offset crank grinding

[lyonsy]

hey
Just investigating off set grinding cranks as iam thinking of ofset grinding a 200 crank.
From 79.55mm stroke to 93.47 which is the same as as the bore for a square engine and giveing a capacity of 3.921L or if i go 94.47 and run the engine 40thou up3.971L which i think is the same size as the 3.9l and 4l engine's.
now whould i be better of seting a 250 crank back then a 200 up and how much can you off set grind a crank with out weaking to much.
i realise this ant cheap ether but iam wanting to build the ultament xflow n/a and will try and chase down one of those twin cam heads hopefully in the next year or 2
now iam told that if i use honda rods i stroke a 200 out to 222ci
or if i use 1600ford rods i destroke the 250 crank.
or i can use a 221 engine but not sure if 221 will have the twin cam head option.
anyways with the twin cam head and a square or slightly under square stroke to bore i should be able to spin the old 200/221/250 to around 9000rpm
mark

 

[Anonymous]

That would be an impressive engine!

Have you tried to get any price quotes from any machinists?

 

[lyonsy]

hey
yeah thats whats i was thinking be cheaper and easyer to build something all ready tried and tested but i wanna learn and i figure this is the best way.
plus i figure i should be able to spin it to 9000rpm once done make power all the way there.
might even make 2 one n/a one turbo
but anyways i had a chat with an x engine recon guy and he said that the 221 crank will bolt in with slight mods and offset grind that as it gives me a bit less grinding and is a very sturdy iron crnk suposidly much beter then 200 or 250 cranks.
also can wayone tell me what the length of the us 200 rods which are forged are?
nah i havent got around to machinst yet i wanna get all my parts first.
unfortenly i cant use the 221 block as its to different to put the twin cam head on so its all got to go in a 200/250 block so ill have t try and chase down a virgen bore log motor block and i all ready have a virgen bore 250 xflow block with rope rear main just need a virgen bore seal type xflow and iam all set for block just anther 3 more of those each to cut up and measure thickness.
2 heads one ported to the max one standard.
5 cranks hopefully 2 virgen cranks.
then i jsut have to wrok out pistons etc.
mark
mark

 

[Anonymous]

can anyone tell me what the length of the us 200 rods which are forged are?

go to the turbo/super/nitrous forum and click on "strong 200 rods"

 

[Anonymous]

Strong 200 rods

http://fordsix.com/forum/viewtopic.php?p=206598#206598

 

[lyonsy]

hey
no good need about 6.5in rod whith the destroked 250 to bring the piston up high enough.
thanks but for that.
oh to stroke a 200 or destroke a 250 about 200-400 per journal
mark

 

[wsa111]

If you have a 200 with a standard or .010 crankshaft, .015 offset will gain you .030 in stroke length.

This would eliminate extensive decking to achieve 0 deck clearance.

My next engine will definately use the offset crank journal grinding.

Any increase in stroke will definately help on torque & saving extensive milling of the deck of the block to achieve o deck clearance. William

 

[Anonymous]

My next engine will definately use the offset crank journal grinding.

I have never asked a machinist what the extra set-up fees for this sservice are.
Have you checked?

 

[lyonsy]

hey
well i got a rough price on a custom crank made to how i want about 4gand aus in machined steel. not as bad as i orginaly thought.
zero decking good in therory but bad in practise unless your decking for when the you hit the rev limiter plus an extra 500rpm so you wont hit anything.
and iam actully looking at destroking a 250 crank if i go that way due to not being able to drop engough stroke.
mark

 

[addo]

I can't see the benefit in destroking here. You aren't able to lighten the block.

 

[lyonsy]

hey
reason for destroking is to gain revs and more revs = more horsepower as the 250 is a very over aquare engine all i wanna do is bring it back to square or slightly under.
mark

 

[xctasy]

The Poms and Yanks did some tests last century. The ideal engine size is about halfway between the biggest and smallest crank used in the block. That is why the Cooper 1071S, 289 Mustang K-code, 302, 327 and 396 Camaros were sweeter than the 1275S, 302 4v, and 350and 427 Camaros. Each use the same block, but the smaller short stroke engines were far sweeter to use.

In the case of Aussie 200 and 250's the best power producer is a 250 with a 221 crank. When you factor in the costs of all the machining, the extra 10 to 15% more revs the engine has to carry to get the same power, its just not worth it.

2700 bucks on, my 221 crank in 250 engine will one day run, but any thing other than the factory dimensions means you are now the engineer, and you have to now what you are aiming for.

One old Ford parts guy said it best. "Do you know more than the Ford motor company?"

Nope.

In my ideal world, I'd love to do a little 200 cube XR engine with a stroke out with 5.25" StarfireHolden Rods (1.900"journal, not 2.124"), 3.35" stroke, aftermarket Rover 4.6 pistons (3.700 or 3.74"), X-flow alloy head, six RS 40 Mikunis and 220 cubes with 320 hp at 5500 rpm from less than 320 kilos of engine.

In practice, the rev range of street engine must have maximum power at less tha 5500 rpm, and maximum torque at less tha 3500 rpm. If you trade off 10 or 20% capacity, you must add 5 or 15% more revs.

Unless the after market or factory has done it for you, don't think outside the square.

