Challenge C4 - under new ownership.

Maybe I was paranoid, but I went through a third round of debugging.  Once the garage was vented, and I had swept and shopped vac'd up the results of the battle, I started digging into the bins.  Pulled out the TPI setups, and a couple intake tubes.  After a little cleanup, at least some of it will go on eBay.  I am kind of hoping I can hit my sell off limit and still hold onto a set of runners and an upper plenum, since they look cool and I'm a hoarder.

After a little sorting and re-boxing, I did a walkaround of the car, and climbed into it for the first time.  Note:  If a grab handle can be added somewhere that does not become a hazard, I want to do so.  Here's what I'm looking at from the driver's seat:

The layout looks good, but with the fuel injected engine going in, the vacuum gauge is not needed.  Maybe a boost gauge should be there in the future.  I am amused by the hour meter.  There is also a slim chance the Trailblazer or S10 cluster will be called into service.  I might even try to resurrect the original cluster for more than just inspection purposes, but that's doubtful.  Speaking of that, it looks like the driver side panel can be removed easily, and I can come up with a way to install the original cluster.  I also need to carefully cut away a bit of the bodywork to uncover the VIN at the base of the windshield.

The other reason I got in was to get a closer look at the wiring.  Looks like an original fusebox has been mounted in the passenger area.

There should be more than enough circuits to handle the 5.3 swap, but I think I'll need a few more relays.  I am also hoping to move it up a bit so it can be reached from outside the car if need be.  When I work on the Trailblazer engine harness, I'm also going to see if it is viable to relocate the PCM into the passenger compartment.  There's a slim chance I'll buy a cheap fuse/relay box, but it would be nice to keep the budget hit to a minimum.  I did not look at the wiring bin too thoroughly, so I need to do that to see if there are more relays stashed in there.

If I can get the time, my next goal is swap the oil pan on the 5.3, and start repositioning everything in the garage for a test fit.  The motor mounts should be here in the next day or two, so if I am really ambitious it could happen this coming weekend.  From there, I'll see what changes need to made for the C channel mount and driveshaft, and start working out cooling, fuel, and wiring routing.  I did drop a PM to stafford1500 to see if there is anything I can do to make lifting up the car easier, and if the front end bodywork can be removed non-destructively.

The team is coming over on Saturday, to look at the car and start strategizing.  I also checked, and the last SCCA autocross in the area is the first weekend of November.  I don't think we will have it running and driving by then, but if so, I'm hoping we can get up there, as that may be our only good chance at a test session before the 2026 Challenge.  With the challenge taking place in mid-April, there is a possibility we may be able to test at a spring event, too.

Tim, the emails should sort you on nose removal. If you want to make it easier to work on the dash, I can explain the process to pull the entire body. You just have to find a place to store. It takes up a whole car space...

In reply to stafford1500 :

Thank you.  Space is one thing I'm short of, so the rest of the body will have to stay on, at least for now.  I think my wiring strategy is going to be planning as many moves ahead as possible, then making sure I have all the necessary tools and parts at hand once I Dukes of Hazzard my way into the car.
I've got some other work to be doing today, but am still putting a little time in the garage.  Cleaned out the spare parts from the hatch area, did a little vacuuming, and am tidying up the shop area so we will have at least a bit of working space.  I may detach the wing to give us more fore/aft room.  Also, the mechanism for the seat sliders appears to still be in place, but is locked up, so I may see about freeing them up in order to make it easier to clean behind/under the seats.  If I have the budget room, I have a race seat but what is in there seems pretty supportive.

I'm kind of stalling on swapping out the oil pan, partially due to limited space right now, and partially because I just don't want to.  At the very least, I should pull the new pan out and give it and the pickup tube a brake clean bath, to get rid of any manufacturing leftovers.

Patrick told me about this one the other day. It's cool to see it in pictures! Looks like a lot of fun.

With the car pointing nose out, the engine hoist and engine/transmission in the back of the garage, something needed to change.  The driveway is a fairly steep hill, so turning the car around seemed like a bad idea.  There was enough room on the driver's side to move everything, if I shuffled the car forwards and backwards to allow it to get there.  Turns out that is a lot easier to do once you figure out how to disengage the parking brake on a C4 Corvette.  With a bunch of tretris-ing, everything is in a better position.

