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Stroker SHO - A Discussion

11/09/2007


With all the talk of boring out the 3.4l, would it be easier to stroke it?

I know you could not get extreme since you'd need to use the stock camshafts, but it you kept it mild couldn't you get away with a custom crank and some different rods? You'd need a tune of course. All this talk once upon a time about the engine being good to higher RPM's except for the accessories makes me think the pistons, rings and liners are up to the task of a little faster piston motion at a given RPM..

I'm just thinking it's a lot easier to gain a little displacement up and down than going wider with the insert.
'71 Torino GT 351C4V shaker convertible (mild mods)
'96 & '98 SHO's 3.4l
'08 Buick Super 5.3l
'08 G6 3.9l hardtop convertible
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As a data point, IIRC, John Hrinsin's SHO V6 is stroked to 3.4L. I
don't know how similar the two engines are in terms of the cylinder
liners though (i.e. if the SHO V6 is as averse to boring)...

Regards,

Jon Heese
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Stroke will not have any problems with the stock cams. Not exactly sure what you mean with that. Stroke is always going to help a street motor and would REALLY help the SHO with torque.
Still none of this is worth the effort IMO.
Boost/nitrous will be the only real ways to add power for the $$$.

James Otting
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Yes, feasible.

But, for the cost of a crank/rods/pistons for a bit more displacement, you could increase displacement more with a roots blower setup.

Ron Porter
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With the HUGE PITA I just had with "any" kind of traction at the
track, and the astronomical costs of cutting out liners and
reinstalling custom liners on a lightweight, tiny little power plant
which is too light to hold the nose down in a launch, would SOMEBODY,
PLEASE, just jam a cast iron 5.0 into one of these please?
It is way smaller than our 3.4, has bolt on goodies for days, weighs
enough to hold the car down, is drooling torque, and can be had by the
millions in any junk yard.
You're going to have to redo the tranny anyhow, trust me on that one.
So just make a plate and mount the AX4N to a 5.0 while it's apart.

Go ahead - TRY to tell me that this is less feasible than putting
oversized sleeves, pistons, rods, and crank into one of our engines.
Eric Lehmann
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Stroke will not have any problems with the stock cams. Not exactly sure what you mean with that. Stroke is always going to help a street motor and would
REALLY help the SHO with torque.
Still none of this is worth the effort IMO.
Boost/nitrous will be the only real ways to add power for the $$$.
James O
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With all the talk of boring out the 3.4l, would it be easier to stroke it?
I know you could not get extreme since you'd need to use the stock
camshafts, but it you kept it mild couldn't you get away with a custom crank
and some different rods? You'd need a tune of course. All this talk once
upon a time about the engine being good to higher RPM's except for the
accessories makes me think the pistons, rings and liners are up to the task
of a little faster piston motion at a given RPM..
I'm just thinking it's a lot easier to gain a little displacement up and
down than going wider with the insert.

71 Torino GT 351C4V shaker convertible (mild mods)
'96 & '98 SHO's 3.4l
'08 Buick Super 5.3l
'08 G6 3.9l hardtop convertible
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Going from memory, part of it is from a stroke increase (basically just offset-ground crank journals) and another bit from oversize pistons.

An engine is an engine (gee, what a profound observation!). The SHO V8 (or V6) is no different than any other V engine out there.

The V6 can be overbored, but not much (thin wall iron block)

Ron Porter
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I didn't understand the cam comment either. On some OHV V8s, though, chanking to a stroke crank with bigger counterweights do get close to the block near the cam IIRC.

Ron Porter
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On most stroker kits they change the cam out from a street cam to a little more high performance one. I'm not sure if the larger displacement would change the dynamic compression or other characteristics.