 

[lyonsy]

hey
iam not really aiming for a street engine iam jsut wanting something that will be a very useful tool in circuit and drags etc.
so when you fitted the 221 crank what you have to do.
cut the big ends down tunnel bore it at 221 journal is the thrust bearings in the same spot or do you have to have to machine in a spot for the thrust bearings?
and no i dont know more then the ford engineers but i do know most engineers look at calculation and 3/4 time the stuff they say wont work will better then the stuff that they do, this is from engineers that have work at ford and holden and quite cause they went out proved it but the higher up enginners say no its cant even with proff in front of them!
plus iam looking for the oppoiste of what ford was trying to and thats revs and if iam taking it to 9000rpm then ive componastated well and truly along with less friction due to less load on the crank its self the rods the pistons
mark

 

[xctasy]

hey
iam not really aiming for a street engine iam jsut wanting something that will be a very useful tool in circuit and drags etc.
so when you fitted the 221 crank what you have to do.
cut the big ends down tunnel bore it at 221 journal is the thrust bearings in the same spot or do you have to have to machine in a spot for the thrust bearings?
and no i dont know more then the ford engineers but i do know most engineers look at calculation and 3/4 time the stuff they say wont work will better then the stuff that they do, this is from engineers that have work at ford and holden and quite cause they went out proved it but the higher up enginners say no its cant even with proff in front of them!
plus iam looking for the oppoiste of what ford was trying to and thats revs and if iam taking it to 9000rpm then ive componastated well and truly along with less friction due to less load on the crank its self the rods the pistons
mark

The purpose of power mods is to do more with less work.


The crank I used was the stock 3.46" stroke 221 crank with long run down hand weld to bring it up to 2.4" main journal, then the fillet radius was reworked.

The crank flange is 5/16" smaller than the 250. The crank to flywheel bolts are six at 2.75 pitch, not six at 3.0" pitch with the 250.

I made up a very expensive spacer which is crimped in place so I could eliminate the old rope seal and use the stock 221 crank flange in the stock 250 block. It doesn't work becasue its very hard to machine up, and may have to be lined bored in place. Rather than do that, I have to rework the crank flange now by welding it up to 3.625" and make it the same as the 250 item. Front crank snout is the same, but I had to do some work on the timing gear set after another stuff up. Nothing drastic. The 3.3 Aussie rods went right on after the pin boss was taken out 15.8 thou to fit the Chevy 305 pistons.Block was decked and bore 56 thou, pistons were taken down 60 thou to suit the block, and the head gasket has to be spaced up 100 thou. Deck register is 9.36", so the piston comes out over 100 thou.

The X-flow 250 block is very heavy, 25 % more than a US 200, 15% heavier than the 221 block.

The fact is the engine is 22 cubes down on the 250. It may have a 1.81:1 rod ratio, and I'm certain it would produce as much power as a the 250 six, but more smoothly. The engine was designed for supercharging and the whole idea was to make it rev like a little 289 , 327 or 402. The result is the crank is going to need a reweld, and its not going anywhere until I finish my other projects. Welding cranks is not a good idea.

Just after I joined this forum in Novmber 2002, Aussie7Mains and alloy dave informed me that ACL made pistons to fit the 3.3 rods to the 250 block.

This is by far the better road to go.

If your car runs to 9000 grand, it'll need either a steel crank or frequent cast iron crank replacements. That's Boss 302 territory, and the heads and pistons, rods and everything have to be perfect.

The cost of perfection is more than 10 grand.

Strokers of any description are not cheap. The rod ratio should yield another 10% specific power, making up for the loss of 22 cubes with ease. There is no reduction in recipricating friction, just in piston side loadings, Basically,in my case, the 10% capacity loss is offset by the best rod ratio. It is a steady state, but on the street, it will have to use more revs than a 250 all the time, 10% more, with 5 to 10% less torque at the low end.


As I've said, 2 000 odd bucks, and that's my limit.

 

[lyonsy]

hey
thanks for the info very helpful might be cheaper to have a crank made in the main and big end journal diamater that is required and set up for the late model rear seal instead of a rope seal.
yeah welding is not the best way to have things unless you heat teat normalize harden stress releave then run for a while before actully using so nay surface tension from the hole procedure is realeave as well.
mark

 

[Anonymous]

Here is a Crank service site:
http://www.flatlanderracing.com/cranksh ... vices.html
Ken

 

[Anonymous]

Some thoughts on journal sizes:
http://victorylibrary.com/mopar/journal.htm

 

[Anonymous]

The Poms and Yanks did some tests last century.

That's funny!
______________

The end result of your build should be big fat torque curve.
So many Hot Rodders over here put an emphasis on the peak HP/TQ #'s. It's the Torque CURVE that's a true indication of a good breathing/ well engineered engine. Cheers

 

[Anlushac11]

8)

Sorry about necro posting but this intrigued me.

I know a main concern is the rod bolts hitting the cam since the cam is ground out to clear the rod bolts so there isnt alot of rom top work with.

I was wondering about this also and using Small Black Chevy 2.00" mains but I think cam clearance is still going to be the main problem.

I also wondered about boring and sleeving block like Mike was looking at doing with the 250 blocks. Be nice if we can get to 2.3L OHC bore as there is a abundance of forged pistons available.

But then again iof Mike can get forged pistons cheap then that might be better.