Zephyr's Lachs M52B30 Stroker Build **ITBs**

[The Dark Side of Will]

Can always do a cable cam too, where the cable pull has varying radii as it opens....

https://www.yellowbullet.com/threads/4150-throttle-body.1016770/

A varying radius pulley is what I was referring to in my TPI 400 anecdote. I thought that's what you were talking about as well.

[ForcedFirebird]

Can always do a cable cam too, where the cable pull has varying radii as it opens....

https://www.yellowbullet.com/threads/4150-throttle-body.1016770/

[moatilliatta]

Nice thing about the MSs54 is it r3vs the motor to 3K before the throttles open. Keeps the on throttle transition smooth.


What about s14/s38 throttle linkage?

[ForcedFirebird]

Hmm interesting thoughts. Won't the ECU just compensate and add more fuel if the throttle is opened completely immediately? The throw on these ITBs is shorter than the single throttle body they are replacing, I was thinking of adjusting the mount point on the pedal to compensate.

What would the cam system you're describing look like? I'm having trouble picturing it.

Based in the last 12yr of coding, no, the ECU cannot compensate for a priming pump in carbs unless heavily coded for huge acell enrich. When I did the m50 ITB project a few years ago, I had to max out all the AE, and it still wasn't happy. That was with only 45mm and 413 ECU. The ms4xx may be able to do a little better since AE is calculated a bit differently.

To put things in perspective an LS1 uses a 75mm TB to make 400 HP, and s54 used six 50mm to make 330hp. Imagine the driveability of the LS had the same ratio of throttle plates. Some rough math says it would be roughly equivalent to a single 120mm, but due to the nature of a round throttle plate, a small angle of plate means big instant air flow (imagine the area of crescent shapes with very low part throttle).

A cam system would consist of two fulcrums slightly offset of each other with the two legs of the levers attache to each other on one end, then the other two ends of the levers attach to the cable, the other to the TB's. Hard to explayulin with text only, but if you look at an m30/m20 TB, the linkage is kinda self explanatory. Not at the shop now, but wouldn't be surprised if the cable driven 24v are similar.

[Metallated]

You may want to do some kind of cam sysem for the throttle linkage. The throttles are actually oversized, even for a modified s54, the transitions from off-idle and low part throttle will bog badly on throttle stab. The DBW system slowly opens the throttle, even when your foot is on the floor. Adding a progressive cam-lever to your throttle linkage will allow it to open slowly at light throttle and progressively open faster as the pedal goes down. Even the VAC kit isn't ideal since the lever is a fixed fulcrum. The m20/m30 TB's are good examples - except in reverse (small movement on the cable = fast throttle plate actuation).

Hmm interesting thoughts. Won't the ECU just compensate and add more fuel if the throttle is opened completely immediately? The throw on these ITBs is shorter than the single throttle body they are replacing, I was thinking of adjusting the mount point on the pedal to compensate.

What would the cam system you're describing look like? I'm having trouble picturing it.

[The Dark Side of Will]

Oh, *THAT* is what becomes waffles...

The engine was (well, still is) one of the last GM 400 crate engines. The production 400 rods are a little thinner at the fork than 350 rods and tend to fail there if pushed, so we weren't interested in pushing it. We redlined it at 5000, which let it do what it needed to do.

Yeah, it is pretty cool looking.

[iansane]

My dad had a TPI 400 Chevy (MOAR TORK!) in a '75ish Jaguar XJ-6. It had the 4L60E trans with 3.07 first and 3.31 rear. He had the TPI throttle cam on it at first, and it was hard to leave a stoplight without chirping the tires. He swapped to much more progressive LT1 throttle cam and the car became a waffleswaffleswaffleswaffleswaffles cat (wakka wakka wakka) and was MUCH easier to drive at parking lot speeds.

I can't even imagine how low the redline must've been on a tpi400. (but god damn is that a cool looking intake)

[The Dark Side of Will]

My dad had a TPI 400 Chevy (MOAR TORK!) in a '75ish Jaguar XJ-6. It had the 4L60E trans with 3.07 first and 3.31 rear. He had the TPI throttle cam on it at first, and it was hard to leave a stoplight without chirping the tires. He swapped to much more progressive LT1 throttle cam and the car became a waffleswaffleswaffleswaffleswaffles cat (wakka wakka wakka) and was MUCH easier to drive at parking lot speeds.

[ForcedFirebird]

You may want to do some kind of cam sysem for the throttle linkage. The throttles are actually oversized, even for a modified s54, the transitions from off-idle and low part throttle will bog badly on throttle stab. The DBW system slowly opens the throttle, even when your foot is on the floor. Adding a progressive cam-lever to your throttle linkage will allow it to open slowly at light throttle and progressively open faster as the pedal goes down. Even the VAC kit isn't ideal since the lever is a fixed fulcrum. The m20/m30 TB's are good examples - except in reverse (small movement on the cable = fast throttle plate actuation).

[Metallated]

Did some thinking and simulation on the bracket and I think the two bolts won't be enough to hold it in place securely without flexing too much.

I added a third bolt hole and made the rib larger. Much sturdier

[Metallated]

Had to make a spacer to ensure that the harness for the injectors would clear the valve cover.
I have photos somewhere but I can't find them right now. The ITBs are bolted on though so that's satisfying!

The next challenge is to create an adapter system for the throttle cable. VAC makes a kit but it's over $300 and seems overly complicated to me.
Here are some photos of the two 3d printed pieces (in white) to get everything in the right location:




I'll be machining the cable to "arm thingy" adapter and probably water jetting and belding/welding the mount for the cable at school. Here's what I want the final mount to look like, hopefully there is enough rigidity. If not I'll add a bracket below.



I'll be posting better photos in the daylight as everything comes together. I miss the can so I'm pretty motivated to wrap this up.

I bought an S54 airbox to try and adapt, but I basically just chopped it up and found out there wasn't going to be room. I'm trying to decide between aluminum and carbon fiber for making one. I might weld one and then later spend the time making a nice carbon fiber one when I feel like it.

[fastestbox]

Also super interested in the ITBs!

[spiDmang]

I'll be following this progress on the ITB's!

[Metallated]

Looks awesome! Did you mock up the valve cover and the injector wire loom? There's one potential tight spot.

Thanks man!

It should be a tight fit. The issue is, if you rotate the throttle bodies down lower to achieve more clearance, they foul on the oil filter housing.

I've mocked it up and it's really tight, we'll see how it all comes together lol

[moatilliatta]

Hmm, so retrofitting a DBW actuator? Or making a conversion to cable?


I also recommend these to anyone who works on their car with jackstands. ESP not on a solid surface.
http://www.amazon.com/ESCO-10498-Jac.../dp/B0019JVIPM