Christian: Only reason I caught that distinction was because I was busted on it before (and on a mustang board!) .

I would also be carefull about going to big on the bore - A 382 is what, a 4.1" bore - we are already talking about not much material if any between the liners.

If you want to go with a big bore setup I would invest in some good liners - check with the shop doing the setup - liners can easily cost from 50-500 each (or more) and can be a BIG factor in how well the motor works out. The bigger you go the pricier of course.


Chris

 

It is MTI that does all the work.

I mentioned before the piston speed of the 4" stroke...it would be high, but with the lightweight forged rotating assembly you get, would it not be something to really worry about? I wouldn't take it much past 6000, maybe 6500 MAX, depending on where my power will be.

Either way you go, MTI is HUGE and has been around a while, so I would figure they know what they are doing. They have been known for making some really sweet cars.

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1983 Monte Carlo, 307 Stroker, TH350, 3.73 10-Bolt - SOLD 8/19/02

Future F-Body Owner

 

Yep, this is a resleaved LS1 dream though

Tough decision, I would say it would depend somewhat on what kind of racing you hope to do. High RPM is nice (big bore), but its hard on parts, larger bore also means more friction from increased surface area of the rings.

More stroke though if taken to higher RPMs, which has been done, might likewise wear bearings faster by attempting to torsion twist even harder due to the increased crank length.

I used to wonder if this was one of the benefits that the 5.0 Ford had over the 305 Chevy back in the 3rd gen era, the 305 was more a truck motor with a small bore long stroke (good for torque, crappy for top end), where the 5.0 has a 3.0" crank, all bore, and as mentioned you can throw more AF in there with larger valves.

What might give you a good generic picture of the whole scenario, is to throw it on Desktop Dyno (or etc) and put similar/same heads/cam on there and see where the differences are.

 

Or you could do both, and get a 422ci LS1, but I don't want to go that far. This will be a street car, and taken to the track once in a while. Most of its time will be spent as a daily driver. Once it hits 100K miles I want to do the rebuild, and do it all at once, and do it right the first time. But deciding between the bore or stroke...tough decision. Each one has its benefeits and its downfalls, but for the purposes I will use the car, I doubt either one would cause any real problems. Either way it should be a strong reliable motor and much more powerful than before.

Thanks for all your responses guys, there was some good discussion made here. I think I will go with the MTI 382 Stroker. You get their Stage 2 Heads, a cam (probably go with the B1), pushrods, springs, lightweight forged internals and a 1 year warranty on their work. Sounds good to me! Now to find out about pricing...

Eric

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1983 Monte Carlo, 307 Stroker, TH350, 3.73 10-Bolt - SOLD 8/19/02

Future F-Body Owner

 

And you've given a great example of what I was trying to explain in my post. Here you've got two engines with less than a 1% difference in displacement, but with totally different characteristics. One isn't necessarly better than the other - it's all a matter of modding the engine to take advantage of its characteristics, and then setting up the rest of the car appropriately.

Given equal displacement, the big-bore/small-stroke does eventually win out. You'll be limited by one of two things in a quest to make power - airflow, or piston speed. The bigger bore gives better airflow potential, and the smaller stroke increases the maximum safe operating speed.

Peak HP isn't everything for a street car, though, so you'll note that many high-perf bikes are going back to a less-oversquare configuration in an attempt to create more usable powerband. F1 cars are still pretty oversquare to the best of my knowledge



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Eric Bryant
'96 Impala SS (LT4 396, T56, "firm" suspension)
'96 GMC K2500 (parts hauler/dune runner)
'92 Roadmaster wagon (winter beater)
'01 Honda Accord LX V6 Coupe (wife's car)
http://www.bryantperformance.com

 

Also I believe that along with the stroker crank for the 382 I should at least have the cylinder walls honed again, mainly to get rid of the piston slap these engines have and to make sure things are nice and smooth again.

