6.2 stroker?

[4x4Dreamer]

This is a question posed by a board I moderate, and we were looking for a good answer. Some think it's been tried and failed, but we're all curious.
Any thoughts on this?

"Ok folks, I thought of something not long ago and would like an opinion if possible....I realized that our 6.2L Detroits are oversquare; meaning the bore is bigger than the stroke..To achieve true "diesel", I'd think the stroke should be longer, making it undersquare...Now, the 6.5L has a longer stroke, but the bore is increased too, still making an oversquare engine...I read that the cranks and rods, pistons, etc will interchange from engine to engine...Say, take a 6.5L crank, find which pistons and rods would be the ones to use, and put them in a good 6.2L block and that would make the stroke longer and the bore would stay the same....Although, this would probably make it not rev quite as high, or as fast (like it does anyways ), I think it would make it produce alot more useable torque...Then add a turbo!! I haven't put a whole lot of thought into this idea yet, nor have I researched it as my internet access is severely limited, but I do have access about twice a week, so if anyone has any supporting opinions, or criticisms, feel free to post them here! I will try and find the actual bore and stroke numbers for these engines later tonight...Later! "

[arveetek]

The 6.2L and 6.5L share the same crankshaft, so both engines have the same stroke (3.80"). The 6.5L just has a larger bore.

The 6.2L bore and stroke is 101mm x 97mm.

The 6.5L bore and stroke is 103mm x 97mm.

Casey

[Peter J. Bierman]

Next to the crank being the same, even the same part# I think? were do you want to stroke to?
If you take off the heads and gasket, you will find that the piston top is flush with the blockdeck.
The only clearance comes from the gasket, so that leaves you about 1 MM of space.

Besides is it an very old theory that a diesel should be long stroke.
What makes the diesel ignite is the compression, determined by the compression ratio.
Making the stroke longer does change the CR.
Both 6.2 and 6.5 have high CR. compared to other same size engines; 21.4
If you want to enlarge displacement you can bore to the biggest oversize and that would make it allmost a 6.6 but that is the best you can do.

;)
Peter

[Brianlar]

I would have to concur with Peter. Stroking a gas engine with room for improvement is one thing. Trying this on a 6.2, wouln't work. These engines are allready high performance. It's just not the same kind of performance that people are used too. They were designed for low end grunt, as you are well aware. Pushing one beyond it's character would be expensive, lengthly, and prone to failure. Maximizing what's already there seems to me to be the best answer to the question. You can bore it out, add a turbo, headers, injection pump, injectors, clean up the intake, and add parts that reduce the load on the engine. All things I would be more than happy to try myself, budget permiting. Except the turbo, In my case, that mod would be impractical.

[jbell]

On topic of 'what can you do to a 6.2 for performance'
anyone make an extra thick head gasket to drop cr down below 21.3 without the expense of going pennisular 18:1 pistons? (In the quest for more power) Or (And I know I'll get laughed at for this) can you double up the stickly orange gaskets without worrying about blowing them out?

[john8662]

Actually, there are new pistons available for lower a compression ratio 6.2. Penn sells 19:1 pistons for the 6.2, and they are a lot cheaper than those used for the 18:1 6.5's. You can also buy the thicker head gaskets from fel-pro, they are mainly used to conpensate for the block being decked.

[jbell]

how thick are the felpro's? enough to get me down to 20:1? (I'd like to avoid a complete engine teardown, I'm just playing around for more power)

I've looked for a decompression plate for the 6.2 -- not to be found. Seems only racers use them, and no one races with a 6.2.... any idea why??

My bad on the penn pistons, I knew they were 19:1, sorry.

[grape]

.010" x the bore diameter = 1 point of compression
shorten the rod with the bushing or cut the piston.

[G. Gearloose]

I've often pondered the theory behind low compression pistons on the IDI 6.2/5.

Wouln't one want as much air as possible in the precombustion chamber, since thats where most of the burning is? Why waste air you've tried so hard to get in there, by leaving it outside the precup?

It suggests increasing the volume of the pre-cups would be the better solution.

Apparently they work anyway, but I wonder if it was the optimal solution, and wonder if I'm going mad.


BTW stroking the 6.2 would require shorter rods and higher side-loads on the pistons, something dimesionally it cannot afford. the rods are already short.

[Dan Wilson]

Lets see. If you offset grind the crank with a .020 under to come out with moving the rod out .010 the extra thikness of the felpro that would yeild a total gain of .020 extra stroke. We do this all th time in out class racing. We are allowed .015 extra stroke in NHRA blueprints. Dont know how much this will effect the CR?
Dan

[4x4Dreamer]

Good stuff guys, keep it comin'.

Is the only reason for running lower compression so you can have more boost? How much benefit does one gain from that? I think the Banks system puts down 10 lbs of boost on average...what could you crank boost up to with 19.1 pistons? What type of gain would that net?

