My 318 dyno results
comments in the quote
The advertised stall rating for my converter is 1800. I've estimated the DCR to be right at the edge for 91 octane pump gas, I can't remember exactly though. Might have been 8.7.
The thing is, already as the car is now, I think it drives nicely (hey, I drove this car for several years with a 125HP 3.9 V6 before the engine swap).
It's the idle, cold starts and hesitations when cold that annoys me the most. And normally, at any condition, if I just blip the throttle the engine will stall. I think it might be to lean at the idle circuit, but it's hard to tell with the valve overlap. Smells rich at the tail pipe, and the AFR gauge goes crazy lean.
What cam would work with my setup?
View attachment 1715151719
Oh that's even a smaller cam and so a higher pressure, I like it!
But a worse stall.
But hang on, this ain't all bad. In fact it's very good.
With this new information, I am fully convinced that your issue is in the tune, namely the T-port sync and the vacuum advance. You are describing symptoms that can be directly linked to the throttle being too far closed at idle.All of them!
So do the T-port sync, and hook up the Vacuum advance to the sparkport. Don't be afraid to reduce the idle timing to 14 or 12 or even 10.
Then I highly recommend a two-stage advance curve; very fast up to 2800 or so, then slowing down to be all in at no sooner than 3400.
And the fast idle speed, on the second highest step,(the kicked down to step), should be fast enough that the vacuum advance is all in.
Your idle stink
may be because you have cranked out the mixture screws in an effort to cover the hesitation. What you need to do is increase the throttle opening to uncover and engage the transfers, and so be able to lean out the idle mixture screws. Of course this will increase the idle speed, and the proper way to reduce it is to decrease the timing.
This will solve you stalling with slammed-shut throttle valves, because now the engine will be able to draw in some fuel from the transfers, the way the factory designed it to.
This will also help solve your raw fuel smell in your exhaust, because with the backed off mixture screws, it is no longer so fat.
This will eliminate your tip-in hesitation. Just remember to sync your pumpshot to the new idle throttle setting.
This should provide a better mixture for the engine when on choke, but the working vacuum advance will make the biggest improvement.
>Those aluminum heads suck a tremendous amount of heat out of the engine, making the engine think it is always cold, and she feels really cold when an iron headed engine would think it's just a little cold. So when the ambient temp is cold, the choke will be really really important, and it starts with the vacuum advance bringing in a lot of timing, to start the fire really really early. I have a 22* can on mine and the engine often wants more.
So at 1500rpm my warm-up rpm, my engine is seeing 14+4+22=40*. To that I occasionally add 8* via my dash-mounted, dial-back, timing device. So that would then total 48*; and it's not too much. Then I don't let her warm up for long, but within 2 or three minutes I am moving, and 3 more gets me on the hiway. Then as I'm cruising along with my foot steady on the pedal,at 60 mph, with the timing now 14+10+22+8=54,I can feel the heads come up to temp, by the surge in speed, as the car increases in mph without throttle input. That's when I take the extra 8* out. This can take 3 to 5, to even 8 miles, depending on the ambient temp.
In an effort to combat the heat loss in the chambers, I run a minimum water temp of 205*F.
>Now,If the exhaust burns your eyes,
then you may have the additional problem of the engine sucking air,most probably from the secondaries not being fully closed, but could be other.
If you cannot get the idle speed down, with the secondaries fully closed but not sticking, and the T-port sync properly set, and the idle timing reduced to about 12*, and the PCV properly functioning; THEN, go look for a vacuum leak, and be sure to check for a leak into the valley, as well.
>Ignore the AFR under 1800rpm; it lies with that cam.
Also, once the beast is running properly, put a vacuum gauge on the manifold and slowly rev the engine up. Watch the gauge. The vacuum should slowly and steadily rise to a peak value and then just hang there for a while.This should happen below 3000rpm and the peak I would expect to be at about 2000with that cam. The lowest rpm that it peaks at, is the first rpm that the air going into the engine, is finally all going in the right direction,namely down! into the cylinders. I would consider that to be the LOWEST stall rating.
>Now let's go play the numbers.
This cam is listed at 208/214/107+5 and grossing it up to advertised, I get about
260/268/107,and that will get you an ICA of 52*. OK and plugging those into the Wallace calculator, I get a DCR of 8.23@166psi with a VP of 137 and that is awesome for a 318. So again, the engine is right on. And this is why your 1800TC is making you happy with that pitiful starter gear.
Read about VP here
V/P Index Calculation
But what Hughes has done with the 102 install is send a bunch of exhaust back into the plenum at low idle, to make it sound fierce,lol; and that is perhaps making your tuning difficult. This, IMO gimmick, also reduces your power extraction time, leaving plenty of energy in the exhaust, to make a nice high-pressure pop out the tailpipe. And of course, there may be plenty of unburned gas in that exhaust.
______________________________________________________________
If I had that cam, I would re-time it to in at 105/106. That would reduce your Dcr to 8.1@162psi and drop the VP to 131. So that's a loss of lowspeed performance of 4.5%. To cover that, I would increase the cylinder pressure with the thinnest headgasket I could find, while keeping the Q to no less than .030. The difference from the popular .039 gasket to the .028 is about 2.5cc, and that would restore the VP to 136.But the pressure would be increased to 168psi, sweet.
What this would do is; open the exhaust a few degrees later, sucking some energy out of the exhaust and putting it into the crank. So the slightly later opening intake valve will see less exhaust travel into the intake. This will decrease the rough idle slightly, and simultaneously clean up the exhaust some.
This will have the added benefit of a smoother more stable idle when the engine is cold and especially on choke.And the longer extraction period will help in the fuel-mileage department
And finally,I would get a 2800TC and stick some 3.91s in there at least, or if hiway comfort is a concern then 3.73s;65=2630@zero-slip. .....................................But that is what I would do.
done,I think,lol