Author Topic: Adnoh's DCP engine  (Read 7626 times)

Adnoh

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Adnoh's DCP engine
« on: July 17, 2010, 08:29:16 AM »
Well as some know I had an engine failure and though I would share the damage and rebuild with everyone.

Adnoh

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« Reply #1 on: July 17, 2010, 08:40:27 AM »
Time to check out the bore. The pre broke piston was in an OEM "A" bore. I have had some debt over the life of this piston as to the stock "A" bore and standard  piston so heres the proff.

I did an out of round and taper test as well seen what bore th eengine willl need to go to.

Adnoh

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« Reply #2 on: July 17, 2010, 08:46:31 AM »
After cleaning up the jug and washing it up it does not look that bad. Looks can be deceiving though. Lets get out the bore gauge and find out.

Adnoh

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« Reply #3 on: July 17, 2010, 08:58:54 AM »
The bore guage does tell the story. Looks like it will need to be bored to a .25 over. The bore is past all most all of it's limits. Time to clean up the head and start collecting data for the P L A N. First the .25 over bore will be entered and the cc's of the head after its cleans and measured.

First I will collect plug data.

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« Reply #4 on: July 17, 2010, 09:09:35 AM »
A few more plug pics

Adnoh

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« Reply #5 on: July 17, 2010, 09:16:00 AM »
Got the plug done time to move on to the head clean up.

Adnoh

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« Reply #6 on: July 17, 2010, 09:26:01 AM »
It looks like the new head cc is 49 and this will be entered into the CR calculation. I will now take the old head gasket and measure it up to add to the spreed sheet for calculation. The ID of the head gasket and the crushed thickness will add cc's to the equation. The bore of the cylinder can not be used. You must use the bore of the gasket.

 Also a few more head pics.

I forgot to get a pic of the gasket cross section. Sorry I will add later. I did get the Number

Adnoh

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« Reply #7 on: July 17, 2010, 10:09:35 AM »
I now have the gasket info to enter for a corrected CR ( compression Ratio). Recap: .25 over bore  for new cylinder volume,head cc of 49, gasket #s for cc. I had a thought of coming up with a easy way to do the math for correction and computation of the numbers. SO I built a spreed sheet to enter the information and made a work book for alteration based on the base line information. The method only required the numbers already taken and the additon of piston crown cc and exhaust port height to top of cylinder. This based on using stock base gasket.

SO I need to find out for this method the cc difference between the piton dome cc and the cylinder volume for the piston crown height. In order to do this I will take a .25 over cylinder and old piston and get to work.

First: I installed a copper wire arond the piston in the ring groove to help seal and hold pistonin place for cc the cylinder.

Second: I installed the piston in the jug ( cylinder) and set the piston crown at the top of the cylinder ( deck).  using a flat bar and bolting it down to the jug using the head studs and some nuts.

Third: I installed a grease seal around the piston land area ( edge of piston crown to top ring) for sealing. Usally the land area is fiquerd into the equation , however for this it is not that critucial.

Fourth: I measured the distance from piston crown edge to deck ( top of cylinder). I willuse this number to calculate the total vloume like I would do for the head gasket and get total CC's.

Fifth: I will get out the fluid and cc using the same method as I did for the head. I then will take this number and subtract it from the volume number to get a correction factor for the piston dome.

Sixth: Enter this into the spreedsheet for the calculation.

The easy method I will call it now can be done by simply mesuring the corrected swept volume of the cylinder by using the bore #  and the top of ehaust to top of deck( top of cylinder). This will give me a correct swept volume in cc's and I can add the gasket, the head, total and then subtract the piston dome and use a formula to find corrected CR.

With this base information in a work book one can change the values and dial in the modafaction and tract changes in CR based on bores, head and deck numbers.  If for some reson you change type of base or use spacer plate a simple change can be made to the calculate the CR effects.

I find this may be usefull for pre port and modafaction change before you blow one up. What if you run the limits of pump gas like I do It will help make slight changed to keep in check. Plus by entering the number ahead of the time you have a working guide to go by. This is just one step in the rebuild process not the only one when you go changing things.  I now have a way to do pre work instead of post work modafactions, I hope.

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« Reply #8 on: July 17, 2010, 10:14:32 AM »
more pics.

Test #1 and #2 had flaws #3 was an accurate number and the one I use.

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« Reply #9 on: July 17, 2010, 10:18:39 AM »
Now I will build the excell speed sheet with the info collected.

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« Reply #10 on: July 29, 2010, 07:30:16 AM »
I tore apart the bottom end and thought I would share some pics. This is gona cost me.

I poped off the drive side case first to clean out some of the chunks as not to tare up the case bottom any more than I have to ( crank turnig with debris wedged in case)  when removing atlernator parts and big ass nut.

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« Reply #11 on: July 29, 2010, 07:33:57 AM »
more pics

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« Reply #12 on: July 29, 2010, 07:37:12 AM »
more pics

hoodlum

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« Reply #13 on: July 29, 2010, 09:06:41 AM »
Wow...What a mess.....No case damage from all of this stuff down there bouncing around?

Adnoh

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« Reply #14 on: July 29, 2010, 03:58:52 PM »
Got pretty lucky. When it let go I had just opened it up off the bottom and it was turning around 7400 rpm and I heard a ting let off and hit the kill switch. It was only about a second but even at a second its Turing 123 revolutions. The crank ran around at least 100 times chewing up the parts. Just imagine the piston top separated from the rest of the piston  and the combustion on the free moving piston top and than the rod slamming it back up a few times. Then the crank locking up from debris. There is some scaring in the bottom but not that bad. The cases are OK. Lucked out. The thing that concerns me more is the bearing OD in the case they show signs of spinning in the case. The drive side may need to be replaced or at least repaired. As I clean them up I will measure and see.