SCCA EMod MGB GT V12 Build

Just a heads up, those Bert trannys are meant for circle track racing and won't work very well for an autocross car. They are meant to only be used hard in high gear, which locks into a direct drive. The clutch is an internal setup that uses motorcycle clutch plates and only works in reverse and low gears and doesn't stand up well to any sort of abuse.

What about a manual valve body "shorty" powerglide? They are only 18" long.

The 5.0 was probably heavy anyway. What's your target weight for this project? that will dictate your engine displacement, and thus the engine.

tpwalsh wrote: The 5.0 was probably heavy anyway. What's your target weight for this project? that will dictate your engine displacement, and thus the engine.

1850 lbs including driver, which I think was possible with the 5.0.

Here's some outside the box thinking for ya....

Does the engine make enough torque and can the rear end be geared such that you could run no transmission? Single speed, direct drive. Still have a clutch so you can launch it, but then it's got no ratios. Saves a lot of weight and a lot of length...

In reply to DILYSI Dave: LSx in any displacement has north of 250 ft lbs from ~ 1800 rpm up. Gear for 15 mph around 2k rpm and see if 7k will get you fast enough for your fastest straight. Or gear for your fastest straight and work the other way.

Even Jeff Kiesel couldn't do it with less than 2 gears...

MrJoshua wrote: In reply to DILYSI Dave: LSx in any displacement has north of 250 ft lbs from ~ 1800 rpm up. Gear for 15 mph around 2k rpm and see if 7k will get you fast enough for your fastest straight. Or gear for your fastest straight and work the other way.

Gear the other way and use a torque converter with a high stall. That could actually work nicely and reduce parasitic losses as well.

My uncle essentially did this with his DSP Omni GLH. Used a 3-speed FWD Torqueflite automatic with a manual valve body and a custom final drive gear so that he only really used 2 gears. Worked great with his 2.5L turbo motor since he could build boost at will using the brakes and the limited slip allowed him to drive right out of the corners.

It doesn't initially seem to make sense, until you think about what you're doing in an autocross, especially as speed increases, the fewer shifts and foot moves allow you to focus on the driving.

Boost a Jag type "S" V6 motor.

^ that could work. I'd definitely be looking at an aluminum blocked motor of some sort. I just looked up the rules and for clarity, anything over 3200cc or 2285cc turbocharged has an extra 100 lb penalty. (1850 lbs total w/ modfied tub penalty). So the question is, what motor can have a super short transmission, is lightweight AND can turn some 12" slicks into smoke even at 70mph? Call that 400hp? I'm sure GRM can find something unusual that fits the bill. The SBF might not have been a bad choice, given the heavy minimum weight, and ease of build to get the required power.

LSJuan?

GM 60*v6 with lockup tourque converter to torque tube. aluminum headed motor, fully dressed, rund 350 lbs. im sure with it being an autox car, you wont need the accessories. which should shed 30-40 lbs. the 3500 makes 260+ out of the box, and ITB's, porting, polishing, and camwork make 325 easy. also, theyre stupid short/narrow. if you go 3100, youll stay at the lower weight box, has the aluminum heads, and should be able to make soime good power. you could also do a hybrid 2.8 with 3100 heads and go boosted. make some good power there.

and if you need a driveshaft, ive got a welder, steady rest, and no fear of failure.

i also know a guy who will pretty much make a driveshaft for anything.

throw out your specs, and ill call him and see. may not have to scrap your drivetrain yet.

tpwalsh wrote: ^ that could work. I'd definitely be looking at an aluminum blocked motor of some sort. I just looked up the rules and for clarity, anything over 3200cc or 2285cc turbocharged has an extra 100 lb penalty. (1850 lbs total w/ modfied tub penalty). So the question is, what motor can have a super short transmission, is lightweight AND can turn some 12" slicks into smoke even at 70mph? Call that 400hp? I'm sure GRM can find something unusual that fits the bill. The SBF might not have been a bad choice, given the heavy minimum weight, and ease of build to get the required power.

After you pass the 3200 cc threshold are you completely unrestricted with motor selection? Seems like a lsx with a supercharger and a low rpm converter shorty glide could have all the torque you could ever need. Similar plan to the clutch with no trans idea above but with a first gear and reverse. Keep the converter stall speed low and you eliminate the mushy disconnected feel of an auto drivetrain.

