strokers

[hermit]

so many different combos out there...anyone got any input on how big you can go and still maintain drivability and some kind of reasonable relyability? i see combos all the way to 806 CID!

[Aussie Mike]

Funny this post should come up. I was browsing through some old Super Stock & Drag Ilustrated mags last night and came across a short article on an 800 Cube Boss motor. The thing was insane. I'll try and find the mag again and see who did it.

Cheers

[ByronRACE]

Generally speaking, large stroke engines are less tolerant of pump gasoline and more prone to breakage. The piston dwell is longer which will usually require either higher octane fuel or a lower compression engine. The piston speeds associated with long stroke engines are much higher at any given engine RPM which can lead to breakage unless the highest quality parts are used in the reciprocating assembly; be prepared to spend $2500 for a crank, $3-4K for a finished iron block, etc. And, lastly, if you do make a large cubic inch engine, make sure you have the right induction and exhaust for it. Throwing your typical 460 carb intake on top of an 800" stroker will yield typical 460 power. You need extremely special induction parts to optimize an engine of that size.

Personally, I think there are much more durable recipies for pump gas. Big bore, moderate stroke, and a power adder like a supercharger can easily exceed the power of an 800" stroker while keeping the piston speeds down, the dwell short, and the compression low...making it very pump gas friendly. This is exactly what I've done. I'm expecting 800-1000hp at the wheels out of 435 cubic inches using a factory ford block and crank; we just fired the beast a week ago. There's video in another thread.

Byron

[Bryan TTM]

i'm new here but not new to hotrods, choppers, or outlaw drag cars...i agree, in a light vehicle a shorter stroke, large bore engine will perform much better especially with a close-ratio tranny...it'll tach faster, detonate less, & have less maintenance...i'm here to learn..my next project will be a Cobra...i've been lurking here for some time now...its an enjoyable way to waste a day

[cobrashoch]

Byron - Byrons pretty much got a good handle in it with a few clevates that need adding. A .030 over bone stock 460 with a offset turned crank to just 4 inches will yeld 480 cubes, and anyone almost anywhere can build such a combo. Using stock internal stuff together with even mild external hot rod parts it will net a engine that has well north of 500lbs of torque in even very mild street tune.
Byrons also right that as the stroke goes up the high dollar stuff has to go in the engine to keep things glued together. Further as the stroke goes up (and displacement) most 385's keep roughly the same horsepower numbers. What changes is the torque band of the engine moves down in rpm's and the torque goes up dramanically.
Bryan TTM - The short stroke, large bore ratios is extreemly old school thinking with todays engines. Also the more you have to buzz a engine to make it run the more you break stuff. Simple physics really. Bore/stroke ratios in even todays racing engines are usially around 10/9 in ratio, to include most new performance cars.
385's have a head called the "c" raised port head that requires a minimum 4.5 inch bore, it can use more due to a huge exhaust valve. Most guys run short rod ratios (sometimes even stock) and usially a slightly shorter 4.3 stroke using that performance head. Dependent on cam selection and bottom end parts selected such engines really buzz hard on the big end. That don't mean that they are any faster in the quarter mile than the moderately stock type stuff though,,,,,,,,,,,,,,,,,,,,,,,,,

cobrashock

[Mark O'Neal]

Well, we do a fair amount of these things, and I would state your practical limit at 572ci. (with an early block) That's at .080 over, although most of the blocks we've sonic'ed would be perfectly happy at 4.500".

We did one (for a truck) that was 572ci with Blue Thunder heads, that were ported on the exhaust side only.

It made 680 HP and aroung 650 ft lbs.

There are only two rules. Tune it so it doesn't detonate or lean out, and understand that it's a big block, so it isn't going to 8,000 in these combinations.

I wouldn't get too awfully tied up in these arcane ratios. They mostly serve for drunken conversation and to start arguements.

99 percent of dead engines are killed by lousy tuneups (once you established it was screwed together correctly). Anybody can get stupid tuning, driving, or building motors, but they seldom kill themselves.

