Camshaft/ intake/ HEI upgrade questions!

[81_Chevy]

thats what i was thinking as well... i think the guy may have had a little to much to drink! 

[81_Chevy]

what do y'all think of this cap? http://www.summitracing.com/parts/SUM-G5236/

i think its pretty cool. i know it will yellow over time but im not concerned about that really, just kind of a show thing for the summer time.

would be kinda cool having your own little light show under your hood 

-Nic

[81_Chevy]

Rich- did you ever get numbers on fuel mileage?

[rich weyand]

Yeah, I'm getting between 10 and 10.5 on the driving I do, which is all around town and up and down the 13* hills on the two-mile-long, 25 mph lane I live on.  Unless I run up to Indy, I hardly ever get over 50!

I am now hyper-tuning the Edelbrock.  I tuned it to perform just fine with stock parts.  Then I had a new exhaust (duals with H-pipe and Flowmaster 40s) put on.   Now I am tweaking the Edelbrock with such tricks as stretching step-up springs.  There is so much vaccum with this cam that even the 8" springs are stepping up the mixture too deep into the throttle for me.  Per Edelbrock, 8" springs are for engines with 16" of idle vacuum, and I must be pulling 18-20, so I stretched the 8" springs by 1/5 of their length to get about 9.5", which gives me a much better step-up spot.  No more balking lean on cracking the throttle, which showed up again after I went to the H-pipe and Flowmasters.

I'm also burnishing metering rods to sizes you can't get from Edelbrock.  .065/.052 is OK, leanish cruise, rich power; .062/.052 is OK, richish cruise, rich power.  I am now taking some .065/.057s down to .064/.055, which is not a stock size, but will be dialed in very close.  Just waiting for replacement batteries for my electronic dial calipers to get here.

Mileage should be close to 11 mpg when I get it dialed in, even with the slow and hilly and stop & go driving I do.

Some things about the long-term impressions on this cam.  First, I like it a lot and it's perfect for the driving I do.  Driveable, excellent out of the hole, very responsive generally.  Also starts really easily, and idles well.  Pulls like anything.  Fantastic around town.  Runs great on the highway at speed.

All that being said, if I drove open-country two-lane highways to work every day, I would probably go with the 12-235-2 or 12-306-4, both of which were recommended to me, the first by Sean Murphy at SMI, and the second by people who really like the 252/260 cams.

The issue here is the 50-90 passing shot.  One thing I can say for the cam that GM puts in the 350/290 engine.  It's anemic as heck off the line, no balls in the bottom, but the 50-90 time makes it a two-lane terror.  The 12-300-4 cam does nicely 50-90, but that other cam was hellish!  When you stomped it and it dropped second, it exploded around slower traffic.

So if you do a lot of two-lane highway driving, the 12-235-2 or 12-306-4 would perhaps be better choices, giving up some oomph in the low end for a bit better passing times on the two-lanes.  Interstate stuff wouldn't matter, because you are not doing the passing thing.  If you mostly do around town, and some off-road and such, and Interstate driving, with less two-lane highway driving, then the 12-300-4 remains the right choice IMO.

[454Man]

Rich... Ditch the eddybroke for a  qjet. I've got the 260h cam 9.5 comp... Via flat tops a/valve reliefs, th350 and 3:42 gears. Get 15Mpgs on the highway

What's under the hood??? If you have to ask maybe we shouldn't race...

[rich weyand]

Well, I don't know what I get on the highway.  I should probably fill a tank, run up to Indy and back, and then see what I used.  Big difference between C and K as well, even with the t-case disengaged. 

When I talked to Sean Murphy at SMI, though, he thought I was doing good for mileage with the setup I had at the time, and that a Qjet wouldn't help much over what I had.  He was curious about how I got the Edelbrock dialed in so well, and once I said I had an NGK A/FR meter, he said, "That would do it."

Once I get everything else done, though (and I'm very close), I may do a Qjet.  No sense doing it before I have everything else done, because Sean needs to know what setup he is tuning for.

