Cascade Crew

Leejo2005 · Member Joined: 12 Jul 2009 Posts: 466 Location: Kennewick

In need of a bit of help here...

I've been pondering getting a new cam for my 305 TPI and I'm trying to figure out if it would be more benefitial to just put 1.6 ratio rockers on. The engine is freshly rebuilt with Trick Flow 30300006 Heads. I've heard the cylinder walls shroud the valves and ultimately restrict flow, and the intake itself is quite restrictive, but I'm sure there is still some room for improvement in the factory valve train. I've been looking at comp cams 08-501/502-8 or 1.6 rockers. Thoughts on those?

MrMike98 · Member Joined: 18 May 2010 Posts: 231 Location: Bremerton

I would only use 1.5, just make up the difference in cam. this will keep the stock geometry, always a good thing...just make sure your springs can handle the xtra lift..
good luck

Leejo2005 · Member Joined: 12 Jul 2009 Posts: 466 Location: Kennewick

Sorry, I meant either keep the stock cam and get 1.6 rockers, or get one of those cams...

The heads say they'll handle up to .540 lift as well.

91RSVert · Posted: Wed Dec 15, 2010 5:37 pm Post subject:

On desktop dyno, it usually only shows 3-5hp gain at max rpm. Honestly, not worth spending the cash unless you HAVE to replace rockers anyway.

IROCDave · Posted: Wed Dec 15, 2010 6:39 pm Post subject:

Trick Flow has a history of over estimating what their valve springs can handle. I wouldnt trust them for more than .500 lift.

Twilightoptics · Posted: Wed Dec 15, 2010 6:52 pm Post subject:

You need to measure the springs to coil bind before you can say "wouldn't use at."

Your springs need to be matched to the cam.

You'll get way more out of the motor with a cam, than with the rockers.

That said, if you need rockers in general or are upgrading to a set of rollers, definitely get 1.6.

izcain · Posted: Thu Dec 16, 2010 8:15 pm Post subject:

If your going to look into swapping rockers be prepared for measuring and purchasing the proper pushrods as well for the proper geometry but you better check those springs first!

Leejo2005 · Member Joined: 12 Jul 2009 Posts: 466 Location: Kennewick

The cam I'm looking at now is .488 int .495 exh supposedly it's a pretty good cam for TPI 305's its comp cams 08-501-8 If I do that I'm going to stick with 1.5 ratio on the rockers and of course check the valve springs max lift and valve-to-piston clearance.

I've never done a head swap before, atleast to aftermarket heads, so I'm gonna get a solid mock up lifter and adj. pushrod to check the geometry also, hopefully I'll be able to knock it out in a weekend when I get home.

izcain · Posted: Fri Dec 17, 2010 4:05 pm Post subject:

I dont pay as much attention to the lift as much as I do the duration when it comes to cam selection for Computer controlled stuff lift is still important though.

Leejo2005 · Member Joined: 12 Jul 2009 Posts: 466 Location: Kennewick

That makes sense. I just don't want to make the mistake I did with my old engine and kill the vacuum and driveability. Although, I am suspicious that the intake I had on it was warped. What effect does the lobe separation have? I am still using the factory roller lifters; should I replace them? They have about 90,000 miles on them but they seemed fine when I had checked them but that can always change...

Does Duration at 050 inch Lift 212 int./218 exh, Lobe Separation (degrees) 112, and .488 Int .495 Exh. sound like a good choice?

The heads I'm running have slightly smaller chambers (56cc), larger valves, and 175cc intake runners. I've bored it out .030 and raised the compression height .010 so the compression should be about 10.3:1 with .031 thick gaskets... I don't know if that's the correct compressed thickness for the head gaskets I have or not though.

Twilightoptics · Posted: Fri Dec 17, 2010 10:58 pm Post subject:

LoL you're still talking a whimpy cam as far as vacuum is concerned.

Ratio shouldn't change your pushrod length unless you're already way out of wack.

I don't even remember what I'm running. It's like 239/247 at .050 and my vacuum is just barely starting to be a noticable issue. Drivability is fine. Milage is another story.

Have your head chambers been actually measured? Where do you come up with the random 56cc number?

What IS your deck height?
Gasket thickness compressed.
Gasket bore dia.
Actual bore size.
Stroke?