369 replies to this topic

[N/A-PWR]

Great Man Ryan,

takes time for it all to sink in, but simply,

if you want power = Big Cam, and the bigger the Cam,  the bigger the bang

[N/A-PWR]

stage 5 coming up DJ

we are getting the facts straight first before we can move on Hey

[SA EH]

So Jonesy are these the numbers you saw on the degree wheel at .050' lifter rise and if so are they what was recommended on the cam card ?

 

 

Here you go Mick

 

 065.JPG   206.52K   9 downloads

[N/A-PWR]

Big bit of Poke in that Cam Jonesy,

I would like to know your inlet port sizes, when you see them next. Dave I

and increase your PSI in the pots by 50 psi too

 

 

But I am decreasing your Engine life, so maybe don't listen to me

 

 

 

300psi pots, is my next challenge in the 208

Edited by TORYPOWER, 30 April 2014 - 10:51 PM.

[warrenm]

How much total timing are you running?

[SA EH]

I tried between 20 - 26 at the drags on the weekend. How much do you think this cam would want Warren?

[warrenm]

If you are using NO2, 25°-28°, but NA I'd be aiming for about 32°-35°, which is what I was using when I run petrol & 10.8cr & the 12 port head, now I'm using methanol I've tried 30°-40° with no changes in et,mph or any other issues, so I keep setting it at 34°.

When you are on 98 are you using an additive as well?

The 12 port motor that I have does ping a little if no additives are used, if it's on avgas no issue. Nulon Pro-strength is what I use with petrol.

[SA EH]

Cheers guys, good info.
Gives me something to play with. I am using a booster on 98 Warren, and it is the nulon one, after a switch from VP.
Reckon I might get some richer needles like you suggested & stick to e85 though, just to keep detonation away, crank the timing, and play with the carby dashpots & springs.

[warrenm]

Just for comparison, I run 10.5:1 and have total advance around 26-27 deg.

 

Why would one motor want an extra 5+ degrees over another? 

Lots of things come into play here ie; cam timing, spark curve, jetting , port flow/shape,combustion chamber shape etc. The 12 port motor with it's current cam does ping slightly if the fuel isn't correct, but when I built the motor I didn't get the phasing on the crank checked, & it does show signs of detonation on #5 plug, all the others are clear. I had this same engine in a UC Torana for a couple of years fitted with efi & a 220° cam. I replicated the spark curve in the efi but had to remove a heap of timing out in the middle of the curve then lifted it back up, it still pinged slightly on the dyno so I added more fuel in that area & it was fine after that.

The 9 port motor has 12.5cr fitted with the same 254° cam from the 12 port motor doesn't ping anything like the 12 port does, port shape/flow etc. comes into play.

Oldjohnno may be able to add more to this.   

If you can get E85, I'd be using it. I'm playing with E85 in mine at the moment.

Edited by warrenm, 01 May 2014 - 12:41 PM.

[SA EH]

How do you modify the spark curve in a bosch electronic dizzy?? I've never done it!
Mine was done on the dyno but I'd like to do it myself.

[warrenm]

When it pinged on the dyno what sort of afr where you aiming at? and what made you put more fuel in instead of taking out a little timing? I'm not questioning your methods at all I'm just curious because I have always wondered whether it's better to have a slightly leaner mix with less spark advance or be a  little on the rich side with more spark advance.

I used a Delco ecu with a locked dizzy, & adjusted the timing within the tune.

It was a couple of years ago, but I think I was aiming at 12.5 afr & ended up with something like 11 something, I'll have to look at the tune which I'll have a look at tomorrow. I think the timing was less than 20° at the points that we added fuel.

[SA EH]

They are  a bit of a pain to do but if you are happy with the total advance which like warren said should be about 12deg initial plus 22 deg in the dizzy for a total of  34deg for your combo ,then you can change springs to get your required curve . I kow a bloke not far from here who can set your curve but it will cost for every change . What usually works for me is to have no centrifugal advance until about 1400rpm then have all 22deg in by 3000rpm . You will have to use Nulon pro strength booster all the time though .

 

Ok so my distributor is set on 12 degrees initial, if i DO have 22 degrees in the dizzy, it should read 34 on the balancer, correct?

Just trying to get my head around this...

[rodomo]

I fiddled the dissy in the grease slapper myself. Look here, it gives the part number of a good dissy to start with if you want to have a go. http://www.gmh-toran...or-bust/page-17

[N/A-PWR]

Good Stuff Rob,

I enjoy reading your work. Dave I

[SA EH]

Yeah good read Rob, i also like reading about someone else's pain & agony over 6 cylinders   

Cheers

[N/A-PWR]

wish, I knew about graphing 30 years ago, but I still remember 17° @ 650 rpm with the Standard Distributor and using the vacuum from a 500 holley and a 41/73 cam. Dave I

 

my self Dyno Tune found the sweet spot while under power to 7000rpm on the street ( real time stresses )