Well, my cam is toast. I had the xe268. The next time the motor is run it will have my home ported sprorstman II's on it. I want something slightly bigger than the 268 but still want to be able to drive it on the street.

Mods:

Sportsman II's
Performer RPM
Hooker Long tubes
Dual 2.5 exhaust
T56 w/ centerforce clutch
I have 3.45 gears in the car now but have a set of 3.70s that will go in it unless I decide to sell them and get a bit lower ratio(higher numberically)

I think that is about all you need to know for a cam choice. I should have around 10:1 compression. I have considered the xe274, but dont know if that will be much different than what I have now or not. If you need to know anything else, just ask.

Thanks

Ben

 

Oh, yeah, I have 1.6 pro magnum roller rockers and 7/8 screw in studs w/ guide plates. I am running a Speed Demon 750 DP.

Ben

 

So the lobes are shot huh?

That stinks

I'd stick with the 268, or at the most, step up to the 274 since I know you want to keep it somewhat streetable.

IMHO, anything more than that with those heads would justify using a SP intake.

 

I'd suggest you use the cam we talked about before the engine was built. Comp 270H. You should get some impressive results with the new heads and the other mods you have done if you were to use the 270H. I'm just not impressed with the XE series at all. Like Ive been saying all along it would have worked well with the 305 heads too, funny all the mags are promoting single pattern cams now with thier builds.

So the lobes got wiped I thought this was running good for a few months, dont see how ecm removal would wipe the cam.

 

Before you just stab another cam in there, especially a bigger one, you need to identify and fix whatever killed the one that's in there *cough* valve springs *cough*. Either you don't have enough spring, or they're installed incorrectly.

Sounds like the cam was going down from day one, it just took a while for it to get to the point that the valve motion was different enough between cyls to be noticeable in the way the engine ran.

Personally I really like the XE series. I had a XE274 in my 400 for a while, it ran like a bat out of hell. That's kind of alot of cam for a street-driven 350 though.

You also need to make absolutely certain the destruction didn't shed metal shavings in your engine, and if so (highly likely) clean them all out; if you don't, you may find yourself grenading a short block next.

 

More important than wether you should go with this cam or that cam,, you should check the lifter bores. Most times a hyd street cam fails becaust the lifter stops spinning in its bore when the motor is running. This will soon lead to a failed cam. if there is a minor bur or grit in the bore wall the new lifter will not spin either
and will fail again.
Clean and check each lifter bore, especially on the lobes that failed. if a new lifter will not spin freely or feels different than the others, get a small brake cylinder hone and hone that bore a little.
Use an electric drill to run the Brake cylinder hone.
Don't get carried away. A little hone job is all that is nessessary.
Wash down and wipe clean the honed bore with brake cleaning spray, lube it with oil and try a new lifter again.
Change the engine's oil BEFORE you fire up the engine.
Change it again after 1/2 to 1 hr breakin.
When you put the cam breakin lube on the lifter, only lube up the bottom with the lube ... Lube the sides that ride in the lifter bore with just oil.
Getting the thick cam breakin lube all over the lifter bore can/will cause it to drag and not spin just like a burr in the bore.

Comp Cams has a tech warning on their site that states that engine oil that is sold now has a zinc additive missing that was in old oil.
The oil companies took it out because all new motors have roller cams and don't need this anti friction additive like a flat tappet cammed motor does. This is going to be a contributing factor in flat tappet cam failures. Using GM's EOS oil additive will help prevent this. DO NOT USE SYNTHETIC OIL for cam break in.
Use plane jane 10w30 oil and GM EOS additive, along with the recommended/included cam lobe lube.

After that you can change to synthetic. These guidlines should help you avoid another pesky lobe failure.

 

Sportsman II heads are a bit critical to cam selection to get good power.
My friend recently spent about a week on the dyno finding out what works and what doesn't with these heads.
Could fill a book with the Dyno print out sheets he made.
But learned a few things .....

Sportsman II's tend to need a larger cam. They need to be ported too. You do not need to remove a ton of metal from these ports but they do need some tweeking to kick the flow up. The larger port volume of these heads tends to favour a larger cam and more rpm.

I'd go with a cam like the Comp XE284H-10 and the steeper rear gear.