I've put tham in Cobras, boats, cars, and fifth wheels (wanna pull Donner Summit at 55 in cruise control?), they don't have any more problems than any other engine.

[Mark O'Neal]

Well, we do a fair amount of these things, and I would state your practical limit at 572ci. (with an early block) That's at .080 over, although most of the blocks we've sonic'ed would be perfectly happy at 4.500".

We did one (for a truck) that was 572ci with Blue Thunder heads, that were ported on the exhaust side only.

It made 680 HP and around 650 ft lbs.

There are only two rules. Tune it so it doesn't detonate or lean out, and understand that it's a big block, so it isn't going to 8,000 in these combinations.

I wouldn't get too awfully tied up in these arcane ratios. They mostly serve for drunken conversation and to start arguements.

99 percent of dead engines are killed by lousy tuneups (once you've established it was screwed together correctly). Anybody can get stupid tuning, driving, or building motors, but they seldom kill themselves. (the motors, that is.. )

I've put them in Cobras, boats, cars, and fifth wheels (wanna pull Donner Summit at 55 in cruise control?), they don't have any more problems than any other engine.

[ByronRACE]

I agree that most stroker engines are killed by tuning problems.

I completely disagree that big strokers "are no more problem than any other engine".

They are more of a problem than other engines, hence the reason they're often killed by tuning problems! When you're talking about large stroke; such as the case of the 800" stroker motors they're talking about; tuning one of these things on pump gas is often IMPOSSIBLE unless the engine was built low compression with the right heads, the right cam timing, etc. I've seen a LOT of really expensive stroker engines that won't take a reasonable amount of timing advance and blow all that potential power right out the tailpipe. A stock geometry engine built properly would run circles around some of these engines. Make sure you know what you're doing before you build something that ends up with a dwell/compression scenerio that simply doesn't work.

Generally speaking, if you stick with aluminum heads and under 4.7" stroke and under 9.5:1 in a 385 series, you'll be OK with premium pump gas. Substitute 11:1 compression and iron heads with big stroke on pump gas, and you're screwed!

514's, 545's, 572's, etc are known combos...they work fine most of the time unless you get crazy with compression. Your 572 is very detonation resistant probably because of those Blue Thunder heads; they are designed extremely well. You also probably didn't build the thing 11:1. These things must be considered more carefully when you are increasing stroke and dwell.

Be careful; it's easy to spend a lot of money the wrong direction and end up back where you started.

Byron

[Mark O'Neal]

Substitute 11:1 compression and iron heads with big stroke on pump gas, and you're screwed!

Sure, but if you substitute 11.0:1 compression and iron heads on a 347 your screwed too. (on pump gas)

A little common sense is required when you're laying out the combination, but there is nothing difficult about it.

I've seen a LOT of really expensive stroker engines that won't take a reasonable amount of timing advance and blow all that potential power right out the tailpipe.

Well, by definition the advance wasn't reasonable (for that combination). It is a sure thing that an iron headed 11.0:1 motor won't accept more cylinder pressure, regardless of how you develop it.

tuning one of these things on pump gas is often IMPOSSIBLE unless the engine was built low compression with the right heads, the right cam timing, etc.

The most basic component of an engine is designing it for the application. We all would like the power that you get with Top Fuel motors, but have to design around the intended, more reasonable, use.

You have to blame the designer/tuner for these problems. A motor is stupid. We are, supposedly, intellectually superior to the engine we are building.

Your 572 is very detonation resistant probably because of those Blue Thunder heads; they are designed extremely well. You also probably didn't build the thing 11:1.

It was 10.0:1, and why would I use 11.0:1? Also I got the numbers backwards. It was 630 HP and 678 ft lbs @ 4,800. It was in MM&FF (I think). Also the aluminum heads are a factor, as is the cam design.

I can build you an engine of any cubic inch spec you want, and make it a problem motor. I can also build you an engine of any cubic inch spec you want with excellent manners.

It's the parts we pick.

[ByronRACE]

The problem, I feel, is that we need a better definition of "drivability" and "reliability" from the author of the post.

