Engine Masters

[SuperBuickGuy]

I think they tested the only things that don't matter.

For those who don't get MTOD, this month they tested rod length theories by using a short and long rod in otherwise identical motors. They talked about what rod length does, then used HP and Torque to measure the results.

Let's put numbers to my assertion, build a 427 SBC and a 427 BBC - then let's talk. Rod length is all about longevity and flow. heck, use a 5.7 LS motor and a 5.7 SBC, 200k is just right for broken in enough to run turbos on a LS, a Gen one will not survive if it's 200k.... all about flow and longevity (the LS lasts longer because there's less stress due to the long stroke and it's typical use). The longer the rod, the less side-loading and the more 'fair' the air flow. (fair, like smooth - used often in boat building, where they fair a boat is making the hull shape smoother). For turbos, having a more constant static pressure aids in making hp because there is less tumbling and also less heat created.

With that same, hypothetical 427, a turbo is going to work lots better on a long stroke small bore then it will on a big bore, short stroke. Even then, it's not comparing apples to apples because the motors would be built for other purposes (size constraints, racing class, etc).

I would be interested to see parasitic losses on either case - but I think they did see a bit of that in the video... but then dismissed it as irrelevant... where it is relevant would be in longevity of the motor. I cannot imagine anyone arguing that a 273 ci motor would last longer or have less parasitic loss if it were making the same hp as a 427 ci motor. While the 273 would get to 8000 rpm faster, the 427 would say "why bother, I make the same hp at 4000 rpm"....

and the bench racing goes on. thoughts?

[RockJustRock]

It's all about geometry. In the 60s bore, stroke and rod length were considered inconsequential until 302s started doing amazing things apparently hitting some kind of "sweet spot". You can geek out all over the place on rod length, piston acceleration and deceleration at various points in the cycle. The question is how much difference is there in comparison to breathing vs. displacement vs. RPM capability? Point is a lot of engines have REALLY goofed up bore, stroke, rod length and do O.K. But f***ed up breathing for RPM capability and you have a lump. Then boost comes along as a great equalizer.

[cstmwgn]

Longevity and long rods for the common man are not always compatible. Unless you are building custom blocks with high deck heights, when you go to a longer rod you typically have to move the pin towards the crown which in most cases shortens the piston which in turns allows it to rock more in the bore.

Don't get me wrong as I have longer rods in my engines but for some reason I don't seem to get 200K out of them before they need to be freshened up.

[65RHDEER]

I don't think they were taking in longevity at all into it it was purely what rod length does for torque and HP. For me it answered the question if I'm building a motor should I be concerned about rod length in regards to HP and Torque. So I'll now use the 5.565 rods with forged pistons I have in my 400 that's been in the shed for 20 years.

I thought this was a really well done Engine Masters, a technical subject that they can afford to find the answers on that answers a big question for us.

[Eric]

I think they tested the only things that don't matter.

For those who don't get MTOD, this month they tested rod length theories by using a short and long rod in otherwise identical motors. They talked about what rod length does, then used HP and Torque to measure the results.

Let's put numbers to my assertion, build a 427 SBC and a 427 BBC - then let's talk. Rod length is all about longevity and flow. heck, use a 5.7 LS motor and a 5.7 SBC, 200k is just right for broken in enough to run turbos on a LS, a Gen one will not survive if it's 200k.... all about flow and longevity (the LS lasts longer because there's less stress due to the long stroke and it's typical use). The longer the rod, the less side-loading and the more 'fair' the air flow. (fair, like smooth - used often in boat building, where they fair a boat is making the hull shape smoother). For turbos, having a more constant static pressure aids in making hp because there is less tumbling and also less heat created.

With that same, hypothetical 427, a turbo is going to work lots better on a long stroke small bore then it will on a big bore, short stroke. Even then, it's not comparing apples to apples because the motors would be built for other purposes (size constraints, racing class, etc).

I would be interested to see parasitic losses on either case - but I think they did see a bit of that in the video... but then dismissed it as irrelevant... where it is relevant would be in longevity of the motor. I cannot imagine anyone arguing that a 273 ci motor would last longer or have less parasitic loss if it were making the same hp as a 427 ci motor. While the 273 would get to 8000 rpm faster, the 427 would say "why bother, I make the same hp at 4000 rpm"....

and the bench racing goes on. thoughts?

I maybe wrong, but I'd think, the engine control, the ls is gifted with, is why 200k is just broken in.
The timing control, and fuel control.
The Gen 1, It is the rings/bores that wear 9 times out of 10 that they need a rebuild, And old fueling systems, ran them a lot longer rich under cold starting, And didn't retard the timing to save itself, If the fuel was junk, or the a/f % too lean.

