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Update on the 2x4 installation on the 389

 
Old 05-15-2019, 07:36 PM
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DZAUTO
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Default Update on the 2x4 installation on the 389

Well, here is a testament to the dependability of a properly rebuilt 2x4 setup. Over 30yrs ago, I put the complete setup in a plastic bag with a packet of desiccant, put them on a shelf and pulled them off the shelf a few weeks ago to put on the 389 in the 51 Chevy------------which is where they started life over 50yrs ago.
I bolted them on, connected everything, put gas to it, positioned the distributor where I felt it should be be, and lit a fire to it.
These old WCFB carbs are simple, easy to rebuild and are VERY dependable.

About 1hr ago, I lit a fire in the rebuilt (new pistons/rings) 389.
I just have to get it tuned, dialed in and get the timing adjusted. But so war, it seems pretty darn close!

I just have these small air cleaners on temporarily to make access for tuning easier. Once it is dialed in, the Batwing will go on permanently.

https://www.youtube.com/watch?v=rqXg...ature=youtu.be

As soon as it's dialed in, it will return to regular daily driver duty.
Ya, ya, ya, ya, ya, ya, I know, it is an ugly, rusty POS--------------and that is how it will remain--------------but mechanically, it will always be ready to rock and roll.

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Old 05-15-2019, 08:54 PM
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Tom, be careful not to scratch the paint with the hood on top of the car.

It will soon be ready to fool the kids stoplight racing. They will be terribly embarrassed.

Last edited by 68hemi; 05-15-2019 at 08:56 PM.
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Old 05-15-2019, 09:18 PM
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Neat sleeper, but I was expecting to see a light blue 389.The kind with the starter on the driver's side of the block.
I have a blown 355 that is fresh and would fit nicely under the hood of this. Because the truck is my wife's, I have some persuading to do first.
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Old 05-15-2019, 10:59 PM
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Originally Posted by 2tired View Post
Neat sleeper, but I was expecting to see a light blue 389.The kind with the starter on the driver's side of the block.
I have a blown 355 that is fresh and would fit nicely under the hood of this. Because the truck is my wife's, I have some persuading to do first.
According to the SPEED PRO piston chart, a .060 over 383 is 389. Which makes sense, because on most V8 engines, a .030in bore will net about 6cubes. Since a 383 is already a .030 over, then the addition of 6 cubes to 383 would make 389 (I always though it would be 388). Thus, that makes it only 11cubes shy of a SB400. Before I broke the piston (replaced all 8 pistons/rings), it ran like a scalded dog. Hopefully the 2x4 setup (which replaces a Z28 intake and Q-jet) will also run great. But anyway, I don't care, I just wanted my old 2x4 setup back on the 51 where it began 50+yrs ago. The only difference is that now it will have a Batwing.
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Old 05-15-2019, 11:06 PM
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DZ, very cool toy and manifold. If you already broke a piston there must have been detonation going on. Watch your tune really careful. The 383 combos are more prone to detonate than the 327.
Might be smart to invest in some dyno time and have them help tune the fuel curve from zero to max RPM just to keep it safe.
Unfortunately Detonation can take out an engine in less than 15 seconds run time.
I hope it runs stronger and gives you more smiles than ever.
Mark
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Old 05-16-2019, 12:17 AM
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Originally Posted by Westlotorn View Post
DZ, very cool toy and manifold. If you already broke a piston there must have been detonation going on. Watch your tune really careful. The 383 combos are more prone to detonate than the 327.
Might be smart to invest in some dyno time and have them help tune the fuel curve from zero to max RPM just to keep it safe.
Unfortunately Detonation can take out an engine in less than 15 seconds run time.
I hope it runs stronger and gives you more smiles than ever.
Mark
That is exactly what happened. I posted all the information in a previous discussion, but here are pictures of the offending piston again.






