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Machine shop called...piston and rod bearing questions


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So I took the engine (in pieces) to the machine shop.  They started with the crank since it had pieces of the rod bearing welded to it.  They were able to clean it up, but need to go to 1.00mm undersize to get all the pits out.  Is that too small?  Do I risk getting into softer material at that depth?  I haven't seen any online options for rod bearings at 1.00mm, but I haven't called Ireland yet.  Is it time to find a good used crank?

 

They also said the pistons are worn too far and have too much clearance and they want to bore the block to 90mm (it's currently at 89.5mm).  I was going to get the custom Ross pistons from Ireland, but wanted some input before I place the order.  I have an E12 head on a 1974 US Tii, so 9.0:1 CR was stock, correct?  Could I go to 9.5:1 with stock cam and stock Kfisch pump, or will I need to upgrade those as well?  It would be nice to get a little more power if it is easy enough to just order the pistons with that spec, as long as I am not needing to upgrade anything else.

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 time to find a good used crank!!!

 

I would think that 9.5 would be fine.

 

When Jeff was still at Ireland, he would get whatever ratio you wanted from Ross-

they're making the things from a slug, so why not-

and would usually be within half a point.

 

To make use of more compression, you'd want more cam, and that

starts down the slippery slope of power versus drivability versus the k-fish fuel delivery rate.

But I'm a big fan of more cam, and I realize that that's a personal problem...

 

 

t

 

 

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On the k fish you can increase the c/r half a point or a whole point and still be able to dial the tune in no sweat, cams are a  different story, they never are really happy with the k fish program. On your crank and block see what the machining and parts cost and compare that to getting a used block and crank and having then machined at a 90mm bore this is that blocks last rebuild.

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You might want to get a quote on re hardening the crank again...after grinding. Another standard sized crank could be more cost effective with a micro polish on journals and crack checking magna flux. Run standard cam install updated valve seals and guides and all valve hardware if in good shape, and keep it simple but it is your call. Good luck keep us updated.. 

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From what I've read over the years, anything other than a stock camshaft with the Kugelfisher injection won't be a happy marriage. 

 

Dunno if he's still there, but Ray Korman had an older German mechanic at his shop who could successfully re-work a K-fish injector pump to work with hotter cam grinds,  But that was some years ago, and he's the only person I've heard of here in the States that could do that.  Were it my tii, I'd stick with the stock cam. 

 

WRT your damaged crankshaft:  You might want to check in your nearest large city (Salt Lake City?) to see if there's a shop that does "hot metal spraying."  This is a technique used to build up parts (like journals) that are worn or damaged, by heating the recipient part and spraying it with liquid metal.  The result is then turned down to the required diameter.  There is such a shop here in Dayton, and they did repair work on damaged crankshafts like yours.  Perhaps there's one i SLC.

mike  

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find  a used  crank thats standard, boring block your options are numerous, I like top end, they are very knowable, have je pistons compression 9.3 was max in us, 74 was detuned to 120 sae. lower compression, different injection pump, 72 and 73 were  130 din,works out to  147 sae hp , you need a 72,73 pump for more squeeze, pacific in sf is where you go  for injection love the stock cam in it been building  tii s 50 years, you can PM me 

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15 hours ago, Mike Self said:

But that was some years ago, and he's the only person I've heard of here in the States that could do that.

 

Bill Holmes at Bavarian Rennsport in Ramona, CA was also proficient at tuning the K-fish injector pump for hotter cams.

 

Mark92131

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OK, so I am getting a little worried the more I read threads here about forged pistons.  I am confused about which forged pistons, if any, are best for longevity and street-only use.  Are Ross, JE and CP pistons all too hard and will wear the cylinder walls? Is one better for my use than others?  Should I find a good block or have mine sleeved and use stock Mahle's at 89.47?  Ugh, this is when a lot of good information is too much information.

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Heres what I would do:

Buy 4 Mahle Tii pistons from W&N (you're lucky some are still available)

Sleeve your block or find a replacement

Replace the crankshaft (finding a core engine might provide you with both crank and block)

And that fresh bore simply must have an equally fresh cylinder head, have the machine shop go thru it as well.

Bite the bullet and use the Mahles, not forged and especially not cheap, import, unknown forged.

Bite the bullet and accept the fact that you will probably be spending $5000 on the engine...alone.

Once you do that, the healing can begin.

Edited by tech71
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As mentioned, a tii runs best with a stock cam. if you go to 292 it'll run lean on WOT from my experience. 

if you do pursue a hotter cam, i'd suggest reaching out to Wes Ingram has he has a solution to enrichen the mixture - one that i used for years on my tii with a 292. It worked well and kept AFR about 12.5 -13 under WOT. 

You should also install a WB sensor to monitor AFR.

KF4.JPG

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Yeah, I'm not considering a hotter cam as I don't want to mess with the Kfisch pump.  My only comment about the cam, was do I need an upgraded cam to get any benefit from a higher CR piston.  If so, then I would stick with the 9:1 CR pistons.  Sounds like 9.5:1 pistons do well with stock cam, so that is my leaning.

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85% of what you read about forged pistons does not apply to the current crop.

(statistically, this means that this ^^^ does not apply either!)

 

After using Ross in a race engine for numerous seasons, I would not hesitate to

use them in a street motor, being mindful not to abuse the motor while stone cold.

 

That said, if Mahle cast are available, I would use them in a heartbeat-

I have used them in race engines for numerous other seasons, and they are good.

 

Finding used blocks is harder than cranks, but again, the head is the soft part of

the engine, so the bottom ends are plenty available, relatively.

 

hth

 

t

 

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On 9/9/2021 at 3:33 PM, Mikesmalaga72 said:

You might want to get a quote on re hardening the crank again...after grinding. Another standard sized crank could be more cost effective with a micro polish on journals and crack checking magna flux. Run standard cam install updated valve seals and guides and all valve hardware if in good shape, and keep it simple but it is your call. Good luck keep us updated.. 

Nobody can duplicate the hardening process used by the factory. The EPA has put an end to that in this country. The hardening process they use now does not work well with these cranks which can distort under the very high temps they are subjected through the gas hardening method they now use. Find a standard crank or one which has only been taken down one step. Ireland has good experience with pistons and offers them at a reasonable price. But, my first choice would be the factory Mahle pistons. Recently I purchased a set from a FAQ member in the rare +1mm oversize and at 9.5:1 compression with piano top crowns.  They were a bargain at $500, considering they are still available from Germany for $1,200 / set. The stocjk pistons are very high quality and installed at tight tolerance, which is what you want for a street car.

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