It is that time! Tear down starts tomorrow on the 97 Express.

[rebelyell]

any plan to retrofit 4.3L V6 Vortec rocker arm stands to this motor's heads ?

 

[L31MaxExpress]

any plan to retrofit 4.3L V6 Vortec rocker arm stands to this motor's heads ?

Not on this one. Has way more spring pressure than I would be comfortable using stock rockers of any kind with. Has 1.55" dual springs that are shimmed up to allow with a max lift of 0.600" with 0.050" from coil bind and have 140# on the seat with 350# open at 0.600". I honestly feel like the spring pressure is probably what the LS7 lifters hate.

 

[L31MaxExpress]

I am working on hopefully resolving a driveline vibration I have had a while now. Figured out my Yoke only had about 1" engagement now with the 10.5FF rear. Looking at where the seal rode on the yoke with the 9.5SF and its matching bolt on style flange it is about 1-1/2" pulled out from where it was. Found a GM 5" aluminum driveshaft in nice condition from the local wrecking yard for $150 that is about 1-3/4" longer than the current shaft but it was from a 1998 Express 4L60E application. Has the same 1350 U-joints but has like an 8" yoke on it. With my shorter 4L80E yoke should be the perfect length. Changing the U-Joints in it and the yoke. Spicer 1350s were $50 ea from Oreilly now. I remember paying like $25 ea in 2013 when I did the 4L85E swap. Getting the steel u-joint cups out of the aluminum shaft has been an absolute fight. I looked around and even considered having a new shaft built. It was a minimum of about $600 and the cheapest option was a Dorman, no thanks. The 0.110" wall heavy duty job was $725 shipped. I looked at the newer van driveshaft specs and the 6.6L diesel and gas vans both used the same 5" aluminum job with 0.087" wall thickness, same as even a 4.3L V6/4L60E shaft. If the stock shaft has survived in my buddies Duramax van I tuned to make about 450 hp and 800 ft/lbs of torque towing a 14,000 lbs trailer it should hold up just fine in mine like it always has. I will get the exact measurement of the old shaft, but it was cut down like 2" years ago for my 4L85E swap. IIRC it is 70" on the dot from U-joint to U-joint cup centerlines if any of my North Texas friends need a useable heavy duty 5" aluminum shaft, ~70" long.

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[L31MaxExpress]

The new to me used 1.5" longer driveshaft with new Spicer joints corrected the driveline vibration I was experiencing. Still has plenty of room for the slip yoke to slide into the transmission for the suspension compression when loaded, towing or traversing dips. I spoke prematurely before, will probably tear into it tomorrow. Just been so darn hot here that the inside of the shop is over 90F even as I type this at 3:00 am. My schedule is so whack right now because of the heat it is not even funny.

That being said, explain this one to me. Made one last datalog this evening. Had two WOT accelerations that I timed in the same area. WTFO as in a passing acceleration why is this pig quicker from 50-90 mph than it is from 30-70 mph? I am talking a full second quicker too, not something attributed to say the time it takes the 4L85E to make its shift. The 30-50 mph run started at ~3,500 rpm in 1st. The 50-90 mph run started at ~3,500 rpm in 2nd. The 30-50 did have to make a shift but it only took 0.15s according to the datalog and actually barked the tires at 50 mph when it shifted at 5,500. The 50-90 mph run was all in 2nd gear. How is that even possible for something with the properties of a brick to accelerate more quickly in a taller gear from a higher speed where it has more aerodynamic loading? Mind blown, I do not understand at all.

The only thing I have is maybe the IATs made that much of a difference. At the start of the run they were 127F on the 30-70 and 101F on the 50-90 at the start of the runs and both dropped as the run progressed. Timing advance was identical though. The other slight difference I noticed was about 1 KPA more manifold pressure at 5,350 rpm on the 70-90 run than the 30-70 run when it was in 2nd gear opposed to 1st and about 15 gms/sec more airflow at the higher speed. Wondering if moving the hood latch up, providing a ~1/2" gap between the hood and core support is actually providing a ram air effect to the Kodiak K&N intake box sealed to the hood. If the hood gap alone made that much difference in the airflow to the airbox, this van needs a 4" tall WRX scoop adapted to the hood, opening into that mostly sealed airbox.

