383 Build Questions

[Joeladam02]

Hi guys.
Please bare with me. I'm a real novice at this stuff, and there's so much information and conflicting opinions on the web that it will make your head spin.
Long story short, I purchased a 70 RR clone for my Dad. What could bring back that nostalgic young man's feeling better than the smell of burning rubber and sound of a high revving Detroit V8?
The car came with an extremely doggy/worn out 1973 400ci. I tried to talk him into the 451 stroker, but he's decided he wants to change it back to a 383 like what came in the car originally.
He wants it to be a nice street car with plenty of low end torque, so he can spin the tires off of it at local car shows, but still run on high octane pump gas, and not overheat the trans without a super high stall.

He purchased an old used 383 B engine and a set of used open chamber 906 heads locally for $300.
The plan is to bore it .030 over, throw in these Keith Black domed pistons KB400-030, clean up the heads (no porting/milling), and use this HMC3245BL Hughes 440 Whiplash Cam.
Car has 3.55 gears, 727 trans, Holley 650 DP carb.

So the question I have is, will this provide sufficient low end torque for his tire burning wants? I'm looking for smiles per dollar with reasonable driveability.
Is there anything else I should be aware of or have done to it? The engine builder isn't really a Mopar guy, but he builds tons of small block Chevy's, and sprint car engines.
Does this sound like a reasonable build that would still run ok on pump gas?
What kind of compression should this make? I tried the compression calculator but I'm unsure of the clearance.
Will it need a high stall torque converter?
Any other suggestions?

I don't expect a miracle here given the scant amount of information I have provided, but any opinion/guidance is greatly appreciated.
Maybe someone out there has performed a similar build.
Thanks.

 

[IQ52]

Let your dad have what he wants. It should run fine on pump gas.

 

[brucedl]

Call Dwayne Porter at Porterracing. He can spec out what you need cam wise and supply cam, lifters, etc. Tell him what you want and he will tell you what you need. Lots of Moparts guys have done business with him and my son bought an intake for his indy headed 508 cu in motor. you will be happy you called him.
http://supercarraces.com/Porterracing.html

A 383 can easily smoke the tires if properly built.

Bruce

 

[383man]

Call Dwayne Porter at Porterracing. He can spec out what you need cam wise and supply cam, lifters, etc. Tell him what you want and he will tell you what you need. Lots of Moparts guys have done business with him and my son bought an intake for his indy headed 508 cu in motor. you will be happy you called him.
http://supercarraces.com/Porterracing.html

A 383 can easily smoke the tires if properly built.

Bruce

Dwayne Porter is very good and one of if not the best head and cam guy there is. I bought my EZ heads from Dwayne and had him do some mild port work. I also have a cam that he speced for my combo and I am very pleased with his work. My pump gas street car will run in the 10's with no trouble through the pipes just like I drive it and alot is because of the cam he speced for me as it makes power and keeps the cyl press low enough for pump gas.

That said the 383 will run very good. I built a mild 383 years ago from a bunch of used parts we had around. It was stock bore and pistons and with 452 iron heads I cut to have a true 9.5 comp. Yes it was an all stock shortblock that I just rebuilt and did not bore it I just honed the cylinders with new rings. I used the old MP .484 cam and used all stock rockers and pushrods. Had the RPM intake and a 750 DP and it was in a 72 Dart with 3.91 gears and headers. Had a 727 and a Turbo Action 10" tight converter. The car weighs 3550 with me in it and that mild 383 ran 12.31 @ 110. I was very pleased at how well it ran for as mild as it was. The 383 will run very good with the right combo. It was the backbone of many Mopar muscle cars. Good luck with it as a nice mild 383 can roast the tires. Heck one New Years I got that 383 Dart out and did a funny car style burnout as I smoked the tires half way up the block and could not believe how much smoke the P245/60-15 street tires layed down. Ron

 

[TekHousE]

I'm fairly certain 383's smoke tyres even when they are stock!

How do I know?? This!:

 

[Joeladam02]

Thanks for the responses guys. I guess the biggest question I have right now is with regards to the KB-400 domed pistons.
According to my calculations, these pistons, the stock heads, and the Hughes 440 Whiplash cam will get me around 9.25:1 compression ratio.
Is that too high for today's 92-93 octane pump gas?
Has anyone else used these domed pistons in a 383?

 

[Banzaiii67]

Thanks for the responses guys. I guess the biggest question I have right now is with regards to the KB-400 domed pistons.
According to my calculations, these pistons, the stock heads, and the Hughes 440 Whiplash cam will get me around 9.25:1 compression ratio.
Is that too high for today's 92-93 octane pump gas?
Has anyone else used these domed pistons in a 383?

