o.k. wierd question. what i'm trying to ask is what is the best combination of bore and stroke for a 350 block? i hear of people building 377, 383, 388 all the time and it seems like the engines really like the different stroke better than the original. or is that just me?
what i'm getting at is just aside from "no replacement for displacement", there seems to be a 'magic' combination that works really well. an instance where everything else being equal, a combination with a smaller displacement will make as much or more power than a larger displacement.
am i making any sense here? :banghead: i'm reading my own post and still don't know if i'm being clear.
so what i have in mind is to build the current high nickel block i have for max power and longevity. seeing as how i do road course track days, i want to build an engine that likes to run.
what i'm thinking so far is:
solid roller cam somewhere in the 290/300* range
6" rods
aluminum heads (taking recommendations here)
MPFI
crank fire ignition
static compression somewhere around 11.0 to 12.0:1
i may have some displacement limits to deal with but so far i think that is 7.0L, n/a. i should be well within that with a production SBC block though.
i'm looking for a combination with a nice flat power curve and will hold together for a long time. i'll be happy to give up 30-40hp for survivability.
the floor is yours... :leaving:

 

I can't help you in regards to the 388 because I've never seen a build up on one. However, either Chevy High Performance or Car Craft did a comparison build up on a 377 & a 383 several months ago. I can't recall specifics on cams & heads(identical on both motors if I remember right) but both were pretty serious motors. As they expected, the 383 made just a bit more torque & the 377 pulled harder on the top end. They ran both combos through their Desktop Drag program & the 383 had a very slight advantage in the 1/4 mile due to the extra torque via the longer stroke. I can dig through my pile of mags if you want specifics- just let me know if you're interested. I know this doesn't address all of your questions but maybe it'll help a little bit.

As for heads, IMHO you'd have a hard time doing any better than a set of AFRs. Which set to use would depend upon your choices in the other areas, but I've found their techs to have a pretty solid understanding of what works best for a given combo.

 

The Dollar seems to be denominator here. I've tried to price out a few fancy combos and the unique parts - like pistons for a 6" rod stroker - run the cost up fast. Custom pistons are easily $700 and for custom cams the sky is the limit (well almost). And forged parts are 'bout double cast. Now for those max c.i. motors they sell aftermarket performance blocks too but for nearly $2K without finish machining/blue-printing.
A boat-racing friend of mine was describing custom blocks with extra bore spacing. Using the old 3.25" stroke but with massive bores and long rods for optimum rod length to stroke ratios. This is how some racers build max power in size/c.i. limited classes (for boats anyways). But I don't expect one to bolt up to a shark. :skep:

 

Clutchdust – Your 350 ci has a 3.48 stroke crank and 4 inch bore. Cubic inch displacements can be arrived at by juggling bore and stroke. 3.750 stroke and standard bore 4 inch piston gives you a 377 ci. So with the 350 block you hear of guys making 383 with a .030 over bore 385 with .040 388 with a .060.

For racing 20 years ago the rage was installing an 3.48 crank in a 400 ci bored +.030 small block. That’s how they make another 377 with somewhat higher rpm ability over the 350 block based 377. It’s old technology based on using modified production parts. In fact you would have to be in the shallow end of the gene pool to even consider building one! Because the 400 ci will run circles around it.

All kind of kit’s abound for 3.750 stroker 377-388 ci. Just buy the lighter weight parts and internally balanced. Get the biggest CFM heads for your price range. Get the biggest valves 2.08/1.60. They come in the AFR 210’s & Dart Pro1 215-227 cc

High compression motors like 12:1+ don’t seem to last. The pressures during each power cycle just beat up everything.

[b]Never overbore more than you need to clean up a cylinder[/] addition boring make for neglible power gains 383-388 ci. The torque that stroker 350's make will smoke a hot 355 ci around a track.

 

