hypothetical 400 build.

[Jrod-13]

So here's the deal, My buddy has a 400 in his bronco/truggy. last sat. it engulfed a bit of silt mud, through the rear main, possibly wiping the crank(its grooved pretty good)

What we have to work with

• stock 400, fairly tired, crank might still be turnable to .030 under, with a 4bbl on it.
• fresh .030 351M, only a few thou on it, was a beautiful motor, but lost oil pressure, waxing the crank.
• access to a plethora of used engine parts
• limited money

Now, a 351M and 400 have the same 10.297 deck height, and both use identical 6.580" rods, with .912 wrist pins, and 2.311" rod journals.

351M pistons have a compression height of 1.947
400 pistons have a compression height of 1.647
stock 351M pistons would then be .020" below the deck
stock 400 pistons would then be .070" below the deck.

dodge rods are 6.123" with a 2.125" journal, and a .984 pin
The pistons could be milled out to the larger diameter of the dodge rod, thats no biggie.

Now lets say we take our 351M long block, that is a MINT engine, that needs a crank. Now lets say our 400 crank is to far gone to be turned, and use normal bearings, say for comparative reasoning, we must take .050 off it to clean it up.

picture offset grinding it, down to a 2.125" journal, allowing for the .050 needed to clean it up, thats giving us and ADDITIONAL .161" of throw.



Now lets crunch some numbers.

stock 400, 10.297" deck height, 4" stroke, 4" bore, 6.580" rod, 1.647" compression height, .070" below the deck.

Our Kustom 400 stroker.
10.297" deck height, 4.030" bore, 4.322" stroke, 6.123" rod, 1.947" compression height, .066" below deck height.

The result would be a 441" stroker, with 9.68:1 compression ratio, just about perfect for pump gas, and using basicly all free parts, and only paying for the crank to be offset ground, and the pistons to be machined to accept dodge rods.

Off course zero decking it would bring the CR up to 11:1..
note we wouldn't be going with 11:1...

thoughts?

[NHRedneck]

11:1 with the stock heads would kill you with so much detonation you wouldnt even know what to do..... i wouldnt go over 9.40:1 with the stock style modified heads..... go nuts with the cheapo build, just to get too excited and forget about the important aspects of the motor and its uses....

[jopes]

I would think that machine work would add up. for about 2400 you can buy a 434 stroker.

[GMCTruxrule]

dude, unless you are planning on running race fuel in it, I wouldn't even run it that high on compression. 9.0:1 would be the highest I would go.

[Halogrinder]

do it and fawk the naysayers


keep the CR down though.

send me yer heads for a bad ass valve job and it be mo betta

[Jrod-13]

I guess I should have said, there would be NO intension on going that high of compression, I just through that out for shits and giggles. This would obivously be a pump gas motor, going with the 9.68:1 CR I stated

Jopes, I looked at the 434 kit a while back, its a nice kit, but if this project ever materlized, it would need to be way under that kinda money... I'm talking spending money on machine work, and bearings, thats about it..

halo, thanks for the offer, but the heads being used are allready rebuild( couple thousand miles ago), but of course will get a little porting before hand.

I realize 400's have a real issue with detonation, which zero decking helps... problem being, there is no way to do it without the compression ratio getting oout of hand, aside form new pistons, which kinda defeats the purpose of it.

[mj]

you do not bore the pistons, you bush the rods to match the pins.

[willys101_4lo]

If you do it, just post a BUNCH of pictures. Speaking for me, and probably the rest of the peanut gallery, I'd love to see how that build goes and see the numbers you're pushing once she's all together.

[bmc69]

Sounds like a fuin project motor in the works. Couple questions/comments about yr numbers and assumptions that I didn't quite understand:

1. What pistons exactly were you including in the equation?..flat-tops..12CC dish..?

2. Zero-decking has no effect on anything but compression unless there is a quench pad present on the heads (i.e. closed-chambers). It's the squish distance between piston top flat and quench pad that helps control detonation. Thus..to gain a quench pad, you would need to get your hands on a set of 302C aussie heads..which is what Jopes and I are running.

3. You can zero-deck the setup and use the Aussie heads and still have a CR in the range you are looking for..you simply dish the piston tops where the head quench pad 'is not'. IIRC correctly, it takes a 32cc dish to achieve around what you are looking for with a zero-decked setup and Aussie heads. Don't take that number as absolutely correct...my memory ain't that good and I'll have to go look at my build notes again.

[bmc69]

Originally Posted by mj

you do not bore the pistons, you bush the rods to match the pins.

you can do either, and it's something of a wash in the effort department.