 

[L31MaxExpress]

Actually saw this a few weeks ago and sent an email last night to VCM who owns HP Tuners in an attempt to get them to sponser a bit of this build and possibly send me an air intake they make. I do not feel bad about asking them to sponser it because I have spent over $5K with them since about 2010 buying tuning credits for PCMs they have had defined for years with no additional tables or settings defined in that time and they probably do not have $300 in material and labor on their ~$700 intake plus shipping from AUS. I feel like it would fit over the radiator of the van very well. It looks like it would be easy to fit an air deflection plate to seal to the vans hood. Considering nothing is out there for any of the vans and the fact it looks like it would fit every GM van from 1971 and on needing that style air intake for LS swaps and the like, would be great to have one to test fit and attempt to adapt.

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[L31MaxExpress]

So what do you suspect can cause a performance degredation and lower MAF readings without the air/fuel ratio being affected? If you guessed plugging catalytic converter(s) you are probably right. Rememeber that #4 misfire I fought a while back? I do not really get on this engine all the time but did last night. It was more sluggish than I remembered but I have not driven it much in a while and I kind of scuffed it off as the Texas heat sapping the power. I now suspect atleast the RH cat is partially plugged from all the prior misfiring. I pulled an older datalog of it running the same tune even and the engine is now moving nearly 70 gms/sec less airflow at higher rpm. Comparing the datalogs back to back, everything looks good under 4,000 rpm, but as soon as it started reving out it is obviously getting strangled. Last night it only moved ~300 gms/sec of airflow at 5,500 rpm where it has moved over 370 gms/sec in the past on the same tune.

The 1500 cat arrangment also placed the catalyst much closer to the engine than the 3500 cat arrangement. I ordered a pair of 3" OBD2 certified ceramic core high flow cats that have a 6" x 3" oval body last night around 11 PM. The cats were here by 4:00 PM. The cats currently on the van are like 12 years old and have seen a lot of heat abuse over the years. I bought a mandrel bent 3" exhaust tubing kit like the 2.5" kit I used on the 1987 G20. The new cats will soon reside behind the transmission crossmember and right in front of the muffler as they do on a stock 3500. The van has a heck of a heatshield there even. GM probably used the same heatshielding on all the van bodies.

New cats seem to be very good quality and I have no idea how they can be as cheap as they are when you look at the price compared to Federal emissions OE cats.

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Here is the OE 3500 catalyst configuration that is getting duplicated.

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[L31MaxExpress]

So I actually got a response from the Australians in Melbourne. Will be interesting to see what happens. They actually corrected me. There apparantly is a HP Tuners here in the US and they have the same VCM logo and what not as the Melbourne VCM Performance guys who sale a ton of performance parts and also sell HP Tuners. Confused yet because I am.

Honestly though I really want to get my hands on that intake setup because it looks like it would be an excellent setup for a lot of EFI SBC or LS swap stuff that has room over the radiator and core support. Would be great for anything with a forward facing throttle body or even a 4" style carb hat on a 4150 style 4bbl throttle body or gasp TBI or Carb. Setup looks like it would have been great on my older TPI setup on my 1983 G20 or even the MAF run TBI setup I ran. I think it would easily fit a B-body like a 90s Impala SS and some earlier F-bodies, A-bodies and G-bodies. It looks like it would have fit my C3 Corvette I had as well that I had plans to put a LT1 into. Also looks useable on the 1980 C10 my parents bought new that I will eventually get around to 6.0L swapping and restoring for my sister as the radiator actually sits a bit below the core support on it.

Being thin in height and long in width and relatively shallow in length, it looks like it would basically hug the radiator mounting brackets and fit anywhere with enough height to let the hood clear.

I like the straight shot it provides into the throttle body with the venturi like shape as well. Definitely love to get my hands on one for testing purposes. This 383 should be able to tax it some to see if can support a 500+ engine. They sell a coupler for that intake for a blower application on their Holden version of the G8 or Caprice so it must work pretty good. Fun part may be squeezing a 4" MAF setup between the throttle body and intake. If the MAF did not fit at that point I would just go speed density on HP Tuners custom 1-bar speed density operating system.