RCF manifold onto ISF

Akite · July 20, 2023

Hello to you all.

I have the dreaded cracked manifold on my 2008 ISF only 65k miles 🥲.

I want to know if i can fit the RCF manifolds to my car as they are far better quality and design i believe.

I can bue these 17104-38090 17105-38090. See image.

However before i do i wanted to know if this will cause me any issues or if you had any other suggestions?

I want to be able to pass mot and want the car to last as long as possible.

Thanks for your help

DAW · July 20, 2023

If you check previous posts about the cracked manifold issue on this forum @Womble72 had GSF manifolds fitted to fix this issue, done by Westfields Lexus/Toyota specialists in Rawreth, Essex. I seem to remember him mentioning having to adjust the heat shield, but best to check his post.

Best of luck getting it sorted👍🏻

Akite · July 20, 2023

Yes i did read that one but i was not sure if these are exactly the same as the ones that where used.

Rob RCF · July 20, 2023

25 minutes ago, Akite said:

Yes i did read that one but i was not sure if these are exactly the same as the ones that where used.

The part number is the same for both RCF and GSF exhaust manifolds so they should fit. You might already know, but fitting them is a difficult job. Try to use a reputable place that has experience with this kind of thing.

I've heard the same thing many times btw, that the ISF ones are prone to cracking and the newer (RCF/GSF) versions aren't.

ubersonic · July 21, 2023

On 7/20/2023 at 12:27 PM, Akite said:

However before i do i wanted to know if this will cause me any issues or if you had any other suggestions?

I want to be able to pass mot and want the car to last as long as possible.

Something worth keeping in mind, is that the cost of buying a set of RCF/GSF manifolds from Lexus is going to exceed the cost of buying a set of stainless ISF performance manifolds form the USA, and shipping them, and paying import taxes.

It's worth thinking about as RCF/GSF manifolds won't last as long, won't add any power, and won't add to the vehicles resale value.

To be clear I'm referring to the catless versions (as the ISF can still pass MOT with just the rear cats, it was heavily over catted form factory to meet JDM emissions) but there are catted versions available too.

EP80 · July 22, 2023

11 hours ago, ubersonic said:

Something worth keeping in mind, is that the cost of buying a set of RCF/GSF manifolds from Lexus is going to exceed the cost of buying a set of stainless ISF performance manifolds form the USA, and shipping them, and paying import taxes.

It's worth thinking about as RCF/GSF manifolds won't last as long, won't add any power, and won't add to the vehicles resale value.

To be clear I'm referring to the catless versions (as the ISF can still pass MOT with just the rear cats, it was heavily over catted form factory to meet JDM emissions) but there are catted versions available too.

Have you witnessed the ISF pass with just the rear cats? I take it that it passed comfortably?

Also wondering about manifolds with cats, the only ones I know of are by Novel and Icode, are there others? Thanks

4969_LXS · July 22, 2023

PPE do make some catted manifolds. @Womble72 noticed an increase in performance with the GSF manifolds. They do flow better and the diameter of the tubing is slightly larger

Akite · July 26, 2023

I would get the PPE ones just cant afford them. I can get a used set of RCF ones for under £1k from an RCF that had under 20k miles on it. I will give this a shot. I just hope im making a good decision as its the same as just replacing the stock one with new. Thanks for your help.

4969_LXS · July 26, 2023

@Akite It's a good choice and it would be the route I would go as its the OEM+ option and good value, they are an improvement over the stock ISF manifolds.

Jgtcracer · July 26, 2023

5 hours ago, Akite said:

I would get the PPE ones just cant afford them. I can get a used set of RCF ones for under £1k from an RCF that had under 20k miles on it. I will give this a shot. I just hope im making a good decision as its the same as just replacing the stock one with new. Thanks for your help.

Is that how much it costs for used manifolds??

That suddenly makes buying a set of aftermarket ones much more appealing!

ubersonic · July 27, 2023

On 7/26/2023 at 3:48 PM, Jgtcracer said:

Is that how much it costs for used manifolds??

That suddenly makes buying a set of aftermarket ones much more appealing!

The factory manifolds each have a cat in them so the scrap value will be high hence driving up the used price, plus the fact they're from a rare car and new OEM set is like £3k so makes sense the used values hold.

Irish ISF · August 6, 2023

I'm currently selling a set of you are interested.