What would you think of just a slight overbore and hone? Would it be worth it? Not really in terms of power, since it wouldn't do very much (~1%), but in terms of reliability?

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1983 Monte Carlo, 307 Stroker, TH350, 3.73 10-Bolt - SOLD 8/19/02

Future F-Body Owner

 

I'd rather have a big bore engine than a stroker. You can fit bigger valves with the increased bore. You might be able to rev it 100-300 rpm higher than the stroker but the rod/stroke ratio starts to play a big part for any engine past 6K.

But, for a street engine that never sees over 6000 rpm, I honestly think the stroker would be a little better for overall street engine performance.

For exhaust note, I think there is a deference. Think about a 305 with dual exhaust and typical mufflers. Now think about a 302 (4" bore, 3" stroke) with the exact same exhaust system that the 305 has. Overall, the 305 will have a deeper sound with a good amount of high frequencies also. Meanwhile, the 302 will have more midrange to it's tone. Think about your stereo. Turn the bass and treble up a little and you have the 305, leave the bass and treble at a normal setting and turn the mid up a little and you have the 302.

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92 RS carb'd 357 5-speed T-tops maroon w/ black cloth interior
650 cfm Double Pumper, stealth intake, dual 12" radiator fans, 10" auxiliary pusher fan, 5" X 12" power steering cooler, 204/214 cam duration @ .050", 420/443 valve lift, 1.75" headers, no cat, 3" PaceSetter catback w/ dual 2.5" tailpipes, 3.73 gears, posi, 245/50/ZR16's up front, 255/50/ZR16's in back
2.070 60 ft, 9.9 @ 71 (1/8), 15.4 @ 87 (1/4) <--old times
100% American (you damn right)

 

Exactly what I was thinking. For one it will produce more power on the low end and I'm not going to worry about RPM because I won't be revving it past 6500 and that will be not very often when I take it that high.

That is exactly what I was referring to. When I hear longer stroke engines they usually sound deeper. Not saying every case is like that, but from what i've seen.

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1983 Monte Carlo, 307 Stroker, TH350, 3.73 10-Bolt - SOLD 8/19/02

Future F-Body Owner

 

I'd say go with a stroker for a daily-driver/street-car, like others have said. I liked the 383 in my '81 Z28, and even when the car had 2.56 gears, it still hauled-a$$ off the line, and yet it could cruise no problem on the highway at "reasonably" low RPM's due to the gearing. Once I put the 3.42's in, it's top-end on the highway was reduced, but off-the-line, seat-of-the-pants torque was unbelieveable!!! It would thrust you hard into the seats when you punched it! Now, if I was building a car that was going to see almost all highway driving, then maybe I'd lean toward a big-bore motor, since it would be happier cruising at higher RPM's, but otherwise, I'd go with the stroker.

In regards to exhaust tone?? To go against what everyone has said so far, is there no way that an equal displacement, but bigger bore motor would actually produce a lower pitch tone than a long-stroke motor?? Just think about this: a 12" subwoofer produces a lower tone than a 10" sub, right?? So therefore, would the "tones" resonating off a larger piston not be lower than those resonating from a smaller piston??? I'm totally posing this question just as a "thinker", but there really could be some truth behind it (although I'm not saying I actually believe that theory, but until someone actually runs two engines side-by-side, through identical exhausts, etc., that are the "same" (displacement) except for bore/stroke, who can say for sure???).

 

Guys, I know this migh be my first post here (i'm not a rookie) but really the bore stroke debate and how they effect TQ at differnet RPMS is rediculous.

First, displacement is displacement.

Second, the stroke/bore is determined in most engine designs by all the other parameters.

Valve Size, Piston Compression Height, Rod Length, Ring Availablity, Deck Height, piston speed, frictional losses etc are far more important choices for me over the Bore/Stroke.