o.k. let me tell you what i'm thinking of and where i am so far. what i currently have is a high nickel 4-bolt factory block, factory forged crank and open chamber 2.02 heads. i have determined that the block has never been bored but needs it. so i'm thinking of a simple .030 over. the crank needs to be undercut .010. and i have no rods so that's completely open right now.
the idea, at least for the time being is to build the engine to suit the 2.02 heads with a 9.5-10:1 compression ratio for the time being. solid roller cam and valve train.
i want to build the bottom as bulletproof as i can so later on i can go to some aluminum heads (right now i'm really considering the trickflow twisted wedge 18* heads).
since i have no rods right now and need new pistons anyway, that combination is wide open. i can't afford the super high tech titanium jobs of course. i don't think i want to go with aluminums for long term durability reasons but my mind could be changed on that.
the crank is just a factory unit so it's not a light weight piece but should be nice and durable. can i have that cut down to increase or decrease stroke?
what would you think about a combination that utilizes a .030" overbore, 6" rods and a slightly destroked crank? looking for power from about 3000-6500+rpm.
to help you get a better idea of what i'm doing here, i'm building a dedicated track car. i have a target weight of >2500#, and plan to run either a 5 or 6 speed dog engagement tranny, lightweight drivetrain, yada, yada, yada. unfortunately, some of this stuff will be done in stages like the aluminum heads will be swapped out later and i'll probably start off with conventional driveshafts and change to aluminum or carbon fiber later on.
the main thing about the engine is i want the bottom end (the part i hope to not have to rebuild a whole lot) to be pretty reliable.
BTW, thanks to all for the input you've contributed so far.

 

Clutch – If your motor is an L-82 it came with a decent forged crank & rods and a high nickel four-bolt block. Good for maybe 500 or so N/A. Rpm is what kills. I won’t get into the 6-inch long rod debate. Because real racers don’t stop at 6 inch rods. 6.125 or 6.250 are more the norm. I’ve heard it all less peak piston acceleration………. I do know that long rods cause the piston to stay around top dead center longer and detonation is a more of a consideration if you’re running on the edge. The way I would look at it. Things like good internal parts can be used on future projects. Changing blocks or bore sizes is only a change of pistons and rings away. The same thing with heads and headers. They don't know what they are bolted to.

You mentioned roller cam. Roller cam and stockish heads should not be used together. I just don't think that spending the money for screw in studs, push rod guides and bigger springs is worth it on anything but the best aftermarket iron heads. I did all that to my double hump heads years ago. You can get a Crane mech solid cam like mine with kit for under $200

Gaining stroke by offset ground and welded up cranks is another BS operation from 20-30 years ago. Shade Tree mechanics and bubbas think up crap like that. I had a moron years ago telling me that he used low hydrogen stick welding and could make a crank stronger than new. He was making some kind of 351 Ford motors into 370 some ci hot rods

Why bother when you can buy any small block stroke you want. They are sizes like 3.50 stroke used by all the circle track 359-ci class racers. Then I’ve seen 3.60, 3.625, 3.70, 3.750, 3.800, 3.835, 3.875, and 4.00. I’ve also come to the conclusion that the best crank to install would be a 3.875 and 4.030 bore to get 396 ci.

I’ve talked to a local builder and he won’t even do another 3.750 stroker 383. The 4.00 inch by 4.030 bore is something like 408 ci, but I’ve been told to stay away from attempting 1/3 to ½ epoxy filled blocks. It might be the real torque monster, but the cost and chance of loss are too high.

For the road race machine you want the widest biggest torque curve average. Use 112 lobe center cams and power bands 3500 rpm are possible. Having to shift too much unsettles the car. That extra down shift entering a turn or having to shift up in the middle of the turn kicks the rear end out. I have a 4 speed and over the years I have considered the non overdrive 5 speeds. Ideally you would want to be changing ratios to best suit a give track.

 

thanks for the input. so far, i'm still thinking .030" overbore, 6" rods and factory stroke, for the time being. i'm still planning on sticking with the production 2.02 heads, just so i can get it going for a while before i drop $2000 on a fully dressed set of aluminum heads. the only reason i'm probably still going to go with the roller cam is just because i know there will be machine work required for the lifters and i might as well have that done now while the engine is still in pieces. when the time comes for the heads, i just want to pull the irons and bolt on the aluminums. don't even want to break the gasket on the timing chain cover. if it's down a little on power with roller/iron heads, i figure it'll just seem like a real kick in the pants when i get the aluminum heads on.

 

I can’t tell if you’re still interested in a long rod combo clutchdust. But just for your information the optimum rod length to stroke ratio for drag racing is 1.8. As a former Pontiac fan I remember this ratio as bragging rights for the stock Pontiac pieces. That makes for about a 6.26” rod to a stock 3.48” Chevy stroke. So now we’re talking custom rods, pistons and maybe expensive heavy metal added to that beautiful stock crank. Then again track racing uses a different ratio for optimum power (longer rod/larger ratio). :bb
Good luck. cardo0

 

LT1er, "...shallow end of the gene pool" for even considering a 377 over a 400? That's kind of a narrow-minded viewpoint.

To this day circle track racers build many destroked 400's. The geometry a 377 gives you is a large bore, short stroke, quick revving engine that can easily see 9000 rpm without excessive metallurgical stress. The rod/stroke ratio of a 377 with 6-inch rods is far superior to a 400 with 6-inch rods. The shorter stroke makes pistons somewhat cheaper due to the fact that you don't have to get custom pistons made with very high pin locations and deep dishes.

