383 build questions??

[SHARP68]

Going to be building the motor soon for street/strip purpose.  Car has 3.55 rear gears & is a 4 speed.  I have a 383 bored .030/flat top speedpros @ zero deck, stock reconditioned rods with arps, lunati 60303 cam, Stealth heads I need to change locks still & have guides & valves checked..a few questions on these..will that cam cause the valves to hit the pistons @ zero deck & are the stock springs on the stealth's good enough for that cam?  Thinking i should be around 10 to 10.5 to 1 comp. not sure what size headgaskets i should go with yet?  I am planning on running my old Offenhauser 360 intake & 1 7/8 headers.  Still need advice on a carb & dist & ignition?  Thinking a 750cfm not sure what is the best size for this build?  Would the mp electronic dist with the mp box be good enough?  Any ideas or recommendations if i am on the right track would be great!  What would be an estimated hp/tq # for this setup?

[randy73]

Holley's website has a carb calculator, it is a best guess scenario, but should let you know. I am running a 750 on my 383 with headers, cam wieand intake and it runs great.  As for the rest, I do not know.
Except, I have a electronic distributor(summit brand) and 1.5 yrs w/zero problems.

[BSB67]

I did not think that zero deck pistons were available for a stock stroke 383.  What is the piston compression height, 1.920"? and did you actually measure the "zero deck". How much did you have the deck cut to get there?

You should be fine with P to V clearance.  But I would still measure.

Some else would need to answer the question that Knows about the springs on the Stealth's.

If you are truly at zero deck, you'll need a gasket that is .040" thick.

If the Stealth's are at 84cc's I think your compression ratio will be closer to 9.5:1.

Run what ever ignition you have.  Spend the money on a better intake.

Maybe 350 hp,but the devil is in the details

750 Holley would be a good choice.

[SHARP68]

I am sure I am wrong on the zero deck height..they are pretty much stock pistons with no machining on the deck I will need to measure when I install.  I was looking @ the summit distributor so that's good to hear it has worked good.  Do you use the chrome box with that?    I was thinking a 750 carb just having a hard time with what brand..I will look into the Holley.  What is wrong with the offenhauser & what would be a better choice?

[SHARP68]

What would be better to go with a mech or vacuum advance, & is it worth the money for an MSD over summits kit or MP kit?

[randy73]

I am sure I am wrong on the zero deck height..they are pretty much stock pistons with no machining on the deck I will need to measure when I install.  I was looking @ the summit distributor so that's good to hear it has worked good.  Do you use the chrome box with that?    I was thinking a 750 carb just having a hard time with what brand..I will look into the Holley.  What is wrong with the offenhauser & what would be a better choice?

Mine is the plain jane version, I am running a edelbrock and my intake is a dual plane. I would run a dual plan intake and I bet you see better than 350rwhp, I would think 375, but I am guessing here. There are so many proven 383 builds on this site, I am having a tough time coming up with what I want to do.

[SHARP68]

Think I am going to run the edelbrock performer rpm..will it have clearance issues with the hood?

[XH29N0G]

If you run a drop base air cleaner it will fit on a 2nd generation with a reasonable size filter.    I am assuming the 68 and 70 are similar as this is what I use in a 70 with a 383.

Check it with putty on four edges of the filter and close the hood slowly. 

Also make sure your driver's side engine mounts are good.

[SHARP68]

From searching on here looks like the K&N 1 1/4 drop base will work.  I am headed in that direction so hopefully no other fit issues.  Thanks for everyones input so far

[frederick]

For carbs have you looked at the Quickfuel Slayer series?
Very competitive price for what you get.
http://www.summitracing.com/parts/qft-sl-750-vs/overview/
http://www.summitracing.com/parts/qft-sl-600-vs/overview/

Pity I bought a new carb before they came out.


edit: Just found a test which compares several 300$ carbs, including the slayer.
http://www.carcraft.com/techarticles/ccrp_1210_seven_budget_carburetors_tested/

[SHARP68]

Yeah those caught my eye..good article on it.  Anyone here use them? 

[c00nhunterjoe]

With a better intake it should make well over 350 hp. I'm running stock 516's and based on my mph and et's I should be around the 375-380 hp mark. Your compression ratio will be your deciding factor.

[SHARP68]

I found my comp height..it is @ 1.848 so with the stealth heads should my comp be around 9.5 to 1.  If so what size head gasket would bring me a little closer to 10?  What is optimal for running off pump gas..I need to figure this out before I get further into this build?

[mhinders]

I found my comp height..it is @ 1.848 so with the stealth heads should my comp be around 9.5 to 1.  If so what size head gasket would bring me a little closer to 10?  What is optimal for running off pump gas..I need to figure this out before I get further into this build?

