Short stroke big blocks, anybody ran one??? - Team Camaro Tech
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post #1 of 41 (permalink) Old Oct 14th, 00, 01:55 PM Thread Starter
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Has anybody ever ran a 3.25" or 3.5" crank in a big block to get one to rpm higher???

I read somewhere that years ago, 348 and 409 cranks were ran in big blocks because of cubic inch rules or something like that.

Any body done it???, and if so, how did the engine run??? pdq67



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post #2 of 41 (permalink) Old Oct 15th, 00, 06:41 PM
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Ok PDQ here goes,

I saw your post over on the other slot under Jeffro and you said no one would answer your stroker question.

You may not like my answer but here it is,the age old answer is there is no substitute for cubic inches,and this still holds true.

I think you would like to shorten the stroke to make the BB rpm quicker, my question is why steal the awsome torque from the BB. Yes it may rpm quicker but how are you going to blow away the small blocks on the big end of the 1/4 with rpm's and no torque.

If you want the BB to go more rpm's there is a limit because of bob weight,in other words the size of all the moving parts.

You can turn a BB just as tight as most SB's if you have the mega bucks for the right lower end parts.

I hope this don't sound smart or any thing it's just my opinion.

Larry
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post #3 of 41 (permalink) Old Oct 15th, 00, 11:04 PM
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Hello ! I agree with Larry 100 %!
how ever i had a 1969 vette with 5 speed richmond and modified LS 7 I personally like high rev engines too,so i carefully blueprinted and balanced all and add manley steelrods . then i used victor manifold and crane custom grind roller cam it rev really well 7500 (powerband 3500-7500) but i havent had the 5 speed with extra low 1-2-3 gear it would not be such a fun to drive since it didnt had good lowend torque. (and it needed 11,5:1 comp ratio!)
if you want engine wich revs go with smallblock,its easy to built 9000 rpm smallblock if you have right parts!

Joni
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post #4 of 41 (permalink) Old Oct 16th, 00, 02:20 PM Thread Starter
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Larry, Larry,

NO, there are no smart a--ed answers. I'm just asking if anybody ever ran a short stroke big block due to cubic inch restrictions because of some class. And if so, how did it run???

I'm wondering if the benefits of the big block splayed valve head is that much better than the wedge designed small block head.

And I know that it takes alota money to make a big block survive at 7500+ rpm's and way above because everything is bigger and heavier which means stuff has to be stronger and lighter(if it will stand the high rpm pounding).

This is why I'm a little miffed at Chevy High Performance for not finishing their head flow test by including the buick 10 degree, the splayed valve and the SB2 heads.

I just wonder what a 4.25" to 4.75" bore/3.25" to 3.5" stroke big block would be like if it was made ratio wise like a full house 302" small block, and I don't mean estimated per my copy of Dyno2000.

I did run a 4.25 bore/3.25 stroke 369" engine through it and came up with 592hp at 7500rpm with only the valve sizes automatically calculated.

A 496", 4.75 bore/ 3.5 stroke one came out at 684hp at 6500rpm. Neither engine has been maxxed out with respect to a balanced design due to the larger cubic inches over the 302.

I would really like to hear from somebody that has ran a big block that would wrap like a 302 just to get their opinion. And thats all. Thanks for the come back. pdq67



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post #5 of 41 (permalink) Old Oct 16th, 00, 07:41 PM
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Hey PDQ,

Say one does get this combo perfected,and say short stroke needs low gears who will be able to shift gears fast enough to keep up with this bad boy. Just Kidding.

I do see now from your last post what your question is,and I'll quit jacking around now and wate with you to see if anyone has actually tried this.

Larry
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post #6 of 41 (permalink) Old Oct 17th, 00, 07:34 AM
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348/409 crankshafts were commonly used in big block engines to get rpms out of them when the Pro-Stock class was just getting started. One proponent of doing this was Reher-Morrison, in Texas, they did a lot of them.

RPM levels were reported to be near 9,500, and favored the latest head porting of the late Lee Sheperd. They won a lot of races with those de-stroker engines.

