Thread: Project Sebring GT Spyder

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Thanks to everyone that commented and I appreciate the compliments.

I'm hoping all of this mini thrash will be paying off soon. We have a long trip planned to Tennessee. Should be about 10 or so hours one way for us. I'll be posting some pictures and maybe a video or two as well as a trip report when we get back. If everything works out, we should be in a better driving and more comfortable car.

Still have a some time before we leave, but looking forward to it.

In my post on the Tail of the Dragon trip, I mentioned that that there was some bad and some ugly.

First the bad stuff. It's a fairly long list and I'll tackle the issues one at a time.

Those damned Holley valve covers blew the gaskets yet again on the way up. I was forced to change one in the hotel parking lot in Townsend. Both were leaking, but the passenger side was the worst. It was absolutely pouring.

Of course, I had some tools, but not enough to complete the job. I had to make a stop at the hardware store in Townsend for a few things as well as going over the mountain to Pigeon Forge where the closest parts house was.

This job took about 3 hours, including waiting for the engine to cool enough to work on. We had lost some oil (it was all over the bottom of the car) so I topped it off.

By the time we made it to Dalton, GA, it was leaking again. This time it seemed to be even worse. There appeared to be some even leaking from the rear main! This got me to wondering about crankcase pressure. I did find that the main -10 breather hose was just before falling off the baffle I had fitted to the valley pan. This loose hose would have rendered the PCV system pretty much useless, but I had a hard time believing that there could have been a lot of pressure with a total of 3 hoses capable of venting the crankcase. I also jacked the car up in the hotel parking lot to check the bellhousing as much as possible and the hoses and other connections on the Accusump accumulator. Satisfied that I had inspected everything I could, I decided to keep a close check on oil level for the next few days to get a handle on how much was leaking. I hedged my bet by arranging to have a U-Haul truck and trailer available if the leak turned out to be the rear main.

Turned out that there was so much oil on the bottom of the car and engine that it was pretty much impossible to determine how much and where it was coming from. On a bright note, it did not appear to be leaking out of the bell housing anymore. A constant check on the oil level showed that it had slowed down a bunch, probably due to getting the PCV system up and running again, but I still had questions about crankcase pressure. I decided to risk the trip home, though.

Sorry, with all these parking lot gymnastics, my wife never thought to get a picture. Too bad, it was a proper “Roadkill” moment for me. I do have some stuff coming up that does have pictures, though.

My first thought was crankcase ventilation. I know some cams with low vacuum can add to the problem. This PCV system looks pretty cool but it's expensive: https://digital.allchevyperformance....street-engine/

V8, I had looked at that and will try it if I can't get a conventional PCV valve to work. I'm working on solving this issue right now.

During the trip home there was a constant stink of oil in the car, so I knew the leak hadn’t magically healed itself. With 8 or so hours on the road, I had plenty of time to stew (in more ways than one) over what to do about this.

As much as I liked the look of the Holley valve covers and Cal Custom coil covers, I decided to ditch them in favor of some stock LS9 covers. They are some of the latest from GM and have the coils bolted directly to the covers with no adapters. I have to say that the engineering on the GM covers was head and shoulders above the Holley covers and the plug wire routing is also much better. The LS9 covers were intended for a supercharged engine, so the baffling should be top notch. The hardware is designed to provide proper bolt torque, so it was a piece of cake to make sure they were tightened to GM specs. I’m much more confident that they will seal as good as can be expected from a center bolt design.



There was one small issue. The breather hose tubes were straight and that wouldn’t work for some of my future plans for covering the ugly coils. Luckily, I had some junk LS valve covers that had tightly curved tubes and it was also lucky that GM had kept these tubes the same diameter over the years. Swapping them out was quick and easy.



Another issue was the location of the breather hoses. They were not in the same places as the Holley covers and required some replumbing on their connections to the air cleaner base. I decided to do most of the new plumbing with steel tubing. I learned a long time ago not to try and force a stiff rubber hose into too tight of a bend because it usually winds up collapsing.



I painted the new covers with some black VHT extreme wrinkle paint. This turned out looking nice and is a much better-looking wrinkle than the wrinkle powder coating on the air cleaner.

