More 451 Stroker questions, issues, and general headaches.

[451Coronet]

So over the past few weeks I've made numerous trips to the machine shop and had all the necessary cutting and grinding to make my steel 3.75" crank from an old 413 fit into my 400 block. When I went to have everything balance they said I need different pistons as the stock 400 pistons will stick out of the block too far. I confirmed this by asking Mopar Action Tech Guru Rick Ehrenberg. So now, what pistons do I use???

This is supposed to be a low buck build, so I would like to keep the stock 400 (4.34) bore. I guess technically I would have a 442 or 443 but I don't want to have to punch the 400 out on top of having to buy new pistons.....and I haven't even had it all balanced yet. I'll likely be using the stock 400 rods as well, I have a good set of LY, but I'm afraid there will be clearance issues in using those (cause there has with everything else) and the 400 rods I imagine are lighter, so I figure less material needed to balance the assembly (again low buck). I'm also using a set of rebuilt 452 casting heads and would like to keep the CR pump gas friendly, and I don't mind paying the extra for premium.

I've read that the KB215s are good, but I can only find them in .030" oversize

Any ideas would be greatly appreciated. Thanks

 

[Meep-Meep]

The problem is the longer stroke in the low deck requires special pistons with a shorter compression height. If you want low buck build a 440 using stock replacement parts.

 

[lewtot184]

kb215 pistons are made in a 4.34 stock bore. they are designed for the open chamber iron head. down side is 10.5:1 compression with pump gas; but they are the cheapest way to go.

 

[451Coronet]

Cool, so 215s it is I guess. Thanks.

And I already have a 440, but it needs a total rebuild. Broke rings and two cylinders (cylinders are FUBAR'd) and bent two pushrods, which I hope was the only damage....at least that's all I've found so far. Just figured it'd be cheaper to build a 451 (443?) stroker than do a complete rebuild on the 440.

I'm guessing milling a stock piston is out of the question.....and prolly more expensive anyway. Nevermind.

Thanks again.

 

[451Coronet]

Ok so 215s are $$77.95 a pop(pet)!! At least according to summitracing.com I don't even have that much in the engine now....total! So what's everyones input on the KB 251s?? Same CH as the 215s but what would be the (dis)advantage of the step head.....other than valve clearance being an advantage?? A HUGE advantage being they are half the price haha

Any input is greatly appreciated thanks.

 

[Garys1969RR]

HI 451, just checked the KB piston website, and the KB 251 has a quench dome, and it needs to be checked on the engine for piston to head clearance. They say it needs to be machined prior to assembly, but I have heard that 1 out of 10 needs machining. Its a .150 dome, so with a .040 head gasket, and the chamber being recessed about .100 " , then the piston would still hit the head. Unless you cut down the dome. I didnt think there that much difference in price. I just built a 451, and going to install it this weekend. But I using the Ross dome piston. And 440 rods. Good luck and let us know what your final results are.

 

[Garys1969RR]

Yes piston selection is a major headache, but critical to getting the right combo for your usage. The Summitt website says the KB 251 runs 341.95 for a set of 8. About the cheapest you will find. But it also says dome machining required. I dont know why they dont list the 215s as a set of 8. Should be cheaper. You might call Summitt, may be over looking some thing. I think the 215 has a lower quench dome and doesnt need machining.

 

[Garys1969RR]

OK the dome on the 215 is .095" And the dome on the 251 is .260" And there in lies your problem. The dome on the 251 must be machined.

 

[Meep-Meep]

All quench dome KB pistons say they require machining or at least checking the dome to chamber clearance.

 

[lewtot184]

the 215 is the most economical way to go. quench dome clearance will need to be checked. 440's are probably the cheapest "b" engine to build.

 

[Cranky]

On a build like this...always check piston height! You can do the math before the build based on factory blue print specs but actual measurements may and do vary from the factory so checking that stuff is important especially if you build with tight dimensions.

 

[Garys1969RR]

Yes, build your engine on the computer first. Work out all dimensions as far as deck height, pin center to piston top which is compression height, C/R, piston to head clearance for quench, etc. Some things like piston to valve clearance can best be determined when the engine is assembled. Saves alot of headaches later on. I've spent hours working all this out on my computer over the past 4 months. Finally ready to install the 451 this weekend. Hope I did my homework right! Lol. Good luck!

 

[Garys1969RR]

Oh yea I forgot -Rod length! Supershafts claims the 400 rod gives a better torque curve, but I think the longer 440 rod works best because it puts the pin location up higher in the piston. So less piston rock? Lets compare final results since you are using the shorter rods, and I using the longer one.

 

[The Shoe]

I've built three 451's. First with the KB pistons and was 10:1 comp with the 400 rod. Second/third were with Wiseco piston and 440 eagle rods. Only difference between the two engines was the compression. The short rod motor would 60 ft 1.46 to 1.50 but would start to labor a bit in high gear. If you are just running on the street, which it sounds like you are, the short rod will give you better "street light to street light perormance" if you will. My second 451 with the long rods didnt 60 ft as well as the short rod motor, but would MPH better.

 

[Garys1969RR]

Well got mine goin this week and totally happy with it so far. Gets tire "chirp" when the 727 hits 2nd gear now. Thats with 2.76 gears at 5000 feet! The 440 never did that in this car, but was a low compression engine. Still gettin it dialed in, and may try a Holley 700 dbl pump carb that I have. The 750 Eddy carb is working great too! Running 906 heads mild porting work, 509 cam, street dominator intake, Ross 14 cc dome pistons. And of course Sonoco 100 octane fuel. I dont drive alot miles in this car.

 

[demonram]

I just had mine dynoed last week 456 ft/lbs and 365 hp at the wheels with 750 1407 Eddy with rpm intake 10.5 comp.. It's got a 355 rear end, 484 lift comp cam, stealth heads and 440 source stroker kit(which I am very happy with). I would like some more horses but I did build for torque and I am super pleased with the outcome. This is on 92/93 premium pump gas of course. It will break em loose when I stomp it at 20 and of course chirp into 2nd.

 

[andyf]

Lots of place make low deck stroker pistons so that shouldn't be a problem. I have a hard time believing that you can actually build a stroker motor though without having the block bored out. You won't be saving yourself any money if you get the engine back together only to find out that it burns a lot of oil because the cylinder walls have too much taper.

 

[451Coronet]

Hey all,
Thanks for all the input, unfortunately I had to put my project on the back burner as I'm in the process of getting a house. So as soon as I've closed, moved in and settled......and pushed the Coronet into that sweet 2 car garage haha The build will move forward.

I'll likely be going with the KB 215s (that's what the machine shop recommended as well) and get those ordered as soon as I have that block bored. Since I'm in no hurry to finish now, I can go thru it and take my time with it.....maybe I'll be able to finish and get everything back together before it gets cold again lol

I really appreciate all the help and info you guys provided, hopefully makes this build a bit easier lol

 

[Garys1969RR]

Any good machine shop will want the pistons there before boring the block.Small Variations in size of pistons will make a difference. Yes order your pistons first.