Rejetting carbs

I would have guessed either 140/190, or 135/190 would give you 13:1 @ WOT. Can't wiat for results with the 135/170 arrangement. Great thread.

 

Hi PP
Have you used this on both sides (front and rear bank)?
JM

 

it just fits in the tail pipe, JM. I'm pretty sure the exhaust mixes in the muffler.

 

just put the 55 idles in ...you can tell it's happier immediately. more a/f readings later when i get a helper.

i think i'd like to drill the 50s out to 52s and see what happens too.

i note that some of these cars came out with 45 idle jets. how on earth did they even run?

 

Probably those F24 emulsion tubes.

 

What was the reason you went to 50's from 55's?
Running too rich? or just another problem?
Mine has 55's and is very cranky underneath the 2500-3000 changeover.
I am pondering going to 50's.

 

55s are a little rich at cruise...not terrible or anything, but not ideal.

ran far too lean with 50s, though.

 

Not on the Std 308 - it has 2 separate compartments. Not sure on the GT4.

 

i can't believe putting in 170 a/c made absolutely NO difference!

i'm now running around 13.8:1 at WOT with 135 mains and 170a/c....same as 135 mains 200a/c

looks like trying the 140 mains is next...which would make millard right on the money all along....which i hate!

 

I bet a 138 main 195 a/c would be perfect if such things existed

 

you can make anything you like!!! i think the 195 might be a bit big, though....it was still leaning out with the 200s quite a lot.

i'm still experimenting...but things happen slowly.

 

About when is your main jet kicking in with your current idle jets? My 55s feel like they turn off at about 3000-3500 and the mains take over. I recently installed platinum plugs (NGKs only had 100 miles on them, but I felt like experimenting) and the car immediately ran better, but it developed a flat spot at 5000-6000rpm. Still trying to figure that one out.....

So I assume you are going to try the 140/170 layout. Keep us posted.

 

i can actually feel that transition more with the throttle position than revs...and the A/F analyser confirms it. about (guessing) 1/3 throttle is where the mains come in...and i've tested it down to 2000rpm. I can tell because that's why it suddenly goes rich (it was much more obvious with the 50 idle jets)

 

Dyno on weds. that should sort it out all in one go. taking an assortment of jets and a/c

will be intersted to see what the output is too.

 

208

 

Please let us know the results, I would love to see how it goes.

 

I forgot about the HC pistons - maybe 220

 

i'm going to double check my float levels tomorrow before i go on the dyno on weds.

i know the specs are 48 and 58.5, but is there any benefit in changing those settings so that, for example, there's less fuel surge around corners or anything like that?

 

benincas did a rebuild...sounds similar specs to mine...200rwhp on their dyno.

 

If they're right, you won't get surge.

 

Must be dyno difference, I had 208.
Great exhaust though - it was worth 20.

 

we'll see.

they're all set at 49. i wasn't smart enough to get closer

 

i just realised that setting the floats HIGHER means the number is lower...i set them at 47mm.

 

http://www.pless.com.au/cars/gt4/rebuild/images/308dyno.JPG

135 mains and 170 a/c

140 mains were too rich, as you can see, but there was no difference in power. basically, just wasting fuel.

Now for the sad bit.

55 idles are definitely too rich, running at about 12.5:1 on cruise.....HOWEVER, it's also too lean as the throttle is just cracked open...this happens a lot...bit of a tail wind....slight downhill...etc...in fact, it happens often enough so there's often misfiring on cruise. 50 idles is what it needs, but it would make it even worse when the throttle is just open a touch.

The dyno guys mentioned drilling out the first progression hole.

i'm thinking....ever diminishing returns!

I'll think about what to do next...if anything.