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Quote:
Originally Posted by manbridge 74 View Post
Post a shot of valves sitting in head? No need to re-install springs.

Be interesting to see how much valve recession over the years.

Here's another view, with one of the cleaner heads (#6). Valves are still dirty, as I intend to replace them.









I suppose I should ask, what is valve recession, and how do you see and/or measure it?

Cheers-

Jake
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'73 911 T Coupe Silver Metallic (in progress...)

Sometimes nothin' can be a real cool hand...
Old 10-01-2017, 06:24 PM
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Quote:
Originally Posted by Trackrash View Post
Its hard to know exactly what you will end up with until assembly. That is when you do the actual measurements to verify your calculations. There are lots of variables. Then there are adjustments that can be made, like cylinder base gaskets.

First find out if your calculations represent real world results. There are those on this board who have done this mod. Hopefully some will chime in.
Yep- makes sense. I'll definitely re-run all the measurements/calcs when I get to that phase.


Quote:
Originally Posted by Trackrash View Post
Have you done the calculations using 2,2 E pistons. Those might be closer to what you want.
According to the chart, 2.2E pistons have a dome volume of 28.4, which results in a CR of 9.64:1. That's much closer to what I was thinking. Perhaps I was a bit over exuberant on my purchase of the 2.2S pistons! Anything with an S just sounds so cool


Quote:
Originally Posted by Trackrash View Post
Are you seriously going to use OE 2,2 pistons?
Yeah, that was the plan. Can I infer from the question that maybe you'd recommend otherwise? The pistons are coming from a well-known Pelican, who I have no reason to doubt when he says they're totally in-spec. Obviously, I'm new at this- but I'd imagine that the critical specs are the ring-groove gaps. Any other suggestions on what to verify before re-using them? (assuming I stick w them...)


Quote:
Originally Posted by Trackrash View Post
What you might want to consider are JE 9,5 to 1 pistons. That is what I used on my recent build. I was able to actually get 9.8 to 1 after I did all the assembly and took my measurements.
Great suggestion. I'm seriously considering it. I love the idea of re-using the OE 2.2S's, but at the same time, there's some piece of mind that comes along with new parts. Did you end up using your stock cylinders?


Quote:
Originally Posted by Trackrash View Post
EDIT: I just read in Bruce Anderson's book "The change in stroke will increase the compression ratio by about 0.55 above what it would have been in the shorter stroke engine.
Therefore the S in the 2,2 was 9.8 to 1 so in the 2,4 it would be 10.35. Looks to match your calcs.
The E piston from the 2,2 was 9.1 so in a 2,4 would be 9.65, right where you want to be.
Great catch! I missed that as well. Does seem to confirm my initial math, at the least...


Thanks again for the great feedback.

Best,

Jake
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'73 911 T Coupe Silver Metallic (in progress...)

Sometimes nothin' can be a real cool hand...
Old 10-01-2017, 06:48 PM
  Pelican Parts Technical Article Directory    Reply With Quote #42 (permalink)
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Valve recession is when the valve sinks into the head due to seat and or valve face wear. The seat and valve can be re-ground but this positions valve even lower which is a real hindrance to low lift flow according to people who flow heads for a living. I imagine slightly less compression as well.

You can search this forum for an idea of how much new valves stand “proud” in new seats.
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Old 10-01-2017, 07:38 PM
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Jake, are you in Washington?? Your location says "SF Bay" but the license plates say otherwise.
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Old 10-02-2017, 07:31 AM
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I think I would go with the JEs or other new pistons. You are talking about 45+ year old pistons with the 2,2s. They MAY be OK, but for a little extra money, new would be the way to go IMO.

It really comes down to your expectations. If you just want to get a motor running or do you want a freshly rebuilt motor that will last for a generation?

The other issue is the iron cylinders you have. They might be OK for a mild street driven motor. Are yours in spec? If you have to hone them, then the old pistons may no longer be a match.

Maybe others that have used iron cylinders in a hotrodded motor will chime in. If you order new pistons, make sure you let them know what type of cylinder you have.

BTW, I used my old cylinders. HOWEVER, they are Mahle nicasils.
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Old 10-02-2017, 08:08 AM
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Quote:
Originally Posted by manbridge 74 View Post
Valve recession is when the valve sinks into the head due to seat and or valve face wear. The seat and valve can be re-ground but this positions valve even lower which is a real hindrance to low lift flow according to people who flow heads for a living. I imagine slightly less compression as well.

You can search this forum for an idea of how much new valves stand ďproudĒ in new seats.
Good to know- I'll check it out. According to receipts there was some head work way back when, so I can imagine the valves have receded a bit.


Quote:
Originally Posted by flat6pilot View Post
Jake, are you in Washington?? Your location says "SF Bay" but the license plates say otherwise.
The car had been in the Bay Area its whole life, until it found its way to a dealer outside of Portand OR, where I picked it up while living in Seattle. I've since moved back to the Bay Area, so it has been a homecoming for both of us Wish I could find the original plates somehow...


Quote:
Originally Posted by Trackrash View Post
I think I would go with the JEs or other new pistons. You are talking about 45+ year old pistons with the 2,2s. They MAY be OK, but for a little extra money, new would be the way to go IMO.

It really comes down to your expectations. If you just want to get a motor running or do you want a freshly rebuilt motor that will last for a generation?

The other issue is the iron cylinders you have. They might be OK for a mild street driven motor. Are yours in spec? If you have to hone them, then the old pistons may no longer be a match.

Maybe others that have used iron cylinders in a hotrodded motor will chime in. If you order new pistons, make sure you let them know what type of cylinder you have.