Another upside to the new covers is that they have a real oil filler hole. With the Holley covers I had to add a -10 bulkhead connection to the valley cover so that I had a place to add oil. This was a pain because I had to rig up a dedicated funnel that fit the -10 connection. This meant that I had to find a place for that funnel every time I went on a trip. And, of course I left it at home this time by accident. I was forced to rig up a funnel setup with some small diameter clear plastic tubing and a plastic hardware store funnel. It took a loooong time to dribble oil into the engine, but it was all I could build on short notice in a hotel parking lot and it did work.

A plastic drink bottle and length of tubing will make a fine funnel in a pinch.
Cut the bottom off the bottle, and a hole in the cap slightly too small for the tubing. Force the tubing in and volia!

Great idea Firebird, but I didn't have any tubing. I had to stop by the hardware store anyhow for that, so I just bought a cheap plastic funnel.

Now on to the PVC system. Just to satisfy myself, I had to work through the breather system and make sure it was working as it should. I had some suspicions about it after thinking on the issue on the way home.

Just a quick recap on my system. I bought a used Mighty Mouse oil separator/catch can that had a breather. The brand is generally considered to be one of the best on the market. I built a baffled breather that attaches to the underside of the valley pan similar to the factory setup on an LS6. The breather vents through a -10 AN (5/8”) hose to the catch can.





The PCV valve screws into the side of the catch can and then to the rear throttle body as close to the center of the intake as I could get it. There is a one-way valve under the breather that seals under vacuum and vents under pressure. The hose connections on the valve covers are plumbed to the air cleaner base and normally just let in fresh air. They could also vent excess pressure if it happens. The people that made the catch can indicated that one 3/8 hose should be enough to vent a 600 HP naturally aspirated engine. I’m not sure I completely agree with that, but my homebuilt breather setup should flow way more than that.

When I installed the oil catch can, it came with a screw in PCV valve. It was a clean setup so I used it, but now I had questions about it working right. I managed to find some numbers stamped on it and they indicated that it was for a four-cylinder Nissan. That was less than confidence inspiring since PCV valves are usually sized by flow for the engines they fit.

I knew that the very early LS engines had a conventional PCV valve with the floating piston like GM and pretty much every other auto maker has used forever. Later LS engines had a “valve” that was just a simple orifice and a very tiny orifice at that. I bought one of the early valves and compared it to the Nissan valve. It was obvious that the LS valve had much more potential for flow since the openings were noticeably larger. Of course, total flow depends on the valve’s internal piston.

This is the old PCV valve.



The new LS valve. Not as clean a setup, but I think I trust it more.



Now, I had to verify that it was actually working. To do that, I made a new cap for the old -10 oil filler I had in the valley cover with a connection to hook up a pressure gauge. White arrow is the pressure tap and the red arrow is the -10 fitting that I found to be lose in the previous post.



I hooked the pressure tap up to my vacuum/pressure gauge. This showed, at idle, there is no crankcase pressure. I still need to check it at cruise and under load just to make sure everything is up to snuff, but for now it’ll have to do.

I checked both the old and new valves as an experiment. At idle, both seemed to work the same, at least as far as the gauge I had showed. Temporarily plugging the fresh air intakes in the valve covers resulted in a small amount of vacuum in the crankcase. Hopefully, this indicates that the rings and rear main are still sealed. I hope to have the car back on the road in a few days and I can check the system under cruise and power.

Not sure if you've seen this before. https://digital.allchevyperformance....qnmA912C19enx8

Thanks for that 34. That is the same valve that V8nutz posted about. For folks that didn't look at the links, they are talking about an adjustable, tunable PCV valve. I found the the info about it and several YouTube videos talking about it. I like the idea and will definitely give it a try if I can't get a standard type valve to work. The only problem I see with it is that it costs $125!

It'll be interesting to see what vacuum you get when driving. I think I need to do some testing on my 5.0 in my Miata, I'll bet it's not doing it's job because I've had a lot of oil leaks in spite of using the best gaskets and sealants. Now making me wonder about the 5.3 in my truck, it has the older style valley vent, may need a puke can at least.

