This topic was raised in a previous post some time ago, but I remember that there wasn't much of a consensus about possible problems involved with installing a 4.37" crank in a BBC.

A few of the concerns, I believe, included the following:

1) small bore/long stroke relationship
2) crank clearancing issues
3) reliability

The block that I will use is a 1972 454 and it has a 4.28" bore. Installation of the big crank will give me a 503 displacement. The objective will be a low RPM daily driver with about 500HP and 550 ft/lbs torque.

Can we discuss the pros and cons again for those who may wish to "build big" (like me)? :D

Thanks, Charles

I figure that my '75 454 P/U core motor's block that I made my 496 out of can swallow a 4.375" crank with minimal grinding b/c it swallowed the 4.25" crank with NO grinding whatsoever..

The new Vortec 8100 motor is a tall deck blocked 494.18" or 495.9" motor, (depending on how you want to calculate it??), motor that has a 4.25" b x 4.37" stroke so if it is good enough for the general, I figure you are fine, imho...

And I don't know whether to call it a 494" or a 496' motor???????

I want to make a 4.625" b x 4.375" s = 588" motor using a standard deck height Merlin Pro/III or a Bowtie block for the ultimate stealth 396 motor!! He, He!! (I would use a 6.45" long custom rod and get matching pistons made)....

pdq67

Please keep in mind that the 8.1 uses a completely new block casting, and among other things, the pan rails are spread further apart.

Buy I sure would welcome any second hand knowledge here. I posted a while back too. not much info except the cautionary type.

Please email me or post any combo info. I am seriosly hung up on getting over 500ci out of my truck block

PDQ67,thanks for the encouragement. Jesus, what kind of cam do you run in a 588???!!!

Milan, here is the basic 503 street combo that I am wanting to build:

454 (.030" over)
GM 063 closed ovals (standard valves w/3-angle valve job, light port work)

Flat top pistons
9.7 Compression Ratio
4.37" forged crank
6.385" forged rods
Balanced Rotating Assembly

RPM Edelbrock intake
800 CFM Qjet Carb
LUNATI 288/296 Hydraulic Cam

This combo in a 67 Chevelle with a TH400, 2400 Converter, and 3.31 posi should be a blast to drive!!

Charles

Go over to SGCOG's site and ask Jake,("Jakeshoe"), to fill you in on the 8100 BB motor b/c he has/had one!!

Here's one link and know there are more...

http://www.nastyz28.com/ubb/Forum5/HTML/009047.html

Please say hello to Jake for me...

pdq67

I sure would like to hear from someone who has built a 454 with a 4.375" crank and if there were any problems encountered. Surely I can't be the only one who has ever considered building this combo???

Wolfplace, what's your experience or thoughts?

Thanks again, Charles

S-O-M sells 4.375" stroked crank motor kits if it interests you..

pdq67

Thanks, PDQ67. Speed-O-Motive does offer a daily driver mountain motor stroker kit (454-510) for about $1800. This is an all-forged kit. I haven't heard much about the quality of their stuff, but it's probably as good as anyone else's.

Thanks, Charles

Any updates on this thread?

If you use a stroker rod, there's probably not that much additoinal work to do for install. On a personal note, I doubt the the gain would be worth the effort. With a 4.28 bore, I would just go with a 4.25 stroke. THe heads you want to use are going to be the limiting factor, at 489CI, they are sucking real hard to keep up. Figure on spending the money on some good heads??, then maybe talk 505CI.

Canfield 310 aluminum heads are dandies, imho for just this type motor.

And don't forget the 6.45" custom rods and JE pistons!!

I would go 360 cc heads and a 290/250/300/260, 110/106, .625"/.625" net lift solid cam for torque for a 588" jobber!!

Just a mild motor is all, BUT BIG!! I figure 3rd and 4th gears will be winners!!

I actually want to scare my big-headed B-I-L by smoking my tires at 75 mph!!

pdq67

I'm gathering parts for my new boat project. I already have the 454 block, 496 pistons and 4.250 crank. But if someone wants to send me a 4.375 crank, rods and pistons, I would be glad to build it up and try it and write up a complete report on the build.:D

The 4.250s drop right in, I would think the 4.375s would fit with very little grinding.

Digging up an old topic, anyone done this yet (4.25"b x 4.375"s)?

