Lushman

Hey folks,
As the title says, looks like Maxbore throttle bodies has gone under/disappeared. Domain is unregistered. I was talking to George back in November and I was going to buy a used OEM TB to send to him. Since then I've had 2 deals on the forum fall through due to red flags, and then I found a used one the other day, which I snapped up.

Long story short, Maxbore is out of the picture, sadly. I know George's work is on the JLS systems ISF, and others. Anybody have throttle body boring/porting done by any other companies they'd recommend? I'm on the west coast if that helps.

Also, don't bother telling me this mod won't give me much gains or is a waste of money. I'll waste my money however I want.
I'm going FBO/Tune and I've got another OEM intake manifold I'll be polishing and port-matching to the TB.

iH8RICERZ

iTrader: (4)

I've heard of a few other guys go with a RCF throttle body. I haven't done any digging/research on what kind of performance gains (if any at all) this mod would provide, but its worth looking into. Also, I think any shop that does port and polish, resurfacing, etc can port TB's...but don't quote me on that.

Lushman

Thanks, IH8.
Yeah, I doubt there's much in terms of performance gains if done in isolation. If done as a complement to the FBO package, I think there's some merit. Southern Cross Motors from Australia claimed about 13whp to a FBO setup for the port/polished intake manifold. It doesn't make much sense to do the manifold and not port-match the TB.

Lushman

I'll share my findings as I go:

SoCal Porting
https://socalporting.com/our-service...-body-porting/

"Service includes:

• Knife edge of front lip
• Port in a velocity stack
• Removal of casting marks
• Port and taper of factory steps before butterfly
• Increase diameter of the TB before and after the throttle blade
• Half shafts available upon request

NOTE: We cannot increase the diameter of the throttle body blade. The precision needed to perform a perfect seal is near impossible without a CNC machine."

My thoughts: This last point about not being able to increase the throttle body blade, and that the diameter is increased only before and after the blade is a service Maxbore used to supply. He'd CNC the interior and build you a new blade. If these guys are one of the leading options, I'll probably use them, but I was really hoping for increased diameter all the way through.

Note to self:
https://www.clublexus.com/forums/is-...d-2-sizes.html
Looks like MMX sells throttle bodies they've done their own in-house CNC work on... I might reach out to them and see if they'd do a one-off. https://www.modernmusclextreme.com/c...le-bodies.aspx

JT2MA71

iTrader: (7)

I sent my RCF throttle body to Icode Japan to do the job. They offer the same work for the IS F TB but the increase isn't much compared to using an RC F TB. That's the route I went for my IS F. You'll need the Prospeed TB adapter. I have not installed it yet since I am also replacing the intake manifold (port matched) and will do the swap at a later time.

Lushman

Awesome reply, thank you!

Did you do it through Top End Motorsports, via iCode directly, or another way? The only way I could find this service was through the Top End Motorsports website, and I didn't see the option for the iCode RCF-ISF adapter plate you mentioned.
https://www.topendmotorsports.com/le...rvice-5132.php

I'm not as familliar with the RFC - what year of RCF throttle body did you use?

JT2MA71

iTrader: (7)

For my IS F, RC F throttle body is for model year 2015, it is stock size, unmodified. Adapter is from Prospeed, link here; Tb adapter.

As for my RC F, that’s the one I sent to a friend in Japan and he had icode do the machining. Very small increase in inside diameter but they mainly smooth out the bore, getting rid of the step right by the throttle plate, and replacing the plate with a titanium one.

Lushman

I misread that initially - I thought you increased the diameter of an RFC throttle body and mounted it to the ISF. I was wondering how a ported RCF throttle body would improve things if it was increased OVER the diameter of the RR racing tuned intake. And yes, I know the RCF throttle body is 84mm and the RR racing tuned intake is 87mm. Again, thanks for adding to the thread.

Lushman

Quick question about the intake manifold - when I approached my local dealership, they don't offer the steel gasket that seals the manifold halves together... did you manage to source a new gasket, or are you re-using the OEM steel gasket?

JT2MA71

iTrader: (7)

I re-used the original gasket. Cleaned the black coating off carefully and then used spray copper sealant.

lobuxracer

iTrader: (2)

I've used silver spray paint on metal headgaskets many times. Works like factory. Besides most metal gaskets can be reused many times without issues.

Lushman

Thanks very much both of you - very useful info. Much appreciated!

Lushman

So, given I'm porting and polishing the intake manifold alongside upgrading the throttle body, I was excited to see an email from RR Racing that offered a phenolic spacer, but was disappointment to see the ISF wasn't on the drop-down list.

I replied to the email, and Rafi replied there should be an ISF offering the ISF version in about 3 weeks. The phenolic spacer is made of Teflon and sits between the intake manifold and the block, and prevents heat-soak into the intake manifold. Given that improvement, I'll likely look at ceramic coating the intake manifold when I'm done all the port-matching. Exciting times!

lobuxracer

iTrader: (2)

All well and good, but the real gains are in the last 15mm of the port where the valve seats. What you're doing doesn't hurt anything, but it's not even in the ballpark of a decent street port on the heads and carefully done valve job. It is extremely tedious to do a meticulous job on two heads with 32 valves but it's totally worth it.

jgscott

iTrader: (1)

Just FYI: I had Maxbore do my TB back back in Jan 2023, and talk to him a few times. I heard recently that he unexpectantly passed away. I don't know anymore than that about.