Longest stroke non-tall deck?

[journeyman]

I know I can fit a 4.25 stroke in the 454, but will the 4.375 fit?

How much modification (relief) would be required for this and is this something to be undertaken only by someone who has experience with relieving blocks for longer strokes?

[Blown65]

If you are grinding to fit a big crank in a stock block, the biggest problem you will find is breaking into water. Unless you fill the bottom up with hardblock.


Corey

[journeyman]

So is ANY grinding (relieving, etc.) required for a 4.25" crank?

I thought (possibly incorrectly) that a 4.25 crank and rotating assy could be installed in a stock block with no relieving whatsoever.

If that were indeed the case (and it may not be), it seams odd that adding 1/16" to the crank's radius to achieve the extra 1/8" stroke would make that much difference in clearance.

[Blown65]

I cannot say with certainty that you will need to grind the block with a 4.25 stroke, but I would say that to get the .060-.080" that you need, you will have to grind a bit. Usually you won't hit water with a 4.25 stroke. Putting a crank in a block that is 1/16" larger will eat up the .060 clearance you ground out. 1/16=.062" If you went to .080" you now have only .018" left. You will now be getting thin on the bottom if you clearance the block again. This is why the aftermarket blocks start looking better and better when building stroker motors.



Hope this helps
Corey

[journeyman]

My assumption all along was that going to a tall deck block in a street vehicle would be complicated as fit becomes an issue with bolt on stuff (including exhaust)

Is that assumption correct?

[Blown65]

For a straight bolt in, the exhaust will not fit because the head will be .400 higher than before, but any muffler shop should be able to make the minor change to bolt up again. Moving the head out farther may cause it to hit your brake booster or other underhood obstructions.The intake manifold requires spacers or a tall deck version ( better choice in my opinion). You will need a distributor with a slip collar to accomodate the taller deck. Everything else will work externally. I guess it up to you to decide if the extra work is worth the effort.

Corey

[journeyman]

Starting to think that 3/8" ain't so necessary afterall.
1/4" seems a lot more practical.

[Blown65]

On a basic 427 build with a .060 overbore the difference in cubic inches is only 15. 496 for the 4.25 stroke and 511 for the 4.375. If you can notice that on a street engine with all else being the same you are a better man than me

If you stick to a 9.8 short deck block things get even easier and you can still build a 496.


Corey

[Big Dave]

The longest safe stroke for a Mark IV two piece rear main seal standard deck block is 4.375" as there is both oil and water running down the pan rail. If you have a Gen V or Gen VI block the oil is above the cam tunnel so you can run a 4.5" inch stroke with a standard deck block (once again you still risk striking water if you get carried away with a grinder.

You will get more torque out of the longer stroke motor which is more important than horsepower. You should be able to feel the difference in the seat of your pants as the difference in power is akin to turning off the A/C in your wife's econo box car that additional six or seven horse power not driving the A/C compressor will be noticable. You will get more than a difference of seven horse power with the bigger motor.

Big Dave

[journeyman]

So what exactly do I need to do to install a 4.25 rotating assy? Is there any interference with everything else being factory?

Will there be clearance problems?

FWIW:
App is a slow turning torque motor.

[Big Dave]

As with any stroker you are going to have clearance issues. The reason the standard deck Mark IV has a 4.500" stroke limit is the cam is in the way so you are talking a reduced base circle cam and H-beam rods to reduce a rod bolt nut from hitting anything. You have to have 0.060" clearance (I use a zip tie to check as I grind if it hits; it is not metal on metal and the plastic absorbs any contact stress) all the way around the entire throw of the crank (cam tunnel, bottom of the cylinder bore, pistons skirts, block pan rails).

Big Dave

[journeyman]

Wait... You mean 4.250", right?

[journeyman]

OK, so I am wondering what 454 do I really have?

It is a 1993 16,000 Lb truck chassis (engine probably built in 1992). I found a little help on Ebay (of all places) with this:

[Big Dave]

If it has a one piece rear main seal or built after 1991 (date code on the block) then you have a Gen V or a Gen VI block. You can check out the casting number on the block at Mortec.com to be sure of what you have. All Gen V and Gen VI blocks are four bolt main one piece rear seals with the Gen VI having roller tappets instead of flat tappets.

Big Dave

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