My reason for proposing a stroker is that it might require fewer parts on a SHO engine since the SHO engine has higher RPM internals than most stock mills, My logic is that we believe Yamaha engineered the engine for 8kish RPM, but that the Ford accessories limited the speed of the production engine. If that is true then the parts count might be less than on a typical engine where the parts are closer to at their maximum piston speed. I'm thinking that unless the piston skirts got in the way, you could change only the crank and rods to get a mild stroker

HiTech SHO
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There's no need to change the cam(s) per se. Compared to the cost of a stroker setup for an OHV V8, the incremental cost of a cam is a pittance. OTOH, for a DOHC........
Rpm on the accessories is not much of an issue. The factory setup is to provide enough accessory rpm to run everything at idle or near-idle. Underdriven pulleys can take care of the rpm issue. If you change the torque peak with amore stroke, the peak torque & HP will come in at a lower rpm anyway (not a bad thing). And just because the engine can turn 8K, it doesn't mean it accomplishes anything. Airflow work on the intake, head ports and exhaust side (as well as cams) would be needed to use it effectively.
Spend the $$$ on getting a 4.6 SOHC to fit. More bang for probably about the same (or less) bucks.
Ron Porter
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Yes, my brother lost a 418W due to cam/rod interference with a 4.1" stroke.
Not sure how much a stroker crank would cost for the SHO V8

James Otting

I also thought the 3.4 V6 SHO was an offset 3.2 crank IIRC

James Otting
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Sorry I was not being clear.

My objective is to run a stroker at the same RPMs as a stocker. Problem is, generally you need upgraded pistons and rings to do this, because a stroker moves the piston farther on each stroke. So the piston has to move faster. Those 8 pistons and hardware get expensive.

So I think the stock SHO pistons could run at the stock redline without any upgrade, saving money and difficulty of finding high performance pistons.

Everyone is saying stock cams would work.

Rods I'm thinking might be findable, or if not, not too expensive to just fab up.

So I'm thinking the main cost of creating a stroker v8 SHO might be just the single custom crankshaft...

HiTechSHO
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If you change the crank, then you have to change either the pistons OR the rods. Generally changing the pistons is preferred because you don't want to shorten the rods.

bjshov8
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You would probably also want to change rods AND pistons. You can also play with rod length, piston offset, etc, to get the power characteristics that you want.

Ron Porter
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Who cares about the rpm? The redline is a function of the way the engine is set up. Granted, having a cushion above the redline is a good idea. Cams determine the redline to a big degree, but I'm sure just adding stroke will drop the power peaks lower in the rpm range.

With an engine this small, I doubt that piston speeds would be an issue with more stroke. You would need/want to do new rods, anyway, as well as the pistons. Getting pistons is not a big deal. You can get whatever setup you want, although they will be custom and will cost a few pennies (!!) more than a set of 350 Chevy pistons off the shelf. Hrinsin had custom Wiseco pistons made for the V6.

But then, after you spend $2-4,000 for the crank, what's a few grand more for rods & pistons??

Then you'll need more $$$ for the therapy sessions when a guy with a $500 Zex kit blows by you!!

Ron Porter
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3.2 V6 has the same crank as the 3.0. Just a bigger bore.

Ron Porter
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Going from memory, part of it is from a stroke increase (basically just offset-ground crank journals) and another bit from oversize pistons.

An engine is an engine (gee, what a profound observation!). The SHO V8 (or V6) is no different than any other V engine out there.

The V6 can be overbored, but not much (thin wall iron block)

Ron Porter
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As a data point, IIRC, John Hrinsin's SHO V6 is stroked to 3.4L. I
don't know how similar the two engines are in terms of the cylinder
liners though (i.e. if the SHO V6 is as averse to boring)...

Regards,
Jon Heese
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Well, you also didn't do any suspension/tire work for the strip. We talked to a
GTP guy a few years ago at Lapeer who was running very low 13s with drag radials
and whatever suspension mods he may have done. A basically stock SHO on nitrous
with DRs will run at least 13.50s like Tom Wallenhorst did. Plus SHO Forum has a
guy who just ran a 12.8x

And their trap speeds were north of 100 mph.


Ron Porter
 


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