Big_Matt

Does anyone know what cfm the carter thermoquad is rated too? I hear that there is things you can do to it to really get it cranking.

davis

Big_Matt,

You need to identify the model of carburetor you have. The Thermoquads can be identified by taking a look at the number stamped into their base plates on the left rear corner of the carburetor. See:



...for a better idea of what I'm talking about.


You probably have a 600 if it is on a Cleveland--if my memory serves me correctly--but my Carter book (now hopelessly lost) seems to me that it had about a million different part numbers and CFM variations for the Thermoquads, so I can't tell you. However, once you get your number, you can ask someone who still has their books like the guys at Carbtech.com. You can ring them up and ask them if you can't easily find someone locally. Alternatively, you can post it here and one of us in the US will do it to save you the long distance rates. Or you can call them yourself at: (714) 990-1484 The number is in SoCal US.


:davis:

xbgs351

They are a nice carby, but you can't readily get hold of new springs, jets and metering rods. This makes them very difficult to tune. If you have a relatively stock motor this isn't such an issue.

GreenMachine

i can't find anyone in Brisbane who will even set the bloody idle on my thermoquad... it's got a massive flat spot that i reckon has something to do with the opening of air doors and/or the primary/secondary changeover while i'm on the throttle (like my amatuer descriptions??), but every "carburettor specialist" i phone says "it's got a WHAT?? piss that off and chuck on a 600 holley..."

and now on topic, i read somewhere that they can flow up to 650cfm... but that might've been the version used on Val's... there's a really good website on them, a link to it was posted in one of the other thermoquad threads...

__________________
351C ZH MARQUISINATOR
Presenting, at great cost to management:
.020 over 351 Clevo, 10:1 comp, ported 302 heads, blueprinted and balanced, custom ground cam, Edelbrock intake, 600 Holley, K&N air filter, Custom Zip-Ties(tm), MSD ignition, Genie extractors, 2 x 2.5" exhaust, 2800rpm stally, rooted C4

Big_Matt

An uncle of mine said he had one go to 980. Now he might be getting old and cant remember that it was 680, or he might have been doing some serious fiddling, also a possibility.

At the moment my running ZH has a 600 Holley, the ZH that hopefully will be running for the first time since Dec 5 in about 1/2 hour, will be running a carter thermoquad. (the one about to run is the white one in my avatar).

Trouble with the 600 Holley I have is that its a square bore so it goes through a bit of petrol in standard driving, not to mention its tuned to rich and the kickdown cable wont let me get into 3rd until about 105 km/hr. Since the carter has a spread bore and bolts on easily, i was thinking of putting it back on my currently running ZH.

brenx

The size or type of the carb has nothing to do with your fuel economy. The weight of your car/the diff ratio and your right foot affect your economy in a big way.

To get better economy you have to make your engine more efficient with the fuel it burns. Develope a few more hp and you'll get more k's to the tank.

Like I keep saying my mates XB coupe runs a 650 double pumper. It's virtually stock apart from;

Cam
Carb
Springs
Exhaust (still runs manifolds)
3.5 open rearend

It develops 163rwkw and it does 440-450k's per tank. Most standard Clevo's struggle to go past 200-300k's per tank I've found. my stock one got nothing over 220k's per tank. Modified that same car gets 350-380k's per tank. It's more efficient even though it rana 3500rpm histall and a 4.11 rearend.

Everyone assumes a 2.77 or 2.92 diff is great but they fail to realise their wasting the fuel on take off. It'd be more efficient with a 3.23 or 3.5.

Brenden

__________________
XB Fairmont (street car) 11.07@123.02mph.

xbgs351

This page should give you enough information to do it yourself.

http://anusf.anu.edu.au/~jgs900/thermoquad.html

xcgxl

Thermoquads have a reputation for set-and-forget reliability. Also it is the only carburettor that will get your ZH through a full NSW blue slip inspection as it is the correct carb to comply ADR27a.
(Most!)Holleys are a dumb design because of the gaskets below fuel level, eg front and rear bowls and accelerator pumps. Thats generally why your car catches fire cause they LEAK!
If your thermoquad (or any carb) has a flat spot it is probably because your accelerator pump is not working. Thermoqauds are notorious for this.

__________________
1978 XC Fairmont GXL, Emerald green, Jade Int. 351C, 750 VAC, C10, 9" LSD
Air, steer, power windows................

STROKEXD

I actually thought that the thermoquads were 850cfm or more for all models. But you can't compare an 850 CT to an 850 Holley...

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Big_Matt

The layout of a carby does effect the fuel ecconomy noticably, ie square bore and spread bore. My holly is a square bore so it goes through a little more for std cruising