What boost can standard carb run

[caymanr26]

I just bought one of mike's (gt turbo spares) completely rebuilt carbs - as well as that the car has

Uprated head gasket
Uprated valve stem seals
Uprated head bolts
Mocal oil cooler
2.5 inch down pipe
Scorpion/Pro-speed exhaust
KTR180 turbo
Tubular manifold
All new gaskets
New distributor cap and arm
ITG Maxogen Air Filter
Cup mod carried out
Braided turbo oil feed
Every Samco concievable
Double Capacity Intercooler
Tappets all just set

So it's going it to South Wales Tuning who have a rolling road in order to get set up on Thursday morning

My question is - what boost pressure can I run safely on a completely standard carb with above mods?

[Mart]

Unless you adjust the carb jetting/fuelling accordingly, ~13psi is the max boost you can run through a standard o.e spec 32dis.

[Tony Walker]

read up the carb articles and make sure the tuning company know the carb and dont just stick a big main jet in it.

Std carb i wouldnt want to go more than 13ish psi even that may be too much on a fresh rebuilt lump.
Main mods to carb are Air corrector jet made smaller to around 0.9/1.0mm
and 2nd stage enrichments drilled up to at mostish 1.4, 2nd stage is for fine tuning really. the ac jet makes most difference and these mods are good up to around 18-20 psi when u need to start monitoring for detonation.

[caymanr26]

Thanks - that helps

I've had a good look through all the receipts tonight and there is quite a bit more done to it than i thought

Firstly it's had a full rebuild about 4000 miles ago, so had new pistons, liners, cam chain, tensioners, crank thrust washers, cranks seals, bottom end gasket set, as well as the uprated head gasket and uprated valve stem seals it also has

Uprated valve springs
Adjustable cam sprocket
High pressure fuel pump
Metal fuel filter

And I also earlier forgot to obligatory forge dump valve and high flow carb top elbow

The engine runs really nicely at the mo but hooked it up to an exhaust emissions tester tonight and was running very rich, no matter how much we turned the mixture screw it made no difference - any ideas on that one too?

[GTphil]

Firstly make sure the idle speed is set correctly, you adjust this with the screw on the bottom of the throttle plate, idle speed wants to be 800/900 rpm, then try the mixture screw again, on the afr meter idle wants to be 13.5/14 if you don't have an afr guage then wind the mixture screw in till the car almost dies then back out 2 or so turns should have you in the right area.

my brothers old carb the mixture screw didn't do anything and when we stripped the carb the bottom bit of the screw had snapped and was wedged in

Also when you do get it running some boost i wouldn't go much past 19/20lb with that blower or the exhaust gas temps will be through the roof.

[caymanr26]

Cheers mate - very useful
By blower do you mean turbo? My intention was to run 14psi ish for a while just til I know everything is working etc then who knows. Is the ktr180 not too good then?

[James5]

Cheers mate - very useful
By blower do you mean turbo? My intention was to run 14psi ish for a while just til I know everything is working etc then who knows. Is the ktr180 not too good then?

Blower yes means turbo.

Nothing wrong with it it's basically a T2 with a lightly bigger T2 compressour housing good for max of 16psi

[Romil Davda]

Cheers mate - very useful
By blower do you mean turbo? My intention was to run 14psi ish for a while just til I know everything is working etc then who knows. Is the ktr180 not too good then?

Blower = Turbo (not some cheap girl)

ktr180 is a very good turbo (IMO). Low down boost and I had mine upto 18psi (with a rejetted carb of course).

[Romil Davda]

good for max of 16psi

20psi if you go by K-Tec's website!!!!

[James5]

20psi if you go by K-Tec's website!!!!

http://www.k-tecracing.com/show_product.asp?id=37

I will go sit in the corner still T2 housing's,

[Jonny5]

ktr180 is a very good turbo (IMO). Low down boost and I had mine upto 18psi (with a rejetted carb of course).

I've ran my ktr180 @17psi for a while, no issues.

[Romil Davda]

http://www.k-tecracing.com/show_product.asp?id=37

I will go sit in the corner still T2 housing's,

LOL... the was for K-Tec buddy!

I am pretty sure at 20psi (or over 17/18), the turbo efficiency will not be 100%. IMO, you dont want the blower maxed out! running at 80/90% should see the turbo right for a good few years (5+ with my current one).

[GTphil]

it's a good "blower" for the five, the smaller turbo's get hotter quicker and after 18lb boost it probably won't make anymore power as you will effectively just be pumping air in that's to hot. Even a massive cooler won't be able to cool the air effectively.

I miss my old t2 turbo at times, just can't beat having power on tap regardless of revs. Its the turn of speed that makes for a fun road car.

I once ran 22lb manifold on a t2, then wondered why it started pissing oil out of the breather system, the above was the reason why. I was lucky tho as it could have been much worse if it wasn't for the 140 main i found in the carb a few years later........

[gttjames]

he says he only wants 14psi - with previous receipts etc, providing all is in order drill 2nd stage to 1.2mm maybe even 1.3mm if need be and run 16psi - that will have you smiling. Worth getting some ac jets in as well if you need to play with them, like said read carb guides in the articles section, all the info you need