i see you have a couple of these cranks forsale on ebay.



now my question is what rod and pistion lengths are people running wiht a 3.8 stroke.

 

Crate zz383/ht383 engines use a studded 5.7" PM rod with a press fit pin, and a rather odd 18cc dished hyperutectic piston with coated skirts and a 1.396" compression height and metric rings, putting it I think .029" in the hole. if you were to use a standard 1.420 or 1.425" compression height piston (standard 383) you could get pretty close ar right at zero deck. I have one of these and they're nice cranks...a friend of mine at a dealership gave me a 300 mile shortblock with a twisted rod thinking it wasn't good for anything. The heads had a bad valvejob on one of the cylinders and they discovered the rod when they pulle the heads so they just ordered a new engine under warranty. The pistons are available from GM but the rods are like backordered, so I just ordered some eagle I beam 4340 rods to replace them...

They say that the 3.8" stroke gives a slight torque advantage with slightly better streetability, and also lets you run a standard bore while increases bore strength for use with nitrous, etc...

I have some gen 1 converted LT1 heads getting sent to my from Lloyd, and with the 52cc combustion chambers, still puts me at 11.3:1 with a thin head gasket.

 

perhaps... but with 30-over pistons being as cheap as any stock-bore ones... it's awefully temping to drop some cash on a 6" rods and a 30-over piston with a compression height to get you 0.005" in the hole on a stock block.

Oh wait a second... that's my plan. Hello 388. Never hurts to get 5 extra cubes.

 

whay is stock deck height.

becuase i want to use a 6" rod as well but what piston hieght would i need.

 

97z,

Stock deck height = 9.025

A 1.125in compression height piston will put you at zero deck.

 

what he said.

Personally I have a set of Wiseco K264A3.

• 4.030" bore
• 1.120" C/H (0.005" in the hole with a 3.8" stroke)
• -15cc dish
• chromoly wristpins w/grovelock spacers/spiroloxs
• 1/16, 1/16, 3/16" ring package
• fits 23* AND 18* valves

 

Cool... put that extra valve relief depth to good use now, ya hear!

-Mindgame

 

Sniff sniff......hmmmm 18x......

 

yeah... I that's "stage 2". Unported Brodix 18x and a sheet-metal intake should flow enough to "wake up" the beast.

Obviously a fairly pricey top end... but with the shortblock in place it shouldn't be quite as bad... and any high-end roller rockers I get now for the ported LT1 heads will swap straight accross... as should the LT1 AS&M headers since the 18x comes in a standard exhaust port.


"Ahhhh... I love it when a plan comes together!" - John "Hannibal" Smith

 

is that a costum piston or off the self

 

Yup. if you could run a 383 piston in there and it brings it up to or close to zero deck, you can also go up to a 6" rod using a matching piston. I'm not like most people, I wont punch out a bore that isn't worn just to fit in some .030" slugs, unless the block has been overheated, has a gajillion miles, a ridge, already have some expensive pistons, etc...

I've seen many blocks with perfect bores that people overbore anyway and I dont understand the reason in that. There is no significant increase (if any) by overboring the block unless the bores are so warped you're loosing ring seal. I'd rather keep a perfect standard bore which makes them that much stronger if you ever choose to go N20 or s/c...and by adding a little more stroke I think that's where your advantage would come from; more streetability with a bigger cam, more torque, etc...you can think of it as a way to get something between a standard 383 and a 396. I'd rather spend that money on some splayed main caps or something other than boring a perfectly good block. It would be nice explaining to people how you have a 388 though when you only sport a .030 bore though I guess it really depends on how good your block is.

1.125 and 1.120" compression height pistons (6" rod) or 1.420" and 1.425" compression height pistons (5.7" rod) are both off he shelf. Piston manufacturers sometimes dont advertise these numbers because people look up pistons often by application or rod/stroke length. There are other compression heights available too, these are just two of the most common ones for 383's. The GM ones for the crate 383 engines are 1.396" though...so they come up at .029" in the hole. Nothing but engine math.

I've done it with no complaints. I like the way with my heads the compression is high, but all I need to do to lower the compression ratio is just pop on some AFR's...get's it where it needs to be for supercharging, etc. I would at that point change the pistons though.

Another $.02

 

That was exactly it though... I got a great deal on forged 30-over pistons (see above). Either I sell these and find some 4" pistons with the same compression height (few exist off the shelf), or I got to 5.7' rods and simply rebuild the 350 I have. I'm not spending money like this for a "forged rebuild"... I'm looking for a stout short block with enough displacement to do 18* valves some justice.

The block has 200 miles on it and is factory fresh... gonna be a real shame punching it out like that. Oh well... the stock one it replaces will be a geat candidate for another 30-over engine for someone else... it's got 180,000 miles on it as does the factory opti-spark.

I'd rather tune a NA engine to always be on tap than constantly pay for nitrous refills. Personal preference really, but having both would be very expensive, and the parts/fuel system/etc... to handle such limits (i.e. over 700 hp) just looks like a huge nightmare I don't want to get into.

I'd be thrilled with 500 hp (or maybe 500rwhp ), any nitrous would have to be above and beyond that point. Seeing how 500 ain't cheap I gotta take it one step at a time.

 

Off the shelf... as was my wiseco set (although the ceramic and anti-friction coatings were applied later). That's the normal CH for a 383 with 6" rods.

If you checkout the JE or Wiseco websites they have catalogues that list pistons first by model (type of piston / target audience / engine block etc..), then by compression heights, then finally by bore. Probably because engine builders think that way... bore is adjustable, CH is more important when designing a rotating assembly (and dealing with quench).

 

I'm waiting on my block height measurement before I decide on Rods and Pistons. I already know that I have to go .035 over, so depending on block height I'll either go with a 9.025 zero deck, 6" rod and a 1.125 ch piston or if I have to deck it to 9.00, go with a 5.850 rod and a 1.250 piston. Diamond has a 4.035 piston with the ch and dish on the shelf. My static compression will be around 11.5:1 and with my cam about 8.6:1 DCR. At any rate not a great selection of pistons out there for my needs, but enough to keep from having to spend $$ on custom slugs. Just waiting to hear from the machine shop.

 

Yeah, mine was kinda the otherway around... if the block's fine for 9.025" (it's only got 200 miles on it) I'll get the 3.800 crank... if not I'll deck it and get the 3.750" with a thin gasket.