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Twin cam head for the L6 from Derek at Datsunworks

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#1121 Derek

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Posted 18 May 2017 - 02:33 AM

HIPing is great for microporosity but does add cost. Repair welds are easier too. But it is limited to internal defects. Anything with a leak path to the surface will not be affected.

 

That's what they explained to me when I was talking to one of their engineers. My main concern has always been micro porosity in the chambers and deck. My hope is that having the castings HIPed will help me sleep at night. Oh and make for a better casting:)

 

We typically don't specify a hip for anything unless a cut up shows more internal porosity than we can live with. Again, cost driven. Sacrificing a casting for EDM slicing is really the only way to know what you have.

Oh you fancy pants facilities with your fancy pants destructive testing and analysis.

 

The foundry is still a production sand cast foundry and I'm doing one casting at a time right now and can't imagine doing anymore than four at a time so that limits my options.  I'm really confident in my metal flow and risering at this point. The casting has mimicked my flow/thermal analysis exactly so I'm very confident that I'm not getting any huge internal inclusions.


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#1122 clarkspeed

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Posted 18 May 2017 - 07:37 PM

You are awesome! Did I already say that in an earlier post?

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#1123 Derek

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Posted 19 May 2017 - 12:58 PM

Got the head back from the foundry and for the first time I have all the parts under one roof. Figured I'd take a family photo:)

 

 

20170707042123-9817c465-me.jpg

 

Guess I better get busy on the milling machine!

 

 

 

 

 

You are awesome! Did I already say that in an earlier post?

 

Aww you're making me blush.


Edited by Derek, 2 weeks ago.

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#1124 depth

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Posted 19 May 2017 - 07:35 PM

Ohh nice

Edited by depth, 19 May 2017 - 07:37 PM.

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#1125 Derek

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Posted 12 June 2017 - 03:00 PM

I'm no expert but isn't there supposed to be something in there?

 

20170707041242-6ddbb730-me.jpg

 

 

Drove the car Saturday nite to pick up a pizza. Ran great. beat it as usual. Parked it overnight. Got up the next morning and fired it up ran a little rough then it ran a lot rough.  Towed it to the shop, pulled the plugs and number 6 shot a geyser of coolant. 

 

20170707041245-8fb1d829-me.jpg

 

The seat beat the chamber until the head deformed and cracked. 

 

Alas poor prototype head....You served me well.  Sniff.


Edited by Derek, 2 weeks ago.

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#1126 JavelinZ

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Posted 12 June 2017 - 04:45 PM

Dang, that sucks. Can't say I've seen that failure very often. Didn't Mazworx install the seats? Then again, experiments, science, and stuff...


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#1127 theczechone

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Posted 12 June 2017 - 05:02 PM

Ouch, do you think the fit was out of spec?

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#1128 Derek

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Posted 12 June 2017 - 05:05 PM

Dang, that sucks. Can't say I've seen that failure very often. Didn't Mazworx install the seats? Then again, experiments, science, and stuff...

 

 

Yea they did but I'm very hesitant to put any blame their way as they most definitely know what they are doing. But I will say I can't come up with any scenario where it was a problem with the casting.


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#1129 Derek

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Posted 12 June 2017 - 05:11 PM

Ouch, do you think the fit was out of spec?

 

Could be. Going to be tough to get an accurate measurement now that the bent valve has had it's way with the bore. The head was never overheated so I don't think it was anything on my end.

 

I was going to change it out at some point with a production head anyway but realistically with the current demand I have for heads it will be 6 months or more before I'll be able to make it happen.  Paying customers come first:)


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#1130 NewZed

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Posted 12 June 2017 - 05:13 PM

Just puzzle-working, but if it ran well when you shut it off in the evening then ran rough when you started it in the morning, doesn't that imply that the seat fell out over night, or just after you shut it down?  The valve was open, the seat dropped, the valve started beating on it as soon as you restarted.

 

And, just for consideration, it seems possible that the valve seat area cracked and let the seat loosen.  I think I see the coolant to chamber crack in your picture, but have you checked the seat area for cracks.

 

Just trying to get the story filled out.



