View Full Version : Frame advise

04-25-2006, 09:18 PM
I just came across this awsome little forum and spent the past few nights being amazed by the weath of knowledge here and can see I will learn alot from everyone.

Im in the very early desing phase of my next project, which will be my biggest one yet! Alittle insight in the basics before I get into the techical side. I have a 92 Chevy Lumina Z34 which is a factory front wheel drive with the 3.4 dohc and an auto. Last year I did a motor swap with the 3.8 and am not satisifed with the transmission options, I refuse to put thousands into a auto tranny In order to have serious power and after all the tranny work end up with mad torque steer. So only other option is a rwd conversion which I know will be a huge amount of work and am not worried one bit. I already have the basic knowledge and am doing this as a learning project.

So onto the question. I recently came across a guy doing a simular conversion using a slightly modified Firebird front & rear clip. Both being grafted on like you would when doing a rebuild on a wrecked vechile. Heres (http://www.cardomain.com/ride/665715) his site. My first question is what do you guys think of this conversion? With sub frame connectors and Im planning a Vet Independent Rear which will have to be grafted in as well. Will it handle a good amout of power, Work will be top quality so Im more worried about strength of the frame and not the work! My main concern is the conection with proper bracing and gussets I think it should be a solid frame but beings this is my first real frame build Im Not to confident yet.

My other option is a one off frame. Before I go into this option I would like to see what you guys think about the first option as I think it would be alot cooler with factory frame rails, giving the factory apperance! The cool factors not my main concern but would be a big plus.

Thanks for any insight!

Regret Nothing - Learn Everything

04-25-2006, 09:30 PM
If I was to do this conversion, I would start with a rollcage that would pick up the front clip and the rear clip of your donor car, under your car. Then I would connect the clip's together under the car, then start cutting the floor out for the tunnel. The roll cage will hold the car together as you fit in all the component's that you need to make fit.

Just my 2c

04-25-2006, 09:56 PM

You do think the connection will hold up to a decent amount of power. The motors going to be right aroung a 600 hp turbo motor.

Thanks for the input!

04-25-2006, 10:29 PM
Ryan, with any sticky tires, the Dana 36 Vette rear will probably shell on you. There is the Dana 44 which might take the strain unless you launch the car real hard. Reguardless, the vette rear is much more complicated to set up in a unibody vehicle, as well as much more expensive to maintain. The Vette rear may have to be narrowed as well. If you must have one , the C5's have front and rear cradles that can be bolted into the chassis, and preserve the geometry somewhat. But have BIG brakes and are the widest.

I have a `92 Beretta that I have been saving to build as a drag car. I'll never get to it, but I had planned to run rectangular tubing to hang the suspension and engine from in the front,.......alll the way to behind the rear suspension. Run a solid axle rear with a triangulated 4-bar, and coil overs in contrast to the strut front suspension. The added advantage is that bringing that tube partway through the floor allows easy attachment of a roll cage. The cage and tubing combination should give you all the strength you would ever need.

You could basicly build this chassis and drop the body over it...........john

04-25-2006, 10:35 PM
Ryan, thanks for the link, great project.

Your Lumina should be quite similar ....... might be some minor differences.
The Firebird doesn't have a rear subframe per se, the rails are stamped sheetmetal welded to the floorpan of the car. It looks like the GP guy just welded mounting points to the floorpan of his car. I wouldn't trust that with 600 ponies! Might be able to use some aftermarket, mandrel bent rear rails to hold the horses and mount the rear end. Since you're planning to use a Vette rear, you'll need something Vette or something custom anyway.

It looks like a ton of work .......... since I did some basic investigation into doing this to a '94 GP myself. A bit of metalshaping and a ton of mechanicing, mixed with a whole bunch of time ought to get the job done! I was looking at a full frame job myself.

I'm with Jeffrey on the cage. With 600 hp, you're gonna need a cage just about anywhere you take it, except to shows and, maybe, on the street! It will stiffen the car considerably, which should help with ahndling that kind of horsepower - or handling with that kind of horsepower.

Cool project! Post pics if you decide to go for it!

Tim D.

04-25-2006, 11:30 PM
Thanks agian guys,

John, The goal for the car is to be a top notch street car with ocassonal track time at both the strip and road course( If I can find one simi close to home). So the vet rear is not a must if it will not withstand the power I have always been under the asumption that irs's are the best route for handling. If Im wrong then in will go a nice 9" which are fairly easy to come across here with the dirt track guys.