With that comp height, no block decking and 80cc Stealth heads, 040 gasket my calcs say that you have about 8.2:1 in static comp. Pistons are .086 down the hole.
If the Stealths are 84cc you are down to 8:1 in static comp, all according to my own spread sheet.

[BSB67]

I found my comp height..it is @ 1.848 so with the stealth heads should my comp be around 9.5 to 1.  If so what size head gasket would bring me a little closer to 10?  What is optimal for running off pump gas..I need to figure this out before I get further into this build?

You should consider stopping now and assessing your situation and goals.  If you are wanting the most performance from the engine, and you really have 1.84 CH pistons, you will be very disappointed.  You are about to give up 60 hp or more.  You should be looking for 10.5:1 with a hp cam.  You cannot get there from where you are now.

What is the part number of the piston?

[SHARP68]

They are the stock cast sealed power 366np.  When I had the machine work done years ago the shop ordered them for the rebuild..that was my fault by not making sure I got a higher comp piston.  What is a good brand to get that is not wildly expensive that would bring
Comp up to 10:1.  Going to run a 750 carb..Rpm intake..lunati 60303 cam..1 7/8 header with the stealth heads.  Can't believe I overlooked this @ the time & not noticing till now   Well if someone needs some stock cast pistons guess they will be up for sale soon. 

[willard]

I was in the same boat - had the same pistons in my 383 and car was dissapointing with 60302 cam and 3.23 gears. When changed to KB400 and stealths milled 0.04" it's a different animal now...
Abandon any mods untill you get right pistons! You may also consider a 438 stroker now...

[BSB67]

I have not looked into a doing a 383 in a long time so maybe something has changed, but I believe that there are no good off the shelf piston options.

On paper, you could go with the 2315 speed pro, cut the block deck to get to zero (probably about a 0.020" cut) mill the heads to 75 cc's or so (probably a .050" cut) and that would put you between 10 and 10.5.  You would need to cut the intake side of the heads about 0.050" so the intake could fit decent, or more if you wanted to run paper gaskets.  The rotating assy would probably need to be rebalanced, and the piston to valve could be a problem depending on cam size.  Then you would need to fly cut the pistons.

I believe that KB has domed, but lower deck piston, but in the end, I don't think that they are any better.

I would contact Diamond to see what it would cost for a semi-custom set of pistons.   Just order the piston with the correct CH to be zero in your block.  Probably cheaper in the long run.

[BSB67]

I was in the same boat - had the same pistons in my 383 and car was dissapointing with 60302 cam and 3.23 gears. When changed to KB400 and stealths milled 0.04" it's a different animal now...
Abandon any mods untill you get right pistons! You may also consider a 438 stroker now...

Why KB did not put a 1.935 CH on that piston is beyond me.  Will they do a custom pin height?

[SHARP68]

The kb400 is rated @ 10:1 with 85cc heads.  Just don't know with the 60303 cam if I will have enough valve clearance.  Don't really want to get into cutting the deck & all that.  They seem reasonably priced also through summit.

[BSB67]

The kb400 is rated @ 10:1 with 85cc heads.  Just don't know with the 60303 cam if I will have enough valve clearance.  Don't really want to get into cutting the deck & all that.  They seem reasonably priced also through summit.

You need to spend a little time figuring out how to calc. the compression ratio.

If you slap that piston in, you will not be at 10:1.  If you use a 0.040 gasket, you will need to cut the block about 0.040 to .050",  If you use a shim gasket at 0.020", you'll need to cut about 0.020"-0.030".

You have to get that piston to within 0.040" of the head (about as close as you should get) to achieve 9:9:1 CR with an 85 cc head.

If you install your crank and a rod/piston in the four corners of the block and measure the compression distance with the 1.848 piston, we can tell you exactly what your CR will be with all other pistons available without cutting your block, or tell you how much you will need to cut the block for any piston choice.

That piston has valve reliefs, so you would be okay with a good size cam I suspect.

[mhinders]

The kb400 is rated @ 10:1 with 85cc heads.  Just don't know with the 60303 cam if I will have enough valve clearance.  Don't really want to get into cutting the deck & all that.  They seem reasonably priced also through summit.

The compression numbers published are often on the high side IMHO. Note that they seem to use a stroke of 3.38 instead of the actual 3.375

With KB400 and 6cc dome, 040 gasket, 85cc heads I get your CR to 9.4:1. Piston 027 down the hole and your quench is 067.
To get to the advertized CR 10:1 a gasket thickness of 0.015 is needed with the KB400 piston, and the quench would be 0.042.

[mhinders]

Why KB did not put a 1.935 CH on that piston is beyond me.  Will they do a custom pin height?

I agree, that would have been perfect...but I guess they think smog-pistons will sell better...

