L29 Intake Mods

**Busted Knuckles** · 12-14-2009, 05:45 AM

I'm rebuilding the 454 for my '97 crewcab dually and decided I needed a good bit more than the stock engine was giving. First, I' swapping heads for some '67 vintage closed chamber pieces. They've been cut for big valves, bowls are blended and the chambers were opened up on a Serdi to unshroud 'em. Next, I decided to take on the intake. If you've ever had one of these clamshell intakes apart, you'll see it's quite a convoluted path from throttle body to port. After the air enters, it's split into 4 very large runners. As the air makes it's way from the bottom and across the top half of the intake, those runners are split into the final 8. At the split, the runners are just a bit bigger than a stock small block port entrance. I don't have a lot of expensive measuring equipment, but I managed to use what I had to determine that if I had a piece of the divider removed so the split didn't happen until a few inches further downstream, the ports at the split would be roughly the same size as a big block oval port. I contacted a machinist buddy of mine who took a look at it and agreed. I left it with him over night and he called the next day and said he thought he had done what I wanted. You can see where the cutter has removed the divider along with what is actually a sliver of the port floor. The divider is completely gone all the way to the roof, I don't know if the pics show that. I'm probably going to make plugs for these openings that fit very close, then J.B. ChemWeld 'em in place. I've tried to weld GM's aluminum before with no success, but I have used JB inside wet flow intakes with absolutely no adverse effects, it looked the same after 30,000 miles as when new, so I'm sure it'll do the trick. I can get a cutter thru the opening to smooth and blend the cutter marks and the front edge of the divider. I can take more pics if needed. I also have bigger injectors, a 214/221 cam and headers. I had planned on stroking this engine, but if this doesn't free up some airfolw, that would have been a waste of time and money, IMHO.
At any rate, here's the pic, let me know what you think.

**N0DIH** · 10-26-2011, 10:46 AM

So what is the long term determination, was it worth it to mod the intake?

**chevy05** · 10-26-2011, 09:16 PM

Do you have any flow comparisons or any way showing what was gained by this.

**N0DIH** · 10-26-2011, 09:45 PM

I can see it moving the powerband upwards a bit, but no real "flow" improvement. Essentially it is shortening the runners, which moves powerband up. The LT1 had really short runners and made good power even with a tiny cam. The TPI 350's had SUPER long runners, but sucked at high rpm power (over 4500 rpm like the L29), but made awesome low end torque. The L29 454 intake has really long runners, to help with low end torque because GM retarded the cam so much it needed them to bring the powerband back in the low end.

**Busted Knuckles** · 10-27-2011, 05:49 AM

I've had a ton of projects get in the way and haven't finished this one yet.
I agree, power band will be moved up a bit, but the most significant change was the removal of the "choke" point, which changed the smallest cross sectional area from approximately the size of a smallblock port to roughly the size of a big block port. I expect not only the power band to move upward, but the top end should be moved a good bit higher as well. If you're going to run peanut ports or other heads with restricted flow, stock is probably fine. However, I'm going to run large ovals, so I felt like something had to be done if I wanted better performance.
This would be an ideal intake for forced induction, it's really got me thinking...

**78mc-bbc** · 10-27-2011, 06:25 AM

hey i dont mean to hijack or anything but did any of the vortec 7.4's come with rectangle port heads? i have a 496 bbc in my monte carlo with brodix rectangle port heads and i am trying to look into fuel injection systems for it?

**Busted Knuckles** · 10-27-2011, 08:23 AM

I think the RamJet can be configured either square or oval port. I'd ditch it's electronics, royal PIA, go with Fast or BigStuff3.

**Stu64** · 05-26-2012, 07:56 AM

Hello,new to this board,I joined up to follow this thread and see how the intake mods work out.
I know this is a truck board and i have a car,but since it's a truck engine i'm not finding any info i need on car boards.
I have a 1997 7.4 with computer that i would like to drop in my car and would like to keep the factory
intake if possible for hood height concerns. I basically would like to build a nice streetable injected BBC,
nothing to wild since it will be a street driven car. Here's my plan so far:
.060 over bore
4.25" stroke crank
6.385 rods
probe forged pistons 4963f =around 10:1 with 119cc heads
aluminum heads 310cc int.runners 119cc chambers 2.25 intake valves 1.88 ex

Lunati cam 54867
Bigger injectors
80mm throttle body

So do you think a modified stock intake will flow to around 5500?? And how much tuning do you think it will take
to get it running decent?

I like the looks of the edelbrock intake but how much taller is it compared to the factory intake? Thanks.....Stu.

**Chevy53** · 05-26-2012, 08:03 AM

You can get a cross ram intake that simulates the high rise one In a more compact short build I think can't you? Not sure how it would wok with your application though or if it's available

-Ziggy-

**Busted Knuckles** · 05-31-2012, 05:46 AM

I haven't seen any 310cc runner oval port heads. There's not nearly enough material to port match the intake to rectangle ports, ovals is about it. I think it should feed a 496 to 6 grand with mods. Check some threads regarding injectors, there are some less expensive ones out there that should work fine.
I actually picked up a '96 short wide for my next project, I have a 489 with open chamber ovals and plan to use it along with a modded intake. I'm going to do the 411 pcm swap, too.
I'd like to have a sporty looking truck with fuel injection that'll idle at 750rpm and run 12's.

**Stu64** · 05-31-2012, 05:04 PM

Yeah i'm not sure about the intake runners or the chambers yet,still haven't received them yet,the seller listed those numbers but i see the exact same part number listed by others and they say 300cc runners and 115cc chambers. I will cc them my self when i get them.
Still deciding on which camshaft Comp Cams or Lunati. They have close duration numbers but the Lunati cams have more lift.

**Busted Knuckles** · 06-01-2012, 04:45 AM

If these are ProComp, make sure you have an excellent machinist, they tend to need a lot of work to get 'em to within spec.

**Stu64** · 06-08-2012, 07:03 PM

Yeah there procomp's ,what kind of work are we talking about?

**Busted Knuckles** · 06-09-2012, 12:02 AM

Seats and guides tend to be all over the place, have those checked very close. I don't think you'll ever get the L29 intake to flow nearly enough, the head ports will be "lazy", velocity will be a good bit lower through the head's ports than with a smaller port head.