have 9.5:1 compression, so i can get away with using only premium gas, and i want to still be able to get 7 miles to the gallon, i want the cam to make enough vacuum to run power brakes, make good torque, and hopefully have a slight lopey sound to it if possible. and i would like to make reliable as possible so i can drive it around, floor it here and there, and have it last a long time.
i figure i would just get a decent rebuild kit, but should i use bolts on the main caps and heads, or studs?
and also how hard would it be to squeeze 400 hp out of it? i know mopar muscle magazine built a 400 hp budget 318 using a junkyard intake, heads and carb...
right now the motor is stock and runs pretty decently, its a 1971 engine with 915 casting J heads - i think 1.88/160 valves it has a 750 edelbrock carb, performer intake, hedman headers.
would you guys have be get a different head? (i cant see myself ever spending $1400 for a pair of aluminum heads)
id like to have my heads rebuilt with a decent set of new 1.88/160 valves, 3 angle valve job, new guides, keepers, seals, springs, and then me and my buddy would smooth out the bowls, portmatch the gaskets, and maybe polish the exhaust ports a little bit.
and another thing. Id like to rebuild my 360 someday. i want it to be a midrange motor that will still make good low end torque since its for my truck.
i want to have 9.5:1 compression, so i can get away with using only premium gas, and i want to still be able to get 7 miles to the gallon, i want the cam to make enough vacuum to run power brakes, make good torque, and hopefully have a slight lopey sound to it if possible. and i would like to make reliable as possible so i can drive it around, floor it here and there, and have it last a long time.
i figure i would just get a decent rebuild kit, but should i use bolts on the main caps and heads, or studs?
and also how hard would it be to squeeze 400 hp out of it? i know mopar muscle magazine built a 400 hp budget 318 using a junkyard intake, heads and carb...
right now the motor is stock and runs pretty decently, its a 1971 engine with 915 casting J heads - i think 1.88/160 valves it has a 750 edelbrock carb, performer intake, hedman headers.
would you guys have be get a different head? (i cant see myself ever spending $1400 for a pair of aluminum heads)
id like to have my heads rebuilt with a decent set of new 1.88/160 valves, 3 angle valve job, new guides, keepers, seals, springs, and then me and my buddy would smooth out the bowls, portmatch the gaskets, and maybe polish the exhaust ports a little bit.
11-06-2010, 08:15 PM
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This is a pretty late reply but thought it would be worth documenting what I've heard... I just put together a 440 with KB and a few folks told me not to use them. From what I gather, some people have probably had trouble with them because they are not clearancing the top piston ring correctly. you need more clearance that "stock" due to the higher temps they see on the KB pistons. If they don't have enough clearance, they can close up, bind and tear the top of the piston apart.
I haven't had any issues with my new engine but it's only be been running for a few months and I don't run it very hard.
Rob in Roseville Ca.
'73 B'cuda 440/727
I haven't had any issues with my new engine but it's only be been running for a few months and I don't run it very hard.
Rob in Roseville Ca.
'73 B'cuda 440/727
Last edited by rfarmelo; 11-06-2010 at 08:21 PM.
11-06-2010, 08:56 PM
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Stickshifted,
For what you are building, the KB pistons are fine. You can run bolts, you dont need studs in your botom end. Overkill for your build. Mopars have awesome bottom end strength. For a midrange truck, I would use your J type heads..with unmilled heads and the 10:1 piston, you will be at 9:5...mill your heads .050 or so and get more compression.......definately port the heads or at least the bowels. I port everything I build.
I would ace the performer intake and give it to a 318 builder...That is junk (unless it is Performer RPM.)..They have 318 type ports....It will slow you down.(experience on a 340) The 340/360 thermoquad intake is by far superior and a great piece!! (if on a budget)Just put an adaptor on it and run the Carter...(I run this set up) the adaptor automatically gives you a taller manifold. Just grind out the center section (see my photos in mybucket showing an thermo intake) Use 323 or no higher than 355 gears if you need some mileage...
Dont go crazy on the cam for what you are doing....Too big and you kill bottom end...Go with a Comp Cams XE 268 or 276..(Mopar Muscle loves the 276 XE)..Will give you a little rump sounding and run power brakes,...Great torque...WIth the compression you are looking for you should easily get 13-15mpg.....Make sure with KB pistons--you file the rings per their instructions to their specs....
I built a 360 with the Summit kit..few years back Hyper Eu pistons--I think those were Federals advertised at 8:5--9.0....kit was 300.00 then.....But they were flat tops--no dish..I shaved my heads .060 and with a cam in your range....I had 150lbs compression per cylinder....It turned out to be 9.5 --It would run on 89 octane but 91-92 would have been ideal..........Those were good pistons--and no filing of rings.......Decent kit with some changes like moly rings..etc
the KBs are good--and they have diff compression ratios....
For what you are building, the KB pistons are fine. You can run bolts, you dont need studs in your botom end. Overkill for your build. Mopars have awesome bottom end strength. For a midrange truck, I would use your J type heads..with unmilled heads and the 10:1 piston, you will be at 9:5...mill your heads .050 or so and get more compression.......definately port the heads or at least the bowels. I port everything I build.
I would ace the performer intake and give it to a 318 builder...That is junk (unless it is Performer RPM.)..They have 318 type ports....It will slow you down.(experience on a 340) The 340/360 thermoquad intake is by far superior and a great piece!! (if on a budget)Just put an adaptor on it and run the Carter...(I run this set up) the adaptor automatically gives you a taller manifold. Just grind out the center section (see my photos in mybucket showing an thermo intake) Use 323 or no higher than 355 gears if you need some mileage...
Dont go crazy on the cam for what you are doing....Too big and you kill bottom end...Go with a Comp Cams XE 268 or 276..(Mopar Muscle loves the 276 XE)..Will give you a little rump sounding and run power brakes,...Great torque...WIth the compression you are looking for you should easily get 13-15mpg.....Make sure with KB pistons--you file the rings per their instructions to their specs....
I built a 360 with the Summit kit..few years back Hyper Eu pistons--I think those were Federals advertised at 8:5--9.0....kit was 300.00 then.....But they were flat tops--no dish..I shaved my heads .060 and with a cam in your range....I had 150lbs compression per cylinder....It turned out to be 9.5 --It would run on 89 octane but 91-92 would have been ideal..........Those were good pistons--and no filing of rings.......Decent kit with some changes like moly rings..etc
the KBs are good--and they have diff compression ratios....
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