I agree that torque is "where it's at" on the street, but you cannot discount the qualities of a good 377. They make excellent race engines, including on the dragstrip where you want a very high revving engine with very steep gears.

...Life's good here at the shallow end of the gene pool. :D

 

Clutchdust:

I’m not an engine combustion R&D engineer, but I can tell you this: any sized engine can be made potent for a specific operating range (higher rpm). A systematically designed induction/engine/exhaust system on a smaller displacement (SBC) will easily out-power a poorly conceived BBC!

I can’t help myself from saying this; if you plan on removing the engine to just freshen, I would really think hard about your future hp/tq goals? A 383 can be done relatively cheaply and provide a larger foundation for your future mod’s! A 396-sbc sounds cool, until the machinist hits a water jacket trying to clearance the oem block to fit the larger crank. Oh, and bust out the ball-peen hammer for the oil pan clearance, because it’s hammer time!

Yes I’m sure your oem forged crank is nice, but, if you plan to stay na and under 500fwhp, a Eagle or Scat 9000 cast steel stroker unit will do the trick. Or you could step up to a 4340-forged unit from said above for +/- $600. As for 6” rods on a 383, you’ll want some stroker specific profiled rods like the Eagle 3D H-beams, their rated for lots of hp at crazy rpm & quite cheap if you shop around. For pistons, I recommend forged units; just in case your wondering, I hate KB’s and not because they’re Hypereutectic! At the time of my part purchases, for an sbc 383 with 6” rods, there was only one choice for off-the-self, semi-dished forged units. It was from SRP, which I bought for somewhere around $450 a set. I needed semi-dished pistons due to the very small c-chamber of my TPiS/AFR heads. You might get away with flat-top pistons with 64-76cc aluminum heads (>11:1c/r), in which case SpeedPro might have a “powerforged” set for around $275. For rings – stay away from the gapless designs!!!!! Use SpeedPro file-fit plasma-moly’s!

I’m a little worried about your cam specs, are you thinking 290-300* @ 0.050”? If so, you better lop about 50-70* off that sucker, or else it’ll idle @ 2000rpm and gurgle up to 4500rpm! Something in the 220-245* @ 0.050” would be a WAY better choice. Personally, I’ll take a higher lift cam with smaller duration, than the other way around! Retrofit roller cams are better than flat tappet, but they’ll cost you big $$$.

As far as aluminum heads go, AFR’s are the way to go if you got the dough. But a cheaper and probably 9.5 tents as effective route would be the cnc’ed 190 or 215, 23* Trickflow’s! I think they’re under $1200 from Summit Racing with high lift springs. The “twisted wedge” design has been associated with premature valve-guide ware issues, although that may have been corrected? I’m sure your 18* idea was just a typo, because 18* heads require custom intakes (read $$ fabricated sheet metal $$) and exhausts. Also, super humongous valves are not always the ticket. They weigh more, and on many sbc heads will lose cfm flow on parts of the lift curve. Good old 2.02/1.60” are the way to go.

BTW, I really wouldn’t recommend going over 11:1c/r for a (no disrespect) non-pro circuit road race engine, especially for operation in the summer Vegas heat! If you want longevity, stay away form knock-ping/detonation like the plague. Also look into a good H-damper, a 7-8qt baffled oil pan (I bought a Canton, but there’s a few good & cheaper track worthy pans out there), don’t use a high-pressure/high-volume oil pump (if you want a little more pressure use the Z28 spring from chevy for $10) and you might want to look into a Accu-Sump, set the rev-limiter to 6200rpm. Yeah I know, 6200rpm sounds wimpy but with the above mentioned 383 parts you can rev up to the limiter stutter all day long safely!

Just my 2-cents, and I’m sure people will have different advice, but I can say this: the above parts will provide reasonably cheap longevity on a road track!

:crazy:NanoBrain :crazy:

 

I think it was HotRod who did an article on how the 350 should have been built. They believe that the 350 should have come with a 400 (4.125) bore with the shorter stroke (I think it was the 327 stroke crank if I remember correctly). Anyway they nded up with a 350ci displacement. They were stating how the larger bore & shorter stroke was more ideal which is kinda the basis I'm using on my new 388 ;) .

 

Very good question. My 350 with the heads and cam set up made 360 HP/ 360 torque. Could dump the clutch at 4000 RPM;'s with slicks and explode off the line with 1.6 60' times. Ran in the 7.7's and high 11's. Really enjoy the 396 stroker but its a total different animal. Slicks are really not an option due to breakage at 3000+ RPM launch. Running with BFG DR's works but the launch is limited to about 2000-2500 RPM's.

