Stroking G-Body Motors

Max Headroom

Master Mechanic
Sep 8, 2011
369
63
I have been working on an idea that would allow most stock, low compression, open chambered head engines from the G-Body era to be stroked by changing only the crank and installing a simple kit. So far in my research, even the rods original rods would be retained. All other things being equal, increasing stroke would increase swept volume and this would, in turn, increase engine compression without changing anything other than the crank. In almost all cases, you could run the pistons you already have, unless you decided to bore the engine while you were at it. While you would still have the same non-performance parts from the rest of the engine, imagine how much better your car would run with just an increase in compression ratio and cubic inches. When you are ready, you can upgrade your cam, add a small 4 bbl, rework/replace your heads, install some shorty headers that don't get in the way. Now you have something that can easily get out of its own way and is much more fun to drive. I believe this will even work with most v and or straight sixes. It will also work with performance engines but there will be due diligence to do and questions to be answered before deciding it's a good idea.

So let me say it before someone else does, why would you go to the trouble of pulling a low performance engine out of the car just to put it back in again. A lot of work for little gain. I say, "Maybe, maybe not!!". Depends on what you start with. Got a V-6 but like it, this could be a cost effective way to improve performance noticeably. Got an Olds 350? This could be step one in some serious torque and hp gains. An sbc 305 may not be the best candidate, not because there would be no improvement but because buying a low compression sbc 350 for cheap and starting with a stroke increase would. However, if 5 liters is you thing, this is a great first step in increasing performance.

After changing the stroke, literally everything else you would do to increase performance on the engine could be done in the car. In other words, "weekend work". Need to save for the next improvement? No issue. The lower end is solid and ready to go.

Got a low compression 350? Stroke it with good bearings, bolts, gaskets and assembly practices and you have a solid bottom end that could handle a lot of upgrades over time and you would already have the advantage of more compression and more cubic inches.

So will you end up with LS performance, maybe (probably) not but how much money will you save and how much less crap will you go through?? Your sh*t already fits under your hood, the wiring harness works, the exhaust doesn't need a hammer or torch to fit and the engine bolts right up to the transmission you have now.

Changing the stroke would be accomplished in one of two ways, depending on how much of a performance increase you were looking for. One way would be less expensive and would be pretty much a do it yourself kind of thing. The second, more expensive way would pave the way for some serious, power adding changes. I can't say more than this because I am doing due diligence for a patent and a partner. Part of my due diligence for a partner is this post. What I would appreciate from the forum is some feedback about the general concept as I have described it here. I am willing to answer what questions I can. I can answer anything that relates to what to expect after making the change, how long it would take, what tools would be required, etc. I am looking for some devils advocate kinds of questions too. I'm not gonna put money into this if it has no value to people like you.

So, if you would be so kind, read, think ask.

Thanks!!!
 
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565bbchevy

Geezer
Aug 8, 2011
8,117
113
Michigan
Sorry but I disagree with pretty much this entire statement.
 

Max Headroom

Master Mechanic
Thread starter
Sep 8, 2011
369
63
Sorry but I disagree with pretty much this entire statement.

If you don't mind my asking, what specifically don't you agree with. Are you saying that an engine can't be stroked by just changing the crank. Under normal circumstances, I agree. However, I have spent a large chunk of time in the last couple of years figuring out a way. There are other things to be done besides changing the crank. I just can't talk about them yet. Or, are you saying that it is not worth the effort for the immediate and downstream gains that can be had? I would really like to know.
 

64nailhead

Goat Herder
Supporting Member
Dec 1, 2014
2,481
113
Upstate NY
The stroke/displacement is only part of the issue with smog motors. The other is the heads, cam and exhaust.

The reason, imo, that the LS platform is taking over is not because of cubic inches, but rather head flow. Making 400 hp with a 325 ci LS is easy. Throw in the bonus of a full 4 bolt main setup with buttress bolts.For a NA build, maybe you can make some headway, and many people including people here are extremely happy with a 400 hp motor that is driveable.But at the end of the day,‘stroking’ a motor isn’t worth Bo Diddly with a stock head and cam.
 

84dragcutlass

Royal Smart Person
Supporting Member
Aug 20, 2009
1,014
113
North Vernon IN
I have to agree with the above statement, even if you took all the time to pull your engine and stroke it once you put it back in the car it would still be a dog and completely choked by every single other system on the engine. Also i don't see a single person that would go to the trouble of yanking their engine out to stroke it without doing an all out build and for that the kits for 383 strokers and the like are already out there and solid platforms. Honestly those times are slowing down anyway, when i was in high school a car with a 383 stroker was the badest beast out there, now its the LS platform.
 

GuysMonteSS

Royal Smart Person
May 21, 2011
1,450
113
Kentville,Nova Scotia,Canada
I have no claim to being an engine stroker expert.
But,I dont think that stock pistons and connecting rods could be used with an increased stroke crankshaft.
I believe that either piston pin height or rod length would need to be changed to accommodate a longer stroke crank and to properly locate the piston top in the block for the desired deck height clearance at Top Dead Center.
Just my thoughts.
Guy
 

motorheadmike

Geezer
Nov 18, 2009
6,651
113
Ottawa, Ontario Canada
Best "quick" solution I could think of:



Oh wait... that isn't even close to how silly this proposed concept is. An engine is an air pump, it doesn't matter how much displacement it has if it cannot flow air in and out efficiently.
 

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