Poor mans 4.5 inch stroke?

[Joey120373]

I'm in the process of gathering parts to build a large cubic inch FE motor based on a BBM block.
This is not going to be a drag race motor by any measure, it's going into a 72 2 wheel drive F250
and the motor will never see much more than ~5500rpm.

Right now the motor is still in the planning stages, I have a block and I've made contact with Blair Patric about a set of his pro port heads. Outside of that nothing else has been nailed down.

My Father and I are enjoying putting this engine together on paper, while both of us agree that the only substitute for cubic inches is more cubic inches, he likes to get a little more adventurous than I do, he's not the one buying all the parts after all .

My initial plan is to just order a 4.375 rotating assembly from Barry R. And call it a day. With a ~4.42 bore ( leave a little room for a rebuild or 2 ) I will have a 537ci motor.

My father would like me to take that crank and offset grind it to the Honda sized rod journals to get as much stroke as can be had before rods start hitting the cam.

Several warning flags pop out at me thinking about this.

First, I know Jay has used a 4.5 inch stroke in his HR motor with a little grinding on the rods, and the smaller overall rod end should help. But outside of bottling it together and measuring it, anything past  what Jay has already done (4.5 inches) scares me a bit.

Secondly, and more importantly, offset grinding the crank that far with such a small journal is not going to leave much in the way of overlap( I calculate ~.180ish ), and it might well hit an oil passage or lightening hole.
I tried to debunk it strictly on overlap, so I looked up long stroke cranks offered for other motors.
Scat offers a BBC 4340 steal forging at 4.75 inches of stroke, given the 2.75 man and 2.2 rod journals this crank would seem to have less than .1 inch of overlap. I think this is not an apples to apples comparison, .1 inches of overlap on a 2.2 inch journal is not the same overall overlap area as a .1 inch overlap on a 1.88 inch journal. But since the proposed 4.5 stroke combo has .080 more overlap it still seems plausible.

Thirdly, even if all this is do-able, the cost of the rods becomes an issue.

Still scares me though, and I'm not sure I'm willing to take a gamble on destroying a $3600 block by trying to get another 15 cubes out of a cheep forged crank.

I decided to offer up a compromise combination, as my father keeps pushing the idea.
If I could offset grind the crank to a 2.086 journal
And use off the shelf 5.4L ford rods, I could get close to or attain a 4.5 stroke for relatively cheap.

While I think it would be great to get all the cubes I can, I'm just not sure it's worth the risk.
So I thought I would offer it up here and get some opinions from the experts.

I know the rod stroke ratio is not going to be great on such a combo, but this  is a whole different debate. My father thinks the shorter the rod the better for this application, I'm not sure that's the case.

Thanks, Joe

[blykins]

RPM says the 4.375" crank is made for a 6.800" rod, but the 6.700" rods will still let the pistons clear the counterweights.  If you used an even shorter rod, it's possible you'll get into a situation where the counterweights will need to be turned down.  Not sure. 

Custom pistons will be necessary for either scenario, so you have any more expense there. 

However, it's a  lot of work for what you'll get back at this power level.  You'll always learn a little bit from going the road less traveled, but you'll have to decide if the extra expense and effort is worth it.

[Joey120373]

Ahh, the old counterweight smacking the piston trick....

Thanks for the info on the RPM crank Brent, I was not aware of the 6.8 rod requirement.
I have seen a few builds that used the 6.7 rod so I was assuming it wasn't a big deal.

I had thought of counterweight interfearance, ran into it years ago when we ( a machinist I worked with at the time and I ) played around with some Chrysler Pistons in s ford 400M.
Ended up having to mill a bit off the Pistons but it worked. But in all the back and forth I've been doing on this project I kinda forgot about that. My other concern was how far out of the bottom of the bore will the piston extend....

Anyway, if the counterweights on that crank are close with a 6.7 rod, then I really don't want to toy around with an even longer stroke and a shorter rod.
 Thanks

[CaptCobrajet]

I use rods shorter than 6.700 on those cranks regularly.  If you offset it, you'll need to re-heat treat it.  It is doable.  I think for longevity, a 2" SBC is as small as I would go.  The rod would need to be custom to get the side clearance to jive with the 2" width of the BBC.  You can't keep a head gasket on a 4.42 bore.  Should stop at 4.350 to have a future service capability.  520 cubes is safe and healthy.

[Joey120373]

Thanks Blair.
Not sure what a good offset grind would cost, let alone the heat treating. But I'm guessing the cost of custom rods alone will be more than I want to spend for the few extra cubes. Think I would rather put the extra money in a good set of heads and bullet proof valve train .

What you say about the head gasket makes sense, I had not really thought about it but there is not a lot of metal there and no head bolts near by.
Not sure if a copper gasket and o-rings would hold up, but I don't really want to go down that road. I'll gladly give up some cubes for long term reliability.

