A couple of personal bests to report ( for those who might be interested ).

12.87 @ 105.14 with a 1.76 60'.

The McCreary Road Star dirt track tires provided decent traction. Dead hooked more or less.
The WOT AFR's were quite lean at 13.4-14:1 however I didn't get into tuning as I just wanted to lay down as many passes as I could. Six passes in total. 12.87-12.98 and 104.9-105.5 mph.
I'm sure there's more in it. Last years best mph was a 106 plus.
This year had a rear gear change from 3.70 ( which broke on my first 12 second pass) to a 3.27. Once the Dana 44 is in with the 3.73's I expect better 60' times and tuning will certainly bring on better trap speeds.
Not too bad for a little Vortec headed 350 and a 3700 lb slug. And 25+ mpg hiway to boot.
For what it's worth....

 

any more info on the combo?

 

Here's an updated copy of my signature.
It would seem that there are a lot faster cars out there with less parts that are quicker so at I know there's room for improvement.
1986 IROC-Z. 350 010 4-bolt block 10.0:1 static cr. 8.04:1 dynamic cr. Vortec heads w/ competition valve job milled to 63cc. Modified for screw in studs and guide plates. Comp Cams: Bee hive springs, Pro Magnum 1.6 rockers, Pro Magnum push rods, XR276HR cam. 670 Holley Street Avenger. RPM Air Gap intake. Cloyes Hex Adjust timing set and cover. Resized stock rods w/ARP bolts. Polished stock cast crank. Speed Pro coated flat top 4 relief pistons. Balanced assembly. Fluidampr balancer. SFI flexplate. MSD small cap distributor. MSD 6AL ignition box. Hedman LT headers w/ stainless 2.5" y-pipe. 3" Flowmaster no cat back exhaust. 700R4 typical mods and upgraded 3-4 clutch pack. TCI Street Fighter 10" convertor. B&M trans cooler. Hurst dual gate shifter. 3" steel driveshaft with Spicer 1350 u-joints. 9 bolt 3.27 Spohn LCA relocation brackets. Boxed LCA's. Edelbrock adjustable pan hard bar and strut tower brace. Energy Suspension polyurethane bushings throughout. McCreary Road Star dirt tires. 12.87 sec. 105.42 mph. 1.77/60'. 3700 lbs w/driver and 1/2 tank of 94 octane. 26(CDN)/23(US) mpg highway.

 

Not bad at all for the kinda weight your carrin' with that gear!

 

I'm hoping the new Sport Coupe will be a little lighter and a little quicker.

 

Get a real carb on there and it'll probably pick up some. Never had good luck with my old 670.

 

I've made a few mods to the 670. The best thing so far has been the power valve channel restriction enlargement. While not doing too much for overall power, I think it's partly responsible, along with very lean primary jetting, for 25+ mpg hiway.
If some secondary tuning dosen't bring along some higher trap speeds, I may decide on one carb for the strip (maybe a mechanical secondary 750) and one for all around performance. I drive this thing a lot and the mileage is great to have.
I'm pretty sure a day at the track will yield a 12.5. Of course I'll probably have to get the 3.70 gear back in there.

 

I messed with the jetting and springs when I had mine, never got it to where it felt good. Throttle response was lazy too. Just for the hell of it one day I put on a 750 DP, throttle response was improved, car felt quicker and still got 22 mpg. That was with my old 305 and 3.42 gears.

 

Don't you find that the double accelerator pumps kill the mileage while city driving?
I appreciate how the mechanical secondaries would give the ultimate in WOT tuning however the trade off for driving around town wouldn't be worth it to me.

 

Mileage will be directly linked to the weight of your right foot, and if you felt the need to you can always back of the secondary lever so you don't get the pump shot on tip in.

 

That's so true however even with a decreased secondary shot it's still going to dig into your economy. That being said it shows how there's going to compromise between ultimate performance and drivability.

 

I never need to get into the secondaries driving around town. Plus, umm I'm not really concerned about mpg I have leaned it out by changing the idle feed restrictors and messed around with the airbleeds though. The engine runs much smoother putting around town and I'm sure the mpg have gone up, just never bother to check it.