V8, I hope to be posting some collected info this week. I have to admit that the adjustable valve is very intriguing and I am very tempted to pay the price.

Now that the PCV and oil leaks were once again thought to be under control (fingers crossed) I spent quite some time under the car cleaning up the mess. Oil was everywhere. After several hours I think I got most of it.

The next thing on the list was the Lucas turn signals in the front. If you recall, I had trouble with one of them and soldered the wires on. Well, this time one was pretty much destroyed when the tire got into it. Mostly, this was my fault because I pulled out some caster during the front end alignment. Remember when I said that the front tires were better centered now? Turns out that was a double edged sword. The Lucas signals are very long at nearly 3 inches! Most of that length is due to the big rubber boot that is needed to cover the weird connections. The tire contacted the boot and proceeded to rip it and the wires it held to shreds. Luckily, this time it was blowing parking light fuses and not turn signal fuses and I was able to make it home without having to deal with it on the road.





There was no way to make the Lucas lights work as they were so I made a sort of British/USA hybrid. I used the front portion of the Lucas rubber boot, which also holds the lens in (it’s complicated, trust me), and an old school 1157 light socket from a Ford, I think. It was hanging on the rack at Orielly’s. I did have to make a couple of new steel plates to hold the new sockets since the Lucas plate had a hole that was too big. I made those from 18 gauge which is very close to what Lucas used.

You can see how much shorter the new setup is than the old Lucas mess.



I now have a bunch of clearance. I also added a nylon mounting point to zip tie the harness to the body.

These two shots show the before and after on the same tire.





Well, let’s see. I have a replica of a classic British car, but it seems to have developed many of the “classic” British car issues. It is determined to leak oil (remember, if there ain’t any oil under ‘em, there ain’t none in ‘em) and I seem to be plagued by Lucas electric problems even though I only have 4 actual Lucas parts in the car. It’s a curse, I tell you, it’s got to be some kind of curse!!!

One other thing that had to be taken care off while I was in Tennessee was a little tweaking on the EFI tune. I noticed that the car would heat up some while making a long uphill pull.

Considering that a stock LS1 wasn’t considered to be overheating until it got over 230, I wasn’t technically overheated. It would hit 225 and the high speed fans would come on. Then the temp would drop back to 218, hit the low speed fans and go right back to 225. This extra temp would cause a little timing rattle under load, so I had to go really easy with the throttle so as to not hurt the engine. I had reprogramed the fan override switch before we left (long story), so I couldn’t turn them on by hand. This would have solved most of the issues since the high speed fans kept the car plenty cool.

I had my tuning laptop with me at the hotel and corrected all this ASAP. First, I reprogrammed to fan override so that it was actually a fan override. High speed fan is now just a flip of a switch away. Anytime the engine was under load, and I saw the temp getting over 210 or so, I would start the fans and have it under 200 in under a minute most of the time.

Next, I pulled 2 degrees of timing out of the complete timing table. Probably a little drastic, but I didn’t want to rattle a ring land off, either. Also, I knew that the Holley software had some timing modifiers built in. One is a temperature modifier. This allowed me to start pulling a little timing at 220 to ward off any temp induced rattle.

The other thing I played with was the knock retard. I hadn’t activated this before because I had read that some aftermarket cams can create noise that fools the knock sensors into thinking they are hearing detonation. This cam seems quiet as far as I can hear (for what that’s worth), but I also had never had any issues with detonation.

After these changes, I never heard any more rattle. It is possible that some of the issue was related to altitude, but the Holley ECU is supposed to have a barometric pressure sensor built in to compensate for that. I may feed some of the timing back in now that I’m back at sea level, but honestly, I haven’t noticed any lose in power through the butt dyno (also for what that’s worth).

I have talked with someone that owns a chassis dyno and while he says he doesn't know anything about Holley ECU’s, he will rent me his dyno by time for as many pulls as I want to make. He says his machine will allow you to load the engine as if it was at a steady state cruise, too. Way more valuable info to me than just doing full throttle pulls for bragging rights.

