"Long Rod" 351-W tech/info needed

[DAVID GAGNARD]

Originally Posted by Mark O'Neal

This is just a bad idea. It's a lot of work and money for no gain.

I'd be more inclined to do a inexpensive version of the 393...or 408, 418, 427.

Respectfully, I don't understand your point....

We're gonna rebuild the engine regardless of what we do.
we have to bore the block....
we have to buy new .030 over pistons/rings either way we go.....
we have to buy new bearing either way we go....
new intake/head/pan/etc. gaskets either way we go...
the 351M/400 rods are free...
machine work is free......

basically the long rod 351W would be the least expensive option,whether or not there is any advantage to the long rod motor over a "standard" rod motor is still up in the air, for every vote for no appreciable gain, there is a vote for some gain, so I call that a "push"......

There is little to no $$$$$ for this rebuild, so inexpensive is # 1.....

If it was my motor/project, I'd go with a 393 stroker,that's my personal preference....I have been impressed with the ones I've seen and driven.....

After the long rod motor, probably the next most inexpensive motor would be something on the order of a 393 or 408 as Keith has eluded to.....
I've given the guy my thoughts/ preference, it's his money, or lack of money and untimately his call.....If not for a pregnant wife and new house going up in a month or two, he would spring for a nice 393/408 without hesitation,but the "Boss" has to approve of this and he has to live with her, not me........
the final decision hasn't been made yet, he has a bunch of spare 4x4 parts/carbs/etc. he's trying to sell and if it goes soon enough, he'll have a few dollars for a budget stroker kit, which is all he needs for a hunting/knock around,weekend truck......

David

[Mark O'Neal]

There is no advantage in running a long rod. He'd be better off just rebuilding the stock engine.

As far as rod length and performance, except in vary narrow circumstances, it is utterly irrelevant.

The narrow circumstances occur when cylinder head size is mismatched to the engine size.

[olddog]

I saw on TV or read where the NASCAR teams run two different rod lengths in the same engine, based on the track. I do not recall which did what, but they claimed one rod length gives them an advantage accellerating out of the corners on the short tracks. The other is better for the long straight aways. If true, they have to be able to measure a difference or they wouldn't bother.

I did do some reading in my engine spec books, in bed the other night. I calculated what wrist pin height would be needed for this combination. No factory piston will fit the bill. I calculated the pin height for several strokers and none matched up. The 331 came the closest. I cannot recall the numbers, but I think it was close enough to possibly work with some machining. I wouldn't trust any of this as I did the math in my head and then slept on it.

[CobraEd]

Originally Posted by olddog

I wouldn't trust any of this as I did the math in my head and then slept on it.

E = MC Squared.


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[CobraEd]

http://www.chevyhiperformance.com/te...ips/index.html

I am getting a headache from this !!!!


.

[Jac Mac]

Originally Posted by CobraEd

http://www.chevyhiperformance.com/te...ips/index.html

I am getting a headache from this !!!!


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Most Chevy books give me a headache too

Ford 400C rod..........................= 6.580"
Ford 351w crank (1/2 stroke......)= 1.750"
Piston for 331w stroker, pin height= 1.165"
Total stack height of combination.= 9.495"
Late model 351w deck height.......= 9.500"

As an aside to this I built a 200cu in straight six Falcon to compete alongside a 202 cu in Holden straight six many years ago. Holden was 3.25" stroke with a 5.25" rod ( 1.61/1 Rod Ratio), Falcon was 3.125 stroke with 6.25 rod (2.0/1) rod ratio.
Series tech guys insisted we initially run the same cam specs, with this the Falcon idled like a baby where the Holden had a distinct lopey idle...just as the article you posted suggests- with the long rod the piston is 'parked' @ TDC during the cam overlap phase that the scavenge effect is virtually killed off at low RPM, now while some might say this was a negative it worked fine in this car & it was competitive from day one...later I plotted out the piston dwell @ TDC versus valve overlap & transferred this on to a 'new' cam profile to suit the Falcon. The Holden guys were not amused
I should point out this was the 'old' cast in head inlet manifold Falcon engine, not the later seperate intake setup.

So, in all the long rod 351 should idle more smoothly than its short rod version given the same cam /head etc, but have a bit extra at the top end.

[DAVID GAGNARD]

Originally Posted by olddog

I saw on TV or read where the NASCAR teams run two different rod lengths in the same engine, based on the track. I do not recall which did what, but they claimed one rod length gives them an advantage accellerating out of the corners on the short tracks. The other is better for the long straight aways. If true, they have to be able to measure a difference or they wouldn't bother.

I did do some reading in my engine spec books, in bed the other night. I calculated what wrist pin height would be needed for this combination. No factory piston will fit the bill. I calculated the pin height for several strokers and none matched up. The 331 came the closest. I cannot recall the numbers, but I think it was close enough to possibly work with some machining. I wouldn't trust any of this as I did the math in my head and then slept on it.

Not only running different rod lengths for different tracks, they also use different bore/strokes combinations for different tracks as well, all staying within the 358 cu.in. limit........
Short tracks,bigger bore,shorter stroke for quick accelaration off the corners,were the rpm range is greater: long tracks, smaller bore, longer stroke were the rpm range is smaller......

Before the compression rule (I think it is 12 to 1 now), Yates Racing was running engines at Talladega/Daytona in the 17 to 1 compression ratio!!!!!!!!!!!!!!!!

David