I'd bet the gen 1 sbc would be just broken in at 200k if you gave it the ls engine management.
The last of the breed, The trucks, go 200k+ without an issue. as those kinda got a good engine management system.

I would think the rod differences is just a small part of the total.

Give the gen 1 the engine management, the low friction ,really thin piston rings. piston coolers, shorter, lighter pistons.
And I'll bet it be a wash.

[SuperBuickGuy]

I maybe wrong, but I'd think, the engine control, the ls is gifted with, is why 200k is just broken in.
The timing control, and fuel control.
The Gen 1, It is the rings/bores that wear 9 times out of 10 that they need a rebuild, And old fueling systems, ran them a lot longer rich under cold starting, And didn't retard the timing to save itself, If the fuel was junk, or the a/f % too lean.

I'd bet the gen 1 sbc would be just broken in at 200k if you gave it the ls engine management.
The last of the breed, The trucks, go 200k+ without an issue. as those kinda got a good engine management system.

I would think the rod differences is just a small part of the total.

Give the gen 1 the engine management, the low friction ,really thin piston rings. piston coolers, shorter, lighter pistons.
And I'll bet it be a wash.

The Gen 1, Vortec, have oil coolers.... that's 90% of the reason they last. Of course, they also have Dexcool - which, if it doesn't get flushed, makes the 200k survival moot because 7 and 8 overheat then crack.... but oil coolers are the reason behind the longevity. Why can I say that, because the TBI and spider motors both enjoy longevity - and the only similarity is the oil cooler.... TBI is not precision control and in many ways is worse then a carb - especially on cold fueling when it's running off tables rather then load.

[Eric]

The Gen 1, Vortec, have oil coolers.... that's 90% of the reason they last. Of course, they also have Dexcool - which, if it doesn't get flushed, makes the 200k survival moot because 7 and 8 overheat then crack.... but oil coolers are the reason behind the longevity. Why can I say that, because the TBI and spider motors both enjoy longevity - and the only similarity is the oil cooler.... TBI is not precision control and in many ways is worse then a carb - especially on cold fueling when it's running off tables rather then load.

The vortec's, don't have piston coolers that squirt oil on the bottom side of the piston.

[SuperBuickGuy]

The vortec's, don't have piston coolers that squirt oil on the bottom side of the piston.

neither do most LS motors

[SuperBuickGuy]

Engine Masters this week.... cheap carbs.

Am I the only one kind of surprised that what was the cheap option was also the best? house brands used to be looked down on (for good reason) but perhaps it's time to revisit this?

[Eric]

Engine Masters this week.... cheap carbs.

Am I the only one kind of surprised that what was the cheap option was also the best? house brands used to be looked down on (for good reason) but perhaps it's time to revisit this?

I'd want to see a retest of the carbs , at 20k miles, then at 40k without touchin it (retuning it)
I'm thinking the cheaper unit isn't going to last.
But then again, A vehicle you are slapping a carb on, isn't most likely driven a lot.
I'm shocked they still produce them. There must be enough used ones out in the wild, to never need to produce another new unit.

[65RHDEER]

I think the Summit took the prize because it was most like a Holley...had better boosters, twin fuel bowels, radius into venturi. And like all Holley vac secondaries, wanted a lighter spring.
Would like to have seen the results of a spring change.

[Thumpin455]

Its always fun seeing ya chevy guys going on about how great your engines are, but then you have cracked heads, blocks, leaks all over, runs hot in places cold in others, wears out fast, needs oil shot under the pistons, and you gotta work to get screw in studs and 6" rods...and then it makes 345ftlbs at the peak and that is 'good' its most amusing. but ya can spin it to 7500 so it uses math to make power. ;) I'm happy chevy finally has a good engine with the LS family.

I didn't see the carb episode was even up until just now. It makes sense to me that they are still making carbs, since most people have no clue what they are doing with one, so throwing a new one on is easier than figuring out why the old one doesn't work right. Its ok, I get cheap cores from ya chevy guys that way.

[RockJustRock]

Main bearings.

[ejs262]

The key takeaway that I noticed, in the rod testing was that the short rod was more sensitive to changes in ignition timing than the longer rod, I attribute this in my mind to the shorter rod having less dwell at TDC, which to me implies that the engine with the longer rod will perform more consistently as outside parameters change IE: air temp, baro, humidity ect. I think I would prefer to run a longer rod due to that, especially on an engine that will be run on the ragged edge.

That being said, I'm not going to build my engine specifically around the connecting rod length either, I'll spend more time looking for light and strong rods.

[Thumpin455]

The oil pan was surprising,and it just so happens the one on my toy has a kick out on it. Nice work Canton. Its not like the one they used, but also I am only spinning it to 6500, sometimes 7000.