1. Bush the rods, cut the pistons for clips and use shjorter wrist pins (or grind sonme shorter)

2. Bore and hone the wrist pin bores in the pistons and keep the press-in pins.

[TANNERJENNINGS24]

why not do a destroked 400 with the 351 crank and make it a high horsepower high rpm motor.
Just my .02

[bmc69]

The problem with the 'high RPM/high HP' approach is that..this engine is for a trail rig, yes?. The 400, or better yet, a stroked 400, gets you the grunt you need at an engine RPM you want it to be at. We design/build our 400s for peak torque in the 2500-2900 RPM range....so the HP numbers are nothing special, but HP is not what yr after here.

[TANNERJENNINGS24]

Originally Posted by bmc69

The problem with the 'high RPM/high HP' approach is that..this engine is for a trail rig, yes?. The 400, or better yet, a stroked 400, gets you the grunt you need at an engine RPM you want it to be at. We design/build our 400s for peak torque in the 2500-2900 RPM range....so the HP numbers are nothing special, but HP is not what yr after here.

Yes this is true but it sounds cooler on the trail when you running 8000-9000 rpm's trying to climb something

[Christoff]

Oh boy Possum and Orrin back at it again. I can't wait to see how this turns out when I get back to Tech this fall.

Good luck with he build.

[TANNERJENNINGS24]

I run a chevy 383 stroker in my hot rod that makes right at 500hp and 550ftlb. of torque.But I've been thinking about putting that motor in my dads scout terra,and building me a destroked 400 for the hot rod.Cause it sounds better running 9-10,000 rpms flying past some punk ass kid in his rice rocket with his jaw droped. LOL.

[bmc69]

Originally Posted by TANNERJENNINGS24

Yes this is true but it sounds cooler on the trail when you running 8000-9000 rpm's trying to climb something

..don't I know that!. For a couple years, i was 'sans trail rig' and took my EB MX racer to several trail events, including Tellico..twice. Nearly 500 HP in that thing..at 7300 RPM. IIRC it didn't even break 200 ft-lbs at 2000 RPM..a six-banger 170 would have more torque at that RPM. Quite the show that was..hee hee....instead of using 'tread lightly' on obstacles, I would say 'assault obstacle with extreme prejudice' more accurately describes the driving technique..(I do NOT want to have to do that again either... ).

Sorry for hijack...

[bmc69]

Originally Posted by TANNERJENNINGS24

I run a chevy 383 stroker in my hot rod that makes right at 500hp and 550ftlb. of torque.But I've been thinking about putting that motor in my dads scout terra,and building me a destroked 400 for the hot rod.Cause it sounds better running 9-10,000 rpms flying past some punk ass kid in his rice rocket with his jaw droped. LOL.

[TANNERJENNINGS24]

Originally Posted by bmc69

Now thats funny.





x2 sorry for the hijack

[Jrod-13]

good info guys!

BMC69, you nailed it on the rpm range thing, for the wheeling we do, low rpm grunt rules. I USED to have a torquey 351W in my truck(power band peaked at about 4500), now I have a high strung 302 in it, that spins to 6800. I'd give anything to have the W back, but it was a matter of needing a motor, and I had the 302 sitting around.

After riding in above mentioned bronco, I was inlove with the grunt of a 400, it's almost like my 7.3

The pistons I used in the comparision were the stock 12cc dish 351M pistons.

as for the bushed vs. boring, I think(for us) boring them would just be simpler(and cheaper) to do.

Getting 2v assuies would be the cats ass, but isn't in the budget. 32CC chambers sounds right for the aussies, IIRC, thats the guy who builds the 434 kit sells, and I believe the stock 400 truck pistons are a 32CC also, I might have to whip out the burret, plexy glass, and ATF to messure them.

[crushu]

Out of curiousity, what are the Aussie heads worth there? I could send them to you guys, no probs.
I have about 10 sets in my Garage, from Standard 302 cleveland ones upto some pretty wild ones.

[Halogrinder]

UH like 50 bucks a set, ill buy all 10 from you

[bmc69]

Originally Posted by Halogrinder

UH like 50 bucks a set, ill buy all 10 from you

..actually I think that they are being given away, just to get them out of Oz. Seems you lot made a whole mess of 'em out of recycled steel from some nuke plant demolition.


Seriously, the ARD1AE closed-chamber stockers go for $275-300 per pair, complete, as-pulled.

[Halogrinder]

I know, i was trying to be sarcastic

[bmc69]

Originally Posted by Halogrinder

I know, i was trying to be sarcastic

..and I was trying to be more sarcastic than you. Guess we both need to work on honing that skill.

[Halogrinder]