[Peter J. Bierman]

Compressing the air takes power which can't be use for propulsion.
The high compression is only for cold starting convieniance, ideal would be 17:1, enough to heat the air to ignite the fuel and to alow high boost pressures like 20 or 25 psi.
Based on my findings and calculations for the Twin Turbo project, you need to take off 1mm of the piston deck to get to 19:1 CR.
That means you have to put in 2 head gaskets :eek: but I doubt if that will hold.
I took off 1mm from the standard pistondeck and it still holds up, however peninsular pistons would be the way to go.
The thickest gasket I could find is 0.1 mm over standard from felpro.
Enlarging the prechambers is a neat option but its hard to keep the contence of all 8 the same which is crucial for balance.

If looking for power, the easiest way is put on a turbo and 4911 injectionpump with matching injector and a big freeflow exhaust.

The hard way is putting on two turbo's with intercoolers, marine pump and injectors, a diesel depot cam and gear drive :D that's what I did or am in the proces of doing.

;)

Peter

[Peter J. Bierman]

Oh, and I forgot, redface.gif
Pumping your boost to 25 psi would not do you any good unless you put in more fuel.
So getting an injectionpump and injectors to get enough fuel to burn in all the air, is the key to more power.

What ever you do, all power gains will cost $, a lot them :D

Peter

[84 Convert]

Correct me if I'm wrong, but isn't turning the crank detrimental to crank longevity due to the need for the radius on the crank journals to be kept for stress relief? Unless it can be cut on an undersize journal to retain it's function, I'd be very leery of turning the crank and getting rid of that radius.

besides, I don't know how much you can really get with this engine block. It seems you'd have to do something major like the extra .25" stroke in the SBC 383 vs 350 stroker. If all you can get is .020" or .040", I think I'd just do the things Peter talked about. There's no way we're ever going to make a 6.2/6.5 block seriously undersquare,if we can at all.

However, if we could get a special forged crank and special pistons with a shorter crown to pin distance, maybe it could work. I still say go fer the turbo and intercool it... MORE FUEL PLEASE!!

Just my .02. (Now that I sound like a total pessimist!)

Gregg

[grape]

call bryant, they will build you anything you want from billet. get your checkbook out though. Our last 3.30" stroke, 1.85" rod crank for our truck was $3800, and that's a fairly common crankshaft.

[Peter J. Bierman]

Going that way you can design and having a couple 4 valve direct injected heads made, devellop a wild cam and eventually have your own block made to get rid off the known weaknesses.
If you can put a fair price on it, I think you will find some custommers here.....

Fun part is you can put your own name on it! :D

Peter

[doncannon]

Peter, How did you get the second turbo on? Special manifold? Oil line for the turbo? thanks in advance,
Don

[Peter J. Bierman]

Build a complete setup from scratch, made manifolds and oillines, intake tubes to and from intercoolers and exhaust all the way.
Did a write up for the dieselpage including all used materials and messurements, it was published in 2003.
In the 2003 book you can read the whole story and a update is in the works. ;)

Peter

[EWC]

Some food for thought

Ford 7.3L pistons : bore 4.1100 " , pin dia. 1.1101 " and compression height 1.950 " . These also have the Ricardo cup .

Chevy 6.5L pistons : bore 4.0551 " , pin dia. 1.2205 " and compression height 2.115 " .

The 6.2L/6.5L rod journals measure 2.400 " .

What if you offset ground the rod journals down to 2.200 " ( big block Chevy ) and bored the 6.5L out .055 " to fit the 7.3L pistons ? Aftermarket rods should be able to handle the extra grunt . One problem would be in using the 7.3L pistons ; the injectors are positioned at the top of the bore while the 6.2L/6.5L are at the bottom . If the wrist pin is not offset , then you should be able to run them " upside down " .

[Peter J. Bierman]

Interesting thought, but why not put in the whole Ford unit and save the trouble?

:D
Peter

[grape]

I have a 599 block at the shop with a broken cylinder wall, I'll grab it later and measure how thick the cylinder walls, are. I'm not sure how much you can bore one of these things. We are boring the small end of the stock rod to accept a larger od wrist pin bushing and having bushings made. With the 7.3 pin being smaller....you could have bushings made without boring the small end of the rod, and get enough offset to make up for the deck difference.

[EWC]

One of the ideas that I had was to use the new rods to set the height of the piston to get lower compression . When you compare a 7.3L piston to a stock 6.5L piston , the 7.3L is shorter and looks smaller . With the rods ( small end 7.3L and big end BBC ) , new pistons and reground crank combo , I feel this could be done fairly cheaply . Even so if you were to use just the 7.3L pistons , new rods could be made that were a little longer and that would be a good thing . One of the problems would be the overbore of .055 " and the resulting thinner walls . On a gas engine a .060 " overbore is usually not a problem but with the higher pressures of a diesel engine , even with 17:1 pistons , there might be problems with blow by or ring sealing .

[Dezman125]

Hi
If the cylinder walls can't take boring for the 7.3 pistons,would the 6.9 pistons still give you the deck height your looking for?
Seeing that these motors are made by International,it would be a lot less painfull saying their are International,or Navstar parts in your motor,insted of saying f*&d parts. ;)

[Peter J. Bierman]

Or, we could be glad those Fords are around, so we can put them in smoke and laugh at after a trafficlight run!
:D :D

Peter

[EWC]

The 6.9L might be a better match as the bore is 4.000 " , pin dia. 1.1101 and compression height is 1.945 " . The 6.2L bore is 3.976 " .