Corvette Forum : DigitalCorvettes.com Corvette Forums banner

1970 Roadster LS7 Conversion

155K views 753 replies 44 participants last post by  JustinEntropyRad 
#1 ·
Hey, looking to gather some insight on the swap I am doing. Starting with a 1970 300HP, 4 speed car and converting over to C4 suspension and LS power. Tips and tricks from anyone who has done this swap are welcome and appreciated.

My budget for this build is $50K, so have to watch the dollars carefully to make it fit. Starting off with Street Shop frame, purchased from a cancelled project. C4 suspension was new but had Dana 36 rear end. Pulled that out, sourced and modified a Viper Dana 44 and installed that with billet half shafts and batwing.

TKO 600 5 speed and centerforce dyad dual disc clutch pressure plate and flywheel assembly purchased. 700hp Mast Motorsports Black Label LS7 on order. Supposed to be dyno'd and broke in this weekend. Should have it here by September 7 or so. OH Yea!

Headers are the current problem. Speedhound when still in business sponsored a 1-3/4" set from Melrose, unfortunately the LS7 runs much better with the 1-7/8" units. No one I can find actually makes a 1-7/8" set other than the frame manufacturer, but at $2k they are priced above what budget can handle. I am working with a Melrose dealer who indicates there is growing interest in the 1-7/8" LS C3 application. Who knows? Anyone have any experience discovering another application that will work?

More photos to come as the project progresses.
 

Attachments

See less See more
1
#604 ·
It sound like you did what I am planning on doing with the duct work under the steering column. I may look into hacking off the end of the elbow that connects to the ball vent and hooking the hose to it, but will probably just run some hose there. I was not impressed with that part of the "sure fit" kit at all. Otherwise good stuff.
We used the aluminum hvac tape on the hood to line up the strikers. I am not sure who came up with that, but yea.. Good one!
Sounds like things are coming along well. Got pictures with the grills in?
 
#606 ·
Photo of the grilles below. If you look you can see the LED fog lights behind the grilles. They are two stage amber and white.

Richard, yea removing it wasn't an option. The VA advertises the perfect fit A/C units, I have yet to see any evidence that the person who develops these kits actually has ever installed them.

Today work continues, I had a couple of electrical gremlins that were nagging at me. So I set to fixing those. One turned out to be tail light wires reversed in the connector on the back of the tail light. The other was a bad pig tail on one of the front directional signals. Another the right blinker indicator was dark, found the light had been dislodged from the tach when the dash was installed. With these cleared up I think the electrical is pretty much done. Famous last words, I know............

The other thing I decided to tackle today was bleeding the brakes and I didn't get very far. Not sure :WTF is going on but I cannot get the master cylinder to push fluid toward the calipers. I have verified the cylinder inside the master cylinder is being moved when the pedal is depressed.

I thought it might be the proportioning valve but when I move to bleeding the front axle same issues. I do have the spring and ball bleeder valves and I cleaned them to be sure they weren't stuck or anything. Fluid just won't move down the lines toward the calipers no matter how much I pump the pedal.

The manual says you have to wedge the proportioning valve open at the rubber boot...... there is no rubber boot in or on my proportioning valve. Tomorrow I plan on removing one of the bleeder valves completely to see it I can get some fluid flowing.

Any wisdom any of you can share on this subject is appreciated.
 

Attachments

#607 ·
It might be that the master needs to be bench bleed, it sonds like there is sill air in the master cylinder valving. Just a thought. I had a similar problem with my wilwood mater and finally got all the small air bubbles out and then it finally pushed the fluid through the lines.

Terry
 
#608 ·
Terry,

As usual your thoughts are golden. I had thought about bench bleeding the master cylinder but just couldn't see why that should be necessary. With your post it was silly not to get it done.

Well same thing once I got it bench bled it started pumping fluid like the world was made of it. I mean I had fluid leaking from everywhere. Literally every joint on the chassis was leaking.

Well the frame came with SS brake lines already installed. I never thought to tighten them, they were already done. Wrong!!! So up on the lift and tighten every connection in the brake lines. Wonder of wonders no more leaks, no idea why I didn't think to check these connections.

I still had to clean up the mess...........

With the roadster now having a rock solid pedal it was time to move on to reupholstering the seats. First I removed all the trim, adjusters and seat back hardware. Then the hog rings off the backs and bottoms. Pulling the old covers off was fairly easy, the foam catch clips came out once the rods were removed.