Using my definition, and my intended use for my cobra, a large stroke doesn't fit the bill.

I want...

-800+ rwhp; something to put the car in the low 10's on street rubber and a chance of 9's on slicks.
-The ability to reduce that peak power down to the 400rwhp range for road race applications.
-2500-7500rpm reliable power band
-750rpm idle
-the ability to let the clutch out at idle and putt-put down the street
-the ability to walk out in the garage on a cold morning, bump the key and drive away
-the ability to hop in the car and take it on a 2000 mile trip and yield at least 14mpg freeway.
-an engine that lasts at least 50,000 hard miles.

I can't achieve the above with an 800" stroker 385, for a variety of reasons.

But the author of the post likely has entirely different goals and objectives...he may be perfectly happy with a 3000-5000rpm power band, for example.

Byron

[jdean]

Byron, you can easily acheive your stated goals with a turbocharged EFI small block, or a turbocharged "smaller" big block vs. a big stroker combo. I've driven a 900 hp twin turbo 4.6 mod motor car that gets 20 mpg and is a daily driver. Idle was about 600 though. Stock cams. With 3" exhaust still very quiet too, except for the whine of the huge fuel pump. I think the intercooler is larger than the gas tank on my Cobra. It turns out there IS a replacement for displacement.....boost. Agreed you can't get this just by stroking a 385 to the max. Turbo boosted small block is my backup plan for power when gas gets to 5-6 bucks a gallon.

But on NA engines, don't you think, especially up to the 572, conventional components and recipes/trade-off considerations are the same as with any other V8 performance engine? Nowadays there is less mystery around long stroke vs. wide bore, and more agreement that this is much less a factor than breathing, compression, timing, tuning etc. in terms of reliability and power.

For example, the design factors for making even 545-557 strokers that turn 7,000....and there are many out there that turn that and more all day long....are no different than other smaller engines. You gotta feed it and select parts that stay together. You make a good point...all things being equal, you make the same power at lower RPM by stroking. Long stroke does not automatically mean the only benefit is low RPM torque.

But with the goal being designed to rev high, you still make the power up top with a big stroke like any wide bore, lesser cubic inch engine. Yeah there is increased piston speed with the big strokers, but up to the 7-8,000 RPM range piston speed differences are not the big issue. The valve train, crankshaft, rods and mains are. They remain the key to living up there, like every other engine combo that revs high.

[cobrashoch]

All engines have strokes, its apparent that there is lots of misinformation and just plain bull#*%@ regarding this subject. To make matters worse 385's have stroker characterists that are unique to 385's, so a compairison to FE's or stroked windsors are just plain not valid. Oh where to begin, lets take a curserary look. First off, there are stock 6.6 rod, 4.5 inch strokers in 385's out there that have over 200,000 miles on them. I know, because my father has built several such engines for dump trucks. So much for the unstreetability issue with strokers.
Next, a stroker does not require special heads to perform. This is because the valves are open longer during the longer stroke, ie- more air goes in and out. Of course better performance heads will always work better, but generally, better breathing heads are only required when you get displacment from boring or supercharging, not stroking. Relatively speaking, this is because large bore displaments crowd the valves in mid lift situations causing torque drops, were if you use stroke the valves are fully open longer relative to the stroke.
But everone knows that a undersquare engines can't rev, now don't we?
Wrong again buco, there is oversquare performance engines out there that can't hit 7g's- and racing undersquare engines that can push 12g's. Besides that, don't confuse hi rpm's with power, we have been somewhere else since the 70's. Very old school. My advice, select a engine builder with experience with 385's, do not adhear to standard hot rod book folklore. And this esp. true with 385's, because almost all of the develomental work done for this class of engines was done through the aftermarket, not the factory.
In a word, you can get allmost any level of streetable power from these engines. That don't mean that it's the smart thing to do however. Enough with the B.S.
cobrashock

[hermit]

looking for a idle around 800-850 max, 2500-6500 rpm range
looking to get 50.000 miles before a rebuild.possibly looking at
fuel injection

[CowtownCobra]

Talk to Keith Craft. He has the windsor strokers down to a science.