I still didn't feel like installing the new pan, but figured it would be a good idea to give it a quick cleanup, just in case.  Good thing I did.  The pickup tube seemed mostly okay, but I got to see this with multiple sprays of brake cleaner:

Here's a bit of what came out.  I know the filter should capture this stuff, but, still, don't want to chance it.

It still had aluminum glitter after multiple rounds and brake cleaner is more expensive than water, so I took the pan out back and spent a few minutes hosing it off.  It's drying right now, but I'll do another round of brake cleaner to see if it is better.  If not, I suppose some soapy water and a scrubbing pad may be in order.  If it weren't for the challenge budget, I'd go with the name brand instead of a clone.

Did a little quick testing now that I have engine mounts.  The long bolts are supposed to be 12mm, but it appears the frame mounts have been hogged out to fit 1/2" bolts at some point.  They need to be about 4.5" long.  If nothing in the Trailblazer's hardware bin, or the hardware that came with the car fits, I'll likely go SAE, just to save some money.  The LS-SBC adapters are about 3/8" thick, so the engine will sit a bit higher than stock.  That should not be a problem as long as I pay attention to the driveshaft angle when I am building my C-channel adapter.  I am hoping I can come up with a way to make it adjustable but still strong enough.

The team got together and looked the car over today.  Lots of good brainstorming, and it was very nice to have several extra sets of eyes on it.  Other than that, not much happened today.  I did go back out to the garage later and started diagramming the wiring in the engine compartment and in the rear hatch area.  Some of it was pretty sun faded, so I'm going to need to take a closer look once I remove the wing, to figure out a bit of which wires go to the fuel pump vs. the taillight.

The oil pan still had a little bit of glitter today, though nowhere near as much as before.  I gave it a cleaning with some dish soap and a scrubbing sponge, rinsed it off, and set it aside.  Since the oil pan swap wasn't happening, I started working on teardown.

First thing to go was the rear wing.  With it gone, I had more room to push the car towards the back of the garage.

After that, I worked on removing the nose, based on instructions from stafford1500 and a_florida_man.  Took a bit of fiddling, but I got it loose, and eastsideWife helped lift it off the body.  It was extremely light, just rather bulky.

Suddenly, tons of room to work, and much less fear of damaging the bodywork.  This also allowed for pulling another panel off and exposing the VIN.  Next step was removing the clutch hydraulics, which also involved crawling in the passenger side so I could stick my head under the driver's side dash and remove the pushrod from the pedal.  I also attempted to remove the clutch pedal, but the hardware holding it was not where I could see it, and there was space for me to touch it with my hand, or attempt (poorly) to put a wrench on it, but not enough for both.  I'll make another try sometime later.  It isn't a high priority.

I turned my attention to the splitter.  Which ended up requiring removing the radiator.

That part was fairly easy, but a bit involved.  The headlight mounts also needed to be loosened to get to a couple of the bolts.  The splitter seemed to be hanging up on something, and it turned out there were a couple small bolts near the back on the underside that went into rivnuts on the frame.  One of the rivnuts had pulled out of the frame, so it was loose on one side, but hung up on the other until I figured it out.

Once it was off, I pulled the power steering, and made a bit of a mess doing so.  But now, there is room up front for my jack to reach the front crossmember.  More importantly, my engine hoist is fairly small, and I am not sure it would have had a long enough reach with the splitter in place.  

That pretty much wraps up today's work.  With everything off the car, there's a lot less working room, once everything is loaded back into the garage.

Next session, I'm planning on positioning the the car where I want it for the engine install, and will put it up on cribbing blocks.  Time (and parts) willing, I'll finally swap out the oil pan.

I'm trying to come up with a way to re-engineer the splitter for easier removal.  I want it to still be secure, but if I could remove it before loading the car on the trailer, that'd be 4" of front overhang removed, and 1" of ground clearance gained.