In the Popular Hot Rodding Engine Masters Challenge in which I took part, getting 365 cu in SBC had alot of interesting solutions. Most guys wanted a long stroke and a bore in the 4.000" range. The results (which will be out soon) state that the long stroke will win. But they are also skewed by all the other parameters and the fact that at least 3 of the top dogs had a minor mechanical failure that kept them out of the running.

There were bores ranging from 3.935 to 4.169, and their accompaning strokes to get 365. Belive me the bore/stroke had nothing to do with who made power, but the parts that went along with that did.

My thoughts would be that a larger bore with a given deck height will give you these advantages: Longer Rod = more piston dwell, and theoretically less timing to get maximum power. Larger Valves = more flow at almost every valve lift which allows you to run a smaller duration cam. A smaller cam will give you more TQ and that is a fact. Larger Chamber Bore = better swirl characteristics which will also reduce timing for max power. Shorter Stroke = piston speed is lower. This means parts like rods dont have to be as strong, which also means they are less expensive and usually lighter. A lighter bottom end is going to make you more power at higher acceleration rates (rpm/sec). The slower piston speeds also mean that the frictional losses by things like the piston pin are lower. (yes the rings will have more surface area, but choices like oil ring tension are much more important for frictional losses. On top of that spending your time worring about ring seal is much more important than the friction caused by them.)

O.k. one more thought. The old adage that the longer stroke has a mechanical advantage is true. Use a breaker bar and you'll get more TQ at the same point. Most of the time you increase your lever arm by a large percentage 50%, 100%. Going from a 3.50" stroke to a 3.75" stroke is 7.14% increase, so you should get 7% more TQ right? with zero friction yes, but an engine is a system and it's alot more complex than that. Think about the "stroker" advantage this way. Years ago someone took a healthy 350 and droped a 400 crank in it. BAM! tons of low end TQ. Must be the stroke. Well it was probably alot of things. If all you change is the bottom end then you will have: more cubes = more TQ, more compression due to the cylinder volume increasing and the chamber volume staying the same = more TQ. A higher percentage increase in low end TQ vs high end TQ (more comonly known as HP) since the heads are the same volume and same flow. A bigger engine needs more flow. (a larger cam or better heads will help that) The intake manifolds tuning is set up for the smaller displacement engine and so it's tuning effects will be moved down the TQ curve also. I have a feeling that the early strokers never took this into account and so they were always TQ monsters. I've even heard that 400's were junk and that 383's would pull better. Well if you give me a 400 and a 383, i'll get both of them strong but the 400 will kick the 383's butt anyday.

O.k. enough of that. Basically there are so many other things that play into account that there has been no "scientific" test that compares a "all bore" engine to a stroker with the same exact parts. ( a good 377 test would be good to see, I bet they would be really close, probably within the dyno's testing accuracy)

Bret

 

Currently, I've got a 383 w/D1-SC but started reading this post and now I think a 414 LT1 (4"stroke x 4.060"bore) sounds pretty sweet--always looking to do something different. I saw that Eagle sells a 4" 1 pc seal 4340 crank that uses a 6" rod. Has anyone on this board done one of these engines? Also, which 4340 rod do you feel is the best, in terms of clearance?

 

Well, I was looking into a set of pistons....I think the compression height would be .875"...that's one tight ring pack. if I calcualted it wrong, someone please correct me.

 

Deck Height = 9.025 if you haven't milled it yet. 9.000 is about normal when it's milled.

Stroke = 4" so take 1/2 of that 2"

Rod Length = 6"

Deck Height - 1/2 Stroke - Rod Length = Compression Height

I just did a 9.025 - 1.75 - 6.25 = 1.025" Comp Height That's the same as a 9.025 - 2 - 6 = 1.025"

You will be safe if you stay with a compression height over a inch.

Bret


BTW you might have block problems running that stroke and you will have to do alot of clearancing, esp around the cam journal. 4" strokes are tricky in old small blocks.

 

Thanks SStrokerAce for clearing that up for me....