Keith Black piston clearance

[nickpohlaandp]

Were they KB or speed pro hypers?

KB's. Same ones I used in my turbo motors. It was a "I'll take some of these, one of those, this thing here" kind of build. All stuff I had around the shop. They had been in one of the turbo engines for about 100 hours or so, but they were perfectly fine. We'd run em in the turbo engines for 1500-2000 hours with no issue.

[nickpohlaandp]

Were they KB or speed pro hypers?Its like anything the tune has to be right! He has no reason to feed me full of bs, they also sell icon forged which would get the job done as well.

Sneaky... you edited your post. I agree, your tune has to be dead on. That's very important. I'm just saying I would never intentionally run nitrous in a motor with hypereutectic pistons again unless it WAS for R&D purposes and someone else was willing to foot the bill if and when disaster strikes.

[Steve.k]

I know some big chevy guys run them with 100 shot no problem. The engines i ran made 550 on dyno was a breeze for them.

[nickpohlaandp]

I know some big chevy guys run them with 100 shot no problem. The engines i ran made 550 on dyno was a breeze for them.

Big difference between 100 on a BBC and 200 on a SBC. I'd be comfortable running a 100 shot on BBC or SBC with hypereutectic with a rather conservative tune, but the larger doses... no thanks. If I'm building an engine I pretty much know before I purchase pistons whether it'll see nitrous or not. If it's going to, it gets forged pistons. If I have an engine brought to me with hypereutectic pistons in it and the owner wants nitrous, I don't recommend anything more than 100 and I warn them of the possible failure, that's all. I don't want to have some dude blow up his motor and point the finger at me. Err on the side of caution, especially when it's not my stuff.

[Steve.k]

I hear ya. I had these lying on shelf thought I'd get away with it. But guess not. New pistons and re-balance and way we go. Should be honest 550-575 cast iron 400 ford.

[cjperformance]

What connecting rods are you using? Stock 400c/351m pin diameter is different to 351c.
I agree, too much clearance to run the kb177's , these are noisey cold at .003" ,,, at .0045" they would sound like a diesel ! Haha.
I run KB149 in a 351c with 150hp shot, no problems, didnt initially build with n2o in mind, just wanted some quick more fun so on went the gas.

[Steve.k]

Cj they are stock 400 rods offset bushed to fut Cleveland pin and give zero deck.

[cjperformance]

Cj they are stock 400 rods offset bushed to fut Cleveland pin and give zero deck.

Ah nice work doing the offset, otherwise you get stuck decking a mountain off to zero them.

[Steve.k]

We installed the offset steel bushing and drilled oiling holes in each side bottom of pin boss. Rodends up 6.61 if I remember correctly.

[cjperformance]

Nice work. They are pretty strong rods in the 400/351m.
I've put them thru a lot, I have a previous build 400 back now for a freshen right now, using the old trw forged dish tops (no longer available I believe) and aussie closed chamber 2V heads. Low mileage but hard work and always ran a 175/200 shot of n2o. Everything still fine.

[Steve.k]

Yes I got the idea from a mini mod trator puller here. He was cleaning house at every event he went to. He was calling it a boss puller. I went over and chatted him and it was a iron headed 408. He had exh plated the heads like ol prostockers. He also took a Motorsport 9424 intake and split in half. Then bolted to 400 block and re-welded to fit. Thing worked wicked. He told me how to bush rods to fit cleveland pin. That combo i built with mild ported 4v iron heads made 551@6200 and 531ftlbs tq at 5000. Very mild build that worked.

[DaveMcLain]

I know some big chevy guys run them with 100 shot no problem. The engines i ran made 550 on dyno was a breeze for them.

Big difference between 100 on a BBC and 200 on a SBC. I'd be comfortable running a 100 shot on BBC or SBC with hypereutectic with a rather conservative tune, but the larger doses... no thanks. If I'm building an engine I pretty much know before I purchase pistons whether it'll see nitrous or not. If it's going to, it gets forged pistons. If I have an engine brought to me with hypereutectic pistons in it and the owner wants nitrous, I don't recommend anything more than 100 and I warn them of the possible failure, that's all. I don't want to have some dude blow up his motor and point the finger at me. Err on the side of caution, especially when it's not my stuff.

I built a low buck 383 Chevy one time for a customer with a jet boat. it had a KB hyper dished piston and a twisted wedge head, stock rods and an Eagle cast crank in a two bolt one piece rear main block. He ran that engine in his boat for years with no problems. I think it would pull about 5000rpm but once in a while he ran a 200 shot on the engine. Then it would pull close to 6000rpm. Anyway he told me that one time he ran a whole bottle of nitrous through the engine in one shot while racing some guy on the river! It never blew up until he sold it to some guy who put it in a pontoon boat. One springtime after the boat had been winterized he didn't hook up the cooling hoses correctly and that killed the poor engine.

[Steve.k]

I think those pistons are alot better than they get credit for. A superstock hemi builder up here told me to keep the ring gaps even looser than what kb recommends. Thats what ive always done and work well.

[cjperformance]

I may have missed it but what intake are you running on this.
The current 400 I have here has an Edelbrock Streetmaster, they have a pretty honkey intake plenum stock but with the plenum opened up and a 2" 4 hole spacer turned into a taper from cloverleaf under the carb to then match the opened up plenum gives a great plenum volume for it and works really well.
I have used the eddy Performer and also Holley Street Dominator on the 400's , both have worked well.

[Steve.k]

I use cleveland intakes and spacers. The 550 hp one had holley strip dominator. This one will have torker.