Had a small amount of time this morning, and decided to try to make a little progress.  First, switched out the drag wheels for a set of Z06 Wheels I picked up a ways back.  Partially because I wanted to see how they looked, and partially because it'll be a lot easier to work around them versus the 30.5" tall slicks.

I might want to see about reducing the fender opening size, but that is pretty far down on the priority list.

Otherwise, I rolled it a bit further back in the garage, and put it up on cribbing blocks.

It'll likely stay in this position until all of the drivetrain mounting is figured out, and wiring/fuel/cooling is also laid out.  The engine mount adapters have 2.25" of adjustment, so if it needs to go forward to fit a driveshaft, hopefully one of the options will work.  It may require notching the front crossmember, but with the coilover conversion, there's no need to worry about the front leaf spring anymore.

The oil pan is finally clean, so I am hoping for the next work session to involve pulling the old one, cutting down the windage tray, and installing the new pan.  At that point, it'll probably make sense to test fit it into the engine, so I'll want to have a decent amount of time.  I'm fairly busy for the next couple days, so it may be closer to the weekend or during it before getting to it.

The body work is isanely light the first time you pick up a big chunk of it, isn't it. I figure the whole body is 70 pounds or so.

Getting the splitter to be easily removable was on my list but never got done. That will make load way easier for sure.

In reply to stafford1500 :

It seems like the nose can't weigh more than 10 lbs.

One thing I can definitely say for your splitter design is it was not going to accidentally fall off.  Still thinking of ways to change the mounting method.  It'd be really neat to come up with a couple of quick release latches in the wheel well or a similar hidden location.  
 

The splitter and the diffuser are the heaviest body parts. They are doing some real work and I did not want them to fall off.

Pins and slots were the original locating and latching methods. Kevin updated a few things when he ran it.

In reply to stafford1500 :

What's your expert opinion on the vertical rear window of the later entries versus the earlier fastback?  Especially as regards to the effectiveness of the wing?  We haven't settled on how we are covering the back hatch, but if the effect is minimal, a flat panel would be a lot easier.  I'd assume the fastback is still noticeably better at autocross speeds, but that is only going off intuition, a little recent reading, and what little aerodynamics lessons I got in M.E. classes 30 years ago. 

I've also considered a steeply sloped rear "window", ala the C5 Z06, and some vortex generators on the back of the B pillar, but without a wind tunnel or even the ability to drive it on the street with some streamers, I'd just be guessing at the effectiveness.

In reply to eastsideTim :

Bad aero can always be beat by more horsepower.

Stampie said:

In reply to eastsideTim :

Bad aero can always be beat by more horsepower.

That may be the 2027 plan.  For 2026, I would not be surprised if the car has similar wheel horsepower as it did before, at least in the autocross.

In reply to eastsideTim :

A sloped rear deck will be better than the flat rear window, but not as good as the swoopy shape of the first iteration. Kevin wanted to be able see out of the back of the car using the mirror. That was the main reason for ditching the swoopy hatch.

Stampie said:

In reply to eastsideTim :

Bad aero can always be beat by more horsepower.

Yes horse pressure can beat drag, especially at autocross speeds, but it starts to add up quick over 60mph.

stafford1500 said:

In reply to eastsideTim :

A sloped rear deck will be better than the flat rear window, but not as good as the swoopy shape of the first iteration. Kevin wanted to be able see out of the back of the car using the mirror. That was the main reason for ditching the swoopy hatch.

Having some rear visibility makes sense to me.  If we have the budget, and the time to make it a fastback, I'll also throw in a cheap rear view camera setup, or make some tiny wide view mirrors to mount at the base of the windshield.

The main reason I'd been dreading dealing with the oil pan swap is the engine is on a set of low rolling stands instead of a normal engine stand, so I'd pretty much be laying on my side for a large chunk of the work.  But I finally got over it and dealt with it today.

The H3 Alpha pan that I had installed before vs the new pan.  The new one is about 1.75" shallower.  In theory, either should fit in the Vette, but the H3 pan would definitely hang lower than the crossmember.

One other part that I didn't want to mess with was cutting down the windage tray.  The front section needed to be removed, and a notch needed to be cut to fit the pickup tube.  I don't have a problem with using an angle grinder, but I'm not used to using it on internal engine parts.

