I bought a vernier cam gear for EF XR6 wagon, and am looking for advice about how to set it up. I have already contacted the cam supplier multiple times, but can't get any helpful answers out of them.

Here's what I'm working with:
- Franklin RH24B cam (254/250º adv, 195/192º @.050", .265/.252” lift at cam, 113º LSA - one step hotter than an XR6 grind)
- head milled .015"/0.38mm
- MLS head gasket (.030"/0.76mm thinner than normal composite)
- replaced timing chain & guides and crank pulley/damper 50-60,000kms ago
- SS Inductions, headers, cat delete and mandrel-bent 2.5" exhaust, so breathing is good
- high-stall torque converter (+/-2800 rpm stall)
- J3 self-programmed chip

The head mill and MLS gasket would move the cam 1.14mm closer to the crank, so would retard the cam gear by 1 degree (1.14mm / 408mm circumference x 360 deg) as the tensioner takes up the slack on the exhaust side. Assuming there is no chain stretch, it would need 1 degree of cam advance to bring it back to straight-up. But beyond that, I'm not sure what cam adjustment I should be aiming for. I do know how to dial in - but not what to dial in.

The car is a daily driver family car, but I have been taking it bracket racing at Night Speed Drag Wars and am looking to improve my times. With the high stall, the launch is good, and 60' times are decent at 2.2 secs. The engine's sweet spot is 3500-4500 rpm. Acceleration drops off noticeably above 5600rpm in 1st and 5350 rpm in 2nd, so I have programmed the shift points to match.

So here's the main question: If I retard the cam further, will I extend the torque curve by an extra couple hundred useable RPM? Or will I gain little and just lose out in the low/mid-range and hurt my 60' times? Or would I be better off advancing the cam a few degrees, for a better launch and midrange, but maybe having to shift at a little lower RPM? And how much adjustment should I be looking for?

I'd love to hear from anyone who has experimented with adjusting cam timing. Thanks for the help.

Try advancing the cam timing....this will improve the 60' times.....you didn't mention what diff gears you have....?????....assuming it has 3.45's.

Yep, running a factory 3.45 LSD, so finishing the quarter-mile part way through third gear.

By advancing the cam timing, am I likely to gain more time on the launch than I will lose at the top end?

Thanks for the help.

What RPM are you passing the line at? if you are still making solid power, advancing the timing will give you better times.

1st gear is from about 2700 rpm stall to 5600 rpm
2nd gear is 3800-5350 rpm
3rd gear is 4000 rpm to crossing the line at 4500-4600 rpm

Shift points are easily tunable, so I can take them down a little if that will give me a fatter torque curve between 2700 rpm and 4600 rpm, where I spend most of the run.

I'd be more inclined to dial in the cam up as per the specs, that should give you a wide power curve for both a good launch and down the straight. I would also try shifting a bit later, your engine should be able to make power a bit higher than std. Especially with the 4-speed as RPM drops a lot between changes I'd be changing around 6000, even then 1st-2nd drops you down to 3700RPM so it's not ideal...

Hey, shyun,

Thanks for the advice. I suspect you are onto it. As I am currently using the factory cam gear, assuming the cam is ground straight up, I am running the cam 1 degree retarded as a result of the head shave and MLS gasket. But I can't get a straight answer from the cam grinder on how it is ground.

I have done the math on the cam specs I do have. Assuming the intake lobe is symmetrical - ie, the peak is right in the middle - the cam is ground 3 degrees retarded. So, running it with the factory cam gear puts me 4 degrees retarded (3 for the cam, 1 for the head work). I will log some acceleration runs with the cam as it is, and also after installing the vernier gear 4 degrees advanced (ie, straight up, per the grind), and see what happens. Do you know if all cam lobes are ground symmetrically?

And you are right on about the shift points. At the last round of Drag Wars, my best time of the night was when I forgot to take it out of first after the burnout, but I caught it before it hit the rev limiter in first on the pass. That run was .05 sec faster than any other that night. So, I will adjust the shift points up. Not sure it's healthy for the old girl (308,000 kms) to be hitting 6000 rpm regularly, but 5800 or so should be safe. Or am I being too careful?

Thanks for the help.

do you know the cam specs? as in intake centreline? if you didnt get the lift @TDC to dial it in, you may need a degree wheel to line up the lobe centreline

Well yeah how far you wanna rev it is really upto you if you think it can take it then sure:P I shift mine at about 6000-6100 when racing, but it doesn't have 300000k's on it!

Don't forget half the point of dialing in the cam is to account for errors in the setup (like the shaved head) but other things can add up as well to cause the timing to be off. On my car i needed 2deg advance on my regrind cam to get it to spec, apparently regrinds need quite a bit more adjustment than billets. Easiest way is to use the lift@TDC method if you have the specs for that.

Camshafts don't have to be symmetrical but I'd have a guess that it is, at least with regards to the points of maximum lift .Also if the cam is 'ground 3 degrees retarded' it should be because that's the way the cam is designed. which means it should have a 110deg intake centerline and 116 exhaust centerline? So if you were to advance it that would put it away from spec. I think the phrasing of cams being ground retarded/advanced is a bit misleading.

ive been told that too, yet every grind i have got off WADE, has been spot on. (3x977b's and my custom grind i have in now)

My one was an AU1645 (AU version of the 977b) that was 2deg off! So there you go

from what i know which is not much

advance or retarding the cam timing will only shift the torque/power curve up or down

it should not give you any more power or torque

Below are the specs from the spec sheet that came with the cam, along with my calculations to fill in the gaps. Assuming the intake lobe is symmetrical, the peak will be 117.5 crank deg ATDC. But the spec says 113.3 crank deg Centreline. I take that to mean that the cam is ground 4 crank deg or 2 cam deg retarded. Is that correct? Or am I on the wrong track?

Crank Deg Valve Deg
Intake Open 9.8 4.9 BTDC
Close 64.8 32.4 ABDC
Duration calculated 254.5 127.3
Centreline calculated 117.5 58.7 ATDC
per spec 113.3 56.7 ATDC

Exhaust Open 54.8 27.4 BBDC
Close 14.6 7.3 ATDC
Duration calculated 249.4 124.7
Centreline calculated 110.1 55.0 BTDC

LSA calculated 227.6 113.8
Overlap calculated 24.4 12.2

Thanks for all the help.