Tim, You were going to go with a full frame, was there a specific reason or did the swap option never come up? Would the front stub mated to rear rails be a strong enough option? The cage is a definte, with ocassonal track time I want to be legit and had planned on the extra support from it.

I bought this car as the second owner, in great shape and have been from the east coast all the way out to Arizona and all over in between in it. It has alot of memories in it, thought out everything I always thought a rwd setup would be make it my perfect car, so now that Im in the position to make it a reality, it will happen. Just a matter of time getting everything lined up! Pictures will come soon hopefully!

Thanks agian guy for you insight!

04-26-2006, 12:37 AM
I'm just a full-frame kinda guy, I guess. My current "hot rod" (85 Monte Carlo) is full-frame, as was my last (79 T-bird). I guess I just like the added rigidity (I've heard all of the arguments about how rigid a unibody is, but they don't seem to feel that way when putting the power to the ground). A full frame is also a bit easier to modify, if needed. I wouldn't be comfortable welding control arm mounts and such to sheetmetal, as I have seen the factory mounts ripped out.

So, no real particular reason, just my personal tastes!

Yeah, the front stub and some real rear rails with subframe connectors ought to work out nicely too. Basically, that ends up being darn close to a full frame anyway :) .

Tim D.

04-26-2006, 04:39 AM
Check out a few of the aftermarket frame manufacturers. Speedway, Alston, Chassis Engineering, Art Morrison, etc. Pick up their catalogs for reference. Get some ideas from their designs.
Auto Weld has some awesome bending services available...
Or you can buy a complete frame bent to your specs.
A lot of the roundy-round suppliers have tons of usable suspension and frame parts so check them out also. A&A Manufacturing has a lot of pieces parts at very reasonable prices.
I am going through this exact same process with my Bad Ast Astro Van build so I may be able to answer a few of your certain to come questions...
Just make sure your welder and welding capabilities are up to speed before you waste a bunch of time building junk....:grin:

04-26-2006, 04:53 AM
I understand what you are looking to do, but I think you are going to great more work for yourself than is need to the job you want done by grafting on parts from other cars in that way. I would have to look at the front frame assy on the Z34 but I am sure that with a little less effort you could make a front end setup that would work. I will do a little search later but I saw where someone did a rear wheel conversion on a Ford Focus using the stock front suspension and a bolt-in kit for the rear 8.8 rear end. The rear bolted inplace where the stock rear suspension was mounted. With a few reinforcements here and there BOOM its done, and they didn't hack the car all up. I believe something similar could be done on yours also. So many times people look to grafting before they look at just modifing. I will do a little looking and see what I can come up with. But this approach is what I would look at.
I believe the guy that did the conversion on the Focus is Shan Hyland Motorsports. (not sure about the spelling :-? )

Jeff Parker
04-26-2006, 05:20 AM
Hmm... 600 horse. Instant carnage for fwd.....Never liked FWD..LOL

If I were doing this, given the road track parameter stated, I would DEFINATELY full frame and cage it. Any suspension tuning will be lost if the chassis flexes.

If it were ME, I would first look for a full frame that has the same wheelbase. Then check for the obstructions, like axle hump, A arm conflicts, etc.
If I could find a shorter or longer frame that fit the body better, I would adjust the frame length. When you cage it, it will dramatically stiffen the car. Common practice when you back-half a car for drag racing.

Just remember, you will have to change steering (Use donor frame's steering) , Add a transmission hump, use donor frames trans x member, and a multitude of other conflicts.

Its almost like you want to strip the car to the bare body, put it on a rotisserie, strip off any and all old frame off the FWD, and graft it onto the new rolling frame. Plan on TONS of work. Hopefully, you have access to at least a 3 car garage that you can tie up for an extended period of time.