#1131 Derek

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Posted 12 June 2017 - 05:18 PM

Just puzzle-working, but if it ran well when you shut it off in the evening then ran rough when you started it in the morning, doesn't that imply that the seat fell out over night, or just after you shut it down?  The valve was open, the seat dropped, the valve started beating on it as soon as you restarted.

 

And, just for consideration, it seems possible that the valve seat area cracked and let the seat loosen.  I think I see the coolant to chamber crack in your picture, but have you checked the seat area for cracks.

 

Just trying to get the story filled out.

Yep that's the way it went down. 

I figured the seat either cracked after it cooled or simply dropped out of the bore because it was oversized. I did a cursory inspection before I left the shop and didn't see any cracks in the casting.


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#1132 rturbo 930

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Posted 12 June 2017 - 07:47 PM

Awww. Man, that really sucks. Time to make it a display piece?

 

I was going to change it out at some point with a production head anyway but realistically with the current demand I have for heads it will be 6 months or more before I'll be able to make it happen.  Paying customers come first:)

 

How many people are on the waiting list? Is there really that much demand? Not knocking the product obviously, but knowing how cheap Datsun owners are, and what this sort of thing costs, figured it would be just a few people buying. Great that there's a demand though.


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#1133 Tony D

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Posted 12 June 2017 - 11:21 PM

Honestly the Corvair 140's do this regularly.

Growing up Air Cooled my standard valve seat installation method was to give a slight interference fit into a hot head (200~250F) with the valve seats in LN2. A jig on a manual arbor press was enough to seat the valves with the slight interference fit--they did not drop in, they were a press-fit even with the differential.

Never dropped a seat.

I think your crack came from the valve beating up into the head as well as other non-compressibles. Our old 77 Impala did this  at 41,000 miles...valve head dropped  off at the friction weld to the stem and sat atop the  piston till I  cranked it at the end of the day...then it was 'rap rap rap' and out the tailpipe comes the  antifreeze... No seat to drop in a cast iron head as I recall but damage was very similar as the valve poked through the  casting to the water jacket, then the valve embedded itself into the piston and beat a bunch of things severely inside the combustion chamber. Not unheard of a valve seat cracks and drops out on it's own as well. Generally on the Corvairs you find if the seat has  dropped it's hanging on the  valve head like a crown. I think you had a valve failure that killed everything else.

Given the cost of the head production, it warrants a casting repair to return it to service.

If you won't, I would. At least give it a shot and see if it can be salvaged. Best this prototype get as many hours and reveal things like this to alter later production models.

Let me know, there are plenty of casting repair places in L.A., and I got an L28 Block going out for billet main caps and a block girdle so it's prepped for 10,000 rpm operation may as well put a head on that will support it. Prototype or not!


Edited by Tony D, 12 June 2017 - 11:31 PM.

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#1134 Derek

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Posted 13 June 2017 - 03:18 AM

Awww. Man, that really sucks. Time to make it a display piece?

 

 

How many people are on the waiting list? Is there really that much demand? Not knocking the product obviously, but knowing how cheap Datsun owners are, and what this sort of thing costs, figured it would be just a few people buying. Great that there's a demand though.

 

Surprisingly there are more than I would have imagined. Rebello has 2 more sold besides the one I'm doing for him now and I have 3 people who either enjoy wasting theirs and my time or are ready to pull the trigger on one.

 

 

 

Honestly the Corvair 140's do this regularly.

Growing up Air Cooled my standard valve seat installation method was to give a slight interference fit into a hot head (200~250F) with the valve seats in LN2. A jig on a manual arbor press was enough to seat the valves with the slight interference fit--they did not drop in, they were a press-fit even with the differential.

Never dropped a seat.

I think your crack came from the valve beating up into the head as well as other non-compressibles. Our old 77 Impala did this  at 41,000 miles...valve head dropped  off at the friction weld to the stem and sat atop the  piston till I  cranked it at the end of the day...then it was 'rap rap rap' and out the tailpipe comes the  antifreeze... No seat to drop in a cast iron head as I recall but damage was very similar as the valve poked through the  casting to the water jacket, then the valve embedded itself into the piston and beat a bunch of things severely inside the combustion chamber. Not unheard of a valve seat cracks and drops out on it's own as well. Generally on the Corvairs you find if the seat has  dropped it's hanging on the  valve head like a crown. I think you had a valve failure that killed everything else.