OK, I have some info on the PCV system. My mechanics vacuum gauge does not appear to be sensitive or consistent enough to give reliable info. It appears to be in vacuum most of the time, but we are only talking a few ounces of vacuum at most. The gauge just can’t react reliably to that. Part of the testing was with the one way valve under the breather disabled eliminating it a possible leak. I have put 500 miles on the car since changing the valve covers and the PCV valve and have not seen any evidence of oil leaks. This driving included a variety of conditions including 80 MPH + on the interstate (honest officer I was just flowin' with the traffic!). I’m still looking at the adjustable PCV valve but think I’m going to drive it like this for a while.

Now on to something else that showed up on the trip that I wasn’t even aware of until I got the car on the lift and doing an after trip inspection. Seems that the polyurethane bushings in the rear control arms were eating themselves.


When I was building the car, I wanted to run the widest tires and deepest rims I could fit. As a result, I moved everything I could inboard on the frame. This included the air bags mounts. Doing this put the lower bag mount off of the centerline of the arm. The force the bag exerts on the arm is causing the arm to want to rotate. I knew this would happen and added the large leaf spring poly bushings thinking they would be strong enough to take the twisting force. Obviously, they weren’t. The arms had rotated far enough to be in danger of extending the bags too far. This could have caused the bags to fail.

My first thought was to replace the poly bushings with Delrin. Delrin is a semi-hard self-lubricating plastic. It machines easy and I had a piece on hand. But, when I disassembled the arm, it was obvious that the actual bushings had not failed. Only bushing flanges had come apart, so they were what was taking all the load. I had a chunk of bronze bushing material in my junk box and thought about just adding thick bronze washers to replace only the bushing flanges. In the end, though, I remade the bushings entirely out of bronze. Luckily, I had installed a grease fitting for the poly bushings in the arms since the bronze parts will need to be greased often. I’ll have to keep a close check on them for wear, but after 500 miles I don’t see evidence of any.





FWIW - This was not the ideal fix for this issue. The permanent repair would be to fab new lower arms with centered bag mounts and offset the upper bag mounts to match. This would eliminate any twisting force on the arm and bushings. There is plenty of room for this since the 255 tires I have on the car now are about the widest I can fit. I have several trips planned for the last half of the year starting very quickly and just don’t have time right now to do any extra fab work. The bronze bushings were a quick fix with an unknown lifespan. The bronze I had came with a bunch of junk that I bought when a local antique restorer passed away and his family was selling his stuff off. It would probably be much cheaper to build new arms and go back to the poly bushings than to buy that chunk of bronze new and make replacement bushings! Time will tell. For now, it’s all good.

OK, at the beginning of this update, I mentioned some ugly. Now that most of the bad is behind us, let’s talk about that.

Most of the trip was fine even though we had a few issues, they were nothing I couldn’t deal with or just ignore in favor of having a good time. It wasn’t until we started home that things went south (no pun intended). I’m talking about heat. The morning started out nice. Humidity was a little high, but this is the south, we were in Georgia and it was to be expected. I can deal with it. However, as the trip progressed it got increasingly hotter in the interior. The “heat dome” thing with the weather was in full force and the air temp on the road was quickly over 100. Heat index was most likely in the one teens, maybe more. The air off the road felt like a furnace, but the real problem was the heat under the dash and in the floor. There was extremely hot air pouring from under the dash and, at one point, if I had removed my left shoe and found blisters on my foot, I would not have been surprised. No exaggeration. We were drinking all the fluid we could and sucking on ice that we bought at every fuel stop. We have traveled by motorcycle before and can deal with heat, but this was nothing short of misery. The last four hours were just a race to see if we could make it home before one of us had a heat stroke. If we had had another 100 miles, I don’t think we could have made it.

By the time we pulled into our driveway, I was completely done. If the old boy that wanted to buy my car in Jackson had been sitting at my house when I got there, he would have gone home with it and that’s not a joke. I was so dehydrated that it took most of 2 days for me to start feeling good again. Not the smartest thing for a 65-year-old man to do! I even mentioned to someone that I email from time to time that I was going to have to fix the heat issue or sell the car. I just couldn’t see us using it for what we wanted to with that kind of heat. This was soon after returning home and I think that was mostly dehydration and fatigue talking, but I did seriously consider as one possibility.

