Camshaft timing help

[jim_howard_pdx]

I am rebuilding my .30 over 351 windsor this week. I have 10/1 compression. Trick Flow Twisted Wedge heads ported to felpro gasket 1262 which is 1 5/16 wide and 2 1/8 inches tall. THIS IS BIG GUYS! I also have an Edelbrock RPM dual plane intake also port matched with modifications to match the air gap model plenum.

I have been running a basically warmed over 3/4 camshaft on this engine. Advertised duration is 278 degrees at .475 lift on the intake, and 288 degrees at .495 lift. 112 degree centerline, and 40 degrees of overlap.

Does anyone recommend I retard the cam 4 degrees to pick up some upper RPM power?

I have been running the cam straight up and it has been great all around. Excellent off idle and acceptable top end.

Straight up it has quartered at 13.7 seconds and 104 mph with 3.25 gears and a C4 Auto running about 1600-1800 stall.

If anyone out there is retarding their cam, what has it done to your low RPM?

Let me know your results NOT YOUR OPINIONS. This is not bench racing time.....This is rubber meets the road time.

[82 GT]

I don't have the answer you're looking for but I will say that something seems wrong with your ET though.
All those mods and only 13.7 ??
Are you having traction problems? What's your 60ft time?

400Hp in that chassis should be good enough for 12's

[lx mike]

retarding the cam is a racers tunning edge to kill bottom end torque to help with traction.

why do you want more topend?? you like to crusie 130-140??

[jim_howard_pdx]

I ran my Mustang up against 4 Cobra 4.6 L cars with 3.25 rear ends and T45 transmissions during this last month.

My greatest victory was 1.5 seconds and the closest Cobra running to me was .7 seconds behind. Look, that is 30 car lengths. So I would say that I do have the 400 horsepower and that my times are right on. I spun a bearing last run, and tore down the engine. When I disassembled my heads I could rattle my intake valves. The car was clearly detonating for at least 6 months. No pinging and no noise, just detonating away silently. With the zero gap piston rings and fresh valves and guides, I should be in the 13.4 arena with slicks. I am hoping to at least be in the 13.5's. Then it is time for some quicker gears.

My computer says that with 4.30 gears and a 2500 RPM stall in the C4 I should run 12.25 seconds. I think that is pretty much on target for the light cam timing that I am running. With a 540 inch lift, 255 degree cam I would certainly be in the late 11's (engine only) and in the early 11's with Nitrous.

My car is set up to corner on the autocross, not to drag. Remember this engine idles like stock. Runs around town like stock. And when you open up the secondaries, ALL HELL BREAKS LOOSE. This is a really fun street engine.

My engine is built to take nitrous, I just do not want to put the pistons through that type of abuse with a daily driven car.

My goal is to run either a Lentco AOD or a Tremec 5 speed and 3.90 gears. That should put me in the 12.3 range and I could still cruise the car when I want.

NOW for cam timing. Retarding the cam is not a racers way of killing low end torque. Think it over. On a dyno, how do we graph HP and Torque? x coord is HP/Torque, y coord is RPM. As you graph the results of the engine you end up with a bell curve. Power starts at some level, swells at maximum, and diminishes back down. When you retard or advance the cams, you are simply shifting this curve UP or DOWN the RPM range.

The simple act of advancing or retarding does not KILL OFF anything! Honda's run about 8 hp more with 2-4 degrees retard on the intake valves and straight up to 2 degrees on the exhaust. Since they are dual overhead cams you can adjust them independently to get maximum power. You can also set the cams for maximum area under the bell curve if you are on a road race course and torque out of the corners is important.

Retarding the cam does not KILL torque. It simply moves it. Now apparently NO ONE is retarding a 3/4 cam out there so I guess it is a coin toss. Try it or leave it straight up.......

[82 GT]

I'm not doubting your 400hp. Check out the analyzer section on this site, type in your car's weight and HP and it will tell you ET potential of your car. I guess about 3300lbs for your car and 400hp and got 11.7 but that's under ideal conditions so I figured 12's

[jim_howard_pdx]

So what are you running et wise now? And what is your rear end ratio?

Mustangs Plus is running a long rod 351W with a build up like mine, 4.11 gears and a t-5 tranny at 12.3 with slicks.

If I was willing to put in a full on solid roller cam of 570 lift at 255 degrees duration at .50 cam lift, I could easily get this car in the 11's with 4.30 gears. Heck, I don't do it because it is a street and highway car designed to blow away corvettes, camaros and cobras. I love a balanced vehicle that does it all and this car is really a treat to drive.