Given the cost of the head production, it warrants a casting repair to return it to service.

If you won't, I would. At least give it a shot and see if it can be salvaged. Best this prototype get as many hours and reveal things like this to alter later production models.

Let me know, there are plenty of casting repair places in L.A., and I got an L28 Block going out for billet main caps and a block girdle so it's prepped for 10,000 rpm operation may as well put a head on that will support it. Prototype or not!

 

The valve is bent a bit but still in one piece. So the problem was most def the seat.

 

If this was a V3 head I would repair it without a thought but since it ultimately was heading for the shelf anyway I'm not going to put anymore resources in it.


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#1135 theczechone

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Posted 13 June 2017 - 04:18 AM

The highest temperature of the head would occur after you parked it, as basically there is no more cooling going once the water pump stops spinning. My guess is that's when the valve seat dropped just like stated before. 

Would be interesting to find out the residual press fit on the seats that have not failed. 

 

In the past i have done a study on different materials used for the small end bushings. I varied the interference level and the material. The small end bushings i was evaluating were made of bronze which has a relatively low yield strength. The rods were heated 400F and the bushings were cooled in liquid nitrogen to reduce the possibility of material removal during the installation. THen the assembly was heat cycled a few times. The bushings were then removed with more liquid nitrogen and measured. It turned out that the bushings with highest initial press had the smallest residual interference. My best explanation was that the bushings yielded under the stress. 

This should not be the case with the seats, however the yield strength of the aluminum is also not the highest. 

 

If you could freeze out the "still functional" seats you could establish an "installed back pressure" and see if it's too high and could cause the casting to yield. 


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#1136 Derek

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Posted 13 June 2017 - 05:09 AM

If the seat doesn't drop in then you are removing metal. It may be at the sub atomic ( I pulled that out of my butt)  level but it's removing metal non the less. So a press fit on an aluminum production head with massive process control is  safe and predictable. On a custom or welded head getting the head heat soaked  ( not just hot) and chilling the seats with nitrogen or equivalent seems like is the only way to ensure a proper fit. Otherwise you are broaching the hole.

 

After more digging and analysis I'm leaning towards incorrect installation. But without a ton of checking and analysis it's really hard to say for sure. The car never runs hot even with the air on in traffic and this was in the evening. I have Speedhut gauges with warning lights so I'm sure I've never overheated it. The valve seat bore is not cracked.  So eliminating those two things really points to defective seat/improper installation.

 

The new heads with the HIP process will most assuredly improve the predictability and resilience of the metal. V3 machines like it's 6061.


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#1137 Tony D

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Posted 13 June 2017 - 06:03 AM

We always used a jig and hand arbor press to seat them. You can feel if they are getting that ball underneath (like you say, broaching) and can stop... if you use a hydraulic press, they just hammer them in there and 10,000 miles  later they're loose and pumping up and down.

Well, I'll repair it. Send it on!

BTW was this a new valve...

At least that  restores my faith in Honda Parts...knowing the valve head didn't drop off!


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#1138 Derek

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Posted 13 June 2017 - 07:32 AM

We always used a jig and hand arbor press to seat them. You can feel if they are getting that ball underneath (like you say, broaching) and can stop... if you use a hydraulic press, they just hammer them in there and 10,000 miles  later they're loose and pumping up and down.

Well, I'll repair it. Send it on!

BTW was this a new valve...

At least that  restores my faith in Honda Parts...knowing the valve head didn't drop off!

 

 

Actually it was a generic aftermarket valve.

 

I think I would regret not hanging on to my first cylinder head so It will be cleaned up an live it's life out in the comfort of a dusty corner of my office:)


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#1139 pkz

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Posted 13 June 2017 - 08:07 PM

What material are your valve seats made of? And what interference did you spec?



#1140 Derek

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Posted 14 June 2017 - 02:07 AM

What material are your valve seats made of? And what interference did you spec?

Chrome moly

I didn't specify a fit. I left that up to them. 


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