Alfa Romeo Forums banner

1 - 20 of 25 Posts

·
Registered
Joined
·
45 Posts
Discussion Starter #1
Good Morning,

I am trying to build my 1750 GTAm Rep in a big hurry and I have hit a snag with the rear Trunion arm which is a later type GTAm unit. It simply does not fit my shell (Mk2 1750 LHD Italian built).

It seems like the floors are too deep and intrude into the space where this bar is normally located. Has anyone run into this problem before and is there any way to solve it? Please see pics below. I would appreciate any feedback. thanks.
 

Attachments

·
Registered
Joined
·
1,143 Posts
that is correct. You have to use a hammer to modify the floor a bit to make the room. too bad this was not done before paint.
 

·
Registered
Joined
·
45 Posts
Discussion Starter #3
Thanks Veep,

I had no idea it would not fit. It is a great pity.

How big a job is it actually? it is a lot of hitting or a small amount?

Thanks for the reply.
 

·
Registered
Joined
·
3,509 Posts
I have had Three GTs with Sliding block installed and have not noticed that the floor was hammered to make the cross piece fit.

And do let us know your final solution.

Ciao

Ken
 

·
Registered
Joined
·
761 Posts
Hi

Ken, I, too, am surprised a 1750 floor needs modifying (or is it a trunnion problem?)... but Veep suggests normal!

Veloce75za, please post some after pics, thanks.

Richard
 

·
Registered
Joined
·
1,143 Posts
It was needed with my car. Also with several others I have seen. Depends on which body-year it seems.
 

·
Registered
Joined
·
3,509 Posts
Ok so the GTs I refer to were on 64 spring GT, a 65 GTA and a 69 GTV Canadian Spec. I guess the GTV is the most relevant to this discussion and it is long sold and I only see it occasionally at vintage races.

Ciao

Ken
 

·
Registered
Joined
·
1,971 Posts
ken

yours may have more room than the late body shells. there are at least 3 different bulk heads in that area for 105 gtv shells i have notice. early 1 stepnose, 2 mid step nose, series 1 1750 and 3 the series 2 1750/2000.

they were updated progressively since over a sharp bump laden with heavy luggage in the trunk, can put a nasty kink in the rear fenders as i recall. a light tap in the rear will make your car look like the titanic heading for the sea floor on the early cars.
 

·
Registered
Joined
·
1,143 Posts
ken

yours may have more room than the late body shells. there are at least 3 different bulk heads in that area for 105 gtv shells i have notice. early 1 stepnose, 2 mid step nose, series 1 1750 and 3 the series 2 1750/2000.

they were updated progressively since over a sharp bump laden with heavy luggage in the trunk, can put a nasty kink in the rear fenders as i recall. a light tap in the rear will make your car look like the titanic heading for the sea floor on the early cars.
as far as I know its the series 2 shell (1750 and further) that has this issue. My shell is a 1972 GTV2000.
 

·
Registered
Joined
·
1,143 Posts
How much of the issue is accuracy of the repro vs. change in body?
how do you mean this? if its a racer that will drive under rules where the car has to comply with homologation papaers and the other rules in class one makes other choices than for a street car. I would not fit a SB on a street car (that would be a watts, if not simply the stock trunion or a alu version of it).
 

·
Registered
Joined
·
641 Posts
We never had this problem??? Perhaps this peace of aluminium is a replica and is not correct in dimensions? But general the floors of chassis after 1970 is deeper following the rules of Fia after protests from Ford agains the homologation of GT / GTA as touring cars... the inner dimension has to be greater, specially the distance over the rear seats between seasts and inner roof , so Alfa did new , deeper rear seats and modified the floors....thus was the second protest of Ford...1968 Alfa just changed the inner roof ...the caset came to enlarge the ditance...
 

·
Registered
Joined
·
2,181 Posts
I think you are misunderstanding ...

The question I raise is whether the reproduction trunnion/cross bar depicted has an identical shape to the original or whether it is the shape of the floor that is the issue here ....

Obviously, the OP uses a reproduction sliding block trunnion/cross bar with a diff modified for Watts.

how do you mean this? if its a racer that will drive under rules where the car has to comply with homologation papaers and the other rules in class one makes other choices than for a street car. I would not fit a SB on a street car (that would be a watts, if not simply the stock trunion or a alu version of it).
 

·
Registered
Joined
·
1,143 Posts
ok clear. As far as I know the repro bars are the same in dimension. Mine is a reprobar too btw. maybe maybe there is a problem?
Other solution may be grinding off the bar..
 

·
Registered
Joined
·
761 Posts
Veloce75za states his trunnion is late type 1750 GTAm....I can find no reference to any differences with earlier type.

Just a quick search in Don Black's magical Competition Reference Handbook states "CRBB System - sliding block rear axle to you and me - Developed for GTA's but useable on all 105 chassis and 101's with modification...."

Alleggerita by Adriaensens/Dasse shows two versions of the trunnion bar; to my eye they are identical in shape but have different end mounting castings -function and type identical and part number appears unchanged! No trunnion fotos in the 1750 GTAm section. However, the same foto is used for homologation documentation purposes for both GTA 1300j and GTAm.

I am leaning towards faulty repro manufacture....

Richard
 

·
Registered
Joined
·
45 Posts
Discussion Starter #18
Mine is a repro for sure. It has come off my race super where it fits absolutely fine and I have been racing with it for a number of seasons. The floor is just too deep on the drivers side (LHD).

I'll check it against the original one and report but I am almost certain the problem is in the body shell. I have no idea how Auto Delta solved this on series 2 cars.
 

·
Registered
Joined
·
11,640 Posts
Autodelta: 5 seconds with a hammer. It's the road car for homologation purposes that needed the interior dimensions.

Sometimes we over think things 🙂
Pete
 

·
Registered
Joined
·
3,509 Posts
Some trunnion Measurements

So I got out my 2 types of original Autodelta sliding block trunnions for Measurement.

But first let me say that the thin ended one came bolted onto my GTA Corsa and I have no reason to think it had not been there since 1966. The thick ended one came on my 64 Sprint GT Bulova racer and will have been installed sometime in the early 1970s. A same type also came on my other Bulova Car, a 69 GTV and also would have been installed in the early 1970s. These last 2 would have been sourced most likely at BOBCOR in Buffalo, 1-1/2 hours from Toronto. These observations leads me to think that the thin ended one is the early version. Alleggerita second edition, IDs that type as the late version. Also note that the thick ended version shown has been broken and weld repaired.

So you can see from the pictures how I took my measurement. Both measure about 16 mm from the straight edge to the top of the trunnion.

So if Veloce75za, the thread starter, can make comparable measurements we might learn something or not.

Regards

Ken

PS: for those interested in such things, the thin ended trunnion weighs 3.345 kg with bolt and the thick ended trunnion weighs 4.635 kg with bolt, reinforcement plate and weld fillet.
 

Attachments

1 - 20 of 25 Posts
Top