Being I’m the only one apparently on the list who actually owns an intake manifold with six inch runners, may be able to transfer how the car responded going from a very heavily welded and reported/raised port LT4 intake:

True it picked up 47ft lbs of torque 3000 rpm but the throttle response is also much quicker. There was an off idle hesitation that has completely cleared itself up. After programming it usually takes at least a couple of tanks of gas for the computer to relearn how to idle. With this intake it cleared up perfectly after about a half a tank of gas.

The car also seems to run smoother overall and for sure you feel the extra torque especially in the higher gears. Say for example a light turn yellow and I’m cruising in 4th gear @ 35mph. Very surprised how much quicker the car picks up speed in higher gears and lower rpm. Do I notice it in first gear? Na….spun the tires before and spins them now.

As far as the loss above 6100 goes: After a couple of months of internalizing and looking at the dyno sheets, the intake did exactly what you would expect a more efficient intake with longer intake runners would do. Shift peak power downward and increase low end.

It did that all right greatly adding power in the lower range. All I need to do now is correct the powerband with the proper cam so that it peaks in the 66-6800 rpm range. and I’m positive the bottom end will be stronger than before and it will also pick up on top because the manifold overall is more efficient. Just a matter of adjusting to the overall change in powerband.

Think you’ll see the car close (if not making over 500 rwhp) in the next couple of months and I’m not sure how many people can say that from a standard 23 degree head, hydraulic cam LTX car.

Would I do it again?............Damn right. Now those expensive stepped headers with reducer merge collectors?? Not so sure about that one.

 

Pics?

 

Hey Denny, that is a great post. Very good information man, very much appreciated. Now according to the Chrysler patent on ram tuning intake runners from way back when your 6" runners plus about 6" of intake port to the valve head should produce a peak centered around about 7000 RPM's. I've seen quite a few dynos on various tuned runner intakes and the Chrysler formula ( 84000 divided by runner length from plenum to the head of the valve equals peak RPM point) is usually in the ballpark. Did you enlarge the cross sectional area of the LT1 manifold? It might take a little more CSA to really let the 6" runner produce full peak HP potential on a hot smallblock though at the loss of some low/mid and throttle response.

The Viper engine uses a pair of single butterfly throttlebodies ( or at least the one I did an engine conversion with did anyway). If I remember right they use a crossover cable to actuate the second one and sync it with the primary that the throttle cable connects to. Usually when I'm working on something this complicated I spend a LOT of time on paper. You need accurate dimensions on your space you have to work with and then detail everything with center to center dimensions, angles, ID, OD, height, width, length and any other dimension you can think of, helps to use a graphics program and do everthing to scale. You need to work out all the details so they appear to work in side views, top views and end views. Even after all that you just can't hardly think of everything but it sure beats hacking the same parts off five times to try to make things work.

Later, Michael

 

There are some picturers of the intake way earlier in this string. Can't believe how long this thing got.

 

The cross sectional is a bit larger (wider) than a LT4 raised port off road gasket. I gasket matched it to this gasket (same as the heads) and had to do some epoxy fill blending about a couple of inches just before it reaches the heads. Didn't bother to measure but I'd guess about .200 inch of taper. Have picturers but not sure if the detail is enough for anyone to tell.

Again, still playing with the combo and it's been so frickin hot here in Dallas that the first cam I'm going to try is still sitting in the box in the car. If it every gets below a 100, just might give it a shot and see what it does. It will get worked out but when you don't have a known variables to work with your the test monkey shot off into space.

 

Well after doing some calculations, I just don't think I can get my design to work with the rectangle ports and my given amount of space. I maybe could get it to work with oval ports but the transition wouldn't be great for airflow.

However, the VH45 heads that I may purchase for my DOHC SBC project have concentric circular intake ports, a prime candidate for this design.

 

Denny dose that intake run flat all the way accross the bottom?

 

I like to hear the story on the exhaust vacuum bungs to the valve cover

 

^

 

The intake is flat on the bottom. Actually thought of having it thermo coated but ended up not doing it.

Did those the same time as the intake hoping to pick up a little more power through better ring sealing and should have waited to do it separately. Don't have a baseline to make any intelligent comments. The guys using vacuum pumps claim they pick up 10-15 hp on top but I have doubts that much is really going on. Should be some vacuum caused by venturi effect but I need to play with that a little to see if it drawing much at all.

Kinda like the expensive headers........good idea at the time. Haven't completely given up on the headers as someone told me you needed to change the cam split to take advantage of them but I haven't been able to substantiate that either.

Again, ya ain't gonna make any yards if ya don't carry the ball. Just trying to do my best at figuring out this stuff.

 

You seems to be doing a good job of that. The rest of us (with less money) will let you do all the expensive research Just tell us how it works out.


Jeremy

 

I've got the guts........somehow I seem to be missing the glory. It would be nice to hit a couple good ***** instead of clobering dirt.

 

Hey I'll be right there with you if this DOHC project gets off the ground. Then maybe we can trade secrets that don't work in hopes of success on a different motor.

Jeremy

 

If any of you have personal problems with each other here I'd appreciate it if you took it to PMs or better yet, to email.

I don't want to have to say this again in this thread, thanks.

 

Hey Mr. Moderator, while your at it I'd appreciate it if you'd delete the posts that have polluted this thread with arguments that have nothing to do with the topic. Can't hurt to ask, can it?