I know a lot of you think that using a 400 block with anything less than a 3.75" stroke is a waste of cubic inches, but I'm thinking about building an engine for a daily driver and the one in the Hot Rod mag a couple of years ago (The 350 Chevy should have built). I have a block and set of new Vortec heads. Clevite makes bearings with thicker shells so spacers won't be needed. I have a line on a standard steel 327 crank that only needs polishing. I can run a Keith Black off-the-shelf hyper flat top piston that will give me 9.9:1 compression and 6" rods. As I see it, this is basically a small block version of the big blocks many of us have read about where a 427 crank is used in a 502 block for a short stroke/big bore high winding motor. If this one is a dog, I still have the block and rods and can convert to a 406 fairly inexpensively. I think that the short stroke/big bore should give me good torque and street economy plus allow me to spin it into the stratosphere if I need to - otherwise, a great R/S ratio mill that should stand up to a lot of torture with that short stroke. Keep in mind this is a daily driver with a moderate cam - basically a very strong 327 with better heads and breathing than a stock one.
Comments, sarcastic remarks, lucid insights welcome. As always, thanks for your help and input.

sounds kinda cool ive never thought about that combo, probably because i dont think much of the 400 blocks.

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chris
1980 Z/28
350 .60 over stock bottom end world products torker2s 280H compcam edel.performer rpm,holly 750 dual feed.
2200 stall,- but still not done.

I am familiar with the article. For those that aren't, you can see it on Air Flow Research's website article database. Go to www.airflowresearch.com (http://www.airflowresearch.com) and check their "article archive" for "the small block chevy should have built."

If you are going for a short stroke, big bore motor, why not try to gain the advantage of the longer rod to allow for the higher compression ratio? They said you can fit about a 6.25'' rod in there with that crank and some short skirt pistons. Sounds like fun to me. And hey, when you are at a show and someone asks about your mill, you can wow them with your exotic choice.

how bout a 3" stroke then your in the bizz for 8000 rpm's but joking u'side i know a guy who has one in a 85 and it flys with the stock 400 heads it is alot faster than a 350

If you're not going to build the motor the same way they did in the magazine then I think it's kind of a crap shoot. The point of that buildup was to make plenty of power utilizing high compression but avoid detonation and/or the need for high octane gas by the unique combo of bore, stroke, rod length and piston. Once you start changing those things it's a different motor.

I considered building that motor myself. I even called the shop that did the work and discussed it with them. My thought was that the mag motor used stock heads and a very mild cam. If you substituted better heads and a bigger cam then you might have a real beast while keeping the basic parts of the setup as designed. The shop didn't seem too interested in helping and offered no opinion of the head/cam upgrade. Maybe I didn't get the right guy or they've had a chance to do some further work but it might be worth the time to call them again and discuss the project with them. As I remember, they were offering the rotating assembly for sale as a kit for anyone that wanted to duplicate the build.

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Scott
'69 400SB, Richmond 5-speed
www.geocities.com/sdenning1 (http://www.geocities.com/sdenning1)

I know a guy that has a setup like that, his is blown (mini blower single carb), it is in a 70 Camaro and runs very strong. He doesn't wind it up at all (cause of the blower), to me it seems that a engine like that would love to rev. I am not a fan of the 400 blocks and unless you just want to be different why not build a bigger engine 377, 383, 406 ect... no replacement for displacement, size does matter. If I were to build that combo I would definetly, build it to rev. I believe they call these overgrown 302's

Royce

this all sounds well and good but this thing is not balanced. A 400 block is stronger than a 350 or any other small block. the problem is they are not used properly. now why would GM spend millions on research, come up with a 350 instead of this 353? The thicher bearings can have problems in the crush fit and can easily spin on the crank. I have seen the development of these engines for 30 years. the only copy from the rodders world was the 302 z28, You need a pre 1963 block 283.........want to know more ask.

[This message has been edited by chevy30 (edited 11-24-2001).]