EVERYTHING in all the bores (it only had about 3000mi on a TOTAL build) looked good, so I just put it back together with the same type new pistons and moly rings.
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Old 05-16-2019, 07:31 AM
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Very cool Tom, I just subscribed to your channel and look forward to more vids from you. That car is going to get more thumbs up than a C7. 2x4 on on s/b Chevy is just about as cool as it gets in my world.
Good Luck
Earl
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Old 05-16-2019, 08:29 AM
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Originally Posted by DZAUTO View Post
According to the SPEED PRO piston chart, a .060 over 383 is 389. Which makes sense, because on most V8 engines, a .030in bore will net about 6cubes. Since a 383 is already a .030 over, then the addition of 6 cubes to 383 would make 389 (I always though it would be 388). Thus, that makes it only 11cubes shy of a SB400. Before I broke the piston (replaced all 8 pistons/rings), it ran like a scalded dog. Hopefully the 2x4 setup (which replaces a Z28 intake and Q-jet) will also run great. But anyway, I don't care, I just wanted my old 2x4 setup back on the 51 where it began 50+yrs ago. The only difference is that now it will have a Batwing.
The 2x4s will work great Tom - it wasn't that long ago that Devildog and 427Hotrod built a "sleeper" 283 that cranked just shy of 500HP (per dyno chart) with dual WCFBs on it...they rock!
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Old 05-16-2019, 08:44 AM
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Thanks for posting the pics of the cratered piston. Everyone "knows" what detonation can do, but it makes a big impression to see actual damage. That Speed Pro piston is probably forged. There are a lot of 383s out there with hypereutectic pistons. Those can shatter like glass - could be a whole lot messier than what you had to deal with.
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Old 05-16-2019, 11:52 AM
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Old 05-16-2019, 02:03 PM
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The Piston In Tom's Picture is a Hypereutectic Sealed Power Piston. Those were tested very hard prior to release. Testing included running strong engines on Nitros, 383's I beileve were tested up to 650 HP, I would have to pull out the old dyno reports.
The last test they did prior to approving a new part was to advance the timing and watch when the piston failed in detonation.
They can hold lots of horsepower but detonation can break an anvil. I have seen ring lands blown apart like that but normally it was in an engine where they started it with excess Starting fluid.
Normal cylinder pressure in a 350 Chevy at wide open throttle is only about 600 PSI. Detonation can run the PSI well above 3,500 PSI and that breaks parts.
A forged in this engine most likely would have failed also. That piston saw some deadly detonation. One piston only Tom? Did the others show similar damage?
Mark
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Old 05-16-2019, 03:17 PM
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Tom, I was around when those pistons were developed. They went through extensive testing including many hours of dyno time at wide open throttle and even Nitros testing.

I went back and found the old Dyno charts from the 383 tests done.
The engine was not a wimp it was a very healthy 383 for that time. I am guessing this was the mid 90's because all the results were faxed to me and my copies are of fax sheets.
Technology has changed a lot in the past 25 years.

The test mule was a Bowtie block, 3.995 bore, so these tests are actually 377 engines not 383 which would be .030 over.
Cast 400 factory crank.
Bowtie Small Port Intake single plane
72 cc Dart II Sportsman Cast Iron Heads
830 CFM Holley
Lunati Cam 260/268 with .544/.567 Lift
91 Octane fuel
Pistons were Hypereutectic and bore clearance was .001 to .0015 part H106P with a ..200 dome. note says these were sized -.005 to accomodate the new block.
When you have a piston factory right there they would make exactly what was needed for the test. No need to waste boring the block to fit when you can make a piston to fit.
Top ring gaps were set at .016 or for nitros applications .018.

This engine in stock form ran strong.
RPM Torque HorsePower Nitros HP
3,400 457 296 299
5,200 459 455 587
6200 406 480 680
6600 366 460

By the time they tested on Nitros the engine had 180 dyno pulls on it.
They also did a wide open throttle test where they put the engine at Max HP and ran it for extended periods, Like 100 hours to test durability.
This was in the old days, many of these tests today are done inside a computer but in the old days it was old school dyno time.

I noticed the Moly Coat was still on your piston skirts Tom, that stuff really helps avoid any piston scuff issues.
Mark

