[Ron H]

My peak HP on a mustang chasis dyno was at 4300 rpm though the curve was pretty flat to 5000 rpm from there. How much higher in rpm would my power curve move if I retarded the timing by 2 degrees? I currently shift at 5000 rpm to achieve my best ET. The cam was set at 104 when installed into the engine fresh. I think my timing chain my have stretched it out to 108*.

[Geoff]

Ron H,
When the chain stretches, it retards the cam. So your cam ICL would be a lower # than 104, not higher, if it was installed at 104 with a new chain. Retarding the cam usually shows the most benefit if the cam was too small in duration for the intended power range.

[Ron H]

I have a 455 30 over with 6x 4 heads mild port 1.77 exhaust valve doug's headers performer rpm 800 cfm Edelbrock AVS carb 231/240 @ 50 485/509 lift ultradyne cam with a TCI breakaway converter about 2400 flash 3.89 gears. The dyno sheets show my peak Torque and HP low in RPM. The cams specs showed install at 106*. Gregg Merrick and some others said set it at 102 so the chain will stretch and it should end up at 106*. The timing chain had 3 keyways. 104* is where it was set. So It probably stretched to 108*. That is advancing it not retarding it. I have always been told advancing the cam moves the power curve down and retarding it moves the power curve up. My question is how much would the power curve move, rpm wise, with a 2* change? I am wanting to move my peak HP up to 5000 RPM from the current 4300 RPm range. I will install a 3000 stall converter and am going to make some suspension changes so I can go faster without tearing back into my engine combo.

[Scott65]

Geoff has it right. Chain stretch retards cam timing in relationship to the crankshaft.

[slowbird]

Hold on now. He installed the cam at 104. If im reading Geoff's post right he is saying that the cam would stretch and the new C/L would be something like 102? Geoff said that retarding the cam makes the C/L number smaller. I believe Geoff has that backwards or I am miss understanding what he is saying. When the chain stretch it does retard the cam timing. If you installed the cam at 104 with chain stretch that might go to 106 which is retarding the cam. If the number gets smaller like 102 you are advancing that cam and that doesnt happen when the chain stretches. Maybe I missed something in Geoff's post.

[gearbanger]

The confusion arises because intake lobe ceter is measured ATDC. So the smaller the number the more advanced it is. Unlike everthing else, which is measured in BTDC, like your ignition timing. 10* is more advanced than 8*. With cam timing, as far as the ICL is concerned, the smaller the number, the more advanced it is.

[Ron H]

Now I am becoming confused!! Ultradyne said install at 106*. I was told to install it at 102* and the chain should stretch putting it at 106*. So it went in at 104* because that is where the keyway left it. If the chain stretched to 108* that would be concidered as advancing or retarding from 104*? Still my question remains, does someone have an idea how much the power curve in my engine would move if I changed the timing 2 degrees? And now would I be retarding or advancing to move the curve up the RPM range?

[slowbird]

If you go from 104 to 108 you are retarding the cam timing. When you retard the cam timing it can (but not always) help make alittle more power higher up in the rpms but you will loose power in the lower rpm range. As to your question about what retarding the timing 2* will do to your power curve, it will more than likely shift the power up the rpm range by a few hundred rpm. Every engine is different and every engine will react differerntly to advancing and retarding the cam timing. Why do you want to retard the timing anyway?

[Ron H]

Because my peak torque and HP numbers are way low on the RPM scale. The dyno showed my peak torque at 2400 rpm and 4300 RPM peak HP. I am falling off at 4800 rpm in 3rd gear at the end of the track. So I want to move the power up the hill so I am pulling hard to at least 5200- 5400. I am running through the traps at 5100 right now, 12.96 @ 106 mph.

[Ron H]

So maybe the chain did not stretch and I am still sitting at 104*?

[slowbird]

Are you sure that the dyno was reading your rpms correct? From the listed combo above you should be peaking somewhere between 4800-5200, I would think. I would double check to make sure that the dyno was reading the rpm correctly first. Then I would try 1.65 rockers before I started playing with the cam timing. Also might want to try a 1 or 2 inch open spacer under your carb. What is your exhaust system like and what size headers are you running? One other thing dont pay any attention to what the dyno says. It is good for making changes on and see what those changes do but dont take the numbers to heart. We dynoed our 400 on a Mustang dyno and on an engine dyno. The Mustang dyno said we had 310hp to the rear wheels. Then engine dyno said we were making 500hp. At the track the car has ran 11.4 at 119mph. The Mustang dyno was good for testing parts but I never paid any attention to what the number were, just what the numbers were doing from one run to the next.