Although some here are correct in the assumption that there is nothing like cubic inches for performance, there have been very successful exceptions to the rule. Remember, however, the shorter stroke engines require loads more rpms to make power, at the serious sacrifice of lower rpm torque/power.
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post #7 of 41 (permalink) Old Oct 17th, 00, 10:05 AM
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My cousin used to race in E-gas in the mid to late '60's. He held the E-gas national 1/4 mile time for a while, having won the Winternationals in, I think, about '65.

He's a SB guy.

He told me the other day that he has a 300 inch motor in his basement, ready to go, that will turn about 11,000+ RPM and put out about 700-800 HP on fuel injection.

Now, that's a revin' motor. I asked him how on earth does a push rod V8 motor ever manage to crank 11,000+ RPM??? Like, how could all that heavy metal, being operated by some long, slender rod, not just turn into a horrendous, smashing, crashing mess in a matter of seconds. My cousin, Gene, says it's all in how you build em'. He learned how to build them the hard way, by blowing up a lot of hardware. He says the secret is very careful blueprinting.

I'm trying to talk him into giving me the motor for my '72 240Z. Nothin' like a Chevy mouse-powered rice burner to make you feel like an all-American hot roddin' boy! And I know, if I got it to hook, that it would simply obliterate any turbo Eclipse or Honda Civic.

Anyway, I just can't imagine a BB ever going 11,000+ RPM, and neither can my cousin Gene. That's why he always raced SB motors. Of course, the tradeoff is that the high rev SB will not make good power at low RPM's and just won't have the monster torque that a big crank behind a big piston will produce.

But, that's all been said many times before.

Personally, I'm running a 396 BB in my '69 Camaro and I think it's great for the street... and I could also use it to pull stumps on the weekend if need be.

Just thought you would like to hear a little drag racing history and some additional thoughts on SB versus BB motors.

Jim
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post #8 of 41 (permalink) Old Oct 17th, 00, 02:35 PM Thread Starter
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I suppose the engine internal components would be made out of that exotic sh-t called "unobtainium".

I've heard of a company that was trying to run a real live "plastic" engine at Indy.
Seems as though the crank was hand laid up carbon fiber/plastic matrix, as was the rods. I'm not too sure it even used oil or water or not. It might have even had ceramic valves, valve springs, pistons and combustion chamber lining to stand the heat of combustion.

Has anybody heard of this stuff???

Anyway, I would think that maybe a titanium crank/rod rotating assembly would lighten it up enough to be able to stand running above 10,000rpm, but I don't know what the fatigue life is for Ti.

Isn't Crower selling some super light weight magnetic rods??

Plus, a 4.75" bore/3.5" stroke big block would have 496 cubic inches so it is "big" when compared to a 302.

This is an interesting topic. Thanks Iman and all for chatting. pdq67



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post #9 of 41 (permalink) Old Oct 17th, 00, 03:21 PM
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Even overhead cam engines, racing type don't enjoy total control from valve springs.

Formula one engines are limited to 10 cylinders, normally aspirated, make upwards of 1,200 horsepower, and have an 11th cylinder made into the block, for an air compressor, for the valve train. The valves do have very weak coil spring sets and are just there to keep the valve from staying open when the engine is being started. air pressure is used to control the valves after the engine starts, stored in a tank in the chassis pod.

RPM levels for almost all the formula one engines is between 16,000 to 17,500.

At the last F-1 race, a competitor had to go into the pits for a shot of air pressure into the storage tank as the on-board compressor had failed to keep up with the demand.

