Cam timing on a stock cam!!! please read!

[jackchan]

ok I have a stock 98 explorer short block with an 1986 speed density stock roller cam, dog bone retainers, etc. My heads are explorer "P" heads with good valve job and milled slightly to accomdate the 52cc min rules. I'll be running a cobra upper and lower (unported) 65mm tb, 75mm mass air meter, #24 injectors, with shorties, X-pipe, and flowmaster 2.5 cat back,4:10 gears etc etc.......................here is my questions:

would It be worth it to throw on a 9 way indexable timing chain set, and run my cam at either -2 degress retard, or -4 degrees retard? I have heard great things from running a stock shortblock at -4 degress. I'm basically wanting to run somewhere in the 12.90's down to 12.50's range.......any insite will be greatly appreciated.
Thanks
Jack

 

[jackchan]

anybody?

 

[795.0]

Advancing a cam helps low rpm power where retarding a cam helps higher rpm power. When I build my motor, I'm going to advance my stock mustang cam 4* while using E7 heads with stock size valves and stock 1.6 rockers. Some aftermarket cams may have some advance/retard already ground in them. Since you're using the stock cam as well, you may be ok. However, since the P heads have larger intake valves, and since they've been milled, you may want to check piston to valve clearance when you degree the cam, just to be on the safe side. Especially if you plan on runing 1.7 rockers.

 

[25thmustang]

Retard it 4 degrees....

This will help a good deal. My dads FS car has it retarded 4 degrees and the car pulls to the 6000 RPM range with his GT40Ps (same work done as yours). You better throw on the indexer and do something with the cam (whatever you decide), youd be a fool not to!

Also to note, if I were you Id drop those Flowmaster mufflers and throw in a set of bullets or another straight through muffler. Sounds like a stupid thing to be picky about, but I can assure you the fastest guys arent running chambered mufflers (theres something small to be gained). And you know all about gaining every slight edge possible!

With that combo, suspension and such, you should be a good bit faster than 12.90s and even 12.50s on DRs. My guess is after some tuning, and learning the combo yuo will be in the 12.2-12.3 range at about 109-110!

 

[Rick 91GT]

Retard it 4 degrees....

This will help a good deal. My dads FS car has it retarded 4 degrees and the car pulls to the 6000 RPM range with his GT40Ps (same work done as yours). You better throw on the indexer and do something with the cam (whatever you decide), youd be a fool not to!

Also to note, if I were you Id drop those Flowmaster mufflers and throw in a set of bullets or another straight through muffler. Sounds like a stupid thing to be picky about, but I can assure you the fastest guys arent running chambered mufflers (theres something small to be gained). And you know all about gaining every slight edge possible!

With that combo, suspension and such, you should be a good bit faster than 12.90s and even 12.50s on DRs. My guess is after some tuning, and learning the combo yuo will be in the 12.2-12.3 range at about 109-110!

GOOD SOUND ADVICE

 

[jackchan]

well I have to wait on my timing chain set to get here but I went ahead and ordered it thursday. I just wanted a second opinion on wheather to run it -4 degrees or not. If I can get it to pull farther in the rpm range with the cam retard, and maybe another couple hundred rpm from a simular trick, hopefully I'll be in the mid to low twelves.
I really should get better mufflers but man do I love those flowmaster sounds.
Rick what size front runner tires are you guys running in Drag radial??
25th....hopefully I'll get the tune right by reynolds........and see what this thing can really do, until then My goal is to just make the first show in bradenton and have a good time with my son, car and friends! Its been nearly 6 years since I've owned a "race car" and nearly that long since I've seen some of my old buds from the trophy stock days......hopefully bradenton will be a blast...
thanks for the replys guys
Jack

 

[Rick 91GT]

DS2- I have the 26" version for mine, with my car in the weeds I was afraid the 25" version wouldn't be enough to get my ride height where I want it.

I have a brand new set of Sportsman fronts on it since I had planned to take the car out on the street but with the alum rods, etc I do not think it will see any street duty.

For a cheap radial it was a 165/R15 VW tire size..lol

 

[Michael Yount]

My thinking is a bit different than others here.

First off, there is a TON of variation in the actual valve timing specs of the factory cams. Second, the old 'advance it for bottom end, retard it for top end' is simply not something that should be thought of as true all the time. There are LOTS of cases where advancing or retarding the timing on a particular combo helped or hurt numbers all across the board. You have to look at the specific combo -- applying a lesson learned on one when it comes to cam timing is rarely applicable to others.

If you're serious about extracting all the potential out of your combo, you first need to have your cam cam doctored to see what you've actually got. tmoss runs a VERY similar set up to what you're trying. He carefully documented his camshaft (they're generally considered to be 210/210 at .050 -- his was 219/212 at .050"!!! Stock cam....), and then hired one of the cam gurus - Buddy Rawls I think - to model his set up and recommend cam timing.

Alternatively, you can install it somewhere - make runs; change the cam timing; make runs -- experiment with it and see what's best. But simply installing it retarded because you think that'll help top end is just guessing. No way around it. And as 25th said -- no matter what - be sure you actually degree it. Don't just select a slot and assume that's gonna put the timing where you wanted it.

 

[Rick 91GT]

Jack, is this a "stock" cam from your personal motor or a "stock" cam from one of your vendors? I guess that is the real question.....

You'll need to degree it and check it all out either way lifter centering, cam bore centering etc, all change things. Have you discussed this with J.B?

 

[25thmustang]

I agree, all comboes want something different. I was speaking more along the lines of what the Factory Stock racers do. They look for the top end and it seems 4 degrees retarded is where most of them run. If you have the desire to go to the track and really test the cam timing, Id do it!

That is also another trick, find the best stock cam. There are a lot of tolerance differences, and I do believe some people will find the ebst cam if you send them a few of them. I have heard the SD cams were slightly better than the MAF cams, but thats just hear say!

Knowing you have a history in racing, and a desire, I think you'll do alright. You will find what works and run some good times!

Dump the flows, i ddi the same and even though I went to another chambered muffler, Im dropping those soon!

 

[jackchan]

well since time is short before bradenton, I won't have time nor resources to throw my cam on a "cam doctor". This cam is the stock 86 factory cam that came in the stock 86 shortblock I pulled from the car. The car is a 1991 GT, and at some point the engine was replaced. I was under the impression it had a 91 shortblock with a stock 86 model set of heads, and boy was I ever wrong, actually it had a set of E7TE heads on a bone stock 86 (flat top pistons and all) shortblock. Anyway, I too have heard the 86-88 SD cams were a small bit better than the 89-91 cams so since I didnt have any other cam except the 98 explorer stock cam I threw in the 86 stock just to make the show in bradenton. Needless to say It will be tough just to get my car together and make the race. After that I'll get more into the changeing timeing, changing cams aspect of it.
I will however tune it thru initial timing and fuel pressure as time permits at bradenton. Right now I have to get my clothes changed and get my butt working on the car!
thanks guys for all the replys