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UmmYeahOk
02-17-2010, 05:27 PM
Ok the owners manual for my 67 GT6 says to use 100 octane. Highest I can find is 91, 93 unleaded. I'm pretty sure my heads have not been upgraded to use unleaded so I'm wondering what to use. Can I use 87, 89? Do I need to use a lead additive to the gas? I'm pretty sure this has come up in conversation before but I've heard of people with lead heads running unleaded with no problems

The other thing I wanted to know is idling. This is my first carb car so I know learning the choke will be fun, but after start up, how long do I need to let the car idle before driving off? Does it matter what temperature the weather is?

poolboy
02-17-2010, 06:02 PM
Assuming that you have the correct gap between the fast idle cam and the fast idle adjustment screw, use only as much choke as is necessary to start the engine. Sit there and reduce the amount of choke as the engine warms.
Other than depressing the accelerator as you pull out the choke knob, keep your foot off, unless you are in a hurry and determined to drive with the choke engaged.

The ZS carb does not really choke by cutting off the air supply as in choking, but rather supplies a rich mixture thru a seperate jet. Keeping your foot off the accelerator allows the fast idle cam to open the throttle disc just enough if it's properly adjusted.
Too much "choke" for too long tends to wash down the cylinder walls.
I'm sure there are lots of people who take off using the choke. I don't and in fact I don't move until I see the temp. gauge start to move. But then I'm seldom in a rush to get anywhere.
Having said all that I doubt if any 2 of us have the same warm -up ritual.

Geo Hahn
02-17-2010, 06:07 PM
Re octane, I think you're going to have to compensate for that in the timing. I use the highest octane available and adjust the timing for no knock. Yes, there can still be knock/ping you can't hear but getting rid of the audible ping has always worked for me.

Absence of lead is another issue (albeit the reason for the octane drop). I drove for a great many years with a stock head and no lead but finally noticed a recession in the valve seats that no amount of adjustment would fix. This came primarily on one exhaust valve right after an 80-90 mph cruise that went on for 3 or 4 hours so I guess I was asking for it.

I now have hardened seats though I don't think waiting until I really needed them was a bad thing. If you do delay getting hardened seats then just make a practice to check the valve clearances regularly.

As for the choke -- temperature is a big factor I think, but even in chilly weather (say 30 degrees) I am off the choke after a half mile or so. I never let the car idle/warm up before driving... I just avoid working the engine enthusiasticly before it is warm.

martx-5
02-17-2010, 06:19 PM
Concerning the octane rating, you can read all about it here. (https://en.wikipedia.org/wiki/Octane_rating) The gist of the article is that in the UK, as well as other parts of the world, octane is figured differently.

Using any high test gas (91 or 93) octane here in the US should be more then satisfactory. You might even try 87, but listen carefully for any pinging.

As far as the heads go, use the unleaded, but keep a periodic check on you valve clearances. If they start to close up over a short period of time (the exhaust valves), then you will have to have head work done. However, some engines run thousands miles before needing any work due to the residual lead on the exhaust valves and seats.

I have no experience with any lead substitutes, so can't comment on their effectiveness. Maybe someone else has.

pjsmetana
02-17-2010, 06:59 PM
Gas = highest you can find without having to go to the race track to get. 91 should be fine.

As far as choke goes, I let every car I have at least start moving the temp needle before going anywhere. But with my Triumph, I don't drive off till I can idle smoothly with no choke at all, and that usually is about 110 degrees F. If you just have the standard OEM gauge, then its about 1/2 way up to the normal operating temp (which is about 180F).

A wise man once told me that American cars = Get in and go, Asian cars = wait a few seconds then drive the dick'ns out of it, British & Italian cars = let the fluids all circulate and get warm... then when its up to normal temp drive the dick'ns out of it, and Any other countries cars = your lucky it actually works so who cares.

DrEntropy
02-17-2010, 07:30 PM
Octane "booster" is basically SnakeOil. As was said, the highest octane you can get is what to burn.

On depression (or demand) carbs like SU's and ZedS, the "choke" is an enrichment device. Below 50*F you likely need to use it in full open, once the thing lights off, go to less choke and just "blip" throttle to keep it goin'. The Triumph and MG engines are cast iron and once the temp gauge moves of the peg it'd be fine to press on. Alloy engines are a different animal.

On initial start, you don't want the thing to rev beyond 2.5~3.0K RPM until the temp gauge shows some temp. Rather than rely on choke for fast idle, better to reduce enrichment and just use the pedal on-and-off to keep it going until it'll idle on it's own.

