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Stuck like a MoFo
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Discussion Starter #1
I am having a hard time in deciding what i want to do. I am planning on another heart for my truck. As of right now the truck is a trail/winter vehicle. I was thinking a MAF inline or i have a 351w on a stand.

With the inline, i need to find one, rebuild it, some slight mods, then swap a harness and puter.

With the stroker, i just need the kit, rebuild it, frame towers and rad.

I am guessing right around the same amount of cash for both.

how do you like your strokers?
I am guessing they run great, how many miles and any probs?

Well since i am new in the stroker area, I am assuming i need to buy the kit first so i know which compoents require which dimension when taking to the machine shop, IE bore size, crank jorunal size. Or do they all use a common kit
 

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i'd go with the stroker, more displacement more power. the bore size is up to you, with what size pistons you want to go with, usually .030 sometimes .020 or .040 over. the stroker comes from the crank and rods, i.e more stroke-stroker motor. as long as it's built correct it should last a while.
 

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Ex Navy Nuke
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393 is probably the most economical stroker out there. 351W block and rods, 393 stroker crank and 302 pistons. Do NOT buy pistons until you take the block to the machine shop. Let him tell you how far it needs to be bored over, don't assume you will need .030" or .020". Then they will want you to get the pistons so they can have them in hand when they do the cylinder boring.
 

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yeah he's right about buying pistons when i did mine, i knew the block had never been machined so i went .030 over, might not have needed it, but like jermils motor, he needed it bored .040 over, so yeah see what the machine shop says about the block.
 

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Sway Is My Fan Club.
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Stroker motor, no question. We were just talking about this tonight in class, longer stroke equals more torque and torque is goooood. :thumbup
 

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Wrenching for a Livin'
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Stuck like a MoFo
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Discussion Starter #8
Yea thats what i thought about the boring and piston size. hell my luck i will prolly need another block.

Anywayz I have seen the kits between 600-1200 on ebay and other companies on the web. IIRC the kits usually include rods, pistons, crank, bearings.

BTW, shouldn;t bother asking this question but how horrible is the MPG?
 

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Wrenching for a Livin'
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Ragged_ol_86 said:
whats a 393 stroker cost to build?? Im not rich so keep that in mind.
mine is gonna be something like 4-5k....im scared to figure up the exact cost
 

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Check out Northern Auto Parts-they have the cheapest 302 stroker kits I've seen so I would guess they're probably the same with the 351's. BTW, 85, what motor do you currently have? If it's a 302 you may see enough improvement by going with a regular 351 build, since you said cost was an issue.
Rick
 

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Sway Is My Fan Club.
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Watch it on stroking that 302, I've heard - maybe it was on here - something said about there are issues with the 347, I think maybe with cooling or the oiling system or something. I don't remember exactly.


Also, I don't see how the MPG would be any more affected between a 351 and 393, unless you really hop it up. I mean, just changing the stroke isn't gonna make your fuel mileage go down. Your fuel system will be more of the concern there. I get the same MPG with my 429 as the 460 guys do. :shrug [460 is just a stroked 429.]
 

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Stuck like a MoFo
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Discussion Starter #12
magnumpi said:
mine is gonna be something like 4-5k....im scared to figure up the exact cost

YEa but you are going diff heads too aren't ya. I am planning on getting the foundation how i want (ie the pistons, crank rods) and then slowly upgrading the outside parts as i get more cash. As i will have limited time to do this since everything is at the rents 2.5 hrs away and i am in a APT at college.


Dallasbronco said:
BTW, 85, what motor do you currently have? If it's a 302 you may see enough improvement by going with a regular 351 build, since you said cost was an issue.
I have the inline and have luved thrashing on it and the almost zero problems from what i have put it through and the prev owner. They WILL rev like most SB's, trust me. :duh Plus they are so fricking easy to work on, and so much space underhood.


Now if i could find a Sprinter 5cyl Benz diesel, then i would prolly swap that in


So i spose next time i am home i will proll tear the motor apart and get the block off to the machine shop
 

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If you are thinking about upgrading the heads anyway, it would be best to do this as a complete build. If the straight 6 is working for ya, why not wait until you can build the 351 the way you want before you do the swap?
 

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Ex Navy Nuke
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No, a stroker is just a different combination of piston and stroke and maybe rod length to give you higher cu. in. displacement. You can make the comperssion as high or as low as any other engine. So you can make a stroker that's still capable of running on 87 octane.
 

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crank trigger
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RLKBOB said:
No, a stroker is just a different combination of piston and stroke and maybe rod length to give you higher cu. in. displacement. You can make the comperssion as high or as low as any other engine. So you can make a stroker that's still capable of running on 87 octane.

10-4, thanks for the info.
what are the minuses of a stroker? less reliable or anything?
 