Let me know how your rebuild works out. I cannot wait to see what the zero gap rings do for my quarter mile times.

[PKRWUD]

generally, retarding it 4 degrees will move your power band up about 850 rpm, and advancing it will bring it down 850 rpm, +/- 150 rpm.

This is not always true, however, and unfortunately, like shoe sizes, every engine's ideal cam degreeing is different. To find the ultimate degrre setting for YOUR cam in YOUR engine, with the mods IT has, you need to install the cam and adjust a couple valves. Then run compression (two cylinders is best), and write it down. Next, move the cam a couple degrees, and do the compression test again. Keep doing this until you have covered at least 4 degrees each side of center, and compare the results. The cam position that yeilded the highest compression numbers is the position that will work the best for YOUR combination of parts.

Or go to a dyno, and do the same thing.

Take care,
~Chris

[jim_howard_pdx]

That is too cool.

This will be simple to do on the engine stand, and I don't have to tear the front end down to change it if I don't like it.

Right now the car develops maximum torque at about 4900 RPM and maximum HP at about 5,800 RPM. That is because of the port work I have done, otherwise max HP would have been about 5,500 to 5,600. I will try a 2 degree retard, a 4 degree retard, and straight up. This will be a fun exercise to show my 19 year old son. He is caught up now in HOT ROD FEVER.

Let the compression testing begin. (I will not have my heads back until next week, so you will need to be patient for my final analysis.

Are you running zero gap rings? Do you know any specific reasons why you should not use them for the street?

Finally, since I will be turning this engine over manually, NO STARTER ON MY ENGINE STAND--DONT EVEN THINK IT.... what do I do to calculate for the hydralic lifter bleed down. Or should I just read it and base my choice on the figures including the bleed down?

Let me know.

[PKRWUD]

C'mon, get a 4 corner stand, and bolt on a starter!

Honestly, I can't vouch for the accuracy of the numbers turning it by hand. It might work just fine that way, but I've always used a starter.

Also, don't sell yourself short. Try it advanced 2 and 4 degrees as well. You just might be surprised.



'nite

[lx mike]

the t-5 and 3.90 gear would make that car a beast and still be able to drive daily. but then traction will come into play!!

[jim_howard_pdx]

The T5 cannot take my current torque of 440 ft pounds. I would need a Tremec since the T45 is based on the 4.6 mod engine with the different bell housing configuration. I would love to try a 6 speed but my torque puts me into the stronger Viper box. That runs 3,900 dollars. With 200 for a scatter shield, 175 for a shifter, 600 for the clutch, 400 for a balanced driveshaft, and 500 to run a clutch pedal and cable setup this puts me at 5,775.00 for a 6 speed set up. OUCH...... A Lentco AOD costs 2,500.00 which includes the 10 inch torque converter, a 1-2-3 shift pattern and OD lockout or hold. This is a palatable investment, but not as fun in the corners.

My son is asking me to bump our cam to a solid lifter 236/246 @.50 5.14 5.24 lift cam. This will put me somewhere in the 485-495 ft lbs of torque and 460-475 hp range with my ported heads. Since the car is basically his now, I will let him play. We can always do a cam change if he feels we are too strong.

I was running a slightly lower lift 4.79 and 4.99 cam a couple of years back at about the same duration. My Mustang ran 0-100 mph in 10 seconds with a 3.55 gear set, smaller carb and stock port configurations. It was awesome until I cracked a piston and threw the rod. Too much distributor advance and too little octane- a deadly combination.

My son wants to hear the beautiful sound of 16 sweet solid tappets singing away happily at 5k+ RPM.

My racer friends think we will get top HP at about 6,500 RPM from what we have seen with Trick Flow head dyno numbers on the flow chart. I will have 504 cfm of flow at 6,500 RPM and 5.14 lift. If I bump the intake lift to 5.60 inches the flow goes to 515 but my streetability goes out the window.

My bottom end will take this all day long if I use some good gas and keep my timing at a sane rate.

I will let you know how it quarters after we break in the new bearings and ring set. My son does not want to use the zero gap rings. None of us racers have any long term experience with them on a street and highway engine. Too bad, I was going to try the zero gap child and albert rings just for the fun of it. And for 15 extra free horsepower.

Now if we could just set up a 4.30 spool for the track, I bet we could hit high 11's with Slicks. That would be really fun.