Modern day valve springs aren't up to the rpm levels we use in some racing, and Pro-Stock is a good example. The average big block Chevy type Pro-Stocker engine runs just 7 seconds at a time, uses 11,000 rpms, and has an average of 1.100 valve lift. Special titanium springs are used, cost $1,700.00 a set of 16, and get changed after between 7 and 10 runs. Individual springs get changed every run if they get sacked early, and the entire set is replaced at the 7 to 10 run level. Springs have 3 to 4 coils, depending on just who made them. Life isn't great.
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post #10 of 41 (permalink) Old Oct 18th, 00, 04:19 PM Thread Starter
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Lets try a 4.75"bore/3.5" stroke 496 bbc with
14.0 to 1CR, fully ported and polished 2.67"/2.17" valve heads, 1500cfm tunnel ram, large stepped headers, solid roller, .800"/.800", 270/276 duration at .050", on 112/108 centers

How about 1221hp at 9500rpm/822t at 6500rpm.

I'm not saying that this combination can be built, but it sure does put out some power.
Add a 5.3" crank and come up with 751 cubic inches and now you get 1149hp at 6500rpm/1032t at 5000rpm. Torque came up a heck of a bunch, while power came down in the street range, interesting isn't it. pdq67



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post #11 of 41 (permalink) Old Oct 19th, 00, 05:26 AM
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With a smaller bore size, the way they were built as early Pro-Stockers were, with the 409 shorter stroke crankshafts, they made about 1050/1060 hp on average, and ran very well. Call Reher-Morrison and ask.
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post #12 of 41 (permalink) Old Oct 19th, 00, 03:47 PM Thread Starter
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That's the picture, Iman. R/M just made some big block Z-28 type engines, didn't they?? pdq67



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post #13 of 41 (permalink) Old Oct 21st, 00, 07:41 AM
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Hey there Ignition man. Back I see, Good to see, how are you on this fine day? And now on this short stroke big block thing, where did those 2.67/2.17 valve heads come from. The bore would have top be at least 5" to acomadate all that, and even then the shrouding would be a an issue. Anyway, Like previously stated, That would take away all that they have going for them by removing the low end those big motors make. And all that weight, those things are over 150 lbs more on the nose than a small block. And untill you get into the mid 8's or the Outlaw Super Street and beyond, A small block is going to be the faster motors anyway. There is one advantage to the big motors though, they do make some big flowing heads for them. A friend tried running a 410" motor for a bit. The cylinder heads flow way more than is possible with a small block, even the buick or pontiac dart heads, and other 15 degree pieces out there. It looked good on the board and it was fast, but it just wasn't there. The small block 414's and 27's are powerful motors. 1400hp plus on the bottle is a lot of fun. Just wanted to add my thoughts Galen

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post #14 of 41 (permalink) Old Oct 21st, 00, 10:44 AM
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I do know that the last of Shepherd's heads with the 409 crank BB engines had 2.300 intake valves, and furnace brazed places, altered guide paths, very relieved valve cutaways.

RPMs were the order of the day, and they used 5 speed transmissions, instead of the 4 speeds they mostly use today. The short strokers made their torque in the upper rpm ranges as well.

As far as no low end torque, they always left against the rev limiter, so getting rpms wasn't a real serious problem. With the extra gear, the torque was in the right place for the mechanical advantage of all the different gear ratios.

After NHRA opened the cubic inch regs to the currect 500 cu/in limit, the racers went back to longer stroke setups, and lower rpm torque setups.
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post #15 of 41 (permalink) Old Oct 21st, 00, 06:55 PM Thread Starter
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Galen,
I came up with the valve sizes from Dyno2000. Plus I mentioned that these combo's may not be buildable.

I would love to see two identical engines built. The first, a full house 302 Z with the BEST "aluminum stock wedge heads" made. No nothing done to them, period.
The second engine would be the first one EXCEPT for a pair of small block style big block aluminum heads with the same sized valves and rocker arm ratio as the wedge heads. Nothing, and I mean nothing different otherwise between the two engines except for timing optimized for each engines combo.
Dyno both and then give us a spreadsheet with the runs hp and t values. This is what I keep talking about with Chevy High Performance not finishing the head test.
I would also like to see the buick 10 degree and the SB2 heads ran on this engine combo. This would put to sleep the big block/small block B.S. differences forever (or until the next time). pdq67

PS. And I do realize the differences in weight, but that can be remedied by the new ZL-1 aluminum block except for its cost.



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