High duration cams

[kylebes1]

Do any of you that have higher duration Shrick, or whatever brand, cams have any issue with the rockers? Any idle issues, or loose of vac?

[Andreas]

I had a 292 deg custom grind in my 2.7 Alpina B3. It had a very rough idle but I would say had no power advantage over the original cam. I don't know what the original was and I no longer have it.

Together with all my other mods (bigger throttle body, 733 AFM, branches, aluminium flywheel, piggy back computer) the car pulled like crazy from low rpm and fizzled out after 5,500 rpm.

I did break a rocker arm once at 7,200 rpm.

Soon I will be building a 3.1 stoker M20 with a 304 deg Schrick cam. Not sure if the cam will work nicely but there is only one way to find out. Schrick claims the cam works best between 5,000 and 7,000 rpm.

[MrK]

I've had a 304 Schrick for a year before I swapped. VERY lopey cam, horrible unburnt fuel smell at idle, and IMO the power band is too high, peaking around 7k rpm, where the intake manifold starts choking the engine. So all in all, I say if you're not going ITBs and getting rockers that can 'rock' 7500rpm all day, then a 304 cam is totally useless.

FYI my cam was in conjunction with high-comp pistons (10.8CR), m30 AFM, 2.7 stroke, piggyback, adj cam gear, and headers (Among other things, but the rest are too tedious to list and not that relevant).

[matt]

Do any of you that have higher duration Shrick, or whatever brand, cams have any issue with the rockers? Any idle issues, or loose of vac?

You will have rocker issues based on max RPM not lift or duration. Reground cams need lash caps or oversize eccentrics, but that's not really a rocker "issue."

You'll lose vacuum too... no way around that with an agressive cam.

[kylebes1]

Sounds like 292 and 304 are extreme.

[e30_325es]

I've enjoyed my last month with my 283 Catcams camshaft. Lopey idle, dunno about loss of vacuum, but have no brake issues at idle. Pulls strong from about 3500rpm all the way to the current stock 6250rpm redline. I do believe it runs a bit rich, but I'll see how much things change with my markD chip that's in the mail, and once I hit a dyno and get an a/f reading. Oh yeah, the headers might change things too.

[MrK]

Oh sorry I forgot to add, YES almost total loss of vacuum around idle, enough to cause a few near-collisions at first when I wasn't used to (or expecting) it. Just remember to rev a bit before trying to use the brakes, if you've been coasting at idle. Otherwise no brakes :D

[cthulu703]

Or you could pull a vacuum resevoir off of say an '83 '84 rabbit with A/C. That might help a little.

[MR 325]

I had a 282 in my old car. It was very nice when it was just a 2.5 but wasn't so great for turbo [boost built a little late].

[Andreas]

I've had a 304 Schrick for a year before I swapped. VERY lopey cam, horrible unburnt fuel smell at idle, and IMO the power band is too high, peaking around 7k rpm, where the intake manifold starts choking the engine. So all in all, I say if you're not going ITBs and getting rockers that can 'rock' 7500rpm all day, then a 304 cam is totally useless.

FYI my cam was in conjunction with high-comp pistons (10.8CR), m30 AFM, 2.7 stroke, piggyback, adj cam gear, and headers (Among other things, but the rest are too tedious to list and not that relevant).

Hi MrK

I would like to ask a few questions.

Did you have to rework the valve reliefs in the pistons to accomodate the high lift and how much could you adjust the cam ?

At what rpm did the power band kick in ?

How much power did the engine make ?

Would it be a good track cam or would you often be out of the power band when coming out of a corner ?

[MrK]

Hi MrK

I would like to ask a few questions.

Did you have to rework the valve reliefs in the pistons to accomodate the high lift and how much could you adjust the cam ?

At what rpm did the power band kick in ?

How much power did the engine make ?

Would it be a good track cam or would you often be out of the power band when coming out of a corner ?

Yes I had to rework the valve reliefs, and I just adjusted the cam back to the point where the marks on the head and block align (stock), because after I shaved the block, the marks weren't aligned.

I'd say the power band kicked in around 4800rpm.

I'm not sure how much power the cam added, but the engine overall was pushing decent hp... I'd say a little above 200 at the crank after some tuning.

I suppose it would only be a good track cam IF the track was fast, and if you had ITBs to make use of the higher power band.

Hope that helped.

[SA E30]

I have a 288 Schrick... Very Rough idle, put the car is pretty dead under 3000rpm, from then on it pulls vey strong till around 6000rpm, when whackin it I rev it will about 6500rpm.

this is on a 328i crank, and 86mm pistons =2.9lt

[Andreas]

Yes I had to rework the valve reliefs, and I just adjusted the cam back to the point where the marks on the head and block align (stock), because after I shaved the block, the marks weren't aligned.

I'd say the power band kicked in around 4800rpm.

I'm not sure how much power the cam added, but the engine overall was pushing decent hp... I'd say a little above 200 at the crank after some tuning.

I suppose it would only be a good track cam IF the track was fast, and if you had ITBs to make use of the higher power band.

Hope that helped.

Yes, it did help. Thank you. Glad to hear that the cam kicks in at 4,800 rpm. I do plan to install ITBs and have many other goodies for high rpm.

[SA E30]

I would say if the power band was around 4800rpm... seems 2 me like it wouldnt be such a great camshaft for the tracks in SA

IMO.

[Andreas]

I would say if the power band was around 4800rpm... seems 2 me like it wouldnt be such a great camshaft for the tracks in SA

Yes, generally I would agree with that sentiment. However, I am hoping that my 3.1 will have enough grunt between 3,000 and 5,000 so as to still provide decent pull out of corners and then really kick in on the straight. Don't want to let that M3 get away ;) .