Moby Dick coming together

[Stachi]

Originally Posted by paul cawson

Having the crank cradle fitted and tightened to the correct torque is possibly more important

I assume that anyone is doing this? But some sources mention "never to bore/hone a RB26 without a dummy head" and all Dummy heads that I've seen today are "big chunks of aluminum". If eg. a 20mm Plate of steel does the same job it would be much easier to get one. 20mm can be easily cut with a laser (~3.5kW) or plasma. Ground flat and parallel and there you go.

Not trying to hijack K.C.'s thread, just out of interest!

Marc

[1990BNR32]

the dummy head i used for my overbore to 87mm was shipped out to me from XS engineering. it is about 2" thick and it is *HEAVY* so I'm pretty sure it's not aluminum.

the explanation i was giving is that you just need something on top of the block and torqued down to the same spec you torque the head to at each head bolt/stud hole because the bores will distort with/without something bolted on.

***

kismet, a question for you... i was under the impression that the Cosworth bearings only come in two sizes, standard and race. from your original post it seems like you were able to get 2 different sizes of main bearings from Eric at XS. did you get 3 standard and 3 race bearings or did you actually get them to send you over or under sized bearings?

[kismetcapitan]

I gave Eric all my measurement specs and I got standard across the board. My rod bearings and four out of seven crank journals match the standard size. Three of them, if I were ordering Nismo bearings, needed to be undersized by .003mm. The difference between the Cosworth sizes though are a whopping .381mm (0.015"). Eric explained that just by scratching off the flash coating of Nismo bearings, you've just taken off at least .003mm if not more. Since Cosworth (and ACL for that matter) do not have coatings and are basic tri-metal, they won't change size as quickly, if at all, every time the crank rests against the bearing, which, depending on your point of view, can be a serious issue.

[Stachi]

Originally Posted by 1990BNR32

the dummy head i used for my overbore to 87mm was shipped out to me from XS engineering. it is about 2" thick and it is *HEAVY* so I'm pretty sure it's not aluminum.

the explanation i was giving is that you just need something on top of the block and torqued down to the same spec you torque the head to at each head bolt/stud hole because the bores will distort with/without something bolted on.

Thanks for that, I think it's enough of a explanation to me.

Marc

[RB26zcar]

This is the torqe plate I had made from a company that makes them for machine shops.



This one I found the pic online

[kismetcapitan]

latest update: my builder found a tiny crack in one of the valve guides. So he's moving onto a spare head. I couldn't see the damned crack, but its there - shine really bright light and squint hard, and there it is. Who knows how long its been there, or how it'd affect things in the long run, but well, there you go. Ask for detail, and you get it, but this build is DRAGGING on and on!

He wasn't happy about the crank clearances on #2 and #3 (he felt there were too tight and he wants exactly .038mm oil clearances, so the block cradles were shaved some ridiculously small amount on those, and now he's happy.

I dropped off a Trust twincore radiator and an HKS Racing BOV (the SSQV leaks over 1.8bar unless you connect the vacuum hose to the throttle bodies instead of the balance pipe (but then the valve doesn't really ever open, causing surge).

New piston wrist pins were fabricated and weigh about 5g apiece more than the HKS pins that had runout. Can't have everything I suppose.

We had a discussion about the squish pads. He wasn't keen on removing them for an interesting reason I hadn't heard before - on top of the lower C/R, he said exhaust gas velocity would go down (and we want fast exhaust gases to spool them turbos!). I guess that's why on the Z-Tune only the intake pads are removed.

Another two weeks...at least.

If anyone wants a head with FULL port work (but one cracked valve guide), PM me.

[1990BNR32]

why not replace the valve guide? xs engineering sells racemax bronze valve guides.

[Stachi]

Originally Posted by 1990BNR32

why not replace the valve guide? xs engineering sells racemax bronze valve guides.

No need for a new head. Will work flawlessly!

Marc

[paul cawson]

Originally Posted by kismetcapitan

New piston wrist pins were fabricated and weigh about 5g apiece more than the HKS pins

You will need to add 30g to the crankshaft counter weight for good balance

[kismetcapitan]

the HKS pins are 20g lighter than stock. So I'm now 15g lighter than stock, where does that leave me in terms of balance?

[kismetcapitan]

Originally Posted by 1990BNR32

why not replace the valve guide? xs engineering sells racemax bronze valve guides.

I asked the same damned question and was told they couldn't do it. Funny, they are capable of a LOT of very precision work, but they can't do valve guides??

[paul cawson]

Originally Posted by kismetcapitan

the HKS pins are 20g lighter than stock. So I'm now 15g lighter than stock, where does that leave me in terms of balance?

You need to get pistons,rods,crank,flywheel,front pulley,clutch cover balanced again as its a new crankshaft

[Stachi]

I searched around a little bit and actually found a good video:

YouTube - Porsche 911 Valve Guide Removal

This Guys speaks like he knows his business (Has written a Book for Sunnen!).
Don't your engine guys have a seat and guide machine?

Marc

[kismetcapitan]

those 911 valve guides are HUGE! RB26 valve guides are slimmer than, well, about the same diameter as superslim cigarettes?

[Stachi]

I didn't say "take the same diameter drill that he uses" If you do, your new guides will fit without using any force

Marc