Basically launching at the same toque level with the 396 as the 350. ET's are a little better with the MPH up about 5MPH. DR's are not as consistent so its much more of a challenge winning bracket races now.

Probably going back to the slicks again and launch at 3000 RPM's with a two step rev limiter.

 

thanks for the input so far guys.
1) yes, i did mean 290-300* total duration.
2) i'm only taking this bore .030" over so i can still have some meat on it later on if i need to freshen it up.
3) i won't use 'eagle' anything because they are chinease made. really sucks too because eagle is out of my home town but i refuse to put chinease metal in my engine. i don't even care what kind of standards they have, it's part politics too. those commie pinko bastards can rot in hell as far as i'm concerned.
4) probably will just use my OEM crank for now. i am only estimating sub 500hp so i'd rather use that $500 for something else (like roller cam).
5) pistons will be speedpro power forged since i can buy them at a discount through one of my vendors.
6) i've heard gapless make buku power but suffer longevity problems due to the increased cylinder pressure. i'd like to, but probably won't go gapless because of that.
7) the engine won't even get started in the vegas summer. nobody drives here from june through august. if we're going to drive, we leave. it's too damn hot to live much less drive!
8) i have a 'decent' baffled pan (hamburger, i think) and you bet i'm planning on an accusump. sure would be nice to go with a dry sump but hell, that costs about as much as most of the new parts i'll be using.
also, i'm planning on a MPFI kit so i don't have to screw with floats and needle valve and all that crap. when i come off a turn, i just want to nail it and go. currently fighting a surge problem associated with cornering with my q-jet, and that's just a 240hp engine.

 

so let's narrow this down just a bit now.
i will not exceed .030" on the overbore so i'm size restricted there. i'm also going to use the 0EM crank so i'm basically stuck with that stroke.
i guess that really does narrow things down then, doesn't it?
so strictly speaking, is there a reason to go with a 6" rod with these other restrictions? or would i just be better off sticking with the 5.7"?
aside from the components i already have, i.e. block, crank and heads (will get changed out later) just about everything else is open to suggestion.

 

Which heads are you using now? Do you want your cam to match yur current heads or your new heads? If you are going to spend a lot of time at higher RPM, 6.0" rods will not due any harms. I suggest zero-decking the deck the going with some quality forged flat-top pistons for a hgih-quench squeeze. 10:1-11:1 (max).

If going with a roller cam (more lift per duration), then check out AFR's Hydra-Rev.

http://www.airflowresearch.com/pages/hydra_rev.htm

 

i want to build the short block strong enough i don't have to screw with it for a while, i.e. planning for future upgrades. just to get the thing running, i'm going to rebuild the iron 2.02 open chambers and maybe go with a demon on my bowtie intake. later on, as money becomes available, the carb/intake/heads will give way to MPFI and aluminum heads yet to be determined. i want to build it for that combination. i don't care if it doesn't make all the power it could right now with the 2.02's and carburetor just so long as i'm not hurting anything.

 

You could get a forged crank with 350 mains and a 3.25 stroke. With a 0.03 overbore, you are at 332 cu in., the oppsite direction for displacment, but should be a nice high reving engine. The rod/stroke ratio would be 1.85!

 

I've always favored the short stroke hi revvers, but the long stroke is a more smooth road engine because of the torque. I had 2 Camaro Z28s with 302's in them and they were real happy little motors!!!

 

I know you are sticking your current crank, but for chits and giggles, I ran a 327 combo through DD2000

4.03 bore x 3.25 stroke
AFR 210 Heads
11.0:1 Compression
850 cfm w/ Single Plane intake
Large headers w/ mufflers
Cam: 112 Lobe Separation, 107 Centerline, 234/242 duration @ 0.05 & 0.539/0.558 lift (assume it would be a solid roller)

450 # TQ @ 5,000 RPM
494 HP @ 6,500 RPM

I kept the same combo but with 4.03 bore and 3.48 stroke (355 cu in)

469 # TQ @ 5,000 RPM
494 HP @ 6,500 RPM

You do not lose some torque going to 327 vs. 350, but the high revving capability and the excellent rod/stroke ratio would make it worth it I think.

 

thanks for the DD. :thumbs:
the numbers you ran look pretty close to what i had in mind (as far as CR, cam, etc.) so that would be a nice, reasonable ballpark. it's also every bit as good as i would have hoped to get out of a little ol' 350 (355). maybe i'll tinker with the combo a little more but that looks like a good baseline to use.
:cheers: