Camshaft recommendations

[DANK-KAGE]

Hey all,

I'm currently looking for a cam grind for my 4K in a Ke30.

I'm torn between a Tighe #104 or a Auckland cams #873.

I'll be running a Weber 45DCOE, heavy duty valve springs and extractors if that has any bearing on the situation.

Does anyone run these daily?

What are people's thoughts on these cams in terms of street-ability and gain?

Any help would be appreciated.

Thanks.

[altezzaclub]

Those are two very different cams.

The 270-280deg (advertised) are usually mild for general driving. I use a Crow 276deg & it has a grumpy idle but drives just as smoothly as a stock cam except it has a tendency to surge on over-run at low speed. It just goes quicker than stock all through the range.

The Tighe 104 is very similar. It will be easy to pull off in traffic, go hard up to 5500 or 6000, then start to run out of breath. For a town car its ideal, I use twin SU carbs and a 4.3 diff. You could easily pick any Tighe cam up to the 424 and drive them in a daily. The cams over 280deg suit an open-road car where you're not starting in traffic a lot.

However Auckland's 873 has durations over 288deg, so it won't have much bottom end. Just think of how much in a piston/crank rotation those valves are actually closed for. The inlet valve will be opening while the exhaust is still open & staying open while the piston goes all the way to the bottom, and then comes up another 100degrees...  so it only closes for the last 80degrees and from that is has to get enough compression to run smoothly. So at low revs it will push the fuel/air mix back out the carb, which is why they run so badly down low. The Auckland #12 cam is closer to the Tighe.

Pay attention to the 50thou duration, that tells you how fast it opens. Some cams open slowly so they have a long duration, but you get bugger-all flow at small openings. A large valve lift is generally good, although it gives the valve springs a hard time, and their timing is crucial when running a skimmed head as there is a greater chance of a valve touching a piston.

Don't forget to get the followers re-surfaced at the same time so the new cam surface has a new follower surface to wear in to.

What sort of compression ratio are you aiming at??  Most ground cams like 10:1 or over. A stock comp ratio just won't get the best out of the cam.

No matter which you pick, tuning the DCOE will make or break it. A choke that is too large will make it a coughing dying dog in traffic, so unless you're moving all the time make sure you err on the side of smaller chokes rather than larger, and make sure the jets work well down low.  If you can get 27mm chokes grab them.  I will always give away top end power for drivability unless its in a rally car.

 

[DANK-KAGE]

Thanks for the reply.

Yeah, I thought I'd look in two directions with the cams.

I'm going quite high with the compression, definitely at least 10:1.

Given I will mainly be on open mountain roads with little traffic and stopping, or track day/rally-ish stuff in the back paddock, would the #873 be better?

As blasphemous as it sounds, given I'm a 19 year old without a semblance of self moderation, I'll probably blow it up.

So my main concern is having fun before it does.

I'll definitely spend a lot of time tuning the carb and getting everything right though.

 

Thanks a lot for replying in such depth, it was really well explained.