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Wrenching for a Livin'
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85f150 said:
YEa but you are going diff heads too aren't ya. I am planning on getting the foundation how i want (ie the pistons, crank rods) and then slowly upgrading the outside parts as i get more cash. As i will have limited time to do this since everything is at the rents 2.5 hrs away and i am in a APT at college.
correct....if you were dead set on it you could probably build a stroker for 3-4 hundred more than a stock rebuild
 

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scorpion, if built correctly it can run a long time, but that depends on how you drive or maintain it, so if you don't maintain it and beat on it, it might not last a long time, a friend of mine has a 383 stroker in his chebby and it's been there for about 115k and still going strong.
 

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Stuck like a MoFo
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Discussion Starter #19
Dallasbronco said:
If you are thinking about upgrading the heads anyway, it would be best to do this as a complete build. If the straight 6 is working for ya, why not wait until you can build the 351 the way you want before you do the swap?

Well right now i would like to keep the compresion low and the easiest way to do that (in realation to changing pistons) is with heads. I can jsut rebuild a set of stock heads and be good for me. I am not out for a ton of power here just more than normal from a SB. I just don't see spedin the coin on a good set of heads for around a 1k.

BTW the 351 is going to take awhile, the six is staying until summer or so when i hope to have the 351 completed. As the snow goes away teh truck won't be driven and i can work hard on it
 

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BroncoBabe said:
Stroker motor, no question. We were just talking about this tonight in class, longer stroke equals more torque and torque is goooood. :thumbup
Sorta kinda but not really (at least not directly). It's really more a case of "transitive equality," I guess ... longer stroke = more displacement, more displacement = more torque.

Peak torque is generally proportional to displacement within a very small range, depending on the peak V.E. of the engine. If you could build several test engines with the same displacement and the same V.E. but different combinations of bore and stroke, you'd find that their peak torque would be extremely similar.

What the bore/stroke ratio affects is the the location of the torque peak. High bore/stroke ratio engines (usually referred to as oversquare, like the 302 at 4.0x3.0) have room for large valves for their displacement, which allows for a greater flow of air, assuming you spin the engine high enough to use the capability. The shorter stroke also reduces piston speed, which makes it easier to spin the motor higher. The penalty is that a larger bore produces a wider, flatter combustion chamber, and you get comparably poor fuel atomization at low engine (piston) speeds, so you suffer for low-end torque.

A square engine (400, 300 six, 4.6L for example) may have the same displacement, and hence the same (or strongly similar) peak torque, but the smaller bore and higher piston speed per RPM produce a better fuel mix at low engine speeds. The penalty here is higher piston speeds imposing a lower limit on redline, plus a smaller bore area limiting peak airflow. If you select your cam profiles and the rest of your induction system to match the natural powerband suggested by the bore/stroke ratio, you basically end up getting the same peak torque at a different RPM. This is one of the primary reasons the factory 300 and 302 were mostly identical in peak torque values, but the 300 gets its torque at about 2/3 the engine speed.

The only way to improve peak torque numbers is to improve V.E. If you can move more air through the engine at the same RPM without sacrificing burn quality, you increase the combustion pressure. Since combustion pressure is hard to measure accurately and almost useless anyway (getting a torque out of a combustion pressure that varies so much as the piston goes through it's cycle is a mathematical PITA), engineers talk about combustion pressure in terms of BMEP (Brake Mean Effective Pressure), which is basically the cylinder pressure averaged over the full cycle minus that cylinder's frictional losses. Sounds compicated, but what it really means is BMEP = (Torque at flywheel in lb-ft) * (conversion factor of 150.8) / (displacement in cubic inches).

BMEP is roughly proportional to the V.E. and the engine's efficiency. It's affected by bore/stroke ratio because of the combustion quality issues, and indirectly because of the airflow capability of the engine -- in other words, it's most directly affected by V.E. If you want to increase peak torque, either improve the combustion quality or improve the V.E. and pack more air into the cylinder (the latter is basically all any sort of forced induction does). Unless you're supercharging, BMEP typically varies over a pretty small range ... as low as about 140 psi for a stock truck engine, to around 200psi for a well built 302 with very good heads (AFR) like this one. Even really hot stuff like the current Kawi ZX-10R engine, which makes 164HP out of a 1.0L engine, still only has a BMEP of 198psi (80 lb-ft out of 61 c.i.).

Basically, you only have so much control over BMEP, and you can only vary it over about a 50% range of increase, at most. I would guess about 160psi to be a little more accurate for most of the warmed over truck engines we'd be likely to build here. What you can control very well is the location of the torque peak. Intake runner size, valve size, cam timing, and intake tuning give you almost complete control over the RPM you achieve your peak BMEP (and hence peak torque) at. This is why the vast majority of modifications for power focus on moving the torque peak up -- it's hard to get more peak torque, but since HP = TQ * RPM / 5252, more RPM at the same peak TQ gives you more power. It's a lot easier to move the torque curve than make it larger.

Yeah, I know I just wandered mostly off topic ( :brownbag ), but this is really good stuff to know if you're planning an engine build and trying to figure out what you can reasonably expect from a combination. Hopefully it'll be at least a little helpful. :thumbup

For those that want a little more info on BMEP, check here.
 
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