Or maybe not.  I don't really care about mileage much.

[454Man]

Dude I had an Eddy... recall kit and all.hit tired of it and went to the junk yard.scored a qjet off a 305 rebuilt it
And been happy ever since :-)
What's under the hood??? If you have to ask maybe we shouldn't race...

[rich weyand]

So I took the NGK A/FR meter off the truck tonight.  It's dialed in where I want it.

When I put the Flowmaster 40s on, the tune changed, so the prior mufflers were holding back pressure.

With this tune, I tried the .062/.052 needles, and the .065/.057 needles.  Ran them for a while and got some readings.  I decided what I really needed was .064/.055 needles.  Which they don't make.  So I used some jeweler's files to file down the .065/.057 needles to .064/.055.  I also figured I needed about a 9.5" (of Hg) step-up springs, which they also don't make, so I stretched the 8" springs by 20%.

Tune now is pretty spot on by the meter, and it drives great.

Next up, I think I'm gonna get that bumper with the fog lights built in and a fold-a-way bumper step for the front.

[81_Chevy]

Hey rich, what do you think of the Lunati 10120700 vs the comp cams 12-300-4?

[rich weyand]

Lunati 10120700 looks more like the equivalent to the Comp cams 12-231-2.  Specs are almost the same.  So you could dyno-sim it on camquest.com and see how the 12-231-2 does against the 12-300-4, and the 12-231-2 results should be spot on the Lunati 10120700.

The 12-231-2 was one of the ones I looked at.  Google that number and my last name and you should see some discussion of it and some dyno charts of the various cams I looked at.

The 12-300-4 has shorter LSA, shorter durations and lower lift than either the Lunati 10120700 or the Comp 12-231-2.

[81_Chevy]

what do you think would work better with a holley 600cfm and aluminum intake?

[rich weyand]

That doesn't matter.  What matters is what you want to do, how you want it to drive.  I got a real stump puller cam, the Comp 12-300-4, which I like for the driving I do.  The 12-231-2 (which is near-the-same-as the Lunati) will have a little more top and a little less on the bottom, and the 12-235-2 will be a little more so yet.

Any of these are good cams for our trucks.  They are all pretty torquey.  What you want to stay away from are the winders, with a lot of horsepower and nothing in the bottom.  The trucks are just too heavy for that.  You don't have enough giddyup off the stoplight, though they make for a two-lane terror with astonishing 50-90 times.

Here are the cam diagrams on the 12-300-4, the 12-231-2 (and pretty much that Lunati) and the 12-235-2.  Open all three in separate windows and switch windows back and forth to see the differences really easily.  These were done with my setup, but should be about the same for yours as long as it is a dual-plane manifold.

Note how they progress from the 12-300-4 to the 12-231-2 to the 12-235-2.  12-300-4 has the most torque in the bottom, but runs out of breath soonest, with the hp rolling over at 4000 rpm at 274 hp.  12-235-2 gives up a bit of torque in the bottom, but the horsepower doesn't roll over until 4500 rpm at 300 hp.  12-231-2, and the Lunati, lie in between.

So here they are in increasing order of top-end horsepower, and decreasing order of low-end torque.

http://users.rcn.com/weyand/smalls/12-300-4small.jpg
http://users.rcn.com/weyand/smalls/12-231-2small.jpg
http://users.rcn.com/weyand/smalls/12-235-2small.jpg

[travisr1988]

Rich, How would that cam do with 4.10s and 31" tires?

[rich weyand]

I have 3.42 and 31s, and full-on starts make the tires complain in RWD.  With 4.10 and 31s, any of these torquey cams (12-300-4, 12-231-2, 12-235-2, 12-238-2) ought to smoke 'em pretty good off the line.  For all-around driving, 12-235-2 is probably best.

[travisr1988]

how about 12-234-2 xe256h? I noticed 12-235-2 is 4x4, mine is 2wd, 12-234-2 shows slightly more torque, will it make any noticeable difference?