1.3sr big flat spot at 4k

[mk3 vinny]

Hi people i have just got my first nova and its a mk1 1.3 sr and i'm not sure if its just me but i think it has a big flat spot at 4K rpm. For example if im doing 70mph in 5th and plant it the car dosn't do anything is this normal. It has the origanal carb on with the twin choke.

possibly this may cause the problem the car has a fast road kent cam in and it hasnt been fitted with an adjustible pully yet so hasnt been set up.

If you are going up through the gears 1st and 2nd are fine but 3rd when you hit 4k it seems to jurk abit then go but the cam kicks in at 3k

What would cause this problem

Or is it just me bearing in mind iv just got rid of my 2.2 astra coupe for this.

[pottersrebel]

sounds like the secondary jet is clogged up or the second choke isnt opening properly, now thats as a stock car racer and we pipe up the carb differently so it could also be the dizzy advance playing up ( slack weights etc ), it does sound more like a carb problem on the secondary choke tho as 4k is roughly when the second choke should kick in.

[conza123]

my 1.3sr does nothing when i plant my foot in 5th.

[mk3 vinny]

right so i will try and get the carb off and get it cleaned properly insted of carb cleaner down the top lol.

And i guess its normal for them not to take off in 5th lol

thanks for the responce lads

[conza123]

right so i will try and get the carb off and get it cleaned properly insted of carb cleaner down the top lol.

And i guess its normal for them not to take off in 5th lol

thanks for the responce lads

yer mine pulls in every gear then you get in to 5th and its like you have hit a brick wall lol

[mk3 vinny]

well it hits that wall abit in 3rd and defo in 4th and 5th there is nothing there.

[marc69]

For everyone where it does nothing, my sR used to be like that until I got the 2nd barrel opening, they often don't work but when they do, in 2nd gear from 2K upwards, with your foot flat, you should actually feel the 2nd barrel open just as it rreaches 4K upwards.

[pottersrebel]

For everyone where it does nothing, my sR used to be like that until I got the 2nd barrel opening, they often don't work but when they do, in 2nd gear from 2K upwards, with your foot flat, you should actually feel the 2nd barrel open just as it rreaches 4K upwards. totally agree with marc69 we pipe our carbs so the second choke opens as soon as it can and you definately know when that second choke kicks in

[mk3 vinny]

well mine dose have a kick in its **** when it hits 3-4k so it might be ok but i was unsure if this was the cam or the carb

when i lift the leaver by hand for it the car dose rev up dose this mean its working right but i have been told you cant tell by that as its an auto choke and opens by the water preasure or something

[marc69]

The 2nd barrel only opens when the pedal is flat (there is a stopper) and then a vacuum opens the barrel but the whole vaccum system on these carbs often fail or are badly adjusted.
When I was testing mine I put ink on the butterfly, if it opens the ink will be washed off with the petrol. Another way to find out if it works is to drive the car in 2nd gear up to 6K rpm.
The first time withe vacuum pipe removed and then attached, you should notice a massive difference, if you don't then it isn't working.

Either way there should be no flat spot, the only thing I can think of is perhaps it is all opening but the fuel pipe for the 2nd barrel isn't reacting?

[mowgli]

my 1.3sr does nothing when i plant my foot in 5th.

is this meant seriously??

if so, it had 72 hp when new..it probably has 65 now... i wouldn't expect it to do anything much in 5th.. it was a cruising/economy gear.. they always needed to be revved high to get any decent speed out of them

[mk3 vinny]

he was pointing out to me that its normalto do that.