Intake centerline in 107 degrees on that cam. With the regular timing marks, mine came to 102 BTDC. I retarded mine 4 degrees and ended up with 106.

atljar - Did you advance/retard your valve timing? I've been told that retarding valve timing drops mph with no significant change in ET. Which would explain why I trap only 1mph more than you with about 50rwhp more than you. I wonder what would change it i set it back to 102 degrees BTDC

 

116.64mph is pretty damb high, I think 1mph is quite a bit,why would it drop mph?

 

As for retarding the cam a few degrees, i surely WOULD NOT. When i do heads on mine, im actaully going to advance it a little bringing down the powerband.

With stock heads, it made peak @ 6100 or so, but was table top flat until 6600ish? Forget exactly, the graph is on my website. All that means was i was shifting at 6600-6700ish. With heads i would expect everything to move up at least 300-500 rpms. That will put you right on the edge of the PCM ability, or maybe even over it. Retarding the cam a few degrees will put you shifting well over 7k. I would actually consider advancing it 4º on the cloyes keyway.




My reply to your email just for anyone...

 

Hmmm... I wonder how many others have tried checking their 847's to see how far off they were? Also, which Cloyes are you using? Mine only goes 2* each way.

I also you on your website your cam liked 14.0 AFR?

Matt.

 

No i never did put a wheel on mine to see where it was. Just used the straight up keyway.

Never heard the argument about ET/mph, I dont really buy it. ET is a matter of traction, mph is hp to put it simply as possible.

Reason for traps being so close. One would be gearing IMO. Im a little steeper to keep me in peak power longer.

Secondly, that 115+ trap and 11 sec timeslip was on the best drag racing day i have ever seen. The DA was -1200 feet, or something around there. That makes a BIG difference. On normal days i was running 113-114 traps and 12.5s (soft launches on drag radials) Should be a 12.1-12.2 car consistently with the setup like i had it on the 11 sec day (skinnies, slicks, no front sway). I would have expected you to trap 118+ or so on that day.

 

I live in British Columbia, Canada we are right at & below sea level here

I'll prolly just take your advice & leave it the way it is right now see & run it _

 

Matt i would ignore those wideband readings. They were having issues with it all day at the shop. It was just a good tool to get everything flat, but heck i already was pretty close as you could see from pull #1, lol. Im not even running on that tune anymore, i went in and saw where i made peak power, averaged out the A/f ratio they gave me, compared it to o2 readings and tweaked it some more.

 

Thanx !

 

I had the 847 in a carbureted 11.3/1 383 with AFR 210 heads, Victor Jr. intake, SLP shorty 1 3/4" headers, Vigilante 3200 converter, 3.73 gear, and 275/50 - 15 drag radials. The car weighed 3500 lb and ran 11.09 at 122.7 mph NA.

I checked the cam timing and found the ICL to be 106, which is 6 degrees advanced. My timing chain only had keyways for +8, 0, and -8 degrees, so the options for ICL were 98, 106, or 114. I stuck with 106 because the DCR was 7.5/1 (using seat timing), which is about perfect.

Mike

 

cool so the cam was 1* off, sweet, what about stock LT1 cranks, how often & how far can they be off?

Matt