I think a 377 would be a better build if your looking for a high rpm motor. I know that you have a line a 327 steel crank and that is maybe the main reason for your intended build. IMHO find a steel 350 3.48" crank and use the 6" rods and I think you'll be much happier. Heck, that combo gives a great 1.72 rod ratio so the reduced detonation theory holds true here as well. I think KB also has pistons for this application so all you'll need to find is the 350 crank which should not be too hard. I seem to remember that the "Engine that Chevy should have built" had a compression of around 11:1, maybe .5 more. The theory was to use more compression to gain hp over other streetable designs. I think a conservative estimate of hp increase per compression point is 5%. Well, that's 17.5 more hp with a 11:1 350 cu.in. motor and 26 hp for a 11.5:1 350 mill. A conservative esimate for hp per cu.in. using 10:1 compression is 1:1 and with a 377 that's still gives 10 hp superiority over the 11:1 "350" design. I may be thinking about this all wrong but my conclusion is the old saying "no replacement for displacement" holds true. Let us know which way you build.

Joseph

Thanks for all the replies!
General consensus is that GM didn't spend millions on the 350 - it was much easier to stroke the 327 than bore it. Smokey Yunick tried for years to get GM to change, but once the tooling, etc. was set up, it was pretty much a done deal. The 350 that GM ended up with was pretty much a compromise of torque and economy.
The heads in the article were AFR 190cc heads for a 305, not a 350. They ran 11:1 to take advantage of aluminum's ability to take more squeeze without detonation. 9.9 or 10 to 1 is about as far as I'd like to push it on the iron Vortecs.
I can get Eagle rods at 6.2", but it still requires a custom piston. I can give up the extra .2" and get off the shelf pistons and if the mill doesn't live up to my expectations, I can always reuse them on just about any other small block project.
I'm curious as to the consensus for intake and carburetion for this mill. Most folks I've talked to recommend a 600cfm carb for all but radical 350's, but how about one that spins as high as this one could?
Thanks again and I look forward to seeing how this thread develops.

i like the 750 vac sec holley have one on my unc's 69 z/28 302

There are many legitimate motor configurations and even more ways to develop more power from each one. However, don't forget the specific intent of the motor built in the article. They were trying to assemble a combination that met their goals of: 400+hp/torque, idled well and ran reliably like a newer car engine, and would run happily on 87 octane "cat pee" gas. They met the goals and more with this particular combo.

If your goals are the same then IMO this is a very interesting motor. It sounds like a great street motor for a daily driver where you'll likely get tired of the lumpy idle, premium gas and frequent tuneups of a more traditional performance motor. Of course, if you want that traditional rumble and all the other characteristics that go with it, then this is probably not the right motor combo for you.

Then again, I just can't help wondering what this motor would do with better heads and just a little more cam! http://www.camaros.net/forum/biggrin.gif

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Scott
'69 400SB, Richmond 5-speed
www.geocities.com/sdenning1 (http://www.geocities.com/sdenning1)

The trick here seems to be the short stroke for rpm's, the long rod for less internal friction and better tdc combustion characteristics and minimum quench along with small combustion chambers for high CR.!

Any engine built this way will be more forgiving of the cat-pee gas we have now and produce goooood power. IMHO. pdq67

Hey isnt that what the 348 is? 3.25 stroke 4.125 bore The pistons were just made funny.

Yes, in a way. It was actually the step-father of the current BB engine we now have.

It runs a SB balancer, timing gears but not chain and fuel pump!

I wish that I had the money to put a set of Z-11, 409/427 heads on a 454 by using specially designed pistons like the Fueling heads use. I would have to make intake manifold port adapters and possibly rocker arms, but I bet that it would be an interestng concept engine design.

I think that if you do an engine parts ratio check, that a 409 is actually ratio-wise, a big 283!! And if GM would have opted for hollow domed forged pistons instead of the heavy solid dome H.C. onec, the engine would have ran and lasted alot better at the high rpm levels the two short stroke engines could operate at. A 409's stroke is only 3.5" long!

The current run of the mill Pro-stock engine limited to 500 inches, runs a 4.7" bore x 3.6" stroke or something very close. And rpm at close to or right at 10,000rpm! pdq67

I was planning to use APR main studs. Should I consider having splayed main caps installed, or will the block/caps hold up to infrequent trips to 7500, keeping in mind that this is 1/2" shorter stroke than the 400 with a much lighter crank.
Thanks again!

Two studs mains should hold it fine.

Chase stud holes and clean as good as you can. Install studs to bottom a shade over finger tight w/ some locking stuff on them, install main caps, then torque to about 30 pounds and let set overnight to make sure the studs are set and straight.

Install crank and spin to check for binding as you do a three to four torque step tighthening sequence. If the sucker spins OK, check for clearance w/ "Plastigage" and you should be ready to go.

Any other advice, guy's? pdq67