Akite · August 7, 2023

Does anyone know if the rcf/gsf manifolds have the same fitment to the rest of the exhaust on an isf? Just checking they will install without having to replace the entire exhaust.

Akite · August 7, 2023

13 hours ago, Irish ISF said:

I'm currently selling a set of you are interested.

When you say a set what car are they from?

Irish ISF · August 8, 2023

On 8/7/2023 at 11:01 AM, Akite said:

When you say a set what car are they from?

ISF, brand new and never fitted to any car. They are PPE right hand drive headers.

Akite · September 5, 2023

Hello. Does anyone know what the little pipes at the base of the manifolds are for on the ones pictured above? They are screwed in after the cats.

ColinBarber · September 5, 2023

25 minutes ago, Akite said:

Hello. Does anyone know what the little pipes at the base of the manifolds are for on the ones pictured above? The are screwed in after the cats.

They are pressure tubes only fitted to the latest Fs with the Gasoline Particulate Filter (GPF) (MY18 onwards). They connect to the Differential Pressure Sensor which measures pressure in the exhaust compared to outside air - if high then the GPFs are clogged and will produce an error.

If you are fitting these to a vehicle without GPFs you would need to find a way to block them.

RichGS11 · September 5, 2023

I don't know of anyone fitting RCF manifolds to an ISF. Nothing in the States saying as such. Most people weld their OEM ones up, or go with PPE/Novel, etc. I cannot see it being an upgrade, purely as I don't think they'll fit and Lexus/Toyota are notorious for creating bottlenecks in their exhaust systems. So stock for stock and for the price, it would be a tough call to see if its worth it.

At best I'd get on a Facebook page or two aimed at the ISF and ask. UK owners tend to be very conservative with their F's and due to the low numbers, most don't play around with them or have experience doing so. I reccomend asking people state side.

I have a set of UK ISF OEM manifolds that are cracked but off the car. They're being welded up and I'll either sell them or keep as spares. If you want pics of where the cracking takes place I can send them over. I changed mine to PPE headers last month on my drive.

ColinBarber · September 5, 2023

20 minutes ago, RichGS11 said:

I don't know of anyone fitting RCF manifolds to an ISF.

It can be done but it isn't a straightforward swap.

Akite · September 5, 2023

Thanks for your help everyone

NothernDan · September 10, 2023

All, having just been through this rigmarole. A quick question.

What makes you think your headers are cracked?

If it's a ticking noise when cold that disappears once the exhaust has gone through its "warm up my cats" cycle then mine had this. Wasn't the headers. Was the high pressure fuel pump. Replaced that, noise gone.

RichGS11 · September 10, 2023

2 hours ago, NothernDan said:

All, having just been through this rigmarole. A quick question.

What makes you think your headers are cracked?

If it's a ticking noise when cold that disappears once the exhaust has gone through its "warm up my cats" cycle then mine had this. Wasn't the headers. Was the high pressure fuel pump. Replaced that, noise gone.

I replaced my headers and the sound went, so did the emissions issue at MOT time. I have a video of the location that mine cracked at, which from watching countless videos on cracked headers, mine was the exact same flange. Did you run a data logging check on yours? I wonder if that would show a fuel issue if it is the pump that's going? Like a quick and easy way to deduce the cause? I can't believe that 'all' ISF headers will crack, but the numbers are quite high.

4969_LXS · September 10, 2023

@NothernDan my drivers side manifold failed not long after I purchased mine 4 years ago.

It ticked on cold start, the give away was that once the CAT heat cycle was completed it got slightly quieter. Then when driving from cold with the window down, the tick increased in frequency with the engine rpm, then as it got warmer it required more throttle to make it tick eventually it sealed once hot.

This was all finally confirmed when I borrowed a friend's borescope and saw soot (carbon deposits) on the heat shield around the manifold.

Akite · September 13, 2023

Hello again so ticking on cold start, yes. I also get a petrol smell if i ever put the foot down. So then using a borascope looked at the manifolds (not easy fyi) and i could see a hairline crack around the rear driver side port.

4969_LXS · September 13, 2023

That's what I could see as well. The petrol smell could also be your boot vents. Mine looked like this when I changed them last month. They'd gone hard and had shrunk. The drivers side had almost fallen off, the one on the far right is new for comparison.