You might consider a modern tight lash solid cam like the new Comp Cams Extreme Energy Mechanicals.
Crane and Crower have good simular street mechanical cams too.
They do make more power then a Hydraulic, are relitively low maintenance.

Something with around 248 to 256 deg intake duration @.050" makes the best power in a mechanical cam.
A good single pattern mechanical cam would be the Comp Magnum 294S-10
248/248 -110 .525"/.525"
The Edelbrock Performer manifold needs to be carefully port matched to the larger port opening of the Sportsman head.
(20hp found here on a past dyno test.)

Many people shy away from useing a mechanical cam on a street motor 'cause they fear they will be constantly be adjusting the valve lash. This is not true. use the recommended valve train parts and adjustment will be only be a routine thing.
I do mine about twice a year. ( the car sits all winter) Takes about 1/2 hr to check and readjust all the valves. Usually only a few need to be touched up a bit. Any extreme varience in valve lash indicates a wear problem.
And you don't get oil all over the place like when adjusting a HYD cammed motor's valves.

Try it....

 

AJ,
Well, i kinda want something a bit bigger than the 268. I want something that will work well w/ my heads but also be streetable so I dont want to go to much larger. Also since the car is going to be painted soon I might start parking it winters and just driving the t bird so I dont get all that salt on my new paint job.

SSC,
I dont think it had anything to do w/ ecm removal. I think it was just coincidence. I had been having a fluttery feeling in the high end for quite a while and it just started to work its way down in the rpm range. I reset the valve lash and it got better, but got worse again real soon. I also put an open element on when I put the demon on so I think that may have also let me hear it more instead of it just beeing a slight feeling.

RB,
I am not sure on exactly what killed it. I wont be using the same springs since I have larger 1.55 pockets on the sportsmans. I have the larger dual springs that came w/ the sportsman heads that are supposed to be good to 600 lift according to wp. One thing I can think of is I still had the stock hardware down to the exhaust rotators on on the 416's. I wondered if those caused there to be to much seat pressure, but dont know for sure if they even make a difference. One other thing that is probably worth mentioning is that I had a hell of a time during cam break in. I had the older stye timing tab instead of the one that mounts behind the water pump. I had a new balancer for the 78. From what I read it was 77 or something when they changed. I had to shut down and restart a few times during break in because I couldnt figure out why it wouldnt run right. It turned out that my timing was EXTREEMLY retarded because I was using the wrong timing tab. I was worried from the start that I may not have got the cam properly broke in. I had already checked and there is metal in the oil. What would be the best way to go about this to keep from tearing stuff up? I will have the motor completely out of the car so I can do whatever is needed.

F-Bird,
I will check the lifter bores and such when I take the motor out. As far as porting the heads, I just finnished the first head tonight other than polishing the chambers. I need to find somewhere to come up w/ a junk set of valves. I basically just reshaped the valve guide bosses, and got rid of all of the casting flash. I left the intake at 80 grit, and pollished the exhaust w/ the S/A kit. I also plan on matching the performer rpm intake to the ports while the motor is out. How streetable are the cams you mention. I have 7/8 inch studs comp pro magnum roller rockers and poly locks so I think that should keep a solid cam from backing off to quickly with the poly locks.

Thanks everyone.

Ben

 

Forget seat pressure on a bunch of stock springs. They don't have any. I'd bet you had 70 lbs or less on the seat, and coil bind at full lift, probably 500-600 lbs. That's what munged the cam.

This is why cam mfrs won't warranty a cam unless you change the springs, following their recommendations for the cam you're using.