Last edited by Westlotorn; 05-16-2019 at 03:20 PM.
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Old 05-16-2019, 03:47 PM
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Originally Posted by Westlotorn View Post
------------------------------------------------------------------------------------------------------------------------------ One piston only Tom? Did the others show similar damage?
Mark
The first thing I did was a compression test (FINALLY, after sitting for 6yrs). No.1 was about 60psi and the other 7 were right at 180.
BUUUUUUUUUUUUT, to be able to inspect for ANY damage on the other 7, BOTH heads and all 8 pistons had to be pulled. Upon very close visual inspection of all pistons, I could not find any obvious damage or cracks. SOOOOOOOOOOOOOO, the decision was made to just replace all 8 pistons/rings---------------------and of course, put my old 2x4 setup back on. NO REGRETS with the way I went.
I think the only thing which will look weird will be the Batwing-------------------only a handful of 56-57 Chevy guys will know what it is. Everyone else is probably going to wonder what the heck is that thing!!!!!!! I don't care, I just wanted one! And the good part is that it will fit!!!!!!!!
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Old 05-16-2019, 05:13 PM
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Tom, normal detonation takes out the top ring land, yours is intact with damage below the top ring land which made me think of some I saw with Starter Fluid damage.
One other thought would be to look at the top ring from that piston to see if it had butt marks on it at the ring gap.
Glad you are going back together with no other damage to fix.
Mark
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Old 05-16-2019, 06:06 PM
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Do you plan on running the quads progressive or parallel?
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Old 05-16-2019, 09:58 PM
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Originally Posted by Westlotorn View Post
Tom, I was around when those pistons were developed. They went through extensive testing including many hours of dyno time at wide open throttle and even Nitros testing.
~snip~
Top ring gaps were set at .016 or for nitros applications .018.
~snip~
Mark
I'm relieved to see that those pistons went through that level of testing during their development as they are what I chose when building my 406. But that ring gap surprises me, my top rings were butting and broke the land between top and second ring on one and probably fractured several more in just a few thousand miles. I replaced them all and based on a recommendation here, opened the top ring gap to 0.023".
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Old 05-16-2019, 11:32 PM
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65 Air Coupe, I suspect your top ring issue had to do with the brand of pistons. Silvolite, Keith Black Hypereutectic pistons need the large ring gaps.

Sealed Power Hypereutectics and every other brand I know of use the same ring gap as a stock aluminum piston.
Many OEM pistons today are Hypereutectic. Sealed Power has contracts with Mercury Marine, even those engines use stock .004 per inch ring gaps.

Keith Black locates the Top Piston Ring closer to the piston head exposing it to more heat. That is the only reason they use large ring gaps in the Hypereutectic pistons they make.
Large ring gaps are unique to pistons with the Top Ring located higher on the piston.
The benefit is a little less un burned fuel with each exhaust. The Down side is more blow by any time you are not at full throttle. Minor difference mind you not a big deal with either piston you choose.
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Old 05-16-2019, 11:44 PM
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Originally Posted by Drothgeb View Post
Do you plan on running the quads progressive or parallel?
I'm going to start out with progressive linkage. But, with an engine this big (remember, the biggest engine to get the 2x4 carbs was a 283), it may be necessary to bring on the front carb at the same time. We'll see how it runs when I finally drive it out the door.
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Old 05-17-2019, 08:57 AM
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Originally Posted by DZAUTO View Post
I'm going to start out with progressive linkage. But, with an engine this big (remember, the biggest engine to get the 2x4 carbs was a 283), it may be necessary to bring on the front carb at the same time. We'll see how it runs when I finally drive it out the door.
I ran my Edelbrocks progressive last year, and never could get them right. Got them parallel right now. Runs much better, but the throttle is very touchy. This is on a 383.

Good luck with yours. Love the patina. Thatís a real sleeper!
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Old 05-17-2019, 08:58 AM
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Originally Posted by Westlotorn View Post
65 Air Coupe, I suspect your top ring issue had to do with the brand of pistons. Silvolite, Keith Black Hypereutectic pistons need the large ring gaps.

Sealed Power Hypereutectics and every other brand I know of use the same ring gap as a stock aluminum piston.
Many OEM pistons today are Hypereutectic. Sealed Power has contracts with Mercury Marine, even those engines use stock .004 per inch ring gaps.

Keith Black locates the Top Piston Ring closer to the piston head exposing it to more heat. That is the only reason they use large ring gaps in the Hypereutectic pistons they make.
Large ring gaps are unique to pistons with the Top Ring located higher on the piston.
The benefit is a little less un burned fuel with each exhaust. The Down side is more blow by any time you are not at full throttle. Minor difference mind you not a big deal with either piston you choose.
Mine are Sealed Power with Perfect Circle rings. What compression ratio were the test motors running? I'm at 11.0:1 but have no evidence of detonation and the rings were clearing butting at their ends. Marks in the cylinders also confirm that. I suspect this is a mystery to which there is no answer. At a 0.023" gap I'm still over 190psi cranking pressure so I apparently didn't give up much in terms of blow by.

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