After a quick cut to remove the front, I tried to use a hole saw to cut a perfect radius for the notch.  That failed miserably, so I just cut as close as I could with a cut off wheel, and then cleaned up with a grinding wheel.  I made sure to de-burr the edges, hosed the whole thing off thoroughly, wiped it dry, then hit it with WD40, and wiped it dry again.

Prepped the new pan, which had a smaller opening for the pickup tube.  Maybe that'll help make up for the shallower depth during cornering. 

Around this point, it started raining, so I had to hurry and drag everything back in the garage, and lost most of my working space.  Still, might as well finish it.  With a lot of careful maneuvering, and suddenly remembering to RTV the joints for the front and rear covers, the new pan is now on.  It just took longer than planned.

If it weren't for the weather slowing things down, I would have tried to get the engine in place today.  As it is, I did pick up some nuts and bolts at the hardware store this morning, so I don't have to dig through bins before doing any test fitting.  I should also pull the driveshaft beforehand, to keep it from getting in the way, and make distances easier to measure.  Tomorrow, I should have some time to spare.

Before getting into today's update, I just wanted to say that after two weeks of being in, around, and under this car, it amazes me that it never won overall.  I guess it is a testament to how strong the competition is on the leading edge at the Challenge.  Anyone involved in this build before I got my hands on it should be incredibly proud.

Today was the big day I've been waiting for:

Took some time to get the engine in, as I was working alone, and had to crawl under to shim the transmission pan with 2x6s multiple times.  At the "stock" location, I was hitting the firewall, so I set the mounts in the next slot forward, about 7/16".  That ended up being the ticket.  Did run into another issue down the line, though.

The adapters spaced out the mounts enough that I could only install one at a time.  I eventually came up with a temporary solution of using a 1/4" through bolt in one side, and jamming a couple of smaller 3/16" bolts in both front and back on the other side.  The solution to this, when the motor comes out is likely to be to slot the frame mounts with a die grinder or dremel, so there is a bit of side to side margin for error.

I didn't get the time to take a lot of measurements before I had to close up, but it looks like the oil pan is either about the same height as the front crossmember or a fraction of an inch low.  It might behoove me to get a shallow pan for the 4L60E, but I didn't get a great look yet.  The oil pan clears fine everywhere.  The front pulley only has about 1/8" clearance, but that should go up 1/8"-1/4" once the the mounts are dealt with.  However, one thing that I need to check first is the driveline angle.  Doesn't need to be perfect, but I need to know if I am raising or lowering the transmission.  If it needs to be raised, I'll have to pull the engine and deal with the mounts (and possibly the crossmember) in order to have clearance for the crank pulley.  If it needs to be lowered, it can stay as is while everything else is test fit around it.

Guess what I got

Totally unsure if the rest of the trans is good, but I have a shallow pan I can dig out of the dumpster.

I also have half of an aluminum driveshaft if you want it 

In reply to Pete. (l33t FS) :

Holy crap!  What caused that?

Binding front U joint.  This kind of carnage usually happens on 4wds with the transfer case cantilevered over the mount, for a lot more flexing action.

Today was busy, but I still snuck out to the garage earlier this evening to take a few rough measurements.  Results are mixed.

The transmission output and differential input appear to be the same height off the ground.  If the chassis is level (a big if), then I think I am good for vertical clearance on the crank pulley, especially once properly sized engine mount through bolts are used.

Then there's the bad part.  The driveshaft that came with the car is too long for my engine/transmission setup.  I have roughly 27.75" from the center line of the u-joint in the differential to the back of the transmission seal.  The driveshaft is 26.75" long u-joint centerline to u-joint centerline.  I did snag a spare driveshaft from Dusterbd13, but it appears to be for an automatic, and is 27.5" long.  I dragged out all my driveshafts, and nothing is that short.  I was thinking my cheap option would be to use the rear part of the S10 2 piece driveshaft, cut it down to length, weld the front u-joint holder into it, and pay to get it balanced.  And hope I don't mess up.

I took off to a small car meet to clear my head at this point.  After getting home, I may have come up with a solution, but want to run it by everyone.  Here is the yoke from the S10.

