Evolution of the 356A T1 & T2 How they differ

[JTR70]

Hey Trevor,
Thanks! I am glad you are finding some interest in this thread. I wanted to document and discuss all of the fine detail differences as the 356A production progressed. I did not realize your car was so close to the official cut-off. I'm sure you can provide alot of great info. Please jump in and add or confirm on any of these changes. I would bet your car has the short bumper bracket mounts and lower reinforcement strut but does it have the "waffle" spacer plate on the tunnel for the track mounts? Also what position is your shifter in? T1 or T2? Thanks for any help. Justin

[Trevor]

I believe the cut off is at 101693, at least when you go to order metal from Zims, Stoddard, etc. that is the cut off they list. My car has the hole with a grommet next to the gas tank, T1 shifter position and no corrugated/waffle metal for the seats tracks on the tunnel. The bumper bracket does not extend all the way to the torsion housing and there is a reinforcement piece. My engine compartment bulkhead wall is like the later T1/T2 that has the pieces for the optional heater and it does not have the Carrera bracket.

I'm not going to lie... I had to go check a few times when you created this thread to go see what my car had. I was really curious.

[JTR70]

Okay Trevor, I was wondering where you had learned the T1 cut-off #. Grommet next to the tank? do you mean the one on the release tube for the optional trunk lock? So, you have a standard T1 tunnel; remember don't buy the later pedistals for the outer track mounts when you put the new floors in. You're gonna mount directly to the floor like on my coupe. I can send you a photo and dimensions of the reinforcement plate/bolt set-up if needed. I am now wondering if the T-2 Style seat track mount arrangement coincided with the change from the wood bottom based "fat-back" front seats to the later thinner T-2 steel pan bottom front seats??? May have an answer one day. There are several more engine compartment details I want to go over with you next. I know what you mean I have looked at both these cars several times and am finding all sorts of small changes. Thanks for the feedback! Justin

[JTR70]

A small evolutionary change also happend with this previously discussed lower front T2 type reinforcement brace/strut.

Again this is an early T1 beehive speedster (83142) with a T-2 style chassis upgrade. Note that it is a slightly tapered but consistent piece.


Now look at this one on a 1959 chassis (107595) a nice little "swoop" added in right at the base of the suspension. My original thought was that is might be for better shock absorber clearance but I don't think it was an issue on the earlier speedster version above. Getting back to Roy's earlier annalysis on "crumple" zones to keep as much energy from transfering into the "A" pillars this looks to me like such a crumple zone. Just looking at this profile you can plainly see its going to give way first right in that little valley under a load.

Going back to this first version on the speedster you can see that it now comprises a very strong tube and would most defintely stabb and collapse the chassis right in front of the splash-pan longitudinal area. The later added in profile I believe was designed to minimize this from happening. All theory of course. I'll have to look at a B and or C chassis but I'll bet they did not change much from 1959. Trevor and Roy; what do your base braces look like? do they have this later relief profile? More trivia to come. Thanks for reading this! Justin

[Trevor]

I honestly don't know what the hole and grommet are for, but you have it pictured in your first picture in this thread and thought I'd confirm that mine has that.

Gotcha on the seats and mounting directly to the floor, although I am planning to go with Speedster seats when I get to the interior.

Pretty fun to go over these details. I'm all about learning and helping others learn.

[JTR70]

Me too! I hope all this may answer a few questions in years to come. Oh, you mean the grommet on the floor of the trunk; yes I am thinking that was either for a parking brake warning light or they rerouted the washer bag hose from my earlier t1 version. Most likely for the washer system. Speedster seats will be nice but it would not make a difference. Thanks! Justin

[roy mawbey]

Justin,

Yes my car 106954 has the 'swoop' as you show. I think you are correct this part will fold before allowing tghe damage to backl further to the 'A' pillar

I attach a poor photo ( only one to hand ) of mine. You can just see the swoop.

By the way I found the info on the damage problems when only one front corner is hit in an accident. On page 62 - 64 of Denis Jenkinsons book 'Porsche 356' he goes into detail about this hitting the corner bumber irons. Full frontal has the a large area to crumple, not nice but lessens the problem to the A pillars. The side swipe produces the nasty tell tale kink in the body panel by the corner of the windscreen. His car was an early 55 pre-A.

His solution to the problem was to remove the front bumper and irons and but aput a thin rubbing 'deco' strip round the front nose. He did say the damage from a side hit was so extensive and expensive as it needed the a complete new frontal assembly fitted to repair.
I doubt he ever realised the effort in the later 'A' cars that Porsche obviusly seem to have made to stop such a lot of damage happening. He wrote his book always refering to the fact his car was an 356A when it obviously a pre-A. But over the years he owned it he changed to a super motor, carrera brakes etc etc.

So interesting you highlighted the modifications to the chassis parts with your photos. I would have non the wiser till you made the comprisions Justin.

Roy



look just behind the yellow 'spax' suspension damper to see the curve.