I'm not an expert by any mean, Dwayne Porter, 383man and IQ52 know much more than I do about building motors, but what I can tell you from my personal experience is that KB400 or KB162 Pistons on a undecked 383 block are anywhere from .024-.080 down in the hole depending on what year the block is. 1970+ 383 blocks are usually .040 or larger below deck with the KB.

Stock Comp Ht is 1.934
KB Piston Comp Ht is 1.908

Speed Pro also make a forged flat top pistons that is .014 below deck (1.920 CH) that may also work, but you'd want to run a smaller cam as it has no valve reliefs.

Given you have 906 heads (88cc) your compression ratio calculation may be lower given the deck height and head gasket consideration.

If you are going to bore it out, you'll want to make sure you give the builder your piston of choice so he can mock it up and cut the deck height for your desired compression ratio. I also strongly recommend you balance your whole assembly with Hyperutectic pistons as they are known to be off in weight from piston to piston.

That whiplash cam is made for low compression motors, If I recall hughes recommends no more the 9:1 compression due to the amount of cylinder pressure it builds. If you consider that cam seriously, the 107 lobe separation will affect power accessories (if equipped) as the vacuum signal will be low. Also tuning a carb with that lobe separation isn't all that much fun, I'd definitely run a Holley.

Whatever you choose, 383/autos like a decent tight stall converter (11" or smaller with a stall speed of 2500+)

 

[The Horvaths]

Take the time to verify cam degreeing too. For low-end torque, I like to run ~4• advanced. But, that really depends on cam profile. A good builder will guide you well.

 

[1wild&crazyguy]

Call Dwayne Porter at Porterracing. He can spec out what you need cam wise and supply cam, lifters, etc. Tell him what you want and he will tell you what you need. Lots of Moparts guys have done business with him and my son bought an intake for his indy headed 508 cu in motor. you will be happy you called him.
http://supercarraces.com/Porterracing.html

A 383 can easily smoke the tires if properly built.

Bruce

For what he's doing, Dwayne Porter is sooooo not needed.

Sounds like his dad wants stock, it will burn tires.

 

[GTX MATT]

Thanks for the responses guys. I guess the biggest question I have right now is with regards to the KB-400 domed pistons.
According to my calculations, these pistons, the stock heads, and the Hughes 440 Whiplash cam will get me around 9.25:1 compression ratio.
Is that too high for today's 92-93 octane pump gas?
Has anyone else used these domed pistons in a 383?

I come up with 8.95:1 with a .039 fel pro, 9.33 with a .021 steel shim Mr. Gasket assuming a 90 CC chamber. I'd run a steel shim, you'll probably end up at 9.5 once they square the decks and the heads, which is right where you want to be on pump fuel.

 

[Joeladam02]

Resurrecting this old thread looking for some more advice because two and a half years later, we still haven't gotten this car to run very well.

In the meantime, here's what we've done:

• Added a Hughes 2400 rpm 11" stall converter
• Removed the Hughes 440 Whiplash cam because the engine builder told us it was building up way too much cylinder pressure with the domed KB pistons. It had very little vacuum, and was a complete dog down low.
• Replaced it with Comp Xtreme Energy Cam CL21-223-4 recommended by some guy at Summit:
  • Basic Operating RPM Range:1,600-5,800
  • Duration at 050 inch Lift:224 int./230 exh.
  • Advertised Duration:268 int./280 exh.
  • Valve Lift with Factory Rocker Arm Ratio:0.477 int./0.480 exh.
  • Lobe Separation (degrees):110

Changing the cam brought the vacuum up to around 7-10hg, and increased overall performance a bit, but it still is not running very well.

Here's the rest of the story:

• Full electronic ignition
• 3.55 gears
• 906 heads
• Fully adjustable rockers
• Bored .40 over Keith Black hypereutectic pistons
• HP manifolds
• Edelbrock Thunder AVS 650cfm carb
• 1 3/4" custom dual exhaust (no H-pipe)
• 727 TF auto trans
• Edelbrock Performer RPM Intake
• Compression tested 160-180 in all cylinders

Unfortunately I have been unable to get a hold of Dwayne Porter. But we did talk to another 383 guy, and he was adamant that the cam was still too big, and the car still did not have enough vacuum, so we should get a different cam (yet again) with greater lobe separation to increase the vacuum. I'm assuming he is recommending this because most of the rest of the car is pretty mild except for the pistons, and this would be the cheapest way to make it run better by increasing vacuum advance. Introducing mechanical advance does help it run, but it starts to ping and kick back on the starter. I think the 650cfm carb might also be a little small for it.