The distance from where the fillet starts to the centerline of the u-joint appears to be just under 2", close enough to just call it that, at least until I get more precise measurements.  The length of the machined area itself is about 5", and the internal splines go back almost 6", I think.  The rear seal on the transmission is flared out.  If it is safe to replace it with a flat seal, I'd gain about an inch of clearance.

So at this point I've got 26.75" (driveshaft) + 2" (distance from u-joint centerline to level machined surface on the yoke) against 27.75" (length from rear-u-joint to rear of transmission seal) + 1" (swap out to flat seal) exactly equaling each other.  There needs to be a little slop, just in case, plus the yoke would bottom out in the transmission way before the rear u-joint could be bolted up.

The first problem could potentially be solved by moving the engine forward a smidge more.  Right now, there is about 1.25" clearance between the main pulley and the steering rack.  I suspect I could move it forward .5" and still be able to fit a belt over the pulley.  I am hoping that should be enough to deal with any potential stacked tolerances or measurement errors.  The oil pan may hit the crossmember in a couple spots, so they'd need to be cut out and plated over(but maybe not, depending on the entirety of the solution).  One issue with this is the mount adapters don't have a spot drilled in them for this setting, and it isn't entirely easy to deal with, as the lower SBC mount bolt would interfere with the front lower LS engine mount bolt.  More on solving this later.

The second problem, I think, has a simpler solution.  Because the yoke is internally splined way further than needed, I could put it in the transmission and see where it bottoms out, then cut off enough of it that it would not bottom out once on the assembled driveshaft.  I am assuming if I can get a nice perpendicular cut on it, then grind and polish a small bevel on the cut end, that I won't cause any balance issues, and I won't risk damaging the transmission seal.

Back to the first problem.  Maybe in addition to moving the engine forward 0.5", I could also raise it about .25"-.5".  While it'd negatively effect COG, I'd think the effect will be fairly minimal.  Might even still be better than it was with the small block Chevy, since I'm running an aluminum block and heads.  It would likely make sense to just get some 3/8" thick aluminum or 1/4" steel plate and make my own mounts at that point.  While it may not be the best idea, I could also only use 3 bolts per side on the LS block.  I could also come up with some sort of offset bolt that can also be used a stud for the SBC bolt.  Raising the engine would also help position the SBC mount inward a bit more and mean I don't have to grind out the frame mount holes as much, or at all.  Throwing numbers in a trig calculator shows the driveshaft angle would only be affected by about a degree, so the u-joints should be fine if I make my C-channel adapter properly.  Moving the engine up a bit may also give enough clearance that no cuts will need to be made to the front crossmember.

I also need to do a quick check to see if the front accessories will fit in the current configuration, and if there are a few changes.  I already know there's a good chance I'll need to modify the hood anyway for height, so that doesn't bother me, but I need to make sure the bracket and PS pump don't interfere with the steering rack or anything else.  Presumably, we could use a Volvo electric pump, but that's an expense I don't want to deal with.

Summarized, please let me know if any of this is wrong, or seems like a bad idea:

1. Re-measure everything as precisely as practical.
2. Check accessory clearance and confirm they will fit, or that a solution will need to be found
3. Find out how far the S10 yoke goes into the transmission before bottoming out, cut it down, then swap it onto the Corvette's driveshaft.
4. Swap out the flared out transmission rear seal with a flat one.
5. Move the engine forward (and possibly up) by modifying the current adapter mounts, or making my own.
6. When installing the engine/transmission for the final time, make sure the driveshaft is already inserted in the transmission, and then bolted to the differential, in case there isn't enough room to do so once it is in its final location.

I tried to follow along but what's the U joint to U joint driveshaft length that you need?

I like the cut down S10 yoke idea and if that gives you enough room I'd go with it and keep the engine as far back and low as you can.

In reply to Stampie :

Based on some prior measurements (I'd need to double check tomorrow when I'm in front of the computer), I'd need the driveshaft to be around 25" long or a bit shorter, assuming I swapped to a flat seal.  That might still require cutting down the yoke.  
 

I should have time tomorrow to re-measure everything and do some more test fitting.