HE cam questions

[godzirra]

so while the truck (1980 720 w/L20B) is at rest for a few days (hopefully not weeks) for steering reconfiguration, I have started to research alternatives to squeeze a couple more horses out of this tough little engine.

I am aware of the Weber 32/36 carb idea, turbo charging, cold-air intake, etc. so I took all the concepts these modifications had in common and reached the basic engineering principle that:

 

more power = more fuel faster + more air faster...duh.

 

I was wondering more specifically about high energy/aftermarket cam shafts, I know the larger/wider lobes allow the valves to stay open longer allowing more intake/exhaust, basically letting the rest of the engine increase its own potential. I found a few that are 246, 236, and 222 I/E duration,  am assuming relatively standard durations of intake/exhaust due to what ever size the lobe is.

I live in a community that is allllll about some drag/dirt track/circuit racing and there is no such thing as a "stock cam shaft" in any of those cars. However as the L20B is not the most popular racing engine around these parts (if its not a 350/351W/383/302-on-steroids etc. it's pretty alien).

 

So any past experiences with installing/the performance of/ the cost vs. gain of any aftermarket cams for an L20B would be greatly appreciated, this is purely philosophical at the moment.

 

Keep in mind, I am not trying to build a rocket ship. keeping it simple, just with a little more umph.

Thanks.

 

(I apologize ahead of time if this topic has been visited already, I just couldn't find a thread dealing specifically with performance cam shafts.)

[flatcat19]

Really?

 

What about this?

 

Or this?

 

There is sooo much information here. 

Saying you searched and came up with nothing is rare. 

Not here. 

[metalmonkey47]

Hey man, LOTS of good performance goodies in GA for L series, just gotta know the right people. What part do you live in?

 

I have a racer brown .475 cam in my LZ and it runs great, but the motor is completely built from every aspect, so it's hard to compare to a healthy stock L20B. Aftermarket cams are a strong way of adding power, but I don't think you would be happy with a 32/36 and a big cam. The 38/38 is even too small for my motor, but much better then the 32/36 as far as performance goes.

 

[datzenmike]

 I know the larger/wider lobes allow the valves to stay open longer allowing more intake/exhaust, basically letting the rest of the engine increase its own potential.

.

The problem is longer duration means more overlap, when both valves are open at the same time. Great for ultra high RPM power but shitty idle, low and mid range power.  What you need is a twin cam head for the L series with variable cam timing.... keep your cake, and eat it too.

[banzai510(hainz)]

Ezist bolt on power is the 38/38 weber. In my opinion hog out the top of manifold to increase the plelum size

 

 

metal monkey that tailgate  the shit!!!!

[godzirra]

flatcat19, no disrespect but I did try looking for specifically L20B performance cams, the results you are linked to are for KE/Napz/other engines which admittedly there are plenty of threads on, not so many stock L20B.

 

I am simply wondering about the direct effects of a high energy cam in a relatively stock L20B (no bells and whistles, maybe a weber carb swap to come.)

 

datzenmike, thank you for the insight, this thing is not going to be busting 6000rpm, on a regular basis :) so as per your information a cam that is closer to stock would be better for mid range rpm? this again is purely philosophical, I am not any where near a cam mod, just investigating. Yes the twin cam head would be fantastic, but finding/paying for one of them is another adventure (I guess that's where the philosophical part comes in).

 

banzai510 / anyone else who mentioned it, I think the weber carb (I will have to read a bit more about the 38/38) will be a little more practical for me and it sounds like general verdict as the first place to start as far as power modifications.

 

metalmonkey47, I am about 45min. south-east of Macon, in Bleckley Co. if you know where that is. I have found almost NO ONE local who messes with them, if you go to any one of the local engine shops (local as in with in about 30-45min or so) who work with racing anything, they always ask first "why are you bothering with that Jap-crap" which instantly starts a very colorful conversation.

[datzenmike]

It all comes down to breathing. The faster and the more air you can get into and out of a head the more power you will make. A cam with more lift and duration allows more air to flow but if you don't make other improvements like a larger or multiple carbs, larger diameter valves, larger better flowing ports, less restrictive intake on the inlet side and less restrictive exhaust pipe and muffler on the outlet side it can't do it's job.

 

The stock cam is a good compromise for power, and economy with lots of low mid range torque where you do most of your driving. Up to 4,500-5,000 the head and cam breath pretty well as they are and don't need much help. Anything you do to add power in this range and above will simply take away from the lower speeds.

 

A general rule is that for every 10 degrees of additional valve duration added, the peak torque (although improved) will move 500 RPMs higher in the rev range.

[godzirra]

Yeah everything under the hood is pretty much stock, with the exception of the exhaust, which is a 14" glasspack, and that is it. I cut the whole line down to just a little past the cab so there is considerably little resistance in exhaust (which DID improve acceleration on a small scale but still it did make a noticeable difference compared to the stock muffler + cat. converter).

 

basically a cam swap is seeming like not entirely worth it without a mess of other additions (for my uses). I did get to compare the cam on the L20B to a 22R cam, theirs is smaller. I believe in this scenario I will refer myself to the saying that I generally ignore: "if it ain't broke, don't fix it".....for now.

 

thanks for the enlightenment

[Stoffregen Motorsports]

27C cam from Rebello. It's a mild cam that works well with a DGV and doesn't require a heavy valve spring. It idles well and pulls from the mid low to the mid high in a stock motor.

 

Other mods I would consider: DGV Weber for sure, good quality header, 2 1/4" exhaust (maybe even 2 1/2" inch), good turbo muffler (quiet) or "lazy S" muffler (loud), recurved distributor and NGK B6ES spark plugs. Assuming all your other things are in order this makes a nice package.

 

NOTE: when taking advice on camshafts, keep in mind engine displacement. A huge cam in a 1600 acts like a much smaller cam in a 2300.

[flatcat19]

flatcat19, no disrespect but I did try looking for specifically L20B performance cams, the results you are linked to are for KE/Napz/other engines which admittedly there are plenty of threads on, not so many stock L20B.

 

I am simply wondering about the direct effects of a high energy cam in a relatively stock L20B (no bells and whistles, maybe a weber carb swap to come.)

 

 

The links I provided were just to show how fast the search process for Ratsun is. 

Using google, type "Ratsun" into the search bar and the subject inquiry.