Need tuning help on 340
It seems to me, if you can get the AFRs down at 12, your fuel system is keeping up.
The 160PSI is indicating a good Dcr, which the 218*cam is trying to achieve.
At 3450, 96 mph is pretty good for an LC 340 with a tiny 218 cam.
If your power-timing is down at 32* or less, to avoid detonation, that is hurting your mph.
What your tach at,crossing the line, and in what gear are you. That makes quite a difference.With a 218 cam you probably want to be trapping at 5400?Or less even. If you are winding it out too far, that could really be hurting you too..
But really , you need to figure out why 32* is detonating.
Are you running oxiginated gas?And what grade?
Heat is the number 1 cause of detonation.Or rather too much of it, in the chamber. Low Compression, open chamber heads, also have trouble with pressure spiking too early.
Ok something is not right here;
I plugged some numbers into the Wallace calculator,and I can't make the numbers come out with your inputs. This is what you supplied; 160psi, 218 cam,8.5 Scr.. No matter how I fudge the numbers, I can't make the 160 psi.
Can you be a little more specific as to the cam? What I need is the ICA; Intake Closing Angle, or an advertised intake duration plus I need the LDA;Lobe Displacement Angle.Then are you absolutely sure the cylinder pressure is 160psi, and that the 8.5Scr is accurate?
Sorry, I could not find the "BracketMaster on the Lunati Website.
I did manage to make it work with 10.5 SCr, a 66*ICA, and got about 165psi. This would be a 284/108 cam in at 104*. But the .050 on a 284 cam is more like 236 to 240;no where near 218*.In any case, this yields a Dcr of 8.23 which as you have discovered is too much for pump gas, and iron heads.
I REALLY appreciate this post. And I'm sorry, I kinda missed it yesterday.
-I do still have the cam card if I can locate it. Also some of what you're saying is what has baffled me all along. I did cc the heads. But don't know exactly where the TRW 8.5 pistons ended up.
-(I couldn't find another timing light yesterday to double check mine, but will do so.)
-I'm pretty sure of the 160# as I wrote it all down carefully. I had one cylinder closer to 155 when I tested it but the rest were very equal.
-The detonation was not happening at 32*, but at 36-37*, then chasing numbers I leaned it more and saw it show up at around 34-35*
MPH at end of quarter: I got out my old time slips. It's usually pretty consistent at 95 mph or so, but on two high 13 runs the MPH #'s are 97.7 and 98.3. So I'm getting something out of the motor, but don't know how to figure DCR etc. Will look for more info.
As for shift points
I know things aren't ideal, but running 3.89 (Ford 9") and a 275/60 tire i usually shift at about 6200-6500, pushing it closer to 7,000 into drive as I'm almost to the finish when I have to get into drive. And yes, an earlier shift might be good. I've been running a mini-spool for several years, but am going to change that and am trying to figure out what I need to do gear-wise.
Before anything else I am re-jetting today. Haven't decided whether to take both the primary AND secondary jets up a step, or try going two steps on the secondaries. And I dropped the initial to 15* last night (which should land me around 30-31*
will check this)
My fastest times were with .116 jets in primaries, and .110's in secondaries. Trying to lean down the very, very rich idle and cruise I had, I've gotten too lean. Now need to fatten it up, I'm thinking I will go with reverse locations, .110's in front, and .116's where it really seems to need more fuel.
Back to locating the cam card for you...
