how to block dod holes?
Kurt.. why do you tap and plug them? The topis is about wether to plug or not, and if you guys feel the need to tap and plug them, why? Do you tap and plug all of them, or ust the stuff that's really pushing the envelope?
Enlighten us on this.. with GM puting seals on the valley cover, I'd personally find it hard to see any leaking potential there, if those seals were to leak, why wouldn't the rest?
Let's get a solid answer on this and put it to rest.
Enlighten us on this.. with GM puting seals on the valley cover, I'd personally find it hard to see any leaking potential there, if those seals were to leak, why wouldn't the rest?
Let's get a solid answer on this and put it to rest.
We do it on some LS2 builds. It gives a positive "no leak" seal with minor additional work. If your block is sealed this way, you can run aftermarket covers also(ours are just fabricated plates that are polished).
The end solid answer is, the builder can do it either way. Both ways work.
Kurt
The end solid answer is, the builder can do it either way. Both ways work.
Kurt
o.k., thanks Kurt, that makes more sense.
So the bottom line is this.. use a GM engine cover, and nothing more is needed, use your own cover/some other cover, it's needed.
Neither using the GM cover, or your own cover is of any real advantage, so tapping/sealing the block in this fashion, or using gm's valley cover are both viable and acceptable options.
So the bottom line is this.. use a GM engine cover, and nothing more is needed, use your own cover/some other cover, it's needed.
Neither using the GM cover, or your own cover is of any real advantage, so tapping/sealing the block in this fashion, or using gm's valley cover are both viable and acceptable options.
Teching In
Joined: Jun 2006
Posts: 37
Likes: 0
From: Amarillo, Texas
Even with the factory cover and the factory O-rings, murphy's law still applies "What can go wrong will go wrong". O-rings can fail. The cover could be warped. These holes are a potential leak in the OILING system of the engine. As an engine builder that built 625hp motors with a 2yr warranty, it scares the hell out of me to trust an O-ring(actually 8 of them) to guard against a potential failure! I think plugging the holes is cheap/easy insurance that there absolutely will be no problem there. At least I'll sleep better at night 
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I don't really have an opinion either way but remember even if it leaks oil just drops through the engine back into the pan. It's an internal leak not an external leak in the oiling system.
Originally Posted by Rock_Daddy
I don't really have an opinion either way but remember even if it leaks oil just drops through the engine back into the pan. It's an internal leak not an external leak in the oiling system.
That has been my point all along... and as for trusting the o rings, I dunno, most of the motor's seals are pretty much made of the same mat'l, just in differnet molds... but I don't see anyone worrying about too many of them, not sure why these would be any different. Saying that the factory seals on the valley cover to me is like saying GM doesn't knwo what they are doing... and I'd like to think that htey probably know better 99.9% of the people on here.
Teching In
Joined: Jun 2006
Posts: 37
Likes: 0
From: Amarillo, Texas
Yes the oil will leak back into the pan, but the DOD holes contain the pressure for the entire oiling system!
As far as GM Knowing what they are doing. For the most part I agree, but they have several other factors to consider, such as cost and ease of assembly.
Let me throw this out there. LS2 blocks were built dual purpose - to be used with DOD in certain applications and not in other applications. I'm sure it's simpler to just add the appropriate cover on the assembly line then to have to worry with plugs or no plugs. Saves GM time time/money/confusion.
There is no argument that plugging the holes is the safest. It's up to you to decide if it's necessary. As an engine builder - I know this - if it blows up - That's all people remember - seldom do the spectators know why - or even care - They just know it blew up. I'm not taking any chances.
As far as GM Knowing what they are doing. For the most part I agree, but they have several other factors to consider, such as cost and ease of assembly.
Let me throw this out there. LS2 blocks were built dual purpose - to be used with DOD in certain applications and not in other applications. I'm sure it's simpler to just add the appropriate cover on the assembly line then to have to worry with plugs or no plugs. Saves GM time time/money/confusion.
There is no argument that plugging the holes is the safest. It's up to you to decide if it's necessary. As an engine builder - I know this - if it blows up - That's all people remember - seldom do the spectators know why - or even care - They just know it blew up. I'm not taking any chances.
Banned
Joined: Aug 2006
Posts: 326
Likes: 0
From: North Bay, CA
Originally Posted by Awesomeperfmachine
Yes the oil will leak back into the pan, but the DOD holes contain the pressure for the entire oiling system!