If it was my motor, I'd tear it all the way down, take the block to the machine shop, and stand there and watch them while they remove the cam bearings and all the oil passage plugs. DO NOT let them waste your time and money vatting it with that stuff still in there; metal shavings will hide in all sorts of places, especially behind the cam bearings. Have them tap the 3 holes around the cam for 1/4" pipe plugs. Get it back with no cam bearings or plugs. Take it to the quarter car wash, get a couple of cans of some kind of engine degreaser that's just diesel fuel in a spray can, and use rifle brushes in all the passages and a wire brush of the toothbrush-looking variety to clean the grooves behind the cam bearings; then car wash the hell out of every hole you can possibly stick the wand in (Butthead opportunity here). When you're all done with that, take it back and have them put the cam bearings and freeze plugs and oil passage plugs in it except for those front 3. Get yourself 3 plugs at the hardware store, drill 2 of them in the center with about a #65 or #70 drill bit, and install those 2 on the sides of the cam (NOT the one above the cam). Look down in the hole next to the rear main cap, where the output from the oil pump goes on its way to the filter; make sure they put one of the 1/2" welch plugs down in that hole, about 1-1/2" down in there. If that plug is not there, the oil will bypass the oil filter, it will simply flow straight from the pump up to the back of the rear cam bearing and then on to the bearings with its load of dirt.

Take the crank to the car wash with you, and do the rifle brush thing to its oil holes too. If it's got damage, get it turned.

Put it back together with new rings & bearings.

The last thing you want is a bunch of metal shavings left hiding in oil passages in the block, with nowhere to go except straight into the bearings the first time you start it up with your new cam.

 

First of all I had new springs as I mentioned before. I had the comp comp springs than were suggested by summit for this cam. I just had the stock retainers and such. As far as cleaning the block how much is that going to cost to do because it will probably be AT LEAST a couple months before I can afford to do everything I need to anyway. My car was keyed and I am trying to save money to have the bumpers and ground effects painted because they arent covering them. That is going to take all of my money for a while. I understand that this needs to be done right, but I just need to know what I am in for because I dont make a lot of money, but I have a lot to pay for.

Ben

 

Ah, I see... my bad. I thought they were old springs. The problem then is probably that they were shimmed too much, i.e. not enough installed height; that cam is close to the edge for them, so even a little error there can be fatal.

Vatting should be $50 or so, with the plug & cam bearing R&R another $20-25 for the 2nd trip. Rings & bearings, and cam bearings, should be around $100-125.

If this is the same short block you're putting the other heads on, I'd suggest being careful and thorough, to avoid re-peats. It would be really a bummer to put it all together, skip over something, and then have it flame out again. It couldn't get much worse than that.

 

The Comp cams 294S-10 cam or a simular cam will have a rough idle, reduced manifold vacuum and will want more initial timing at idle. Once the motor is warmed up it will run fine with a steady rough idle at about 800/900rpm. Give it as much initial timing as it wants. Some where between 20 and 32 deg initial advance at idle.
The strongest part of its power band will be from 3000 rpm up.

But it will make strong power with either the Performer RPM or Vic jr intake and your heads.

The Poly lock rocker adjustment nut system tends to unexpectedly "back off" much more readially that a stock type ball & jam nut rocker.

Just be sure you lock down the lock set screw nice and tight.

Follow Comp cams valve spring recomendations for this cam.
Your present springs may or may not be suitable. The only way to tell for sure is to measure the pressures at the installed height spec and open spec.
You want neither too much pressure nor too little.
Either can result in increased unnessessary wear or cam damage.

You may want to experiment with installing this cam in a more advanced position to enhance the average torque curve.

 

Well, i have the heads pretty much done other than some polishing on the combustion chambers. They are not perfect, but I dont think I did bad for this being my first set that I have ported. Anyway, I am really kind of thinking of going with a mechanical cam. I am also kind of considering a stroking the motor if I have it appart if I cant find a 400. Do you think that the magnum cam would do well, or should I go with a dual pattern like the xe solid cams?

Here is a pic of some of my porting.

Ben

 

2

 

3

 

ttt

 

Well, I have the motor out, and I have the intake off. I pulled the lifter out that I had so little lift after this ordeal, and a couple others. The one that was real bad was dished in real far. The other 2 I pulled out seemed to be on their way but not near as bad.

This had been my first cam swap. I didnt check seat pressure or anything because I just didnt really realize that I needed to. I just used the recomended springs and installed them with the rest of the stock hardware. I also had problems with the break in period, and had to shut down the motor and restart it quite a few times because I had the wrong timing tab, and when I would try to set the timing, I was setting it so far retarded that it would hardly run. My question is, could the break in troubles or anything else have caused this, or is it pretty much definately have to be because of a seat pressure problem?

Thanks

Ben