Head and pistons

[Polara383500]

I have to rebuild my 68 383! It has 906 heads that are pretty bad! I was wondering if the bottom end is ok can I do a Mancini rebuild kit .030 over and and run stealth heads with mild cam? I hear about the two diff heads one is open and one is closed but just want to know if it will work and if not what do I need to to to make it work?

 

[oldkimmer]

U can use the stealths as long as the pistons u use are not above the deck surface. Kim

 

[Polara383500]

Right now what’s in there are below so if I go back to orig I should be good?

 

[440Coronet500]

You should define your build, what performance level do you want. Compression, cam, converter stall, and rear gear all play a part. 440'

 

[Polara383500]

You should define your build, what performance level do you want. Compression, cam, converter stall, and rear gear all play a part. 440'

Just would like to have a lil cam nothing big would like to keep the rest stock drive train! I have 335’s with suregrip! Just a cruiser to goto some lil car show hangouts! I only was thinking the stealth heads cause there a lil cheaper then what’s out there and heard good things!

 

[PurpleBeeper]

On a related note..... if you're thinking of putting in pistons, then you might as well resurface the crank, put in new bearings and recondition the rods with high strength bolts. That probably only adds another $300 to your build. Also....the ORIGINAL 68/69 383 pistons stuck up above the deck if I remember correctly, so maybe double check what you have right now. Your plan of a mild cam & whatever heads you can put together relatively cheaply, with the 3.55's, sounds like a good plan.

 

[Polara383500]

On a related note..... if you're thinking of putting in pistons, then you might as well resurface the crank, put in new bearings and recondition the rods with high strength bolts. That probably only adds another $300 to your build. Also....the ORIGINAL 68/69 383 pistons stuck up above the deck if I remember correctly, so maybe double check what you have right now. Your plan of a mild cam & whatever heads you can put together relatively cheaply, with the 3.55's, sounds like a good plan.

I have a buddy in fla that has some 906 that has milled work done just needs a valve job!!400$+sh I was gonna by the Mancini rebuild kits that has all new pistons and stuff just have to gets fasteners!!

 

[65-440]

My .030 over 383 is running stealth heads with no issues. Coming up on 4yrs since the build. Pistons are .019" below deck, felpro .040" head gasket... I have to look at my blueprint sheet for exhaust valve to piston clearance, I can remember off top of my head. I think it was something like .009", could be wrong though...comp xe 268H cam, not going to lie it runs really strong. Definitely surprised me coming from a 440.

 

[66Satellite47]

My .030 over 383 is running stealth heads with no issues. Coming up on 4yrs since the build. Pistons are .019" below deck, felpro .040" head gasket... I have to look at my blueprint sheet for exhaust valve to piston clearance, I can remember off top of my head. I think it was something like .009", could be wrong though...comp xe 268H cam, not going to lie it runs really strong. Definitely surprised me coming from a 440.

I hope your piston to valve is much larger than .009. I've run a couple of mine as close as .075 and that was borderline with good valve springs. A better number is .100 in my opinion.

 

[Polara383500]

My .030 over 383 is running stealth heads with no issues. Coming up on 4yrs since the build. Pistons are .019" below deck, felpro .040" head gasket... I have to look at my blueprint sheet for exhaust valve to piston clearance, I can remember off top of my head. I think it was something like .009", could be wrong though...comp xe 268H cam, not going to lie it runs really strong. Definitely surprised me coming from a 440.

With the big valves you had no issues with a stock bottom end?

 

[66Satellite47]

With the big valves you had no issues with a stock bottom end?

Big valves have nothing to do with the "bottom end". Valve size, piston design/valve notch, cam profile, measured piston to valve all need to be checked/measured.

 

[Polara383500]

Big valves have nothing to do with the "bottom end". Valve size, piston design/valve notch, cam profile, measured piston to valve all need to be checked/measured.

Gotcha so going with stealth heads I have to change rod length or just diff pistons?

 

[oldkimmer]

Just pistons. Kim

 

[33 IMP]

906s are oem open chamber heads. Meaning there is an open space all the way around the combustion chamber.
The stealth are closed chamber, meaning there is a flat area on one side of the chamber. This means that you will get a compression ratio increase from the 906 to the stealth.
Supposedly the 383 pistons in the 68/69 383 hipo motors had a positive deck height, meaning that the pistons stuck out of the top of the block a little. They may have supposed to have been, but production tolerances make that questionable.
You probably wont need to change pistons, unless you want to use a cam with lift so big that you dont have enough valve to piston clearance. You certainly wont have to change connecting rods. Pushrods? Maybe. Probably head bolts. If your pistons that you want to use DO stick out of the block, thicker head gaskets solve that problem.
BUT! As 66satellite47 says, EVERYTHING has to be checked when you change stuff.

 

[wagonman]

Looked on 440 source and the only offer 1 style head 80cc and looks to be a closed chamber. I had a set and the valve job was crap. On the 440 in my 68 R/R I went with 906s and larger Milodon valves, pocket ported and a good valve job. KB reverse dome quench pistons and the Comp HE 268. I can run 86 octane without a wimper and it gets 18mpg on the interstate at 75 to 85. By the time you buy the Stealths have them checked and fixed you could use the heads you have for less $$. JMO

 

[66Satellite47]

Since we still don't know what he's got now for parts and how he intends to use the car, advise is impossible. A Source head should work with whatever he has with the correct head gasket and not too large a cam.

 

[65-440]

I hope your piston to valve is much larger than .009. I've run a couple of mine as close as .075 and that was borderline with good valve springs. A better number is .100 in my opinion.

Like I said I could be wrong, my sheet is in my box at my shop. I'll check that # tomorrow! Exhaust is really the one that matters, I remember it being closer than intake but can't remember the exact #....I agree .009" probably isn't accurate!

 

[65-440]

With the big valves you had no issues with a stock bottom end?

Only thing stock on the bottom is block, crank and rods....I forget which speed pro kit i used. I wanted a mild build to run on 87 octane. Compression ended up at 9.44:1....
When I got the stealth heads I immediately disassembled and cleaned. Lapped the valves, put it back together and verified valve install height. Intakes were even as were the exhausts. So far I'm pleased with them. I weighed the cost of buying these vs building my factory iron ones and it didn't make sense to spend money on the old ones. It's a street car not a race car!

 

[Polara383500]

Only thing stock on the bottom is block, crank and rods....I forget which speed pro kit i used. I wanted a mild build to run on 87 octane. Compression ended up at 9.44:1....
When I got the stealth heads I immediately disassembled and cleaned. Lapped the valves, put it back together and verified valve install height. Intakes were even as were the exhausts. So far I'm pleased with them. I weighed the cost of buying these vs building my factory iron ones and it didn't make sense to spend money on the old ones. It's a street car not a race car!

Thanks

 

[65-440]

I hope your piston to valve is much larger than .009. I've run a couple of mine as close as .075 and that was borderline with good valve springs. A better number is .100 in my opinion.

Checked my sheet today, .057" on intake and .137" exhaust....