Flinkly said:
i had the octopus in both my gt6's and both had the carbon canister to the front right of the engine. what carbon canister ever went on the firewall?
I've painted when the master cylinders are out for repair due to hydraulic fluid eating the old paint on the deck underneath, but obviously have never had the canister or BPDWA out & never painted underneath there. I guess it's time.
This is the early Mk3 US setup, standardized I think until the power brake booster became an option. What years were your GT6's? Did they have the brake booster? Did they have the original engines? A wild card with the layout of stuff under the hood in GT6's is that they often had their engines replaced with other engines, either earlier or later engines. If a replacement setup was plumbed for the charcoal canister up at the front right, it of course makes more sense & is easier just to extend the line from the old firewall location to up front than re-doing all the othe stuff.
Flinkly said:
the only other evaporative setup i've seen or heard abuot was that small cone shaped thing hooked up to the carbs and valve cover, and ususally placed over the intake.
That is the Positive Crankcase Ventilation valve, it is not *really* associated with & predates the evaporative loss & emissions control systems. It is present on the original-model GT6, just as a PCV system. As the emission control & evaporative loss systems were added & modified, they often hooked into the intake vacuum via different connections with the PCV valve. This is why it's important to know if the intake manifold had a port on top or not to narrow things down: depending on the year & the presence or absence of some other items, if it's there it will indicate whether or not the PCV valve was utilized in the setup (or if it was not, then as the point from which vacuum was drawn for the brake booster.
As mentioned, photos in shop manuals are generally only of the 1st GT6 engine, without emissions changes, which show the PCV valve & offer no information for other cars. That misleads folks into thinking everything is wrong under the hood when it doesn't look the same.
Tinster: I am very familiar with GT6's, but only familiar with TR6's to the extent of knowing what TR6 engine parts are needed for a GT6 from suppliers who only offer parts for Spitfire & TR6. I can tell you that the intake manifold on GT6's with no port on top was a short-ish run & setup. The port is usually there on TR6 manifolks too, as I've noticed. It is just a place from which to get vacuum: either for the PCV (its original purpose, as it dumps the goopy vapor into the intake manifold like most PCV systems), or in some later cars, for vacuum for the brake booster. Vacuum has at times also been made available at different places on the carbs: variable at the little ports that hook to the vacuum advance on the distributor), or not (the larger plastic ports at the back of some of the later emissions-spec cars, which thus used the no-vacuum-port-until-brake-booster intake manifold.
I need to point out in all this confusing stuff about the US emissions-spec cars that the underhood GT6 emissions setups were NOT complex, did NOT really affect power, & seem confusing & complex only because they changed a few times & there is so little documentation. They were basically a matter of moving hoses around, doing things that didn't amount to much as far as performance. The real changes that were done to decrease emissiions & which affected power were simply: increasing the head thickness to lower compression. The other emissions stuff was just confined to cold-start features in the carbs (& a barely more conservative needle). Once the car is warmed up, the only emissions equipment operating is pretty much the fat casting on the low-compression head.
Here is a quote from a letter received 2/25/1980 from Michael Barratt of the factory Jaguar Rover Triumph Competition Department East (maybe a few others will remember that JRT was Triumph's poppa for a while after British Leyland split):
"Please be advised that the GT-6 Competition Preparation Manual is in the process of being updated to accomodate specifcations that were made since 1968, as compression ratios range all the way from 9.5:1 to 7.4:1 on later emission engines.
"However, the datum point is the 8.5:1 compression ratio with a cylinder head of 3.460. The only modifications that were made to the engine on later models, was to achieve a lower compression ratio, was to cut the head casting thickness. Therefore, regardless of the original thickness of your cylinder head, to achieve a compression ratio of 10.25:1, it is still neccessary to mill for a final thickness of 3.375."
So when you have the head off for a rebuild or whatever, have it milled for 8.5:1 or 9:1 (don't get greedy!) to get back up there in performance. As the later heads actually flowed better than the earlier heads, you'll actually be getting ahead. Folks in areas which must meet emissions test should consider a catalytic converter, which today are much better-performing & not the parasites they were originally.
The problem is that engines have blown over the years & were replaced by engines from cars of other years. The decision must then be made whether to set it up for the engine (mostly involving just the presence of various vacuum ports on the carbs & on the intake manifold, or the presence of a vacuum retard distributor), or for the year of the car. Practically, if possible, it's best to set it up for the year of the car, so when you order parts they'll fit & you don't have to go all Sherlock Holmes on the car & then try to explain what you want to the parts vendor.
<div class="ubbcode-block"><div class="ubbcode-header">Quote:]ozzie, If you can fix the system you have, they work great, but most of the time the little vacuum on the bottom of the carbs is gone. [/QUOTE]
The little brass vacuum port under the left carb goes to the vacuum advance on the distributor. If there was a small brass vacuum takeoff on top of the right carb, then it was for one of the variations that had the canister at the front right. If there are 2 large plastic nipples for vacuum at the top right rear of both cars, then they were for *either* the firewall-canister setup, or for one of the front-of-the-engine canister setups.
Here also is where a scrambling occurs. If someone's gotten replacement carbs for a car with different vacuum ports, then they've had to figure a different way to hook things up. No matter what you've got, there'll be a way to set it up functionally correct, usually following one of the original setups. The errors come with hooking things up to the wrong place, or leaving a vacuum port open not knowing what it's for.
Pictures of your carbs, intake manifold, firewall, & a commission number (VIN) would help!
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