[JTR70]

Thanks for the confirmation photo of your car Roy! The Dennis Jenkins description of the damage the bumper irons can help to create makes perfect sense. Also the fact that his car was a Pre-A which surely had the same bumper mounting configuration as my early T1. Thanks again for the input! Justin

Heading back into the engine compartment after the brief description of the rear bulkhead wall changes.

The spot-welded/ non-removable Pushrod version engine tray extension or shelf. Here is a change that came full circle ending temporarily in 1955 with the introduction of the 4-cam Carrera motor option and then starting back up again sometime in late 1958 or early 1959 T2. This welded in version would also continue all the way through productions end in '65.

Beginning in 1956 with the introduction of the 356AT1 ALL chassis were built "carrera" ready with all the specialized bracketry and shrouding to install this engine. To make a run of carrera's an easier order to fill the large pushrod version frame mounted tray was made removable. Instead of spot welds it was just bolted into position. Photo above shows the smaller and narrower 4-cam version perimeter tray with pre-stamped holes for the pushrod version tray closed off with bolts just above it.

Example above is a '58 T2. Note that the pushrod tray is still removable and the 4-cam perimeter tin was still being installed. However by this time the factory was slowly phasing out the installation of those 4-cam conversion components. This 58 T2 has the later firewall discussed earlier and no oil tank, filter or fuel pump brackets as found on ALL earlier 56-57 T1 chassis. The tack strip which holds the rubber seal all along this lower 4-cam tin was also no longer installed as on the earlier T1's.


By contrast here is a 1956 T1 Pushrod car with Everything there to install a 4-cam right down the pre-punched holes for the oiltank which was also stopped in the T2 run.

Jumping back ahead to this 1959 T2 chassis you'll notice that ALL the 4-cam tin is now gone. It is simply the frame rails, cross-member and this pushrod version enclosure/shelf. It had went back to the pre-A chassis configuration before the Carrera option; right down to the spot-welded push-rod version closing shelf. Note that the holes were still punched in the mounting flange from the days when it still was removable.

Same thing for this outer cross-member; as it to still carries the holes as well. So by sometime in 1958 and for sure all of 1959 not just "anyone" could be pulled from the production line and be ordered as a Carrera as in previous years. Thanks for reading this! Justin

Trevor, do you have pre-punched holes for an oil tank in your left side closing wall? I'm sure Roy's car looks like my example '59 chassis...

[roy mawbey]

Yes, Justin,
I am sure my chassis looks like yours.

Roy

[Trevor]

Trevor, do you have pre-punched holes for an oil tank in your left side closing wall? I'm sure Roy's car looks like my example '59 chassis...

I'm not sure which hole you mean Justin but here is a picture of the left (drivers) side.

[JTR70]

Thanks for the confirmation pic Trevor. So the later T1 cars were no longer being pre-punched for the oil tank. Your car also does not have the lower strip for the rubber seal. Here's the holes and base strip:

All the early 56 and very early 57's where pre-punch with the 3 large holes for the oil tank. they also came with mount mount strip for the rubber seal. Your car was no longer being out fitted with this. My best guess at this change would be at the introduction of the 101 series chassis. This why I was so desperate for an early donor chassis; it had everything I needed to repair my car. Thanks again Trevor! Justin

BTW: just noticed that the routing of the cable release tube was slightly changed...

[Trevor]

Cool details, thank you Justin.

[JTR70]

Thank you trevor! More to come....

[JTR70]

The last hold-over Carrera motor optional piece for the T1 and T2 chassis was the removable left rear fender brace. Like the removable pushed shelf/extension an optional unboltable left rear brace to make way for the oil tank would make a 4-cam conversion all the more easier. This of course started on the 1956 T1 cars and continued as far as I can tell all the way up to very, very late 1958 and 59.

Up until the introduction of the 4-cam motor both rear fender brace were welded in permanent like this right side example above. This is another item that would come full circle and become fixed once again up until productions end in 1965.

Left side brace was indenticle but had verticle mount plates on each end with a threaded nutter. The shot above clearly shows the two larger bolts which would secure the base. If the car became an actual carrera the pre-drilled holes would be closed-off by the same bolts only with a nut and washer instead.

On a side note if the car was fitted with an oil tank the factory guys made no bones about the pre-welded mount tab on the fender skin. They simply torched the ear off and left the old spot welded base. Original example above.


Again this 1958 T2 coupe still retained the removable left rear fender brace. Top bolt is covered in paper but the lump is visible. Trevors previous photo show his car to still have it as well.


This 1959 chassis shows the change back to a welded and fixed brace. However a close look shows this one to be a removable version which has been welded on. I can only guess they stopped punching the two holes and they still had alot of removable versions to use up.


Mount flanges with nutters both top and bottom but welded onto the chassis. Roy, does your car have this set up? Thanks for reading this! Justin

[roy mawbey]

Justin,

I will check to see if the rear braces have nuts or just plain welding.

I do know the area those braces attach to on the rear wing ( fender seem to be really good at collecting wet mud to eventually rust. I know I did some welding around there on mine, but never removed the braces.

I always thought the conversion to runa carrera motor would be relativily simple chassis wise. How wrong I was in my thinking. so many modifications to make that happen.

This has been an interesting thread indeed.

Roy