[gearbanger]

I definitely am not trying to discredit Greg Merrick, I have called him for advice many times. But I have never heard it advised to install the cam 4 degrees advanced to anticipate chain stretch. That seems like alot to me. I would have installed the cam on what Ultradyne said. If you installed it 4 degrees advanced from what they said, I would say you are definetly missing some top end. Reinstall it like they said and see what happens.

[slowbird]

What is the lobe seperation on the cam?

[screamingchief]

Not to oversimplify things here,but if your planning on moving up to a 3000 convertor with your current combo,why not just swap in a little bigger cam to move the RPM range up where you want it?

That cam is'nt all that "big" for a 455 with ported heads (even lightly ported) and the power is where I would expect it to be for that combo for the most part,advancing and retarding will make some subtle changes sure,but likely not enough for what your looking to do here IMO.

That is virtually the same cam I'm putting in my 455 (mines a crower #60210) with 240ish #96's and I have a basically stock bottom end,so I've chosen it to maximize the midrange trq/hp and keep the RPMs under the 5500 "safe" limit for the bottom end.

Plus its a "driver" so I'm not remotely worried about squeezing every last tenth/mph out of it possible...

Only reason I can thnk of to not use a bigger cam here would be driveability issues if this still see's some street use and you need to maintain some vacuum for power brakes or the like...

If the cam was ground with a wider LSA this might have worked well enough, but these cams ground with the "tighter" 110-108 LSA's tend to "concentrate" the power band into a tighter RPM range than the wider LSA cams do.

I would consider using the next larger cam,and degree it in with some advance to get the RPM range where you want it,the larger cam will move the RPM range up more,and you can "aim" that with your degreeing "fine tuning".

I plan on adding 1.65 rockers on mine if I feel like squeezing a few more RPMs out of mine,I installed mine @ 104 and figure it may "loose" a couple degrees to chain slack over time.

JMO/FWIW...

[screamingchief]

Slowbird,if it's the ultradyne I think it is,its a 110 LSA.

[gearbanger]

What intake do you have on it?

[Ron H]

It's a 110 LSA. I have Doug's headers 3" pypes x change. Those numbers were with the dumps open. I think if I go to a 3000 stall i will be in the power range faster out of the hole. I do still drive it on the street. I have no power accesories so i am not worried about vacuum. The guy on the dyno dialed things to my take so they should have been close. I have been considering going to a hydraulic or solid roller cam. Cost is a bit of an issue. I am thinking if I get my suspension set up and change the converter and go to a 29.9" slick instead of the 28" Drag Radials i should be able to get 12.50's here in Salt Lake over the 12.96's I have been running. I am also buying a Cliff Q jet so I may end up with more power on the top end over the Edelbrack AVS carb I have now. I am also going to run 8 am lines and sump my gas tank and go to an electric pump. That might make the difference without messing with the cam, heads, converter etc. Though I think a converter change will make a difference. Especially hearing all the gains from others that went to a Continental Converter.

[Lee]

I ran the same cam, except on a 108LSA, for quite a few years, until a few months back.

If you are running best when shifting at 5000, then you either: a) the altitude is doing something odd with the powerband;, b) your tachometer is off; or c) you need better valvesprings or a better machine shop to properly set up those springs.

Even with my tighter LSA, I was running best when shifting at 5200 to 5400 rpm. When I pulled the heads to have them set up for the new cam (solid, UD 280/280) the locks were pretty hammered and we suspect I was actually having some valve float/bounce.

[screamingchief]

I think with your current cam the 3000 convertor wont show much gain,it'll just move it past peak torque quicker,and the taller tires wont help that situation much either IMO.

If it were me I would get a nice solid cam in it,something like the UD 247/259 @ .050 solid (280/292 rated),this would couple nicely with the 3000 convertor and move the RPM range up just enough to help out here,yet not too much.

The Q-jet should definately be a better choice than your current carb,I too would be curious to know what intake we're talking about here as well.

[screamingchief]

Oh yeah,your numbers,at your altitude are plenty respectable for your combination IMO.

I know I'd be plenty happy with them...

Corrected to sea level you'd be at/around 12.27/111.96.

http://www.wallaceracing.com/altitudecorrection.htm