Maine Vette

Well, as some of you may recall from my post a while back my 454 rebuild is now well underway.

Previous post: http://forums.corvetteforum.com/show...teardown+today

With the help of a local performance engine shop I've made some pretty good progress with putting together a good combo for a strong street performance motor. Here's the combo:

The block has been bored 0.030", decked & align honed
Stock crank
Eagle I-beam connecting rods
SRP forged pistons, 26cc dome
AFR 305 aluminum heads, as cast (CR should be around 10.2:1)
Hydraulic roller cam, custom grind (Specs TBD)
Exhaust will be headers w/ dual exhaust out the back

As you can see the one major item missing is the intake. Once that decision is made we can go ahead and pick the cam specs (ok, so maybe there are two big decisions left ). I know the intake issue has come up many times, but I'd like to know what you guys think would work best with this specific setup. I know the Torker II fits under the stock hood, but with my 3.08 gears it seems that an intake designed for midrange performance would be better suited to this buildup. What about the performer (not performer RPM) with a drop base air cleaner, or would that be too small?

If this were your motor, and you wanted to stick with the stock hood, what would you do?

Doug Brandon

If you want to stick with the stock hood, I would go with rect port heads, and the factory LS6 intake. I have one on mine and with a 3/4" open spacer, it makes very good power. I will have it dyno'd in june and will post the results.

MsVetteMan

Edelbrock air gap!!

lvjohn

I have a 71 BB with the stock hood, i used the Edelbrock Performer with a drop base air cleaner and a 2.5 air filter works great no clearence problems.

BigBlockk

The camshaft should be matched to the compression ratio of the engine, not the intake manifold.

BigBlockk

Later.....

bashcraft

Actually, the camshaft should be chosen for the desired characteristics of the engine (horsepower range, torque range, idle, etc.) and then all other components should be matched to the camshaft, including compression ratio, heads, intake, exhaust, rear gearing, etc..

Maine Vette

Not to put my thread off-topic, but doesn't camshaft selection also depend on the motors ability to breath (just one of many factors)?

So how does the LS-6 intake compare to my stock LS-5 intake? Any thoughts on how it would compare to an Edelbrock Performer Intake?

bashcraft

Originally Posted by bashcraft
...all other components should be matched to the camshaft, including compression ratio, heads, intake, exhaust, rear gearing, etc..

68/70Vette

I once had an L88 clone engine and a 3:08 rear end gear ratio. The L88 had the stock cam shaft which meant it had a lot of overlap duration. The car, with the L88/3.08 combination and a stock Muncie, was pretty lethargic at off idle and low engine rpm. (Of course, things got really exciting above 4000 rpm.) I installed a Richmond 5 speed. It has a "underdrive" first gear. With a 3.08 grear end and the Richmond in first gear, I had pretty much the same gearing as a Muncie in first gear and a car with a 4.11: rear end. This dramatically improved performance at low rpms during street driving.

(If you want to keep your 3:08 rear end, and want a "performance" cam shaft, you might want to consider a Richmond 5 speed. know Keisler is a forum sponsor, but I think their 5 speed, an overdrive 5th gear, will mean you'd need something like, say a 3.73:1, etc rear end)

Maine Vette

I'll probably install a new tranny and rear end sometime down the line which is why I opted for the AFR 305's. Some smaller heads would probably be better suited to my current set-up, but I wanted to get some heads I could grow into.

Bashcraft - thanks, guess I missed your post somehow.

shafrs3

The LS-5 is an oval port, I believe the LS-6 is a rectangular intake.

Maine Vette

Ahhh, I see. Is the LS-6 intake steel, or is it aluminum?

That actually raises another question though. The AFR 305's are rectangular port heads. Pretty much all the intakes I've mentioned, or seen mentioned thus far, are available only in oval port. How much of a no-no is mixing head and intake port type?

Am I correct to assume that using a rectangular intake with oval heads is a bigger no-no than using an oval intake with rectangular heads?

VetteLS6

LS6 intake is aluminum and large port....it would be like putting a plug in the way without the correct intake in place for the head's design....not to mention gaskets.

bashcraft

I've seen people use an oval port intake with rectangular port heads, and was told it works fairly well. One advantage when using a cam with a lot of overlap, is that the mismatch somewhat reduces reversion.

On the other hand, using a rectangular port intake on oval port heads will have major sealing issues, along with the obvious port mismatch.

63mako

The LS-6 intake is a good choice for your application. They are getting expensive in a correct date code version. Try GMPP, I think they still sell these new. It will fit under the L88 hood and match the head port configuration. Also It is a GM part.

GOSFAST

Both these intakes were recently tested on a couple of units we built. The LS-5 unit was a cast intake, part #6263753, and found it not a good choice for a performance setup. The LS-6 unit is an aluminum intake, part #3963569, another bad choice in our opinion. The LS-5 is the oval port and the LS-6 is the square port. Both intakes actually
"choked off" both units. The LS-5 was a 496" stroker, the LS-6 is a 454", both were cast iron headed units. Both intakes seem to a be of a "low" design, evidently for hood clearance. I would say just about any decent aftermarket intake would be a better choice. Thanks, Gary in N.Y.

P.S. Neither unit showed any gain when ONLY headers were factored into the program. Both units made identical power, respectively, with the factory exhaust manifolds. We've just recently begun a program testing "extrude-honed" exhaust's for 100% stock appearing cars.

Maine Vette

Seems to be lots of agreement in this thread.

By "Choked off" do you mean the intakes were too restrictive and didn't allow the motor to breath efficiently?

pauvil

what are the am specs?? intake question, yes, but 3:08 isn't going to like a big cam even with a stick, as far as the hood, any of the suggested solutions will work, I like stock stuff myself.

Maine Vette

Cam specs are to be determined. It's not going to be anything too radical though.

Based on what I've heard here I think I'm going to mention the Performer (despite the mis-match in port shape) or stock LS6 intake to my performance shop guy. If I remember correctly, he's planning to run the choices though a PC simulator so the results should be interesting.

Just thinking out loud here but, as for the Torker II, I'm not sure it's going to suit my needs. Sure, it will give great top end, but at the expense of low end and mid range power. With my 3.08's I just don't think I'll be using all that top end. Zwede has a dyno run posted on his homepage showing his motors performance before and after installing the Torker II. It does a nice job up top, but low & mid range (<4,000 RPM) took a fair hit which is where I expect to run 90% of the time.

Anyway, I'll see what the performance shop says tomorrow when I bounce my thoughts off them. On a side note, they were scheduled to balance my rotating assembly today!

pauvil

sounds good!! just remember, the 3:08's will make a big am fall on it's face down bottom, if your auto, a stall converter will help. The problem is that the cam needs to get into it's rpm range to start making power.