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Stag, 2500 & 2000 Forum

350/350 transplant

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350/350 transplant
#1
  This topic is about my 1972 Triumph Stag
stagitall Avatar
stagitall Paul Martin
Smallwood, NY, USA   USA
I purchased a stag with a 350/th350 transplant I need help locating a manufacturer or company
that has or can make an adaptor for the speedo. and tach.
any input would be greatly appreciated
Thanks
Paul

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ugmw177 Mike Williams
Charlotte, NC, USA   USA
I had a stag about 10 years ago that had a 4.3/350 THM installed. I was able to source the correct speedo drive gears...there are several online calculators that you can use to figure the need and then search GM speedometer gears for suitable dealers [they made a bunch of them].

As for the tach, it is electric and calibrated for a v8--should be the same if you have a 350--just use the negative lead on the coil for the pickup if standard ignition or use the "TACH" lead on the HEI Dist Cap if HEI.

stagitall Avatar
stagitall Paul Martin
Smallwood, NY, USA   USA
Mike, Thanks for the info, I will start my research and let you know how the story ends LOL

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Dayton China Dayton Carpenter
Le Sueur, MN, USA   USA
I have the speedo bullets that can be used in GM transmissions but have the british speedo threads. I have done several 4.3 Chevy conversions in Stags and Spitfires.

Since the stag speedo cable on the transmission side was not a threaded type you need to use a MGB cable. With this set-up you can use your stag speedometer and chage out the GM plastic gear ends to dial in an accurate Speedometer reading. Please PM if you are interested.


Dayton

romeo Nick R
Melbourne, FL, USA   USA
Can the stag frame, differential, and rear suspension handle 200 hp and handle nice at curves ?
I never drove a stag, and I don't know if it squats down at over 80 mph, like the gt6 suspension.
What are the stag dimensions frame and chassis wheel to wheel ?
Does it become front heavy with a 350, versus the aluminum original engine or other aluminum engine ?
I assumed the 350 is cast iron, maybe it's a bad assumption with the new aluminum engines.
Does the stag have any stronger chassis than the GT6, and what is the final weight with the 350 ?

StagByTriumph Avatar
StagByTriumph Glenn Merrell
Lafayette, CO, USA   USA
In reply to # 1503419 by romeo Can the stag frame, differential, and rear suspension handle 200 hp and handle nice at curves ?
I never drove a stag, and I don't know if it squats down at over 80 mph, like the gt6 suspension.
What are the stag dimensions frame and chassis wheel to wheel ?
Does it become front heavy with a 350, versus the aluminum original engine or other aluminum engine ?
I assumed the 350 is cast iron, maybe it's a bad assumption with the new aluminum engines.
Does the stag have any stronger chassis than the GT6, and what is the final weight with the 350 ?

Hi Nick,

The Stag drive line was designed to handle over 200 hp, IIRC , 250bhp. But if you are going to be dumping the clutch for burnouts, you will destroy the OE trans, diff and UJ axles over a very short time.

If you like the Stag styling but want to put in a big displacement V8, I recommend you go to a Corvette driveline. If you use the stock Stag driveline for over 250 bhp I recommend an automatic transmission matched for the engine might be a bit easier on the stock drive line life. There is a guy in Kokomo who has a lot of brackets for converting Stags to Corvette drive-lines.

The Stag is a 50 year old classic Grand Touring vehicle with full independent suspension, so it handles well in curves and also highway cruise. But it ain't no Ferrari, the stock Stag has a lot of body roll being a 2+2 Grand Touring design for overall comfort and handling. A lot of today's cars handle and perform far better than a 50 year old classic. The allure of a Stag is the unique styling of its 50 year old lines, and the stock Triumph V8 sound is superb and unmatched anywhere. I have also autocrossed several Stags and if you understand how they handle, I have run faster times than a GT6 - unless it is Joe Curry is behind the wheel of one of his highly modified racing Spitty's and he does not over steer off the course into the cones ...

As for suspension "squat" over 80 mph, that depends mainly on body aerodynamics unless it is a special suspension setup - I am not aware the GT6 has any such special features to lower the suspension over 80 mph like on my Jaguar.
The Stag is very stable at 80 and above and was designed for a top speed over 120mph. I have driven a 280bhp+ conversion Stag to something over indicated 140 max MPH on the Speedo and it was very stable, but that also had modified suspension and front spoiler.

The Original Triumph Stag V8 is a 3 liter cast iron Block with aluminum heads only used in the Stag, it was not all aluminum, it was not the Buick all aluminum 212 CID V8, it was not the Rover 3.5 aluminum V8 like in the TR8.
The whole Triumph Stag V8 engine assembly complete with accessories weighs about 425 US pounds.
If you install a lighter all aluminum engine like the Rover V8 or crate Chevy LT V8, yes you need to re spring the front to match the weight differences, and also should adjust the power steering pump to a lower pressure setting along with a long list of other modifications.

The Stag body is a monocoque or unibody like modern cars, and it is designed for a small displacement V8, 3-4 liters.
A GT6 is pretty much a hardtop Spitfire, body on frame with some beefed up suspension for a straight 2 liter 6 cylinder.

You can get weights for various American V8's by doing a google search. There are several sites that list engine weights for a whole range of V8 engines.

In my experience, Stags are worth much more when restored to OE specifications with the all original engine/drive-line as collector vehicles. Stag Conversions - unless done with a full overall restoration and very professionally done, are difficult to sell.

Have fun!
.



Glenn Merrell, a.k.a. StagByTriumph / Garage
1968 TRG TR250; 1973 Mimosa Triumph Stag; 2000 XJ8; 2001 XJ8
"The BEST Trophies are: Miles on the Odometer; Stone Chips in the paint; Dead Bugs on the Windscreen (and the occasional smell of manure!)" an S by T Original quote!

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