The 350 Engine Chevrolet Should Have Built (http://purplesagetradingpost.com/sumner/techinfo/350%20chevy%20engine.html)

I have been fascinated since the early 90's with the idea of long rod to stroke ratios and this article is pretty amazing.

I just wish they had done a side by side comparison taking a "regular" 350 and bolting on the same upper side (heads/intake/carb) and seeing what the difference was between them.

What's are your thoughts? How much difference? I know the Camaro 302's and Boss 302's were nasty partly because of the short stroke and long rods.

All those views and no opinions?

I know the Camaro 302's and Boss 302's were nasty partly because of the short stroke and long rods.

I don't believe that's the case. I had a 259" Studebaker motor with a r/s ratio of 2.04 and it sure wasn't 'nasty'. To get a 2.04 r/s ratio in a 302 you'd need a 6.125" rod. 302 Chevy's used a 5.7" rod and the Fords had a 5.15" rod, not very long at all.

I clearly remember this article in HOTROD. I found it interesting.
I am in favor of, and agree with the benefits of a longer rod. And here it comes------BUUUUUUUUUUUUUUUUUUT, for a durable, long life engine, I am very cautious about short pistons (more prone to wobble in the cylinder). Although, I am also quick to realize that the wobble (increased piston slap) of a short piston may be reduced because of the decreased angle of a long rod.
My opinion?
I really don't know! :confused:

And now, a couple of comments about HOTROD magazine.
There used to be lots of good tech articles (like the one above) that were practical and applicable to us poor boys. But I finally got tired of all the excessive ads, high dollar unrealistic vehicles and tech articles that were clearly infomercials! Finally let my subscription expire after 40 loyal years to HR.
One particular tech article in HOTROD MANY years ago, that I did, and it was good, was boring/stroking a SB400 to 420ci. It was pretty basic and simple. Offset grind the rod journals (of a stock, cast 400 crank) to small rod journal size and use a set of reconditioned 327 small journal rods. I built a boat engine like this (this was before the readily available stroker cranks for a SB400), and it has been a great engine, for not much more than the cost of doing a quality rebuild of a SB400. And doing a quality rebuild of a SB400 doesn't cost much more than rebuilding a 350. Of course today, USEABLE SB400 blocks are becoming increasingly scarce!

Seriously- I don't think it's worth it. The investment required to use longer rods doesn't deliver enough to justify the cost, especially in a true street engine from 2,500-5,000 rpm. If you want a 6-inch rod, that's not too tough, but is it really worth measurable power or extended durability? Not really.

An investment in better heads or valvetrain or even exhaust (like a well-designed step header or something) would deliver more bang for the same bucks.

And now, a couple of comments about HOTROD magazine.
There used to be lots of good tech articles (like the one above) that were practical and applicable to us poor boys. But I finally got tired of all the excessive ads, high dollar unrealistic vehicles and tech articles that were clearly infomercials! Finally let my subscription expire after 40 loyal years to HR.
Yeah, I expect articles; and I expect advertising--but when the article IS the advertising, I get peeved. My subscriptions to the mainstream magazines have all expired. I buy one off the stand now and then--not many of 'em, and fewer as time goes by.

There's nothing wrong with the 400 block/350 crank engine--but--unless you have class rules limiting displacement, you might just as well build the 400 with the 400 crank.

Remember the old 348 "W" engine? Same bore 'n' stroke as the "Hot Rod" 400 block/350 stroke.

I will bet that if you hop up and as well as cam that 259" Stude, it will run like a "scalded-dog"!!!

And this is why I'm looking hard at using 6.25" SJ long rods along w/ 6" rod 350 flat-top pistons and 50 cc chamber heads in/on my next junk292/301/306!!

pdq67

PS., a Z-28 has a 1.9 R/S ratio and a 302 Ford like a 1.7 and it appears that a 1.7 r/s ratio is great for max torque production IF everything else is matched and I say this b/c of the 455 Buick engine at like 1.6999(??) or so...!!

PS., a Z-28 has a 1.9 R/S ratio and a 302 Ford like a 1.7 and it appears that a 1.7 r/s ratio is great for max torque production IF everything else is matched and I say this b/c of the 455 Buick engine at like 1.6999(??) or so...!!

Interesting idea... anyone else back up the 1.7:1 ratio ideal? Everything seems to point to my ever-increasing appreciation for the LS-series engines. The stock engines are a 3.622" stroke with a 6.098" connecting rod for a, you guessed it, 1.68:1 ratio.

My opinion?
I really don't know!

This is why I wish they had compared two engines with similar displacement but noticeably different bore/strokes but otherwise identical bolt-on hardware. The fact that the engine was able to make the same power on 87 or 92 octane on 10-year old technology still fascinates me.

Look close at where the piston is DITH when the rod is tangent, (i.e., 90 degrees), to the crank b/c this is the point of max torque transfer if not mistaken.

I want to say that it should be at 73 degree's ATDC crank rotation or very close one way or the other.

That said, you also need to consider rpm vs torque point and rod/stroke ratio b/c we consider engines like long rods b/c they help hold piston side thrust down at rpm.

I think that this is the main difference between a Z-28 and a Blue oval 302!

And then closely examine Honda's S2000 ultra-high rpm 4-banger engine for r/s and bore/rod length and bore/stroke ratio's too!

I'm w/ you b/c this crap is fascinating to me also!!

pdq67

PS., And very closely watch the cam timing events too!!!!!! DCR vs SCR here is all...

If I had the time or more importantly the money I would like to recreate the experiment in the article with a standard 350 and try to minimize all the variables, basically make it a top-end swap between the two engines.

To take it a step further... you could run three engines at almost the same displacement which would be another interesting comparison.

Engine #1 - 4.165 bore x 3.00 stroke = 327
Engine #2 - 4.000 bore x 3.25 stroke = 327
Engine #3 - 3.736 bore x 3.75 stroke = 329

Run the comparison with the same top end swapped from engine to engine. I guess GM has done this very test.

As an aside I was looking for an article from 2005 called the Great Bore vs Stroke Shootout which might have this kind of test but I cant seem to find a copy. :(

Hot Rod's Dave Frieburger said he was going to do a short/long rod magazine test and never did!!

The closest test there is like this is in Ed Staffel's great book "How to Build Max Performance Chevy Rat Motors" on page 51 where a test was done holding everything the same except stroke!

478", 509", 525", 541" and finally a 573" engine! Very interesting by me!

pdq67