[turbohunter]

Thanks Blair.
Not sure what a good offset grind would cost, let alone the heat treating.

Had it done recently. $600 in SoCal dollars.

[Joey120373]

Had it done recently. $600 in SoCal dollars.

With the heat treating?

So $700(?)for the crank, $600 for the machine work
And .... Still don't know..$1500 for custom rods?

Hmm, those last few cubes start getting expensive. They always do I suppose .

[jayb]

I've done the Honda rod journal thing, and won't go back there; that setup did not last.

I think that if you went to the 2.0 SBC rod and offset ground to fit that, it may be your best bet.  I had my high  riser all set to go with the 4.5" stroke, but when I got to some of the higher lift cams (0.750"+) the grinding required to make the rods clear got to be excessive.  If I'd had a 0.650"-0.700" lift cam the 4.5" stroke and BBC rods would have been fine.  Seems like the same general idea would probably apply to the SBC rods.

[Drew Pojedinec]

I know I know, this is an FE forum.  I love Fe's.
That said, this isn't a race motor, this is just a big cube engine to go into a 3/4 ton truck.

Why not look in the 460 direction if you need big cubic inches?  521ci 545ci etc are all very common, easily done with a stock block and have proven to be very reliable.

Just tossing that out.
If you stay FE, take lotsa pictures and post them, not a lot of folks going that big with an FE.

Good luck

[garyv]

I'm with Drew on this one.
Can't beat a 460 based engine for cheap TQ for a truck.
I have one in my 78 F 150 and it's great.
Also have a 511 cube tunnel port 
460 is WAY cheaper.
my 2 cents
garyv

[turbohunter]

That was the offset grind and nitriding price. Induction hardening may be cheaper.
I mention SoCal dollars because the price may vary where you are. But at least you have a reference point.

[Joey120373]

I know I know, this is an FE forum.  I love Fe's.
That said, this isn't a race motor, this is just a big cube engine to go into a 3/4 ton truck.

Why not look in the 460 direction if you need big cubic inches?  521ci 545ci etc are all very common, easily done with a stock block and have proven to be very reliable.

Just tossing that out.
If you stay FE, take lotsa pictures and post them, not a lot of folks going that big with an FE.

Good luck

Gotta laugh! You are absolutely 110% correct, and I do apreciate your willingness to bring it up on this forum. My father, who is ever the tinkerer, would love me to put a stroked 540 caddy motor in the truck. It also offers a substantial torque curve for much, much less money. I told him that if I wanted the cheepest motor, I would go with a 557 385 motor.
That set off a week long discussion where I was finally able to prove that, bang for buck, a 557 385 with the new AFR heads was undoubtebly king of the hill, both in ease of making gobs of power and price. I even managed to talk myself into it for a couple of days.

But I came to my senses, cost be dambed I love the FE, I have since high school . And have always thought the 385 was a great motor.... For someone else to put in their car.

So I couldn't agree and yet disagree with you more! 

Jay, if a 4.5 stroke and 2.2 rods will clear with some grinding.
Would it hold true that a 4.6 inch stroke with 2.0 inch rods would also clear?  I would think that the 2.0 rod would gain ~ .100 more clearance because the big end is that much smaller. So adding another .100 stroke would soak up .050 of that. But still should have roughly .050 more clearance that your high riser. Or do I have my wires crossed.....

Can anyone give me a ballpark figure on custom rods?

[Joey120373]

Correction, offset grinding to a 4.6 inch stroke is really pushing it, unless my wires are still crossed, max theoreticle stroke would be 4.375+0.200. So maybe shoot for a 4.55 stroke.....

[Joey120373]

I'm with Drew on this one.
Can't beat a 460 based engine for cheap TQ for a truck.
I have one in my 78 F 150 and it's great.
Also have a 511 cube tunnel port 
460 is WAY cheaper.
my 2 cents
garyv

Well.... Yea... The 460 is great stroked 460 even better, but a 511 tunnel port, now that's just cool.
To me, even a Boss headed 385 motor takes a back seat to a tunnel port or cammer.

I even contemplated doing a Kasse headed 557 boss9 motor, I think in the end the cost would have been comprable. A bit scary to think what kind of power that would make.

But like I said before, I've been dreaming since high school about building a hopped up FE, that was a long time ago. Back then my ultimate build was going to be a cross bolted 427 block with a 428 crank and a set of tunnel port heads. That was the early 90s though, and by then finding good FE parts was impossible, especially for a 19 year old kid with no money.

[Drew Pojedinec]

But I came to my senses, cost be dambed I love the FE

Well, your logic is sound.  Just felt I needed to add those two cents.  (and remember, post lots of pictures)