There was some surface rust on the frames. I cleaned that up and repainted. No broken springs but one of the pressed nuts was loose so I welded that back into place.

I am also doing a seat mod....... I purchased three point racing harnesses for seat belts. There is only one that is DOT approved for legal street use. The original seat frames are being used so I figured that opening up both sides of the shoulder belt holes through both seats would provide the perfect pass through for the shoulder harnesses.

With hardware already purchased for the seat frames it only took 8 screws to add the shoulder brackets necessary to pass through the upholstery. Openings in the foam were easily cut and now the seat back frames are ready. (photo)

The upper front trim bars on top of the seats were opened up on each end to support the mod. I drilled 5 holes in each opening then used a die grinder and files to open it up and finish the edges. Masking and a quick shot of paint and they are ready for install.

Tomorrow I tackle putting on new foam and seat upholstery.
 

Attachments

#609 ·
Today was stretch the envelope day. I have never done upholstery before but with Al's video giving the basics I was able to stumble through getting the seat backs done today. (photo)
IMHO they came out looking good for a first time effort.

There were times today when I wasn't sure it was gonna happen. There is a reason upholstery is expensive and I now have a firm grasp as to the reasons why.

In the end the seat backs are done and from what I understand they are the harder of the two pieces. So tomorrow I plan on finishing the seat bottoms and hopefully installing the completed seats in the vette.
 

Attachments

#612 ·
Thanks guys,

The rear seat belt connects at the original shoulder belt anchor. There is a short single strap and a detachable buckle right before it splits into the two shoulder straps.

So it's a quick disconnect at the buckle and the seat folds forward. The straps stay in the seats, so fold the seat back and connect the buckle, good to go.

Once they are installed, I'll take a couple of photos and post them.

How's the VetteBeam coming along?
 
#616 · (Edited)
I want pics!!! (OK- I just read to post after this one!)

I've got a bunch of parts on the way- Car is actually sitting on all fours- as in tires-suspension- done!!! Got several spools of wire coming to finish up the rear wiring...As always that earning a living thing keeps getting in the way!!!

Would love to have it ready for Labor Day weekend- but I do have a Plan B to take up to the 20th Corvette Museum get together.

Richard

PS-OK...a video will do...

Looks like you'll be doing a shake down drive this weekend!
 
#614 ·
Today was a catch up day, doing things like installing the battery box seal, installing the Stingray scripts, hood weather strip, deck lid guides, new wiper blades and the lower windshield stainless.

The horn didn't work so that got fixed by removing the horn switch out of the steering wheel and cleaning the contact surfaces. The chrome strips on the door panels that separate the lower carpet from the door panel got installed too. I'm waiting for some door panel clips to arrive so the door panels can be installed.

I tried to call Mast for support on programming the gauges but missed the tech guy. So will try again tomorrow.

On a final note, I tested the clutch so she moved under her own power for the first time today. It was only a couple of feet but she moved. I have an appointment in town on Monday to get her aligned. So this weekend I will be putting it around the block to make sure it's road worthy.

:cheers:
 
#615 ·
7T those seats are top notch, you do great work Sir! You better slow down you want have anything to work on over the winter :smack




:cheers:
Mark
 
#618 ·
Thanks guys for the kind words.

Brent, Bring your car and come on out. I'll help you do whatever needs doing.

Richard,

I did a video of the seats and harnesses. Check post 613........ :cheers: Glad to hear your making progress on plan A. When we gonna get a video of it firing up?
 
#619 ·
Weather strip day........ Installed the deck lid and both doors today. Along with programming the temperature gauge and oil pressure gauge. The computer allows use of the existing sensors to provide data to just about any type of gauge you want to install. You have to build a table with what the computer shows to what you want the gauge to show.

It mostly worked.............. :rolling: The ECT (engine coolant temp) gauge was spot on. Soon as it was entered it worked and appears in the correct range. One down......

The other programmable gauge is the oil pressure. It didn't go so well, I entered the parameters and it reads 20 lbs with just the key on. Hmmmmmmmmm. Don't know if it's the gauge or software, for now the gauge appears at fault as it sits at 20lbs without power and it should read 0. I will try disconnecting the power lead tomorrow to see if it goes back to zero. I'm also contacting the gauge builder for his opinion.

