Stroker engine

[Doug'sL81]

Hello everyone,

My question is: if a 350 is bored 0.030 and has a 400 crankshaft stuffed into it, it's a 383. What would the displacement be if it was bored 0.060? Is there a formula to calculate this?

Thanks

Doug

 

[Ken]

bore X bore X stroke X 0.7854 X number of cylinders

_ken

 

[sscam69]

I believe its 388 right off the top of my head.

Thats pretty much maxing out the block. I would not recommend going that big of an overbore with a real high performance engine. Risky if you ask me.

 

[Doug'sL81]

Thanks for the info. The (free) block I got, had to be bored .060 because it was sitting out for a long time and water was in the cylinders. It’s not going to be a real hi-performance engine. I’m following a recipe for a mild mouse from Chevy Hi-performance Magazine. A 383 with a 274 grind comp cam, AFR 195 heads, Air Gap intake, 750 Barry Grant carb this combo should reach about 400 to 425 HP and about 450 Ft. Lbs. of torque. I’m not interested in ¼ miles, drags or any of that stuff. I’m going for the fun factor. Again thanks for the info.

 

[Blue82]

Doug, I built the medium rare mouse but bored it .030 over and used a 454 TBI instead of a carb. It really woke up my 82.

I'm glad they wrote that article because it really helps give novices like me a starting point toward a well matched engine and we can take it from there.

 

[Mpit69]

Can someone post the locations of the article, I forgot where it is?

 

[Doug'sL81]

Mpit69,

Blue82’s mouse recipe came from the “7 spicy power combos” in Sept. 2001 to get there go to www.cheveyhiperformance.com in the upper right corner is a pic of an engine and the text says “Tech Articles, the best of CHP tech articles, top 40 tech stories”, click on that then scroll down to sidebars and click on engines, then scroll down about 8 articles and click on 7 spicy engine combos. I got my recipe from 2002 CHP I forget the month and it lists engine combos using a music theme, I think mine was muzak mouse or punk rock mouse, pretty much the same thing as the 7 spicy combos. The website does not have that article in it yet. Hope this helps. Blue82, you're right about those articles helping us novices. I did alot of research before settling on that combo. I spoke to many people who are experts and they all said it was a good combo for my needs. I'm not too concerned about boring 0.060 over and I know that block is finished as far as any future rebuild, but it'll do for me.

 

[Blue82]

I forgot about the article you used. It came out after I began moving toward my setup. I'll have to go back and dig it up and let y'all know which one it is.

This was my first hi-perf. build up so even with all the research I did before hand I still wasn't confident that I would have a good combo in the end. I'm already tempted to get a different SB and start slowly building up a better platform.

Speed is definitely addictive and expensive!

 

[Stallion]

Can you explain what you mean by "bore"? And when you say you put a 400 crankshaft in it, what does that mean? Why does this change the volume of the block as you suggest?

Thanks!

 

[Ken]

Bore:
To make a hole in or through, with or as if with a drill.

Bore:
The cylinder hole itself.

Bored:
To increase the diameter of the cylinder.

Bore diameter:
The diameter of the cylinders, usually measured in either inches or millimeters. When a cylinder is bored out due to scored walls, it is usually increased in "ten thousanths" of an inch (0.01") or 0.25 mm.

Bore-stroke ratio:
The relation between the diameter of the cylinder bore and the length of the stroke of the piston. If the stroke is longer than the cylinder bore diameter then the engine is called a long stroke engine. If the stroke is shorter than the cylinder bore diameter then the engine is called a short stroke engine. If the stroke is the same as the distance of the cylinder bore diameter then the engine is called a square engine

_ken

 

[Bullitt]

PAW (Performance Automotive Warehouse) sells many stroker kits, including a punched out 350 to 388 cubic inches. I'm away from home and don't have the phone number handy, but do a search through this forum and you'll find it in a previous post of mine. Strokers are boss! :cool

--Bullitt

 

[sscam69]

Chevy made different engines with different amouts of displacement (volume).

You gotta ask yourself "how can I make a glass of water hold more water?"

1. You can make the glass taller
2. You can increase the diameter.

With a "stroker" you can do both.

See a stock SBC 350 has a 4" diameter bore and a 3.48" stroke. In other words how far up and down the piston will move.

With a "stroker" you are basically putting in a bigger crankshaft that what was intended.

