Jeff's winter 2012 20v engine build

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dr.occa
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Re: Jeff's winter 2012 20v engine build

Postby dr.occa » Thu Jan 17, 2013 2:01 pm

Jeff, please continue.

I'm interested in what you have to say. I don't mind listening.

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Re: Jeff's winter 2012 20v engine build

Postby burdickjp » Thu Jan 17, 2013 5:10 pm

dr.occa wrote:Jeff, please continue. I'm interested in what you have to say. I don't mind listening.


I appreciate it. Tony had to get his troll in. I'm glad we can now have a good discussion.

Dan, and Tony, brought up a good point. I think next week I'm going to assemble a cylinder on the shortblock and run the piston up to TDC, then put a head on and cast the combustion chamber in silicone. I'll do this both for the AE101 and AE111 heads. This should give a good indication of the squish in the chamber with AE111 pistons. If I do this right it will allow me to put together much better pistons for next year's shortblock. Unless, of course, they happen quickly or this shortblock gets slowed down.
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Re: Jeff's winter 2012 20v engine build

Postby burdickjp » Thu Feb 14, 2013 8:23 pm

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So this is a ( not very good ) cross section of a mold of an AE101 head over the top of AE111 pistons. It's not very good because I have to thin the silicone to get it to flow out and it's hard to work with like that. I would normal do this at TDC, but these pistons stand just BARELY proud of the deck, so this piston is positioned down the bore to simulate a 0.75mm headgasket. The volume this mold fills is sometimes referred to as the "clearance volume".

This mold is cross-sectioned down the middle. On the left is the center intake valve, split in two. On the right it gous between the two exhaust valves. At the bottom you can just barely see the indentation in the mold made by the dowe of the AE111 pistons. This shows how short that dome really is. On the exhaust side you can see the prominent squish, and how far the dome is from it' making a small volume between the dome and the squish. When the cross-section of the chamber gets smaller it slow the travel of the flame. If it's small enough the flame won't propogate, and you get squish! half-assed squish is bad. Well executed squish is good!

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This second picture is a top view of this mold. Here you can see the silicone didn't flow well betwen the intake and exhaust valves. That's fine, we're looking elsewhere in the port anyway. The prominent squish on the intake side is evident here.

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This third picture is a cut made between the intake and exhaust valves. On the left you can see the dome stops well before the curve of the wall of the head. Otherwise the cross section of the volume is quite good from the spark plug, which is on the far left, across the dome. Once again, for the compression ratio that can be achieved from these pistons they offer a damned good clearance volume geometry.

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I flipped this piece over to show the profile the piston dome follows. The cut on the left is the bisection of the mold. The cut on the right goes from the spark plug down the center of the intake squish pad between the center valve and a side valve. The squish there is very prominent. Just to the left of it is the profile of the piston dome. I have heard some say that the cross section leading from the dome to the intake side of the clearance volume is insufficient for flame propogation, specifically on AE111 heads. This shows the cross section is maintained rather well through this area. This is very similar on the AE111 head. This cut also shows the clearance allowed between the AE101 head and AE111 piston.

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This last picture is of the bisection cut of the same mold piece shown above. The exhaust side squish is on the left. Here you can prominently see the exhaust valve relief. It is worth looking at the angle of the relief. This actually says something, believe it or not. On some pistons the valve relief is machined parallel to piston travel. Others, such as this one, is parallel to valve travel. My assumption is that this is based on the relationship between piston and valve travel. It is also worth noting that the clearance volume retains a respectable cross section in a section that tends to be compromised.

What does all of this mean? It means the AE111 piston do very well with the AE101 head. It also shows many areas for improvement, particularly where the dome does not extend to the walls of the bore. This would involve changing the shape of the squish pads and the combustion face of the head quite a bit. The advantage of the AE101 head over the AE111 in this regard is that there is more metal to work with to do so.

