Cam timing question

[MOTORHEAD]

Given our cobras relativley light weight, I'm thinking maybe I should retard my cam from the mfr suggested 110deg centerline timing to move the torque range higher since these cars usually have more than enough at the low end. Anyone done this? if so, how did it work out for you ?

[RICK LAKE]

MOTORHEAD The 2 cams I have run and a 4 degree total for all torque. My car is 2705 pounds in weight with 1/2 tank of fuel and no driver. First motor was a 452 with 9.0 compression. power was 448 torque and 368 HP with a hydro lifter cam of 501-533" I did have work done on the heads. Car was very drivable. Down side was smoking tires in first 2 gears. These where BFG tires. I changed the car over time to a 482 motor with 10.5 compression. Power is 620 ft of torque and 530 HP. I went to a 335/35 r17 tire and they just blowup unless I roll on and off the throttle. I am going to advance the timing 2 degress to kill some of the torque. Will loose about 30ft of torque off idle. cams specs are 587"-607" hydro roller. If you just adjust your driving style, you will be fine. The trick is learning to drive all over again with more power. I am happy with running torque motors over HP motors. They make good power and last longer with running in a lower rpm range IMO. It's sad to say, That I can pull trees out with the cobra better than the truck. Rick L.

[HighPlainsDrifter]

Hi,
To move the power band up a couple hundred rpm you would retard the cam.
Rick if you advance the cam it will have more torque down low.
Either way you would need to check piston to valve clearance again.
Perry.

[Gaz64]

Depends on the effort involved to change your timing.

If your have easy access to the cam gear AND you have a vernier adjustable cam gear then you could retard it 2 degrees to start with.

But as noted above, any timing change would necessitate a piston to valve clearance check.

In your case, retarding the cam timing closes up the exhaust valve to piston clearance at TDC.

Generally, if you want to move the torque band higher, because the engine has too much low speed torque, you're better off fitting a larger camshaft.
It will give you less low speed torque and more high speed power.
If then you have insufficient torque, you could then advance the cam allowing for valve clearance on the inlet at TDC.

[blykins]

Generally, retarding the cam timing makes the engine a little more fussy down low. Harder to tune, a little more "rough around the edges." I usually run my street engines on a 104-105 ICL. The guys that own these engines tell me how much snappier they are down low in comparison to other engines they have owned. Advanced cam timing makes an engine much more sweeter to cruise around in.

Will it make that much of a difference so that it will be more docile on the bottom end? Probably not. Anything above 300 hp in these cars produces traction control issues.

[MOTORHEAD]

Thanks for the info guys.
Barry: thanks for your input, I'll go with your suggestion.

[RICK LAKE]

Highplainsdrifter You are correct with checking valve clearance to head. The pistons I have had there top machined for any clearance problem and only running .607" lift, There was still over .075" clearance before the piston work. This is tight for a motor of mine but alot of guys run motor tighter.
Check my other cam card, Crane cams builds in 4 degrees advance to start. I retarded the timing a total of 8 degrees, not 4. It's 4 degrees on the crankshaft gear. With the hydro rollers and the little bit of pump up and bleed down the clearance has been fine. Have to remember that my motors see a max of 6,200 rpms and the msd chip cuts in about 2-300 rpms before max setting. The fog has cleared, thanks for the correction. Wouldn't want to give someone bad or wrong info. Rick L. Ps too much heat in NJ

[Rick Parker]

I want to know the nuts and bolts of what is done to a claimed "Legal" Vintage HiPo 289 such as in a GT350 used in Historic Racing to allow it to use a shift point of near 8000 rpm frequently and live. Those that feel qualified please expand on this. Whenever I go to the races it seems like the engines in the GT350's are always in a higher state of tune, turning what seems to be considerably higher RPMs and faster.

[blykins]

Because they are not "legal"......

