What if...? Question on retarding cam...
 

Whats the deal on retarding the cam? See here for a link of retarding the stock cam 4 degrees. Why????

http://www.alternativeauto.com/waterbox/index.html

What do you think would happen if I retarded my cam in my completely stock motor? Is the stock cam installed straight up or already retarded? Would this hurt drivability, emmisions etc.? Anyone willing to try this or have tried this before?

Retarding the cam is said to give you some more topend power by giving up a little down low. Doing this on a stock 5.0 may or may not be helpful I don't know. On performance motors it is something to look at. Most aftermarket cams come with a advance or retard ground in them allready.

Yes, there are significant power gains associated with backing the stock cams up, in stock motors. Retarding cams is an 'old timers trick' to make up for a 'lack of' cam. You probably wont have the same results backing up a bigger cam in your 302.

I have heard a few different suggestions on how to find the best place to install your cam. The best way is to dyno your engine with the cam in multiple positions.

Right now we are in the process of backing the cam up even more in my friends NMRA R/S car. We are going to test it at 6 and 8. We are not sure if the results are going to be what we hope they are, but you dont know until you try.

In most stock cams, there is 1 degree of advance ground in.

Andy

does anyone know what it would do if i retarted my stock cam 4 degrees with the mods i have listed below?

It would move your powerband up about 750 rpms, meaning where ever you flatten out now, you would continue pulling for another 750 rpms, +/-100 rpm. However, you wouldn't start pulling at the same spot you do now. That too would move up. For example, let's say now you start to pull at 3000 rpms, and flatten out around 4900 rpms. If you retarded your cam 4 degrees, you wouldn't start pulling until after 3600 rpms, but you would continue to pull up to or past 5500 rpms, conservatively.

Take care,
~Chris

Agreed. Completely. However, if a dyno isn't in your future, the best method to determine the optimum cam timing for any specific engine is to install the cam in several positions (+4, +2, 0, -2, -4, -6), and run a compression test in each. Which ever cam position creates the highest compression is the best cam position for that specific engine.

Take care,
~Chris

Chris I have tested that method on two different cars and I have had mixed results.

The first car was a friends 83 with a 351w. It has 11:1 static compression ratio (approximately) and a cam similiar to the TFS stage 2. The further we advanced the cam, the more cylinder pressure we obtained. We ran the car on the street with the cam at -4 and +4. The car ran much better at +4!

The second car was another friends 91 lx. It is a NMRA Real Street spec car. Its a .030 over 302, stock cam, custom flat top pistons, zero decked, 58cc chambers, and a .037 squish distance. The static calculates out to about 10.2:1. Also in that case the further we advanced the cam the more cylinder pressure we got. We know from all the NMRA Factory Stock, and Real Street stuff we have done, that isnt where the cams like to be. 4 degrees advanced (where we got the most cylinder pressure) is exactly the opposite of where we know they run best.

I'm going to have my Pure Street engine on the dyno most of the winter. I will be testing multiple cam grinds, and also the position they are installed. I believe theres more to be learned, yet.

Andy

Chris and Andy
 

Chris. i was planning on putting an E cam in cause one of my lifters is bad, so it will give me and excuse to get a cam, but i dont think i am going to. If i can squeeze more power out of my stock compnents and all it will cost me is my labor and some gaskets, then i think it is worth it.

so i should go in increments and test cylinder pressure of each setting on the cam gear? the one with the highest is the best? is that what you want me to do?

hey guys any suggestions of more power to squeeze out of my stock components would be helpful. i already know did all of the mods that i can think of so far. if retarding/advancing the cam will help, i will do that too.

Re: Chris and Andy
 

You'll need to get a timing set with a multi keyed crank gear. That's how you change the cam timing, but otherwise, yes, that's it. Assemble it minus the intake, timing cover, etc. and do a compression test on two cylinders. Then back off the rockers, remove the chain and rotate the crank gear according to the way the manufacturer has it set up to move 2 degrees. Reinstall the chain, adjust the valves, and test those two cylinders again. if you have a degree wheel, you really should degree the cam each time to verify that you did it right. Relying on the instructions that come with the timing set isn't the best idea. Anyway, go from one extreme to the other, and then compare your results. It's been my experience that the setting that produces the highest readings is the setting that is best suited for the combination of parts in that engine.

Take care,
~Chris

Thanks guys!
 

Wow, this was a very helpful thread! Its like squeezing every drop of water from a rock in a desert the easy way. For those who have access to a dyno and will be running these different timings, please post your results. You don't have to give specifics but just the general findings is enough. TIA...