There is no argument that plugging the holes is the safest. It's up to you to decide if it's necessary. As an engine builder - I know this - if it blows up - That's all people remember - seldom do the spectators know why - or even care - They just know it blew up. I'm not taking any chances.
There is no argument that plugging the holes is the safest. It's up to you to decide if it's necessary. As an engine builder - I know this - if it blows up - That's all people remember - seldom do the spectators know why - or even care - They just know it blew up. I'm not taking any chances.
Can't see why this is even an arguement.....part of building performance motors is the elimination of any weakspots or potential's for failure. GM can warrenty(or fight you in court) a blown motor, for a engine builder 20 min of labor to potentially save 10k+ in a blowup is a no-brainer.
Launching!
Joined: Dec 2005
Posts: 214
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From: Brandon, MS
I may be totally wrong... but those holes don't even see oil flow if the DoD manifold is not installed. The oil feeds into the DoD solenoid manifold at the back of the engine (you can see it on the picture of the LS2 block at the top right of the lifter area) then feeds to those lifter holes. No manifold = no oil
Sorry to revive old thread, but a year ago I had to replace cam and lifters for one cylinder from these seals failing and loosing oil pressure. {probable results from a high performance pump} Hind site I should have done a complete tear down because now a year later i have another failed lifter and damaged cam.
This time all new lifter set, cam, rebuild. I will be plugging the dod passages before reassemble. Oh these were not cheap lifters they were Lunati high rpm. This time was not a failure of seal but most likely residual damage from last year when i didn't rebuild.
This time all new lifter set, cam, rebuild. I will be plugging the dod passages before reassemble. Oh these were not cheap lifters they were Lunati high rpm. This time was not a failure of seal but most likely residual damage from last year when i didn't rebuild. 
I found DOD oil ring seals leaking and for years every engine block out of the car I work on gets 1/8 aluminum blue pipe plugs with thread sealant install.
Leaks out of DOD towers cause loss of oil pressure and that's UN-acceptable.
I know GM does a great job with their engines but time and pressure causes the valley cover plate to warp over time (remember there are 6 holes rite under pushing up to 80 plus psi at times and sustain 40 psi at cruising speed pushing that valley cover plate up when hot)
Here is a modern easy way...
http://www.enginelabs.com/news/tech-...delete-afmdod/
Leaks out of DOD towers cause loss of oil pressure and that's UN-acceptable.
I know GM does a great job with their engines but time and pressure causes the valley cover plate to warp over time (remember there are 6 holes rite under pushing up to 80 plus psi at times and sustain 40 psi at cruising speed pushing that valley cover plate up when hot)
Here is a modern easy way...
http://www.enginelabs.com/news/tech-...delete-afmdod/
Kurt "427" hit it on the nose, the only reason I see the need to plug them is for aftermarket valley covers that do no have the o-rings to plug them off. GM stated a while back those o-rings in the valley cover can hold back around 75 psi, and that is when the high pressure relief is supposed to go off.
Now if you are running more PSI than that, than it would be a good idea to plug those with a NPT fitting.
I have never plugged those holes in my 5 LS builds and as far as I know never had any leakage. Now I can see them starting to seep in an older motor with some miles on it, when the o-rings start to get hard/brittle.
What Camster linked is a great simple idea. Probably take you 10-15 minutes to rivet those up, maybe even put a dab of hi-temp rtv over the top and call it good. Unless the engine is torn down to the bare block to the point you can clean the passages, I don't like the idea of drilling into those and risking metal shards clogging up anything.
Now if you are running more PSI than that, than it would be a good idea to plug those with a NPT fitting.
I have never plugged those holes in my 5 LS builds and as far as I know never had any leakage. Now I can see them starting to seep in an older motor with some miles on it, when the o-rings start to get hard/brittle.
What Camster linked is a great simple idea. Probably take you 10-15 minutes to rivet those up, maybe even put a dab of hi-temp rtv over the top and call it good. Unless the engine is torn down to the bare block to the point you can clean the passages, I don't like the idea of drilling into those and risking metal shards clogging up anything.
Last edited by 07NBSChevy; May 2, 2017 at 03:34 AM.
Teching In
Joined: Apr 2017
Posts: 7
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Dod delete When I removed my dod stuff, i changed to a Hummer pan , which has a lower pressure relief valve, and change the oil pump to a standard ls2 which is a lower flow pump. All new lifters and an asa cam. 4.8 cover with o- rings. My running pressures should be lower.