The old man really wants to be able to chirp the tires from a stop and spin a little without holding the brake. Right now, it won't even spin the 255 15 BFGs when you are stopped on an uphill, and holding the brake. It's a dog.

So, the question is, how do I make this thing run? Given the current setup, would it be wiser to switch to a smaller cam with more vacuum (as recommended by another builder)? Or since we have domed pistons, should we start trying to introduce more airflow by changing the heads, headers, intake, bigger carb, etc.? I'm beginning to think the domed pistons were a bad idea unless you go all out on a lot of the other stuff...Might have been better off with flat tops and the Hughes cam in hindsight...
All opinions welcome. I am getting kind of tired of just throwing parts at this thing, and I'm not sure if dropping $2k on a set of aftermarket heads would really help me out. Looking for streetable bottom end fun, not necessarily 150 mph. Even a 13-13.5 second 1/4 would probably be delightful. Thanks!

 

[moper]

You need to do some basic diagnosis. You did right with the pistons and pulling the Hughs cam. Least IMO. Do a compression test and see where it's at. With the cams you got and run, you still have a problem if it's only pulling 7-10". Were any of the cams actually degreed up installation?

 

[Joeladam02]

You need to do some basic diagnosis. You did right with the pistons and pulling the Hughs cam. Least IMO. Do a compression test and see where it's at. With the cams you got and run, you still have a problem if it's only pulling 7-10". Were any of the cams actually degreed up installation?

One cylinder had approx 160 lbs. the rest had 180 lbs. The cam was not degreed on installation. The local engine builder told us it was not necessary. ???
He also said that the one cylinder with the 160 lbs. compression probably didn't seat the rings well, and it was nothing to worry about.
Also did a smoke test for the vacuum. No leaks. Manifold vac was 8-11. Port was 7-10. It fluctuates a bit. Not sure why. Maybe because of the one cylinder running at 160 compression, when the rest are 180...

 

[beanhead]

Hmm. I use the next cam up from yours the 21-224-4 (230°/236°at .050) in a 440 with an 850 carb, and once I fixed the leaks (from under the valley pan into the chambers) I get a fairly steady 15" vacuum at idle, with my initial timing at 20 deg. Check your plugs for any signs of oil as this indicates hard to detect leaks under the valley pan, or valve guides..depending on how much and how fast the vacuum gauge moves it can mean valve not opening or closing properly

 

[moper]

Your machinist is not a performance guy. He's a 'git-er-dun type and best avoided IMO. One cylinder down 12% is a problem, and not degreeing the cam is what flat rate guys would do. Not someone concerned with real performance. The vaccum needle will bounce because of that one, but not bounce like mad. If it bounces a lot constantly, and/or have lower than expected vacuum, you have another issue. I'm guessing that's from the cam not being degreed. Although if the valve job is crap it will do it too.

 

[Garys1969RR]

Last 383 I built had the 915 heads, comp cams .488/.491 lift hyd cam, dome pistons, Street Dominator intake. It was a real dog for awhile until we installed a new elec ign box. That brought it to life! Ran 13.5 in the quarter mile in a 3800 lb Super Bee! Now with the addition of a 100 Horse shot of nitrous, it runs low 12s. Make sure your ignition system is throwing out strong sparks, and set ign timing to 18 to 20 initial, 38 total mech advance. If that doesn't do it, throw some nitrous at it. Then it will smoke the tires!

 

[moper]

I'll add - when properly set up the 383 is a GREAT engine. I've run the piss out of some and they will very much hold their own with "bigger" and "badder". But they do need some special attention to get really good.

 

[Banzaiii67]

how were the valve adjusted? You said you have adjustable rocker arms, the procedure is different if you have adjustable valvetrain with hydraulic lifters

1 3/4" exhaust seems real small, I suppose that's normal with exhaust manifolds.

 

[Joeladam02]

Thanks for all of the responses. They've really helped to validate my sanity through this ordeal.
I was able to complete a compression test with the Comp XE268H-10 cam today, and the results were stunningly low across the board, considering we have the domed KB pistons. In order of the cylinder numbers, we got: 109,110,110,114,105,105,108,97. I assumed we would be significantly higher than this. Maybe not?
Could not degreeing the cam, or not properly adjusting the rocker arms cause this? I have a feeling neither of these things were done.

 

[miller]

Could not degreeing the cam, or not properly adjusting the rocker arms cause this?

Especially effected by cam timing...degreeing it in is a must. Though, you've got to keep in mind, it's also the overall parts package, needs to work together. Seems your stepping in the right direction, but it makes a huge difference how the build is done, just like that cam set-up.
I'll toss in, I agree the exhaust is too small. Not letting it 'breath'...should be 2 1/4" to 2 1/2" (even better).