I have a new CNC Bowtie block that I plan on building into a short deck (9.8) 572. 4.375 x 4.560.

I know that a 4.25 stroke is no problem. I am wondering if any body has done a 4.375 stroke in a 9.8 deck, and if so where there any problems?

I am leaning towards aluminum rods. I figure it would be easier with aluminum ords since it is very easy to order a custom length. I also have a set of billet +.250 Crower rods I may run instead. This a street / strip that I plan on spraying with some very heavy nitrous (up to 500 hp) hence the reason for the possibilty of aluminum rods.

Any opinions ?

Thanks,

John

I would hesitate to use the aluminum rods if it is a street engine and with the size of the big ends you may have clearance issues with the 4-3/8" stroke. As far as the +.250" rods and the 9.8" deck, that puts the pin only height only 1.22" down. Sounds like you'd be kind of pushing it to me! A 427 is 1.76" and a 454 is 1.645" down by comparison.

I'd ask a qualified engine builder like Mike Lewis (aka wolfplace here on TC) what his thoughts are.

Thanks David. I am beggining to wonder if the 4.375 stroke deal is going to work, particularily with the nitrous pistons ring pack requirerments. This motor may and up being a 555.

As far as the aluminum rods I am aware of the fact they do not have the cycle life of steel rods. This motor will see the street only for a quick trip to the local car shows. The main reason for the aluminum rods is the buffer they provide or the heavy nitrous.

Originally posted by 69 Ratt Vette:
Thanks David. I am beggining to wonder if the 4.375 stroke deal is going to work, particularily with the nitrous pistons ring pack requirerments. This motor may and up being a 555.

As far as the aluminum rods I am aware of the fact they do not have the cycle life of steel rods. This motor will see the street only for a quick trip to the local car shows. The main reason for the aluminum rods is the buffer they provide or the heavy nitrous. =
Hi Ken,

I'm not a big nitrous guy but as I recall you are planning on leanin on this deal pretty good & I would opt for the shorter stroke.
I don't think you will be able to get the rings down far enough & with the aluminum rods you are going to probably have enough grinding as it is with the shorter stroke.
Nice thing about the bowtie block is you won't find the main oil passage when grinding :rolleyes:

I agree with the aluminum rods for a heavy nitrous engine though as they do make excellent shock absorbers if the tune is off a little :D
You might go here & post a few questions to Joe as he does a lot of big nitrous stuff
MRE (http://mreracing.proboards22.com/index.cgi)

Be sure to tell Joe I said "HI" ;)

I want to build a 588"er! 4.625" b x 4.375" s motor using a 9.8" Merlin III or Pro block. I figure it would be the ultimate 396", "stealth", motor... He, He!!

S-O-M sells a kit for the 572"er so I figure it is fine. I really wouldn't rpm her, but rather cam her for max. midrange grunt and then gear and tire accordingly..

I will say that my '75, 454" P/U block swallowed my 496's rotating assembly with no grinding whatsoever except a schosh on the oil pump for the nut..

I honestly think a 4.375" crank should drop right in with minimal grinding if stock type aftermarket 6.45" long rods are used.. This way she will still have a half-way decent R/S ratio, imho.. And JE can make pistons for this combination b/c I asked them..

pdq67

pdq67

If it were not for the plan of 7500 rpms and a LOT of nitrous, I would not be so hesitant with the 4.375 stroke. With this level of nitrous use you need the first ring to be down at least .375 (probably a little more) I do not know if there is enough room for the other rings. I will do some more research. One nice thing about the aluminum rods is I could run a shorter rod and get the CH to a more desirable measurement. Of course this is not a real desirable situation either. HHMMM a 555 would not be a bad compromise :D