Don_R
02-17-2010, 07:55 PM
I run cheap old 87 in my Spit. Haven't had any issues with it. Tried the higher octane fuels and saw no benefit for the additional cost. When I build a higher compression motor I may need to revisit the better fuels.

TR3driver
02-17-2010, 08:14 PM
Well, I drive the TR3 to work (unless it's raining), so I start driving pretty much as soon as the engine is running smoothly. You'll learn yourself pretty quick how much choke it 'wants', as too much will produce clouds of black smoke and rough running; while too little will be hard to start. Try it yourself, learn what "too rich" sounds (and feels) like, it has a different sound than "too lean". If the engine runs smoothly, it's "just right".

The 'project' TR3 doesn't like much choke, so I've only been pulling the knob perhaps 1" for starting, then reducing to perhaps 3/4" before driving. Within a mile, I'm down to 1/2" which really just holds the idle up a bit. Then I make a point to check and release it fully after getting on the freeway (which is only slightly more than a mile from my house).

For octane, you want enough to keep the engine from knocking under all conditions with the timing set to specification. More than that is a waste of money. If it still knocks on premium, back off the initial timing adjustment until it doesn't.

Octane boosters do so little and cost too much to be practical. When they say "raises octane by 4-6 points", they mean that it raises the octane by 0.4 - 0.6 of ONE number. The sole exception, IMO, are the ones that do actually contain significant amounts of MMT (which introduces it's own set of problems, like plug fouling).

Lead is a separate topic. While valve recession (due to lack of lead) is real, it's a rare occurrence, especially on car engines that have previously run on leaded fuel. IMO the best advice is to save the money you would have spent on lead substitutes (most of which don't actually work anyway) and, if you do get into significant valve recession, use the money you've saved to pay for the valve job. The valve recession doesn't actually hurt anything, in the sense that the valves seats are going to be replaced anyway.

swift6
02-17-2010, 09:28 PM
The suggested octane ratings listed in the owners manuals for these cars has caused more confusion than probably any other entry. Not only were the octanes figured differently then, and still are, but the gasoline formulations are also entirely different. To top it off, in the US, the gasoline formulations can change from one large metropolitan area to another. Which really means that all the tuning info in the manuals are also best thought of as "starting points" for proper tuning and not gospel. Lots of good advice on letting the engine tell you where it likes the timing for its final setting.

As far as the choke, I typically use full choke to start the engine, then immediately reduce the choke (to about half way), and am on my way. Light throttle applications with the choke on and typically within a 1/2 mile the choke knob can go fully home (off). At least that is how the TR6 works. The TR8 has "water/automatic" chokes.

The fluids in the engine aren't the only ones that need to be warmed up. Idling doesn't warm up the transmission or differential fluids. Driving warms them all up together and warms the engine oil and coolant faster than idling.

Roger
02-18-2010, 10:48 AM
Well said Shawn!

Warm-up idling has been a much-discussed topic for many years, but I'll add my two-penn'orth to the pot.
The biggest enemy of moving parts is moisture. An idling engine produces lots of it, and doesn't get rid of it well. This is even more true of an idling, cold engine with mixture enrichment (choke).
So my own rules are:

1. As a general rule, don't start an engine unless you're going to use it, and if it's a good 'un, not a beater, use it for at least 20 minutes.

2. Use as much choke as you need to get started, and dispense with it as soon as you can. You'll very soon learn when that is - my Europa TC needs choke for no more than 2 minutes even when cold - and believe me, it has been cold in Texas this winter, at times.

3. Drive it as soon as it'll pull - don't warm it up idling, just don't cane it until temperatures are at operating level.

3. If you feel you must warm up, use a hand throttle or equivalent and set revs at 2,000+. You don't have one? Don't warm up then. An interesting sidenote - the recommended warm-up for a Cosworth DFV is 4,000rpm.

UmmYeahOk
02-18-2010, 11:37 AM
thanks everyone fir your input.


The suggested octane ratings listed in the owners manuals for these cars has caused more confusion than probably any other entry. Not only were the octanes figured differently then, and still are, but the gasoline formulations are also entirely different. To top it off, in the US, the gasoline formulations can change from one large metropolitan area to another. Which really means that all the tuning info in the manuals are also best thought of as "starting points" for proper tuning and not gospel. Lots of good advice on letting the engine tell you where it likes the timing for its final setting.


the other thing is not only does today's fuels not have lead, but have at least 10% ethanol in them. I wonder what damage that could do. I already hate using ethanol in modern cars. It burns quicker (poorer fuel economy) and despite being home grown I've notice that gas is twice if not more expensive than when we didn't have it, and yet I'm still paying for 90% gas. Not to mention that our normal foods cost more since EVERYTHING uses corn... ...even livestock.



