A Project Is Brewing...

[Captain Obvious]

re-build kit is on its way from ztherapy so i'll be finishing up the carbies while the head is in the shop. i've already cleaned 'em out, beveled the bottom of the pistons and polished the bottoms/sides to get every bit of flow they have to offer.

 

I'm not sure I understand what you did to the carbs... You took some material off the bottom of the suction pistons? Have you got any pics of that?

[rossiz]

patcon: agreed, the sensors have a lifespan. iirc, the wideband with a heater are designed for permanent install (as in oem) but are definitely affected by poor running conditions, moisture, etc. bottom line is once i get her running well i don't see the need to constantly be staring at those little led readouts when i'm supposed to be enjoying the drive

cap'n: that's exactly what we were trying to do - and from the look of the pulley setup, the front pulley seemed to be attached to the center shaft and the back pulley appeared to be attached to the harmonic balancer plate, which is rubber isolated and drilled for balancing. i had the shop do the cutting and they were just as surprised as i was when the thing fell apart. i'm guessing this design was different from the one you worked on because it was originally set up as a 3-row, with the outer (front-most) pulley bolted onto the center assy.

at any rate, probably not a bad thing to have a new balancer - no worries of the thing separating on me.

re: the carb piston milling - i beveled off the outer corner of the pistons to soften air flow past the moving obstruction. to be clear, i'm not some flowmaster genius inventing this idea - saw it on the zt "just su" video and thought it looked like a pretty good idea. i'm traveling at present, so will post some pics when i get back this weekend.

[240260280z]

SU Mod Info on this site:

http://www.classiczcars.com/topic/40478-su-mod-lifted-from-the-net/

[rossiz]

thanks blue - i went through that and it looks like some pretty good ideas. my mods are pretty mild, just trying for the low fruit without introducing too many other variables. once i get the new lump together, installed, running and tuned (wow, sounds like a lot of work eh?) i'll work on more mods to keep from getting bored

[Mark Maras]

 Geoff

Have you thought about trying the new carb set-up on your old engine first? You could tune & balance them on a known engine then swap the whole set-up onto the new engine. A few tweaks to allow for the new build & it should run great. It would also be very interesting to compare the performance difference between the FI & the SUs on a known engine.

Mark

[rossiz]

hey mark,

yes i have thought about that and i may wind up doing it depending on how the timing works out with the new build. it would be a great comparison to see how they work, and might even make the eventual engine swap quicker if i've already got the intake set up and running. the fuel pump, choke linkage, vacuum lines, etc. will be in place and i could probably get it done over a weekend if the stars lined up correctly....

one thing that's a little sticky is that i'm torn between going mechanical or electric with the fuel pump. i like the simplicity and rock-solid dependability of the mechanical, but it does force the fuel lines to route around the front of the engine vs. coming off the firewall with electric. i've bought one of each to play with (both pretty cheap, so no biggie) and will have to use the electric for the current setup as i don't want to cut a hole in the side of the n42 head (want to sell it) but if mechanical is the way to go i've got no problem modifying my p79 to take the mech pump.

i've read glowing reports and strident vitriol regarding both approaches, so i'm still pondering...

[Captain Obvious]

I'm not up on the details of the different pulley designs, but I do know they changed a bunch of different times over the years. You can't see it in the pics, but the one I was messing with was cracked where the drive key went into the center hub. So since the pulley was already ruined, I figured I couldn't make it any worse! Your machinist must've been very surprised when the pulley ring fell off in his hand. I imagine there were a few choice words said at that point!

 

About your carbs and the suction piston beveling, I've never seen that modification before. Not saying that I'm up on all the carb stuff, but I've just never seen that one even mentioned before. Looks like it couldn't hurt.

 

And as for your order of events, I think it would be a great idea to toss your carbs onto your existing engine and work out all the other infrastructure stuff before you do the swap. It would be just one less variable in the mix when it comes to getting your new engine running well.

 

Good luck with the project and let me know if there's anything I can do from the other end of the country to help!

[siteunseen]

Everything I've read lately tells me I need an electric pump.  The mechanical ones play out above 5,000 RPM but Dizeased (Guy) says all his run fine with the mechanical pump.  I'll stick with the mechanical through break-in and just see how it does after I can run it up.  A fellow member with the cam I'll be using says his float chambers can't refill fast enough after 5,000 and our cam's peak is 6,600.

 

Decisions, decisions.   

[Mark Maras]

 I ran my SUs a little on the rich side with ATF & a mech. pump. The engine always ran strong with that combo. (everything stock) There were countless 6 grand shifts and a few "lost in the moment" 6 1/2 - 7 grand shifts. I could feel the power peak about 5500, but that wasn't lack of fuel.

 That said & remembering your goals, I'd just stay with the elec. pump. They are easy to diagnose & fairly reliable unless they are made by Lucas. The orig. with a regulator or a lower pressure quiet pump such as the RX7 pump. It is likely the elec. pump from a 74 260 would be a bolt in too.

Mark

[rossiz]

attacked the head today - 45 min and i threw my hands up and yelled "roped & tied!"

 

 

will take it in for clean-up and surfacing, cc for current volume and shave if necessary to get c/r up to 9.75:1

 

some goodies came in as well:

 

new single-row balancer

 

ztherapy rebuild kit

[rossiz]

and these just showed up on my doorstep

 

[240260280z]

Is that for a V8?