[ERA Chas]

While searching for info, I found this thread which touches on many of the points I'm looking for.
I'm an FE guy and need info on 385's for a Chev-experienced builder friend.
Would the experienced guys in this thread mind sharing the basics of bigger 385's? Specifically, iron block selection; what's out there and what's smart to do a 4.500 x 4.500 572? Frpp, Arias, OE? - quality counts. Can you recommend quality rotating components for this size? Obviously BT heads make sense but any other suggestions appreciated.
Not looking to do a Kaase-level engine but quality parts and experienced-based advice welcomed.
Thanks for any help.

[ERA Chas]

Return to top for help

[ScatStroker]

Originally Posted by ERA Chas

While searching for info, I found this thread which touches on many of the points I'm looking for.
I'm an FE guy and need info on 385's for a Chev-experienced builder friend.
Would the experienced guys in this thread mind sharing the basics of bigger 385's? Specifically, iron block selection; what's out there and what's smart to do a 4.500 x 4.500 572? Frpp, Arias, OE? - quality counts. Can you recommend quality rotating components for this size? Obviously BT heads make sense but any other suggestions appreciated.
Not looking to do a Kaase-level engine but quality parts and experienced-based advice welcomed.
Thanks for any help.

The most common builds are 4.30" and 4.50" stroke combinations - Readily available from most any manufacture. Bore sizes are generally .030" or .080" over, anymore and you're usually dealing with an A460 or Eliminator aftermarket block. Most stock blocks can go .080" and make a 557, the largest and most common big stroker.

FRPP relabels their cranks and rods, they're usually Scat's. Pistons are Probe pistons currently. For a street/strip type build we usually use a Scat Series9000 crank, Scat rods and Probe forged dish pistons - As an entry level. There are lots of brands available if you're specific to something but the above is probably the most common, and has been proven to be reliable. Depending on the heads there are a number of different valve reliefs - SCJ's, A heads, ect. so that is another variable you need to address. Diamond has a large selection to accomidate the alternative valve relief combo's.

SCJ's are great heads for a mild motor, A460's are usually our next step. BT's, Edelbrocks, and others are also available but the two above our usually our preference for mild or straight forward, easy builds.

If you have more specifics let me know but that should get you started on the general items...

Brian
www.Adperformance.com

[ByronRACE]

Bore depends on the block; you will have to sonic test to see how far you can go. Some blocks can only go .030 or .060...others can go .120. Here's proof:

http://misn.com/~frd460/blocksummit.html

Stroke up to 4.5" can be done on a production block without a problem. There are FORGED 4.5" stroke cranks out now...by the way. No need to use a cast part.

Personally, I'd use a D9TE block (longer bores, better piston stability) and a forged 4.5" crank on a production block converted to blue-thunder billet splayed 4-bolt caps on 2,3,4. A good H-beam rod. Good Forged pistons. Screw-in freeze plugs. Fill the block to the middle of the freeze plug holes with devcon or hard-blok. You now have a bottom end capable of 1000+hp before failure.

I'd also spend time on www.460ford.com and read through all the engine tech stuff...there is a lot of REAL knowledge on there from people abusing these engines to the limit.

Byron

[Excaliber]

Byron, good point of just what IS 'drivability' or 'streetable', it depends on what your comparing it to. I started with a 12.5 to 1 C.R., radical solid roller cam and 'drag race' only dual carbs. Whew, what a nightmare on the street!

I went to 9.5 to 1, smaller vacuum secondary carbs and a still pretty aggressive flat tappet cam for a more 'streetable' build. However, the motor idles at 1100 or so rpm, can't get much lower, and does not like anything below 2000 rpm. You COULD say it's not 'street friendly', but from where I came from, it's night and day difference (on pump gas no less). I find it very comfortable on the street and really like that 'lumpy idle'. I wish it would idle at a lower rpm, but hey, 1100 'aint that bad'!

[ByronRACE]

A Cobra with a smooth idle is just WRONG.

Yes, easier to drive. But WRONG.

Byron