The last item that was discovered today was that the tach isn't working. I suspect a wire off on the back of the tach. I gotta pull the dash to look........... UGH!!!!!!!! two more steps backwards.
 
#620 ·
Fixed the clutch throw, had to make a longer pin for the clutch arm. Then on to removing the drivers side dash.......

Lowered the column and pulled the dash out far enough to disconnect the tach leads. After checking them over it appears they were in the correct locations for operation. :WTF

The gauge guy is saying it's the computer. The computer guy is saying it's the gauge. How do you test the tach output on the ecm?

I spent the rest of the day putting this all back.
 
#621 ·
What brand gauges do you have? On the auto meter gauges they have a jumper or a selector switch for 4 & 8 cylinder hook up, not sure if maybe yours has something similar that could affect the operation of the tack.

Are you certain that you are hooked into the tack lead from the ECU?

Just a thought?

Terry
 
#622 · (Edited)
Terry thanks for the response.

No switch or configuration port. The tach is a custom unit built by Corvette Instruments. It's a later model Corvette tach modified to accept the tach signal from the Mast ECU. The tach wire runs from the ECU directly to a connector (that is buried deep under the dash). The other side of that connector runs directly to the tach.

That is why I wanted to know if there was a way to read a tach signal. If not I will disconnect at the ECU and do some basic ohms testing to determine if the wire has continuity and the correct connection is in place.

The computer reads rpm fine so I believe the ECU is generating a signal I need a way to confirm that signal is being delivered to the tach. This separates the problem space to either the ECU or tach unit.
 
#625 ·
Okay, Okay! 7T,
I just checked out your vids on youtube and I'm just stoked, I haven't been into the vette much for a few weeks but your car is killing me!! Just too cool!
I love the seat belts, and the seats look great. The colors on the car are killer, I've got to get back to serious work! How did you come up with the seat belts? Taking them through the seat backs like that is genius, looks factory! I need to pick your brain on some of these things, I wish I were further along. Great to see you haven't slowed down.
Thanks for the pep rally,
Bill
 
#626 ·
Bill,

Wow!!!! Thanks for your kind words. Haven't slowed down a bit, well maybe a little if the wife is amorous. :D

The seat belt idea came from the fact that left and right hardware supports and bezels were available. That and the seat back frames for both sides having duplicate cut outs for seat belts. So all I needed to do was double up on left and right hardware and I had the perfect pass through for a 4 point harness.

It made more sense to go to the 3 point as it eliminates the need for a crossover bar and supporting structure. The seat belts are Rally 3's from Scroth Racing. It's a bit of a challenge to get the buckles through the seats but as you see from the results in the video it is doable.

Today I worked on getting the door panels installed. The drivers side was fairly uneventful, it went on with the usual struggle but nothing that made me want to roll the whole project outside and set it on fire.

Then came the passenger side. :rolling: The Corvette gods were against me all the way. The internal lock lever and door handle were to low and the new door panel wouldn't clear them without pushing it out of reasonable limits. So off comes the panel for some cutting of slots on the actuator. This raised them about 1/4" and made a world of difference. I was able to get the internal handle on and went on to the door pull loop.

Of course the threads for securing the loop were off and I had to drill a new hole. Got that drilled and started the threading process. And as you may have anticipated about 3 turns in the tap broke off.................. Grrrrrrrrrrrrrrrrrrrrrrrrr :devil

So everything has to come back apart in favor of getting a broken tap out of a hole. Removing the internal door handle stripped the cast pot metal. :WTF I had a spare and swapped some parts out to repair the damage.

The broken tap would not spin out so drive it out with a punch and start over. Well that didn't work out either.
While driving out the broken tap the 1/8" metal backing separated at the spot welds and of course dropped into the bottom of the door. Grrrrrrrrrrrrrrrrrrr...........

A magnet on a flexible shaft retrieved it after about 20 minutes of unsuccessful attempts. By this time my patience is pretty fried. A few choice words are not repeatable here.

Over at the bench the tap was driven out with prejudice and the subsequent self taping screw failed. Off to Ace hardware for a replacement tap and an additional 5 gallons of premium for the first trip around the block.

The new tap proved successful, I welded the part back in place securing it with the intended screw. So the whole world changed back into my favor. The door panel is now on and looks pretty good. Not to good a photo.