After a few days, I was feeling more like myself and decided to tackle the issue that I brought home with me. Leaky valve covers and heat were at the top of my list.

I knew the heat I was feeling was way, way too much to be simply radiated through the firewall. I had used a bunch of insulation there. In some places there was four layers. I had ridden in some Cobras before and noticed extreme heat in the footwells. I was determined to eliminate this problem during construction which is why I used so much insulation.

No, what I was feeling had to be direct air leaks from the engine bay. No other explanation short of actual fire.

I felt like any leaks would have to be mostly where the metal firewall tied into the fiberglass body. I had fiberglassed some flanges that I cut out of the original ‘glass firewall to the body and these overlapped the metal firewall by a good bit. The body flanges were fastened to the firewall flanges with several bolts. However, there were a few places where this was not possible. These were the places where I focused my first attention.

I removed the inner fenders for access and then focused a powerful work light on the inside of the car at the areas I thought might be the problem. Sure enough, there were some downright huge gaps! Some of this was very puzzling because I had used some 3M seam sealer in some of these areas during construction. I can’t remember the part number, but it was in strips that could be molded by hand like modeling clay. It must have not been able to stand the conditions because it was nowhere to be found. Not a trace! After seeing the massive air gaps, it was no wonder that the temperature was so high. The air coming through these holes had been heated to exhaust manifold temp or close to it.

I used a couple of 3M products to reseal these holes. One was #08367 urethane seam sealer. It comes in tube that will fit in a standard caulking gun. I rigged up an “applicator” with a few fittings and some tubing that would allow me to reach into the deep cavities. It worked for about 80% of the areas, but in the end I had to resort to using disposable gloves and just squirting some on my finger and applying it by hand. Even though I was wearing gloves, I still managed to get some of it on my hands. I will say that if it sticks on the car as well as it stuck to my fingers, I won’t have to worry about this stuff falling out. It took 3 or 4 days for the stuff to wear off. No soap or even solvent would cut it.

I also used some 3M urethane expanding foam in a couple of places. I don’t have the numbers at hand, but it is closed cell so it won’t absorb moisture and it’s grey/black, so it blends in. I used that on the lower holes because they were so large.

Here are a couple of pictures of the light shining through the gaps. The yellow light is the translucent fiberglass of the body flanges, but the white light is a hole. I also found some other holes this way. Some were bolt holes with nutserts that I didn’t use. A couple were gaps where the individual panels of the firewall didn’t seal even though I ran a bead of silicone between them. I even found a few places where pop rivets had lost their mandrels. None of the new holes were very big, but together they added up to a substantial leak.





This is the applicator I rigged up. This is the first version with ¼” tubing, but the seam sealer was too thick to work well with the small tube. I had to make it over using 3/8” tubing.



After driving the car on a 450-mile trip last week, I think I can say the heat issue is about 1000% better. It’s not as hot weather wise as it was before, but I was never terribly uncomfortable. There was a little warmth in the footwells later in the day, but not even close to the temp it was before. Maybe now when I get around to sealing the top with side windows, the AC might actually have a fighting chance to keep us cool.

BTW – That mini road trip was to the Gulf Coast area to visit an upholstery shop. While I’m down there for Cruizin’ the Coast in October, I’m going to have them do some repairs to the top. I’m also taking to them about maybe making a new top. While I was there, I couldn’t resist cruising a few miles on Highway 90 that runs along the beach. It was a nice day to just cruise and enjoy the weather and the car.

Mike that sounds miserable. Glad you were able to plug the gaps and that helped! My MR2 convertible can be challenging on a 100 degree day, some of the seals attached to the new OEM softtop roof are starting to leak that makes going thru a car wash a interesting experience. It seems like the sound level is higher riding the 50 mile round trip to work every day I work!. It's amazing what little cracks can do! Glad your rehydrated and things are cooling down!