There are minor restictions. No CVT unless it came with one, must be an automotive engine, etc, but otherwise it's free. LS1 + supercharger seems really heavy and high up to me. A cammed Al blocked 5.3 should be all you'd need to spin the tires anywhere. The LS is cliche, but at least the powerglide is light, strong and short.

LSx ALU block, bored out w/ 4.8 short stroke crank and rev it out like a wannabe Wankel w/ correctly geared 2spd.

GameboyRMH wrote: Even Jeff Kiesel couldn't do it with less than 2 gears...

Jeff has a rotary, not a V8.

I was searching to see if anyone had compiled a list of short gearboxes and found this:

http://www.rakeway.co.uk/page21.html

You can be sure it's not gonna be cheap though.

Finally got the rocker arms, machined from one chunk of aluminum, pictures don't do justice.

[URL=http://smg.photobucket.com/user/loosecannon/media/MGB-GT/IMG_1462_zps0a9ccc50.jpg.html][/URL] [URL=http://smg.photobucket.com/user/loosecannon/media/MGB-GT/IMG_1455_zps6a70edf5.jpg.html][/URL]

[URL=http://smg.photobucket.com/user/loosecannon/media/MGB-GT/IMG_1457_zps3bf049cd.jpg.html][/URL]

[URL=http://smg.photobucket.com/user/loosecannon/media/MGB-GT/IMG_1456_zps66cb64ab.jpg.html][/URL]

Especially pictures that don't show up!

Those look very nice,seems odd to spend a ton o money on rockers and use $30 bike shocks.Don't get me wrong I roll in the same way most of the time just say'n.

I was at Gimli last summer for a road race weekend/evening autox and your car was brought up by a couple locals...gist of the conversion was you need to stop changing everything before you even drive that combo.I'd jam a boosted ecotech(just stock even to get it rolling under its own power)just to get it out and sorted,add power later with bigger boost later without tearing the entire car apart to start over.

Just my .02 since I've lost track of how many times in 36 pgs the car has totally changed direction and drivetrains,suspensions,chassis,body etc etc without actually hitting the track much.

I love the long term development of this car.

kevlarcorolla wrote: Those look very nice,seems odd to spend a ton o money on rockers and use $30 bike shocks.Don't get me wrong I roll in the same way most of the time just say'n. I was at Gimli last summer for a road race weekend/evening autox and your car was brought up by a couple locals...gist of the conversion was you need to stop changing everything before you even drive that combo.I'd jam a boosted ecotech(just stock even to get it rolling under its own power)just to get it out and sorted,add power later with bigger boost later without tearing the entire car apart to start over. Just my .02 since I've lost track of how many times in 36 pgs the car has totally changed direction and drivetrains,suspensions,chassis,body etc etc without actually hitting the track much.

I think most people would agree that there's no need to spend $2000+ on a part when a $200 part does exactly the same thing. My Ohlins triple adjustable bike shocks have never been a problem. What has been a problem is the engine being too heavy and underpowered (both the V12 and to a lesser extent the V8), poor front suspension geometry and weight. I have only changed things as it has become necessary to change things, I don't believe in flogging a dead horse. Had I known of the problems I was going to run into beforehand, I would have started off with a tube frame, fiberglass bodied, boosted small engine right from the beginning, and you wouldn't have 36 interesting and sometimes drama filled pages of build blog to read. BTW-I got a screaming deal on the rocker arms, just like I got a screaming deal on the shocks.

Its ok I get it,I totally live in that world of using what I can get cheap and adapt it to my needs.I also suffered from the lack of focus you appear to have as well,I've worked hard over the last couple of projects to rectify that.

Now before I buy parts/build anything I define what I want to do with the car,how I'd like to get there and set a timeframe to keep from losing interest/changing goals.

With my scratch built car I spent close to 6 months designing/researching and then gathering parts.Went from paper to setting FTD at its first event in 8 months(about 3 months past the deadline however).Much better results than my previous projects.

I'm very much looking forward to seeing this bugger getting done and hitting the track again.

I have started to install the rocker arms: [URL=http://smg.photobucket.com/user/loosecannon/media/MGB-GT/IMG_1209_zps66bb3a65.jpg.html][/URL] [URL=http://smg.photobucket.com/user/loosecannon/media/MGB-GT/IMG_1210_zps9af8ef65.jpg.html][/URL]

Epic build!