The trip around the block was fun. The engine was running a little hot, normal for a new engine. A small coolant leak will need to be tracked down and fixed. Other than that I had a great time revving the engine just to piss off the neighbors. :D

All the hard work and patience paid off today. The satisfaction of driving a multiple year project for the first time is rather unique. As Bill so eloquently puts it "I'm just stoked".

More to come, alignment on Monday then it's time to stretch it out on the highway.
 

Attachments

#628 ·
Thanks for the seat belt info! Those belts are really nice, and not as expensive as I would've thought, not a lot more than new standard belts. I didn't remember the factory seats have actual cutouts there.
Man, your door panel saga made me laugh. :smack If that ain't the way it goes sometimes! I'm glad you got it sorted out though, it helps to have the right tools (welder) available (I'll buy a good tool at the drop of a hat) to be able to overcome obstacles. Congrats on the first drive! Awesome...
Bill

Hey, is that a later t&t column with an early horn button?
 
#630 ·
Thanks Pops

Hey, is that a later t&t column with an early horn button?
Nope, the tilt is original to the car.

Brent, I occasionally drink too, but usually after I finish some milestone... like eating lunch. :D

Video of her moving will be a bit tough as I'm the only one who will be driving it for awhile yet. Wife doesn't do video so I will need some help to get that done. Wonder what Spielberg is doing next week? :rolling:

Today I worked on some minor things, like fixing the coolant leak, running the dribble tube from the radiator and sealing up the neck on the windshield washer tank. After that two more trips around the block and a couple of beers to celebrate.

Then on to ripping the old soft top off the frame. It was much harder to remove than I expected it should be. Which means it must be really fun to put a new one back on.
 
#629 ·
Sometimes when things are going to sh#t and I feel my anxiety rising, it is best to just walk away and have a beer.
Unfortunately for me that means I drink a lot more than I work. :laughing:
Glad you stuck it out and got it done. Can't wait for some video of her moving.
This is a huge deal. :cheers:
 
#632 ·
No other words to describe it, today was just a crappy day.

I was supposed to drive the vette to the alignment shop today for alignment. I left about an hour early to make the 20 minute drive. Got about 3 miles from home and the vette overheated, check engine light came on as expected at about 235* and I pulled into an Exxon station to let her cool down. All the time wondering why it's running so friggin' hot.

After about 15 minutes a lady in a minivan shows up to air up a tire and of course I am parked in front of the water and air terminal. I get in to move the car and no power, it won't start. The volt meter shows zip, zero, nada, flat line......

:WTF Are you kidding me? I had to push it out of the way. Humiliating........... So at this point I call the alignment shop and reset the appointment for Wednesday, then call the tow service. Of course there were several people who stopped to tell me how great the car looked. Well it might look good but it's flatter than day old beer.

One guy stopped and really liked the car. From the sticker on his pickup he was an afgan veteran and offered to help in any way he could. I thanked him for his service and for his offer of help but told him the tow service was on the way. What a great guy, thanks to all you veterans out there!!!!!

I got the car home at about 11:30 and dove right in trying to figure out :WTF happened. I traced the electrical failure to a junction block that had melted wire back about 1/2" on the two main leads. Maybe I didn't tighten that nut all the way because there was obvious resistance. I dunno, the two 8 gauge wires connecting the alternator and starter terminated there. It was the alternator wire that melted.

I took the alternator off and readied it for a trip to the local auto parts store for testing. It tested fine.......

The heat problem was next. From what I am hearing from Mast this was likely a steam issue. Evidently this is a regular challenge with these LS engines and getting the air out of the cooling system is a hard thing to do. I was schooled on how to do that so will try that once I get the electrical system back up and operational.

What they told me to do was open the air vents on both heads by loosening up the crossover steam pipe. Start the engine and keep adding coolant until a steady stream is coming out both vents then tighten them down. I didn't do that initially so I can't say if it works or not. Got to be a better way than allowing the loose crossover to spray coolant all over the place? What did you other LS swap guys do to purge the heads of air? Josh do you have any words of wisdom here?

I did move the steam vent to higher up on the radiator hose, although subsequently I learned from Mast that wasn't really necessary. They told me it just needs a vent into the radiator return stream.

So for now the car is grounded until I get the electrics fixed and once I get it running again bleed the cooling system of the unwanted air. Hopefully I can get that all done tomorrow in time for another test run to discover if all this work actually fixed anything.

I know, I know...... it's called working the bugs out. It's common with most builds but dang it, I want to drive it hard and see what it can do.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top