So we're going to look at some different pistons for build B ( not this engine but the next one ). Plan of action here is to determine how deep valve pockets need to be based on the profile of these camshafts. This will dictate much of the shape of the dome. The remaining sections of dome will be squish, and the head and dome will be modified to create a cohesively designed clearance volume.
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Re: Jeff's winter 2012 20v engine build

Postby burdickjp » Tue Mar 19, 2013 9:42 am

I ordered up some Clevite rod bearings, as they're a bit thinner than the thinnest OEM bearings, which allows me to widen my rod bearing clearances a bit.
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So I measured them up, and came out with 0.046mm clearances all around. Fantastic. I then plastigauged to check, and came out even across the board.

Installing rods is best done using the bolt stretch method.
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Here's a good looking bottom end.
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Re: Jeff's winter 2012 20v engine build

Postby 8-Eight_Six-6 » Wed Mar 20, 2013 2:31 pm

I really enjoy reading everything. I too am one of those people who like to ask "Why" and have immense attention to detail. Nothing is perfect, no matter how many times I hear "It's proven to work the best xxx way" I always enjoy a challenge and thinking outside the box. Also thank you for posting such detailed information! I look forward to your updates and consider this to be the best build thread on C4AG :) I also measure/check things like 100 times haha it's better to find out you have a problem and admit a mistake off the Dyno then be cleaning up the mistake on the dyno.
Good Luck!

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Re: Jeff's winter 2012 20v engine build

Postby burdickjp » Wed Mar 20, 2013 6:40 pm

8-Eight_Six-6 wrote:I really enjoy reading everything. I too am one of those people who like to ask "Why" and have immense attention to detail. Nothing is perfect, no matter how many times I hear "It's proven to work the best xxx way" I always enjoy a challenge and thinking outside the box. Also thank you for posting such detailed information! I look forward to your updates and consider this to be the best build thread on C4AG :) I also measure/check things like 100 times haha it's better to find out you have a problem and admit a mistake off the Dyno then be cleaning up the mistake on the dyno.
Good Luck!


Thank you very much! I appreciate the kind words. You have to pay attention to the little things or something as silly as piston-to-valve clearance could wreck your day. I'd feel like a dunce if my engine popped before it even made it off the dyno.

I went up to Apex Auto Machine near Chicago to talk about a cylinder head I'd dropped off there a few years ago to have the chambers welded up, because it tends to be something I suck at, and can require fun things, like welding in ovens. They did the welding work on the head, and talked me into finishing it up. There's some good to that, and some bad. Good is a fresh head. Bad is someone else had their paws in the ports ( not Apex ) and we'll have to see how it goes. They should be cutting seats to my specs. I'll be doing final assembly. I think that head is going on this bottom end, with Ferrea valves and PonCams. That should round out this build nicely.
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Re: Jeff's winter 2012 20v engine build

Postby riddleyo » Sun Feb 16, 2014 4:46 pm

Great read, great attention to detail. Yes, I'm raising the dead on this thread. Where are the updates!?

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Re: Jeff's winter 2012 20v engine build

Postby burdickjp » Mon Feb 17, 2014 7:31 am

riddleyo wrote:Great read, great attention to detail. Yes, I'm raising the dead on this thread. Where are the updates!?


I've been putting effort into this thing:

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Re: Jeff's winter 2012 20v engine build

Postby TheOxyMorin » Mon Feb 17, 2014 10:03 pm

Love the research and development, really cool to see the angles of the ports. Hope to see more soon!

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Re: Jeff's winter 2012 20v engine build

Postby riddleyo » Thu Feb 20, 2014 5:51 pm

Pretty cool. Is that just a square of aluminum spacer painted red holding up the COPs? Will they be attached to the valve cover in any way?

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Re: Jeff's winter 2012 20v engine build

Postby burdickjp » Thu Feb 20, 2014 6:02 pm

riddleyo wrote:Pretty cool. Is that just a square of aluminum spacer painted red holding up the COPs? Will they be attached to the valve cover in any way?


That's machinists dye, used to determine the locations of drilled and tapped holes for the COP hardware. Notice there's a center line mark and sweep marks of the hardware hole of the COPs. We then drilled and tapped where the sweep intersected the center line. The squares were then welded to the valve cover.
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