i want to see the proof...

I have seen people ask how come 90% of the time when a Rod let's go why is it always #1 or #8...we all also know the plenums are not really big enough for higher HP then stock.. these cylinders do not get there fair shake... #1 and #8 are at the shallow ends of these plenums.. can someone tell me these two are not related?? my thoughts #1 and #8 are not getting pushed down like the rest..there just isnt enough volume of air... there more so getting yanked down by the rod....im asking because i plan on running the 467 with the race cover...i also want bigger plenums..if there is any chance my thoughts are true or even close..ill give up the 467 and run a 42...

I think you also have to consider where they are located on the crank and block. Consider what is flexing and twisiting.

As to your questions Swamps now with the engine dyno that reads cylinder temps and pressure should be able to answer that question definitively.

wouldnt even PSI help with the flexing and twisting?? air PSI can do some prety amzing things just like water can make a 1/4" square stock round when it freezes..maybe it wouldnt twist and flex so much if the air was pushing it rather then the crank and rod yanking it down..

i hope he will see this thread..thanks tarm..

Interested to say the least but seeing as what all is going on in the cylinder I think anything much over 50 lbs wouldn't make that much of a difference. I read somewhere its not really the up and down when the rod let's go its usually the rotation going back up from bdc that gets them the sudden up movement from all the momentum going down

Consider what the effects would be and where they would be most severe with the block flexing and twisting along with the crank walking and itself at the ends flexing of the centerline

the piston "yanking" the air down is how all n/a engines operate, it's how they make vacuum. if these cyl's are pulling air in as opposed to there being pressure from the turbo then you could have a lean condition and possibly detonation which when left unattended will destroy stuff, like rods, cranks, wrist pins, etc. But there should be evidence of detonation on these cyl's if that were the case.

I'm running flat plenums to fit my 467. I would think it has more to do with 1/8 being on the end of the crank and flex.

TARM said:

Consider what the effects would be and where they would be most severe with the block flexing and twisting along with the crank walking and itself at the ends flexing of the centerline

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So could this phenomena be attributed to the connecting rod to crankshaft side clearance becoming out of spec?

Consider which cylinder has the fueling and timing changes 'implemented' when the chip is switched from one position to another? ..and how that might affect torsional stresses on the block...I wonder if anyone has ever looked into this?

Also, our cylinder head flow bench doesn't reveal a significant difference in airflow through the valve on any of the intake tracts...which was rather surprising. Even probing around in the intake bowls with pitot tubes...shows very evenly distributed air flow on all valves...

I wouldn't be overly concerned with the size of the intake plenum either...underneath the plenum there is quite the 'reservoir' for the air to be evenly distributed to the individual runners.

..just my thoughts.

Good thoughts Dave, it would be great to identify and resolve this problem

Sure would be nice to figure it out.. My recent failure was #8

What position is the #1 cylinder in when #8 is TDC and vice verse?

OSCS said:

What position is the #1 cylinder in when #8 is TDC and vice verse?

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3 & 8 are 'companion' cylinders...

when either of those pistons is at TDC (or any other deg before or after TDC)..then every internal engine component is in exactly the same location. At TDC for example...one will be finishing up the exhaust stroke, and the other will be finishing up the compression stroke.

OSCS said:

Sure would be nice to figure it out.. My recent failure was #8

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thanks a lot guy's
your loss got my attention.. I have the same turbo..the last 2 or 3 resent let goes on a few different forums ran the same turbo..I don't know for sure but I think they where running flat plenums as well .I think you need to for this turbo to fit..I also know there hasn't been a failure in long time then all of sudden there are a few not holding up so well.....there is a possibility they went to this turbo after there motor let go and they up dated there sig..but I cant afford to do this twice and I really want to try this turbo out....but not for the cost of a rod letting go...

Ron's Power Stroke said:

thanks a lot guy's
your loss got my attention.. I have the same turbo..the last 2 or 3 resent let goes on a few different forums ran the same turbo..I don't know for sure but I think they where running flat plenums as well .I think you need to for this turbo to fit..I also know there hasn't been a failure in long time then all of sudden there are a few not holding up so well.....there is a possibility they went to this turbo after there motor let go and they up dated there sig..but I cant afford to do this twice and I really want to try this turbo out....but not for the cost of a rod letting go...

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I thought ocss was running a a s366? I really don't think that running a s467 over say a gt42 has anything to do with rods letting go. I would say cylinder pressure has the biggest role in it.

4.0l sahara said:

I thought ocss was running a a s366? I really don't think that running a s467 over say a gt42 has anything to do with rods letting go. I would say cylinder pressure has the biggest role in it.

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correct i run a 366

Ron's Power Stroke said:

thanks a lot guy's
your loss got my attention.. I have the same turbo..the last 2 or 3 resent let goes on a few different forums ran the same turbo..I don't know for sure but I think they where running flat plenums as well .I think you need to for this turbo to fit..I also know there hasn't been a failure in long time then all of sudden there are a few not holding up so well.....there is a possibility they went to this turbo after there motor let go and they up dated there sig..but I cant afford to do this twice and I really want to try this turbo out....but not for the cost of a rod letting go...

Click to expand...

After the post that golfer made i really dont see the flat plenums being the culpret and i do run a set of irate flat plenums. While cylinder pressure is a big deal I dont think it played a role in my failure as i was gated from the get go. I think tunning played the biggest role in my failure. If i were you i would run whatever turbo/ injector combo you like (with in reason) and have the guy with the best track record for keeping engines alive play with it.. cough, cough matt.. its what i plan on doing when my 70k forged long block gets here hopefully next week.

I do have Matt's tunes..going onto a motor with 98k..I cant wait to try it out...for some reason I thought you had the same turbo.. maybe because of the plenum ordeal you went through..I know it should flow even at idle and your not really making or using boost at idle.. what about at WOT building boost and making things move faster?? or is this how golfer did the test?? i wish i had the coins..id just rebuild with billit rod's and not worry about it..

FWIW Ron, You can use the "Beans" Billet aluminum plenums with the Turbonetics mount kit and the S467. Its tight, but it works, we have used it on a couple trucks.

I don't see it being an issue, but just throwing it out there as an option

thanks Nate..that is a answer i was looking for when i got the turbo..i guess i was asking the wrong people lol. looking at the outlet of the turbo there is a block with a couple of threaded bolt holes... i was wondering if that block could be ground down?? it would let the turbo outlet drop a little more... i wish i had a pic to show better what i mean...this may not be an issue but id feel better if i had the volume and not go backwards....