[RICK LAKE]

Rick Parker Rick, you are a smart guy and the rule book is silly. Rumor has it that over the next couple years the rules will be revisited and changes will be made. This is a big money event. I bet that half of the 289 motors are not stock bore anymore. I have seen so called 289 with stroker kits running from 331 to 347. 500+ hp on race fuel. Compression in the 12.5 and higher. Guys are sandbagging to not get caught. When you can watch a GT-350 chase a GT-40 around the track, you know there is something going on. Remember, it's only cheating IF you get caught. Rick l

[Rick Parker]

Motorhead: I didn't mean to Hijack your thread. I should have opened this in the Small Block forum, sorry. The Moderators may move it if they wish.
Rick L: I don't have an SCCA rule book to refer to but I'm certain they all run Race Gas of varying types and they all have 12.5:1 compression (or more) what race engine doesn't. It's not the displacement that's allowing these engines to RPM & sound as they do..compare videos (will attach some in a hour) of a Full on 289 CObra and a full on GT 350. I'm beginnning to think it has to do with the (limitations of the cam timing) imposed by the Webers typically used on all the Cobras in Vintage car racing be it in the US or UK. It's not the increased displacement that is allowing this to happen. Maybe the Cobra guys just aren't preparing their engines or driving the cars (with rare exception) as aggresively as the GT350 drivers. I always come away feeling like this is the case after attending Historics with the FIA Cobras and GT350's especially if they are in the same race. Anyone else care to comment????

http://www.youtube.com/watch?v=tQraQ...eature=related

http://www.youtube.com/watch?v=tQraQ...eature=related

http://www.youtube.com/watch?v=btqQr...feature=fvwrel

[RICK LAKE]

Rick Parker You are right about the 350 drivers. Saw them at the Glen a couple of weeks ago. I think some of the reason is that a mustang cost and value to repair is about 1/3 the cost of a cobra. Mustang is cheaper in parts to maintain.
As far as what carbs these guys are running, it's been proven that webers of the 48MM size on a 289 make about 35HP and 20 pounds of torque over a single carb if setup right. Webers also need a different camshaft than a carb does. There has been HEAVY discusion about which cam design is better and makes more power. There is a guy on this forumn running 58 MM Olbergs. Motor is max preformance to the nines. HP is over 750 and this is a 20+ year old motor. The best carb and single plane manifold, carb of 1,100 cfm came up short on power in the mid range by almost 20HP. This motor is a 482 that will turn 7,800 rpms. It has a small power band from 4,800- 7,800 rpms. This motor sings once it's cleared out in the power band.
Colin can drive a GT -350, question would be the trans, that's no stock box setup. I can't see his other foot and the shift almost sound like my clutchless 5 speed. Bottom line is we go to see them race. Every one want to win the trophy. Question is who is cheating and by how much. People that own and race these car have silly money and see these car as just that. You and me would have a different feeling about this. I am only autocrossing my car because of the amount of money, blood, sweat and hours lost of sleep put into this car. If I ever crashed this car, it wouldn't get repaired, I go fishing. Rick L. Ps Aluminum body CSX cobras are worth about 300K+ and aluminum body parts to replace about 3 times the cost of fiberglass or steel. GT-350 in good shape 75-100K. This may have something to do with driving like a wildman

[MOTORHEAD]

Rick P.: No problem w/ hijack, I got what I was looking for, so feel free to "pick the bones". I witnessed the GT 350 Mustang vs Cobra disparity you're talking about at a couple of vintage events, didn't think much about it at the time.
I think Rick L. has part of the answer with the value situation. compared to an original Cobra, a Mustang is practicly a "throw-away" device.

[Rick Parker]

Yea, maybe many of the guys that have them (CSX's) are just happy to have a place to go drive them in the way they were ment to be. It still hurts to be rooting for the Cobras and see them consistantly become backmarkers.........

[MOTORHEAD]

As long as we have strayed from my original path here's another OT question;
FE rocker shaft rocker arm oiling holes: UP or DOWN ????

[blykins]

Down.....