1. As a general rule, don't start an engine unless you're going to use it, and if it's a good 'un, not a beater, use it for at least 20 minutes.

This could be a problem. I want to drive this car but work, shopping, and the majority of car shows would take less than 20 minutes. Will I need to make my commute longer?

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]2. Use as much choke as you need to get started, and dispense with it as soon as you can. You'll very soon learn when that is - my Europa TC needs choke for no more than 2 minutes even when cold - and believe me, it has been cold in Texas this winter, at times.[/QUOTE]
Record breaking winter actually. I believe there may still be some snow left over from last thursday. At least there was some yesterday.
<div class="ubbcode-block"><div class="ubbcode-header">Quote:]
3. Drive it as soon as it'll pull - don't warm it up idling, just don't cane it until temperatures are at operating level.

3. If you feel you must warm up, use a hand throttle or equivalent and set revs at 2,000+. You don't have one? Don't warm up then. An interesting sidenote - the recommended warm-up for a Cosworth DFV is 4,000rpm.[/QUOTE]

So from what most people here are saying, start the car, don't let it idle too long. Either accelerate in park slightly, if you're having trouble getting the heat up. Once it idles fine, you can drive with the choke on if you're impatient enough, just baby it though.

Guess I'll figure out what it likes when the time comes

BTW is this why morons leave their cars running while they run inside convient stores? I've always wanted to hope in and drive off just cause, but thought the punishment wasn't worth the lesson.

You think they do it because they're carbed? I always thought it was cuz they were lazy and the vehicle was such junk that no one wanted to steal it. Someone told me though that they may be deisel.

swift6
02-18-2010, 01:22 PM
Yes, ethanol seems to be another evil that we have to deal with. Not only can it effect older rubber found in the fuel line but if it sits for too long the ethanol can seperate from the gasoline. When this happens, the water that the ethanol absorbs can also seperate, then you have three liquids in the same tank (water, ethanol and gasoline). Replace all of your fuel lines with new and you should be fine. Keep an eye on the diaphragms in the carburetors, there are ethanol resistant rebuild kits for the standards fuel pumps too. Then, as long as you drive it, ethanol shouldn't be that big of a problem.

20-30 minutes is a good rule of thumb to get all of the fluids, including transmission and differential, up to a solid operating temperature. Shorter drives tend to be hard on cars due to an increased build up of condensation, especially in the engine. Take it for longer drives occasionaly to burn off that condensation and it should be okay. BTW, this appllies to your Mustang as well, not just older carbureted cars. Short commutes with stop and go traffic are the definition of extreme conditions for oil life in an engine, all engines. Besides, what is the point of being an automotive enthusiast if you don't spend more than twenty minutes behind the wheel.

Idling a warm engine doesn't hurt it, diesel or gas. The key there is warm engine. Even newer cars, with full computerized fuel controls, are not reccomended to idle too long while trying to warm up.

The people that leave their cars idling while they run into a convenience store are being lazy. Probably the same guys that think driving like an idiot to leap frog one more car in stop and go traffic will actually get them to their destination quick enough to be worth the risk.

JonnyRotten
02-18-2010, 08:20 PM
I just bought a tr3a.I called a Triumph restoration place in pa. that has a two year waiting list.I specifically asked if I needed to add lead.He said if I drive around 3000 miles a year it would be fine on unleaded.more miles would require a valve adjustment every three years or so.

glemon
02-18-2010, 09:32 PM
As others have said use full choke or whatever it takes to start the car the car, back off as soon as possible, too rich a mixture (choke) can result in unburned gas in the bores, which will dissolve your oil and can lead to premature wear.

Second issue with choke/cold running is oil circulation, the hesitation you may get on a cold day before fully warmed up affects drivability, but cold oil that may not have reached all the bearing surfaces affects longevity. While the 20w-50 many use on "our" cars helps hot oil pressure levels it does not flow as easily into all the places it needs to go, hence the advice to take it easy (low load and RPM) until warm up.

There are different schools of thought on the best way to do this, many of the old owners manuals suggest taking off as soon as started and driving conservatily at low rpm at steady speed until fully warm, and advice against long idling for warm up, I think this is probably because of the concern about dumping fuel in the cylinder bores.

Problem is it is kind of hard sometimes to drive at a low rpm low load steady speed in modern traffic conditions, so many take the intuitive approach and let it sit and idle for warm up. Which is what I generally do, but as I said back of the choke as it warms so you aren't feeding too much gas in.

As far as the 20 minutes or more, yes I agree that is ideal, but not always practical, you should still be able to enjoy tens of thousands of miles of trouble free motoring with a little care and common sense and help from the forum!