The V8 Owners Forum -

I've just fitted a Weber 600cfm carb and a Harcourt single plane manifold. The previous setup was a Weber 500cfm and a performer 3.51 dual plane mani.

Heres the results from today.

Brief rundown:

1. First run nasp on bigger carb and new manifold. Part throttle AFR just about right, but going quite lean at WOT.

2. Fitted biggest jets I had to the secondaries and tried again. Still a bit lean at WOT.

3. Opened out my biggest jets by 0.4mm and refitted them. AFR at WOT just about spot on. And she made 244bhp, which is 25bhp more than the old carb and manifold. So thats good eh?

Through these runs I measured manifold vac. At part throttle she was pulling about 26" which dropped off to probably about 1" at WOT. The vac secondary flaps were opening to about 75%.

Then we added some gas. I started with 100hp shot.
Heres the results:

1. First run with 100hp 1:1 nitrous to fuel ratio. Rich as fook. Run aborted.

2. Second pass with 100 fuel and 150 nitrous. AFR dipped lean at activation for less than a second. Then went to almost spot on AFR for the remainder of the pass. But at 5500rpm it started to lean off a tad. During these passes I checked the secondary vac flaps and they were opening to around the 75% mark still. Even on the final pass they opened the same amount, so I'm happy they are not being held shut by the nitrous blowing into the manifold. Now!! Read on chaps...... :

3. 3rd nitrous pass. 200 fuel and 275 nitrous. AFR went erratic at activation while the pulsing ran its 1.8 second time out. Then with the pulsoids fully open the AFR went ideal for about 4 seconds at WOT. But we then had to abort the run because it started raining tyres



and

Are they a special tread for off road?

They are now Ged

Perry.

Good results apart from the tyres of course, what do you think caused it, not enough pressure seeing as it is the outer section that appears to have disintergrated or purely the abrasive nature of the rollers?

Kevin.

Kev!
I guess they just got too hot between runs???

A bit of a bummer really. As they had at least 2.5mm of slick tread left.

I had been keeping my eye on tyre pressure. But I didnt bother getting my infra red thermoter out to check temps. Too busy with AFR info I guess. I'll know better next time eh??

Perry

F------ Hooligan Perry
You still going next weekend?????

Yes mate. I'm just getting the wheels off now so the tyre man can fit my old ET Streets !!

The swollen mass you can see on the tyre was actually bubbling like melted suger. The rollers kept the middle flat, but under the top skin of the tyre, the whole lot has become molten. The outer edge was where it escaped. You can see the ragged edge where the skin on the wall has ruptuired to let all this stuff out. Now the tyres have cooled. all the swelling has gone down and all you can see is rough patches.