I don't recall anybody here doing it. Kind of a PITA way to get 500 cu.in.

I don't recall anybody here doing it. Kind of a PITA way to get 500 cu.in.
=
Ya think :D

Thanks, bluerebl, for reviving this old thread. A lot of topics seem to recycle over and over again anyway.

It basically comes down to whether or not its' a good idea or a bad idea from a realiability standpoint. If most of you engine builders consider it a combo that will have a short life, then I will just go with the 4.25" crank.

Man, it would sure be nice to find some article addressing this issue by Super Chevy, PHR, etc. A basic 454 BBC street stroker buildup using the big crank.

If this combo is a low rpm engine (redlines around 5500 rpms), it would seem to me to have as good a street life as any other BBC that is supposedly "street driven" that has over 500 cubic inches and revs 6000 - 6500 rpms, or more. The 063 heads should provide decent flow up to 5500. I realize new aftermarket heads would greatly improve breathing, but the 063's are all I have with the bare block, no crank, rods, or pistons. Hence, the idea to build a big low budget, low rpm torque brute that would live happliy on the street.

Thanks. Charles

I just picked up a new tall deck block with a fresh 4.310 bore. Going to look into this some for the future.

Has anyone done an offset grind on the stock crank to get the extra stroke and used the smaller diameter bearings to get the 503?

Th 4.310 x 4.375 takes it to 510. 4.350 x 4.375 makes a 520. 4.350 x 4.25 makes a 505. With all the available 496 assemblies out there, you have to wonder if it's really worth the aggravation to jump from a 4.25 crank 496 with off the shelf parts to a 4.375 crank 510 that may call for custom parts and block grinding.

I have a tall deck 427 (cherry block) ready for a 0.030" overbore that would love to swallow a 4.37" stroke crankshaft. According to a sonic check my cylinder walls will easily handle a .125" overbore with ease.

Heck, I would go to a 4.5" stroke if I could. At least I wouldn't have the rod to crank ratio issues as a standard 9.8" deck block would have. I just don't think a production block could swallow a 4.5" crank.

Anyone else have any info on if a production Mark IV can swallow a 4.5" crank?

If so, there would be the trouble of finding pistons that would work too.......



Thanks.

Here's what I ahve been able to come up with. Using stock SRP pistons, there are plenty of possibilities - this is for a tall deck.

Tall deck

4.25" crank, use 6.535 rod with 1.52" ht piston, .020 cut to "0" deck
use 6.800 rod with 1.27" ht piston, .005 cut to "0" deck

4.375" crank,use 6.700 rod with 1.27"ht piston, .020 cut gets you to .021 deck.

4.5" crank,use 6.535 rod with 1.395" ht piston, .020 cut gets you to "0" deck

Block clearance on the later 427 tall deck blocks is not a problem, even with a regular rod (at least on my block). My TD has a minimum of .243" clearance when mocked up with a 4" crank and stock GM rod. No question, this block will take a 4.375" crank with no clearancing. You would have to mock up a 4.5" crank with H-beam rods, but have been told it will require clearancing.

SHort block aside, the real issue becomes the oil pan in a stock chassis. Spoke with Stef's Performance. They do have a 4.5" deep (front) pan that will clear a 4.5" crank. It will need stroker notches. Was advised the rods should have the better bolts (L19's ??) installed as these have a smaller bolt head. A custom alum pan is in the $400.00 range, this included the stroker notches, integral windage screen, kickouts. Was told, the kickouts do not go all the way back on the drivers side, pan is notched here to clear the oil filter.

After exploring the options, I have come to the conclusion that it is easier and possibly more effective to just go with a 4.25" stroke. Leaning to a 4.350 x 4.250 for a 505" motor. This can be done with as high end parts as you want or can even be done on a real tight budget with one of the Scat cast stroker cranks, 6.535 Ibeam rods and 1.52" ht hyper pistons, all depends on how hard you want to hammer it.

I read where a h/d truck tall deck block can be made to take a 4.625" crank and then max. bore it to 4.375" or so to come up w/ a 550"+ engine like in the old days before the aftermarket big bore blocks were around like they are today.

It might just be 4.350" b x 4.600" s tho???

Probably alotta grinding when an aftermarket block is available now...

pdq67

http://www.chevelles.com/forums/showthread.php?t=164165&highlight=tall+deck