04-26-2006, 05:51 AM
I know that this is Ford stuff but it will give you some ideas on what I am talking about. Ford Focus V-8 Conversion (http://www.ford-v8-focus.com/images/productsnew1.html)
The full frame ideas are great ideas and would work excellent for what you are wanting to do. You can use a 2x3 .083 wall tubing to do your frame if your reinforce it with at least a 4 point roll bar but better a 6pt. Or you could use a 2x4 tubing and an under floor x-brace and be fine with that. It really depends on what kind of driving/racing you are plaining on doing and how aggressive you are going to be with it. It really just depends on what you want out of your car performance wise. There are tons of different ways to do what you are doing. You just have to figure out what you want out of you car then the chassis can be designed and done to fit that need.
From what you were describing from you frist post by grafting from other cars I was under te impression that you were wanting something that would perform but still be a daily driver. If so then I would concider fabing a conversion kit to fit you vehical, something along the lines of the Focus kit.

04-26-2006, 06:50 AM
Good timing..I'm tackling a similar project right now and figured on putting up another post about it soon. I'm doing a RWD conversion also, with a custom frame under it. See this post from a while ago, it has some solidworks pictures of my frame. http://www.metalmeet.com/forum/showthread.php?t=4744 Since that post I've had the custom frame rails bent by Autoweld which someone already posted a link to...Ron is about 20 minutes from me and the work is awesome, I highly recommend him, I've heard about him for years but this is first time I've needed his bending skills. Tell him Jason from Audioriginals sent you :)
That frame in those pictues isn't as beefy as you see on some cars, but again it's going under a unibody so I figure I'll be fine, I'll probably end up with a roll cage as well but that hasn't been designed yet. Frame is 2x3x11gauge. Last night I welded the main front frame rails to the drive loop crossmember, once I get some more together I'll post some picts.

I also considered the splicing or modifying options but personally I've never been a fan of trying to get a good strong weld of any kind of beefy steel to a modern unibody car....even the unibody frame rails I was cutting in this project were about 4-5 layers of thin metal...not really even touching each other to well...I would hate to try and get something substantial welded to that. While I was designing I had found a link to a guy doing a first generation probe RWD with some serious HP...he welded to the car to attach the four link rails etc...it just didn't look like a good idea to me...I'd give you that link but his pictures are now gone.

04-27-2006, 09:45 PM
Thanks agian guys, you have al given me alot more of a responce than I expected. Ive been alittle busy so Im going to try and address what I can think of!
Tim- The sheetmetal was more main concern with the GP I linked. I think Im leaning towards a full frame, as I want to get away than the strut setup and go with a trick coilover setup. And If Im going to go through the hassle with adapting a front slip to new rails I just as well go one step farther and do a whole new frame.
Mark- Thanks for the link, I have already come across autoweld and am very impressed with there work. I am teaching myself Autodesk Inventor so I think I might have to go with them for my rails! As far as the circle track guys I have been in the sport a few years and have access to some of the best suppliers and never really thought about using them for frame parts for my street car! Time to get all the cataloges out! You have pictures of your astro I have always been a big fan of the S family, My first build was a 350 S10. Will always love those things!

Thanks again guys

04-27-2006, 09:58 PM
Round 2, tring to get caught up to everyone!

Jeff, The stock full frame idea came up and I have been searching for awhile. The S10 Blazer and G bodys are both fairly close. The only conflict I have is I am tring to keep as much frame hidden as possible, and if I go with a full frame I will either loss a lot of foot wheel space or have a huge fram hanging out the bottom. One other option I thought about is The S10 frame and doing what is called a stock floor bodydrop where they actully section the frame and drop it from like 4 inches to 2 inches high which leads to strength issues I belive.

Jason, The whole thin sheet metal is why I have decided aginst the grafting, Was auto weld able to use your Solidworks desings or was that just for roughing the idea up? I woould Like to see so pictures when ever you get them, Anything different I love to study!

Thanks agian guys I am trully amazed by the help here, I have been to several boards and get the same one responce "With alot of money and the right person to do the work it can be done. But would be to much work for us!"

04-29-2006, 03:39 PM
Hey Ryan. Ron from Autoweld prefers templates to drawings. I used the solidworks to line everything up and let me be able to see it as I was designing...it was a bit tricky as I had to work around the car, it's "from scratch" but there are some things that just had to go in certain places...I started with that, drew it in SW, filled in the rest and made templates from the drawing and fit them on the car. Autoweld like the templates so he can bend and adjust as he goes, I gave him flat cardboard templates and his bends were dead on, he only had to adjust one bend from my template, I had two bends too close together so he had to space them out a bit. I've been out of town for work but I'll get some picts up this week as I get some more welded.