For example a 400c.i. SBC has a 4" diameter with a 3.75" stroke BUT the beauty of it is you can drop in a crankshaft intended for a 400c.i. engine into a 350 c.i. engine.

Now instead of a 3.48" stroke you have a 3.75" stroke. You just made the glass of water taller (i.e. more volume) Whats cool is that you can increase the diameter of the cylinder as well. A 350 can be bored out to a .06 overbore within safe limits. Typically the blocks are bored out to .03.

Once you do the math a 4.03 bore x 3.75" stroke gives you 383 cubic inches of displacement. If you go with a 4.06 bore you'll get 388c.i.

More displacement means more power.

Because of the longer stroke and essentially the longer throw of the crank 383's make more low end torque as a result of both more displacement and longer throw.BUT they tend not to be to rev happy. But can be made to be if you use a longer rod

 

[Stallion]

Okay, I think I see what you mean. Kind of a confusing topic, but I understand for the most part. Thanks!

 

[MaineShark]

Just out of curiosity, about how much does a 383 conversion usually cost? (just ballpark numbers)

Joe

 

[sscam69]

It varies because of machine work.

You have to machine down the main journals to fit the 350 main journals. I forgot the specs.

Because the crank is "wider" you also have to clearance the block so that the connecting rods don't hit the pan rails. You also have to use a balancer for a "400" block as well as a flywheel. If you stick with a 5.7" rod or go a 6" rod you have to keep the total length of the assembly below the deck height. So if you keep the longer throw & standard or longer rod you have to cut down the height of the piston. Sometimes this calls for custom pistons which can run anywhere from $300-$600+.

If you shop around a lot of company's (i.e. SDPC, Summit, Jegs etc) already have "stroker" kits ready and eliminate all the guess work. The only thing have to worry about is the additional machininng to the block and the journals. AND that all depends on your local machine shop or where ever you buy the kit from.


Sometimes its just easier to buy the shorblock already assembled unless your the do it yourselfer.

Frank

 

[Ken]

Sometimes its just easier to buy the shorblock already assembled unless your the do it yourselfer.

Not to mention cheaper. I learned the hard way when building my 417ci engine. :eyerole

_ken

 

[rgtrough]

strokers rule!

Hey guys, I was planning on building a 383 torque monster and stick it in a '79 or '80 shark when I found my '74 coupe with the original engine already stroked. It is all I expected plus some. The down side is now I have a '78 small block, a 400 harmonic balancer, an already machined 400 crank, and 5.7" rods. If someone is interested in buying these componets email me. I'm willing to deal.
The statement about longer rods providing higher rpms, what lenght 6"? My next step is Sportman II heads, Holley Street Dominator dual plane intake, 286 Comp Cam, Crane roller rockers. I am wanting to be able to exceed 6000 rpms. Any suggestions? :cool

Bud

 

[Ken]

The person at PANIC's Tech Paper and Data Chart put together a pretty good description of Connecting Rod vs. Stroke Analysis:

The ratio between the connecting rod length and the stroke length of a motor greatly affects the way it performs, and how long it lasts. This ratio (normally represented by "n") can be calculated as follows:

Ratio "n" = Rod Length ÷ Stroke

The rod’s length is measured (for this purpose) from the center of the piston-pin opening to the center of the big-end bore, not overall. There is a small range of ratios for most conventional piston engines: the rod is between roughly 1.4 and 2.2 times the stroke length. It’s not possible for the rod to be the same length as the stroke, and rods much longer than twice the stroke make the motor very tall, and are not practical for most purposes (although used for racing).

more...

Most engine builders find that a rod/stroke ratio of approximately 1.75 is optimal.

_ken

 

[rgtrough]

Rod/stroke ratio

So Ken, 6.0 rods, 3.75 stroke = 1.6 rod/stroke ratio
1.75 rod/stroke ratio, 3.75 stroke=6.56" rods
Is this my answer for higher rpms?

 

[Ken]

The longer the length, the more torque you can apply for any given force.

• Ratios of 1.8 or higher are referred to as long or "slow"; i.e., "torque motors"
• Ratios from 1.65 to 1.79 are middle value ratios; i.e., street motors
• Rods ratios of less than 1.64 are designated as short or "fast"; i.e., high rpm race motors.

It's up to you.

_ken