[SHARP68]

It rates the kb400 @ 10:1 with 85 cc the stealth heads are 84.  Could I mill just the heads to get to where I need be or does the deck need to be done also?  If I just milled the heads the intake would need to be cut also right?  Thanks again for all the help.  It's a #s matching block other than it having to be bored .30 I don't really want to cut more on the block. 

[BSB67]

It rates the kb400 @ 10:1 with 85 cc the stealth heads are 84.  Could I mill just the heads to get to where I need be or does the deck need to be done also?  If I just milled the heads the intake would need to be cut also right?  Thanks again for all the help.  It's a #s matching block other than it having to be bored .30 I don't really want to cut more on the block. 

If you deck the block, you'll lose the stamping on the pad unless you direct the machine shop to keep the pad untouched.  Then you'll have a step between the head surface and the pad.

The bore will need to be checked to assure that the piston bore clearance is appropriate and adjusted as needed.  If it is too loose, you might end up with a little piston slap.

You will likely not achieve the desired quench distance if you don't deck the block.  You will need to remove more material from the heads than the block to achieve the same CR.

you should remove the same amount from the intake side of the head as the amount that you remove from both the head and the block.  If you only removing 0.020" total, you probably won't need to mill the intake side

[SHARP68]

Going to be talking to my machinist next week & get this figured out..hopefully I can trade up the stock pistons & get what I need then go from there as far as machine work.  Thank you all again for the awesome input I have received I am learning a lot along the way

[willard]

Probably nobody wants these LoPo 366NP pistons... I have 8 such door stops
When changing pistons double check the bores!!! I went from 366NP (0.030 over) to KB400 also 30 over and get blowby and oil consumption and power down... I hade to ONCE AGAIN dissassembly the block, bore to 0.040 and buy ANOTHER set of KB400, now 0.040 over...

If you want 8 ea 0.030 over KB400 with 500 miles on them, I have them in my garage. But I'm in Poland so shipping's not cheap 

[JB400]

My advice is to let the machine shop advise you on ordering your pistons.  Drop off your block, then order your pistons.

[randy73]

My advice is to let the machine shop advise you on ordering your pistons.  Drop off your block, then order your pistons.

+1

Seen many many people bitch all the time about buying a piston, cam,etc.. somebody recommended and then find out it did not work for their setup.

[SHARP68]

The machine shop is going to be able to trade up the unused stock pistons for what I need..I should be where I need to be now & back on track for my build..

[firefighter3931]

Look at Mancini for a set of Diamond forged pistons....about $200 more than a SpeedPro slug but it will be lighter and should have a better compression height. I recommended these to TuffCat for his 383 build 

http://chucker54.stores.yahoo.net/manciniracing6.html



Ron

[willard]

I'm afraid with open chamber heads or stealths theor pistons gonna suck as they advertise tje CR using 72cc chambers:

"Compression based on 72cc cylinder heads, Contact Mancini Racing for additional information."

so custom height is needed anyway.

[firefighter3931]

I'm afraid with open chamber heads or stealths theor pistons gonna suck as they advertise tje CR using 72cc chambers:

"Compression based on 72cc cylinder heads, Contact Mancini Racing for additional information."

so custom height is needed anyway.

Any flat top piston with a 383 is not going to be ideal. Even a zero deck flat top with valve reliefs will yield low static numbers unless you reduce the chamber volume on the cylinder head. 

You could ask Diamond to build a small dome into the 383 piston to increse the static compression. Diamond does make such a piston for the 440....it's advertised as a race piston for the Edelbrock RPM....comp is 13:1 

By my calculations ; using an 84cc chamber, zero deck piston, .040 head gasket you would need a 10cc Dome to achieve 10.5:1 static compression.


Ron

[BSB67]

The machine shop is going to be able to trade up the unused stock pistons for what I need..I should be where I need to be now & back on track for my build..

Be specific.  What are they going to trade-up to?  Again, there is no good choice.  Some are just worse than others.

[SHARP68]

I am in the process of working with the machine shop to correct this..they are being cool so far as long as it had been 3 years almost..I am not rich so they actually suggested the kb400s & milling the heads to get where I needed to be..diamonds we be great but not in my budget..I will make it work in the end hopefully!

[SHARP68]

I agree there is not very good choices..just have to make due with what we have.  383 is a bum motor by most but I know if you work it right it can be a great reliable street motor.  I am hopefully getting there & again thank you to everyone's input!

[Supercharged Riot]

Im running into issues with finding a good set of pistons as well
Not a lot of support for the 383 compared to the 440

[JB400]

Try finding a set for a 400.  My dad waited 5 years for the right ones

[Supercharged Riot]

Was he building a non stroker 400 Engine?

[JB400]

he was building a stroker.  This was in the 90's.