1970 Roadster LS7 Conversion - Corvette Forum : DigitalCorvettes.com Corvette Forums

7TRoadster · 08-26-2011, 12:09 AM

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.

stingr4y · 08-26-2011, 05:02 AM

I'm in!

Any before pics?

Topless82 · 08-26-2011, 05:04 AM

Post some detailed pictures of the c4 suspension install, I am going to try and add 1990 suspension to my 82 frame but using a dana36 rear and want to keep the monoleaf front and c4 cradle

7TRoadster · 08-26-2011, 10:48 AM

Board will only let me load one photo.

7TRoadster · 08-26-2011, 10:58 AM

About the best photo I currently have on file, only one side but you should be able to see the layout.

Curby · 08-26-2011, 11:53 AM

That is going to be one awesome car when done.

I wonder if there is any information on what is required to put the C4 suspension peices on the C3 chassis. I know you purchased the chassis already modified.

I can get my hands on C4's really cheap these days. I would love to drop some weight off the front of my 72 with aluminum control arms, a coil-over suspension, and a rack & pinion steering system from a C4.

7TRoadster · 08-26-2011, 01:52 PM

I have seen a couple of stock frames converted, done by individuals but nothing in kit form. It worked but no way to tell how well without pushing it and I understand any owners reluctance to having someone else run their car hard. I didn't even ask. I felt it was important to go with the aftermarket frame to get the C4 suspension designed into the structure. It was lighter, stronger and offered more clearance than a stock frame.

You might call Tray at Street Shop and ask if he has anything. Jody at Vettaid also might know of something.

Topless82 · 08-26-2011, 02:11 PM

Quote:

Originally Posted by 7TRoadster

I have seen a couple of stock frames converted, done by individuals but nothing in kit form. It worked but no way to tell how well without pushing it and I understand any owners reluctance to having someone else run their car hard. I didn't even ask. I felt it was important to go with the aftermarket frame to get the C4 suspension designed into the structure. It was lighter, stronger and offered more clearance than a stock frame.

You might call Tray at Street Shop and ask if he has anything. Jody at Vettaid also might know of something.

how much was your frame?

rtj · 08-26-2011, 04:22 PM

Have you considered using BB Hooker side pipes and fabricating the transition pieces?

riggs 74 · 08-26-2011, 04:56 PM

Nice setup, I will be following this build. As far as headers, some have used standard big block headers (1 7/8) cut off the header flange and welded on LS headed flanges, Not sure if this helps you. I bought My LS headers from vette aid, I believe they are 1 3/4, in any case they are the same size as the exhaust ports on my 225 TF heads, so the motor should breathe pretty good.

What is you build time for this project, or is this build as you have time?

Riggs

7TRoadster · 08-26-2011, 05:40 PM

I purchased the frame as part of a complete chassis, but I believe the frames are available bare at roughly $5600. I haven't priced checked them in over a year so perhaps a quote is a good idea.

Consider that you will likely pay half that to have a fab shop do the front end and it comes into perspective pretty fast.

I am doing the work myself in my home shop. It is more of a build as I have the $ than time although most of the large purchases are done now. I am building this one for myself so no deadline or customer waiting. Hope to have on the road spring-summer next year.

I hadn't thought of replacing the flange on a BB header set but great idea! Might even be able to go 2" with that setup. How did the spacing on the holes of the LS flange match the BB pipes?

riggs 74 · 08-26-2011, 06:08 PM

I've not done it, but from what I have read you will have to spread the primary's just a bit to line up with the LS pattern, I'm told it's no big deal. A good time to fit the big block headers would be while the body is still off the frame so you can align them how you would want them to fit, and then be able to tac weld the headers to the flange while its still on the car. I would think that would be the easiest.
You might even be able to pick up a used, fairly new set of big block headers for cheap on ebay or craigs list to keep the cost down even more.

Riggs.

7TRoadster · 08-26-2011, 11:11 PM

Thanks so much for the idea, I will go that route if the other doesn't work out. Got word just this afternoon from Jody at Vettaid, he is going to have Melrose make up some sets of 1-7/8" units. There is a minimum order so there will be a few sets left over but just a few. If you want a pair give him a shout soon. Price is undetermined but is expected to be slightly higher than the 1-3/4" units he currently offers.

When I get mine I will post a photo.

TimAT · 08-27-2011, 02:06 PM

I sure wish GM had used something to designate the LS motors other than "LS". Everytime I see a thread with "LS7" in it, I get all excited. I'm thinking it's a real LS-7 as in 454/460 BB type thing.

Ray Y · 08-29-2011, 03:39 PM

Sounds really sweet!! Keep us updated with lots of pics and details. I have a heavily resto-moded '70 roadster too and I'm always intereted to see more.