davep_96

So I ran some tests on my 355 and I found out that I have bad rings in one cylinder and a bad head gasket. I was going to pull the engine anyways to install a new cam and torque converter, but now that I have to replace the rings I'm thinking about getting a 383 crank. I was wondering what all I need to do to put it in. I've heard that some machining has to be done and then I've heard that by using an aftermarket crank none has to be done. Also would I need to get a new oil pump, oil pan, pistons, or anything else? Here is my current setup:

Block is from a 89 pickup. Stock crank/rods, cast flat top pistons, new oil pump(stock), stock oil pan. Need any more info let me know.

A new cast crank is fairly cheap so if that's all I need to buy I might as well do it but i'm on a budget so if I need a bunch of other things I might not be able to. Thanks, Dave.

bummys_hotrod

If you get an after market crank make sure that it will clear with no modification. I got my kit from eagle and I had to do no clearancing. The crank is a 400 crank. Make sure if you decide to do this with only buying the crank that you get the engine balanced. You can use the old pistons, and rods if they are in good shape. Just put some new rings on them and get new bearings while your down there. You can take the pistons and rods to your local machine shop and they can recondition them for you for very cheap. I found it cheaper just to buy the kit because it came balanced and would fit with no modification. 715 bucks from CNC motorsports. 9.9-1 compression with 64cc heads. Perfect to run 93 octane. Good luck with your decision. Just remember take your time and do the job right the first time, you wont have to pull the motor again. Very depressing.

Viprklr

iTrader: (5)

My understandiing is that you can get a 383 with 5.7" rods. No clearancing. To do a 383 with 6" rods though some block clearancing is required. I had to grind down 4 different places on my block at the oil pan lip to make it rotate freely.

New pistons are required if you're going to any kind of 383. The block is opened up 30 thousandths. Rings alone won't do it.

Sonix

iTrader: (1)

Uhh, ok guys focus here.
If you do a 383, from your 355, you're already .030" over. If you can clean up the bore with a hone, that's just fine and dandy - BUT you still need new pistons. 383 pistons are the same BORE as 355 pistons, but have a different pin height. You EITHER need to get 383 pistons (and re-use your 5.7" rods) OR you can get 5.65" rods (from a 400cid application).
I would recommend the new pistons rather than rods...
Remember that the extra stroke will make your compression skyrocket, so you'll want/need dished pistons most likely.

crank - $200
pistons - $150
rings $50
balance job - $200

That's about what you're looking at, not including the other incidentals (fluids, gaskets, etc etc)

Viprklr

iTrader: (5)

Der. Knew that. I'm an

davep_96

Thanks for the replies guys.

So there's no way that I can use the pistons I already have?
What would the compression be with dished pistons? With flat tops? I have stock vortec heads.

Sonix

iTrader: (1)

Didja not read my reply?
If you want to reuse your existing pistons (roughly $100 for pistons, and they are a wear part), you can, but you'll need shorter rods (roughly $200, not a wear item).

Hence why I recommended new pistons rather than new rods.

Keep in mind you will want to balance it either way.

Depends on the dish size. Do the math. Google keith black, they've got a good calculator on their site.

davep_96

Ok so new pistons is the way to go. Am I fine with cast or do I need to get hyper? What is the redline for each type of piston? Does the redline change between 355 and 383 with the same type of pistons?

Sonix

iTrader: (1)

No, there's no set redline for each.
It's arguable, but some would say that the longer stroke would increase the force on the pistons, therby lowering your "redline".

Your redline is more affected by your valve train than by your rotating assembly.

If you do not balance your rotating assembly, i'd put the redline at 6000RPM. If you do, you can rev it as high as your valvetrain will allow (probably around 6000 anyway).

Piston material does not really affect the strength due to RPM. Other parts (read - rod bolts) will fail first. If you have a very high compression ratio, boost, nitrous, that's when you'd want forged pistons.

Hyper is a good middle ground. Stronger than cast, cheaper than forged. They run snug so they don't make noise, etc. The main reason for hyper is that they are very "shiny", which helps reflect heat back into the cylinder. Rather than absorbing it. Hypers also don't grow much, hence the snug clearance. If you're not going to make more than 350HP you're fine with cast. If you're going to push upwards of 450HP i'd definately want hypers. If you're going higher, using nitrous (more than a 150HP shot) or a blower or something, then i'd do forged.

Actually, i'd probably use cast either way, and then just open up my ring gaps. Pistons don't fail from normal use, typically they fail from detonation anyway. Avoid that and you're laughing.

davep_96

oh ok. I always thought max rpm was determined by the material used in the rotating assembly. So then what part of the valve train limits/determines max rpm? And just to make sure we are on the same page, we are talking about max rpm before stuff starts to break, not where the engine makes top hp correct?

What do you mean by balancing? I thought cranks came either internally or externally balanced?

Sonix

iTrader: (1)

Not to be rude- but I'd highly recommend you grab a book by David Vizard and read up. There's lots of info to know, and missing one tidbit can be very expensive. Vizards "how to rebuild your SBC" is my bible for these matters.

balancing - internal vs external is simply a 400cid vs a "every other small block" type of thing.

Your engine will be internally balanced. You will need to have the crankshaft matched to the pistons, rods, rings, etc. If you buy new pistons they will be heavier/lighter than the counterweights on the crank, so they spin it up and check that - then add/remove weight as needed. If you have an externally balanced engine you need to include your flywheel/flexplate in that, because that part is "external" to the engine, but is required during balancing.


Valve train - Mostly the cam. Your engine won't rev any higher than the cam will allow. You need valve springs to keep up with the cam. Your intake manifold must be able to allow the engine to breath (not TPI for example).
Your valve train won't let your engine rev any higher than say 6000RPM with a stock cam and stock valve springs. You could hold your foot on the pedal until it gets tired, it just won't flow enough air.

Your rotating assembly will determine how long it will live at a certain RPM yes. However pistons RARELY die from RPM. They die from detonation, dropped valves, heat, etc etc. Rod bolts/rods are a main failure. Crankshafts rarely snap in half, etc etc.

davep_96

oh you're not being rude. This was my first engine build so I'm still new to the game. One more question. The engine right now has a comp 262h cam and a performer rpm intake. I was going to step it up to either a 274 or 284 cam and a 3000 rpm torqe converter. I want to do that and a 383, but if my budget doesn't allow, which one would give me a faster 1/4 mile time, the 355 with the 284 cam, or a 383 with the cam I have now. Either way I will get the appropriate torque converter and carb. The carb now is a 600 holley.

Sonix

iTrader: (1)

I'd do the stroker setup first.
Do the cam later down the line.

I'd leave the carb for a while, you're not losing much HP due to a slightly undersized carb.