Thread: piston and rod types for a 383

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Hey guys.

right im almost definate that im goin to build a 383 rather than a 350, as my big heavy landy will needs loads of torque to haul its fat arse out of the mud at high speed

when i did my piston research (mostly cortesy of david vizard) i found that the hypereutectic pistons produced more power as they were more stable and could run much smaller piston to wall clearances

if my stoker prob isnt going to exceed 5500rpm, and i aint racing (well i go rallying but it aint speed!), then could i get away with not having forged pistons? kieth black hypers for example? that way i save money and gain a horse or two. i know i'll need a 4bolt block, but are forged pistons REALLY needed?

also is it worth goin for 6" rods rather than 5.7" rods? is there much cost/performance difference. i know it puts less horizontal stress on the crank, but how much is this worth?

cheers dudes
lobster

lobster, I'm gonna show you these guys just because you may not know about them. First up is a skinny-budget stroker kit that uses the short 400 rods. One of the options is hyper pistons for $105, so for $565, you'd have an operational kit....
http://www.speedomotive.com/Budget%20383.htm
Nodular iron crank, 5.7 rods, hypers.....although they have made a mistake in the specs shown on the right (300 cc Dart heads)...
http://www.speedomotive.com/383%20Mighty%20Mouse.htm
Nodular iron crank, forged pistons, 400 rods......
http://www.speedomotive.com/383Forged.htm
Nodular iron crank, forged pistons, 5.7 rods.....
http://www.speedomotive.com/383%20PR...OKER%20KIT.htm
Forged crank, forged 5.7 I-beam rods, forged pistons.....
http://www.speedomotive.com/BUDGET%2...RANK%20KIT.htm
Forged steel crank, forged steel 6" H-beam rods, forged pistons....
http://www.speedomotive.com/383%20AL...RANK%20KIT.htm

As far as rod length, I always refer back to a paper written by Ron Iskenderian, son of the famous "Camfather" Ed Iskenderian. If these guys don't know the straight skinny on rods, then I suspect nobody does......See tech tip #2005.....
http://www.iskycams.com/techtips.php

Cheers Richard.

Ive actually looked at speedmotive before, and their prices are great. However ive found another place (who some one here probably suggested) who are a bit priceyer but looks REAL good quality.

From speed motive i can get a rotating assembly for 600, but with adding the cost of excternal balancing and also the KB pistons it brings it up to 820 or so.

www.gofaststuff.com who you probably know well do an internally balanced package with KB pistons for 900.

spec:
Kit #13055 Eagle SBC 383 Stroker Rotating Assembly, Cast/Steel "INTERNAL" Balance Eagle 3.75 Stroke Crank, Eagle 5.7" Bushed SIR Rods, Keith Black FLAT Top Pistons #KB135 .020, .030, .040, .060 pistons, 11.6:1 w/58 cc heads, 10.9:1 comp w/64 cc heads, 9.6:1 with 76 cc heads, Speed Pro Moly Rings & Clevite Bearings.

for the few extra dollars i think an internally balenced eagle set would be better. what does every one think?

cheers for the link as well... looks like there is no advantage in 6" rods unless im building a high rpm dragster!

as for the block... 1 or 2 piece seal? is all the same price

I'm the one that pointed you to gofast.com.

It is one of the best deals I've found for a rotating assembly after several months of searching.

There is a mis-print in the description for that kit however. The KB-135 pistons are D-Cup with 18cc dish, not flat tops as indicated, and will yield about a 9.6:1 Static CR with a .040 quench using 64cc Vortec heads.

I've talked to gofast and the rods are already clearanced, so if you get the balanced assembly it is ready to drop in out of the box. You can also get press pin rods as an option if you want.

1pc rear main seal is less leak prone than the older 2pc setup. Use a one piece rubber pan gasket as well.

Assembly is plenty strong for a 6000rpm or less engine.

Hats off to Maincap then.

to be honest the d-cup would be better anyway! on british pump gas (around 93 oct. but up to 98 can be bought) a comp ratio of 9.6:1 would probably be about right. if not theres always thicker head gaskets and combustion camber enlarging/polishing

excuse my ignorance, but what are press pin rods?

lobster, I suggest you lose the idea that you can alter compression ratio with the head gasket thickness. Compression ratio is set with combustion chamber cc's and the piston crown configuration. You'll want to use the head gasket thickness to set your squish (0.035"-0.040") after you have your c.r. all figured out.

Lobster,

Piston Wrist Pins are either "fixed" to the rods via a press fit, and then pivot only in the piston, or the rods are bushed and the pin then free to float in both the rod end and the piston.

Some say that a pressed pin offers increased longevity, which may be better for a street engine. A floating pin offers less friction but adds expense and must be retained at each end, side to side, by clips that are installed in the piston.

In my opinion a floating pin offers little increased efficiency for a lower RPM street application, and a pressed pin rod offers increased stability.

Originally posted by techinspector1
lobster, I suggest you lose the idea that you can alter compression ratio with the head gasket thickness. Compression ratio is set with combustion chamber cc's and the piston crown configuration. You'll want to use the head gasket thickness to set your squish (0.035"-0.040") after you have your c.r. all figured out.

Tech,you know that Cometic makes gaskets in thickness's of .027,.036,.040,.045,.051,.060,.065 etc. all the way to .120.Please explain why a thicker gasket won't change the comp. ratio.

Originally posted by erik erikson
Tech,you know that Cometic makes gaskets in thickness's of .027,.036,.040,.045,.051,.060,.065 etc. all the way to .120.Please explain why a thicker gasket won't change the comp. ratio.

It WILL change the c.r., but it will also change the squish. It's easier to control detonation with a thinner gasket to make a tighter squish even though you will increase c.r. slightly than to try to lower c.r. with a thicker gasket and compromise your squish figure.

Originally posted by techinspector1
It WILL change the c.r., but it will also change the squish. It's easier to control detonation with a thinner gasket to make a tighter squish even though you will increase c.r. slightly than to try to lower c.r. with a thicker gasket and compromise your squish figure.

I think people might be reading to much into (squish).It is a little over kill to play with decking the block to come up with the right combo or finding the right piston height .Sure I do this, but not on a stocker type rebuild.As long as I don't have more than 9.25 to 1 on a stock rebuild I really don't get that excited about it.Most people don't have the money and or time in a stocker type rebuild to do this.Now when someone try's to build a 550 h.p. small block on pump gas then I will look at.