BTW, I used my old cylinders. HOWEVER, they are Mahle nicasils.
Thanks for the feedback. My original priority list had reliability at the top- so your advice on the pistons is well received.

Not sure if my C's are in spec, but I hope to measure them soon.

I would consider a new matching set of P's and C's if I could find something that makes sense (both from a $ and CR standpoint)... closest thing our host appears to offer is a new set of 84mm 2.4S P's and nikasil C's (911-103-944-01-OEM); $4k for a slight CR bump to 8.5:1. Seems a bit spendy for what I'm after.


More to come...


-Jake
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Old 10-02-2017, 09:10 PM
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I'm right in the middle of rebuilding a very original '72 911T MFI motor for a customer.

Since he is retired and on a budget, we went with simply regrinding the T cams to E spec, and sourcing some low mileage 2.2E pistons which will go in the original cast iron cylinders which were still well in spec. Leaving the ports stock. This should net around 170hp, which is right at the limit of power output before you need an auxiliary oil cooler.

This makes for a really nice street motor with a very wide power band, and doesn't necessitate a bunch of other upgrades which can drive up the cost. It's easy to get carried away with upgrades, and the cost adds up in a hurry.

There is nothing wrong with a set of used Mahle pistons, so long as they are within spec. The most critical measurement is the ring land gap.

BTW, Mahle pistons are very overstated on their compression ratio. Theoretically when you put 2.2 pistons in a 2.4, it should bump the CR up another .55 points above what it would be with the short stroke. But when you actually measure everything out, it usually ends up just a tad under their supposed 2.2 spec.
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Old 10-07-2017, 07:51 AM
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Agree that the used Mahle pistons should be okay. I don't have any experience with the JEs and Ted steered me away from them. Maybe talk to Ted and see if his opinion of JE has changed since you're working with him anyways.
Old 10-07-2017, 01:08 PM
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Quote:
Originally Posted by Inkblot View Post
Here's another view, with one of the cleaner heads (#6). Valves are still dirty, as I intend to replace them.



















I suppose I should ask, what is valve recession, and how do you see and/or measure it?



Cheers-



Jake


You need a new valve to check it, measure from the spring pocket to the top of the new valve stem there is a spec for this. If itís to deep you need new seats to correct it.


Sent from my iPhone using Tapatalk
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Old 10-07-2017, 03:19 PM
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Quote:
Originally Posted by Tyson Schmidt View Post
...This makes for a really nice street motor with a very wide power band, and doesn't necessitate a bunch of other upgrades which can drive up the cost. It's easy to get carried away with upgrades, and the cost adds up in a hurry.

There is nothing wrong with a set of used Mahle pistons, so long as they are within spec. The most critical measurement is the ring land gap.

BTW, Mahle pistons are very overstated on their compression ratio. Theoretically when you put 2.2 pistons in a 2.4, it should bump the CR up another .55 points above what it would be with the short stroke. But when you actually measure everything out, it usually ends up just a tad under their supposed 2.2 spec.
Good to know! I figured the actual CR must end up below the formulaic CR, but couldn't figure out which part of the equation was typically off. Sounds like the Mahle piston dome volumes might work out to be a bit lower than spec- that would definitely explain it.



Quote:
Originally Posted by MST0118 View Post
Agree that the used Mahle pistons should be okay. I don't have any experience with the JEs and Ted steered me away from them. Maybe talk to Ted and see if his opinion of JE has changed since you're working with him anyways.
Ted hasn't changed his opinion But, to his credit, he's quick to point out that he's a machinist, not an engine builder.



Quote:
Originally Posted by cgarr View Post
You need a new valve to check it, measure from the spring pocket to the top of the new valve stem there is a spec for this. If itís to deep you need new seats to correct it.
Very cool- I wasn't planning on ordering my new valves yet, but now I have an excuse...


Thanks all for the great feedback.


- Jake
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Sometimes nothin' can be a real cool hand...
Old 10-08-2017, 08:05 PM
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Now that everything is out and apart, I've been spending a ton of time trying to clean everything and get it organized enough to send out to the corresponding experts (pretty much all from this forum) for whatever's needed (machining, grinding, blasting, coating, plating, et al).

I've been using a cheap Harbor Freight parts cleaner with mineral spirits for most things, and warm, diluted simple green for some of the other bits. I'm not trying to get everything perfect at this stage, as most everything will end up getting cleaned and/or blasted. I guess I'm embarrassed to send the parts out if they're too dirty. Plus, though laborious, it's kinda fun to get to know the ins and outs of each part.









Ted from German Precision suggested that I get the major parts steam cleaned at San Jose Steam Cleaners. Those guys were great- fast and efficient. I'm not sure what I was expecting, but it's a really simple process. I just showed up, put my parts right on the ground, and they went blasting away with some impressively loud steam wands.

I shoulda done this first! They did in about 20 minutes what woulda taken me many, many hours hunched over the parts cleaner with a wire brush.







The mag case cleaned up pretty good, but did reveal a lot of corrosion on the outside (previously covered by a thick layer of oily gunk). After reading a ton about mag parts here, it seems that this is pretty normal- and as long as it's not affecting any machined surfaces (it's not) I can just leave it as is, and maybe coat everything with some Gibbs spray. I'd really like to clean it up though, but haven't decided which way to go. Consensus here seems to be soda blasting, or possibly elbow grease and a wire brush. I'm striking out trying to find a local soda blaster (I tried Accessories Plus in Belmont, but they don't do soda and couldn't recommend anyone. They're super helpful for other stuff, fwiw). So I'll probably hack at it w a brush and see if I get anywhere.





Good times!

- Jake
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Sometimes nothin' can be a real cool hand...
Old 10-08-2017, 09:01 PM
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