Aftermarket exhaust manifolds

[BARNPOT2000]

Hi all, I'm contemplating swapping my  stock manifold for a straight through pipe type without cats. Toyosports sounded good but are unavailable. Has anyone got any preferences for the offerings on ebay, such as the "Gravity" one?

[s12vea]

You have a late car I would just keep the stock setup, The stock system with tte sounds just right.

[Iain]

I have the gravity one. No issues to report and been on about 6 months now.

Decent company to deal with aswell.

[BARNPOT2000]

Thanks, did you notice any change to the exhaust sound/performance with the Gravity manifold? Also what made you go for the gravity rather than decatting the original please?

[1979scotte]

Thanks, did you notice any change to the exhaust sound/performance with the Gravity manifold? Also what made you go for the gravity rather than decatting the original please?

Decating the original is a PITA.
Why expose yourself to all that nasty crap inside?
Then have these hollow chambers to spoil the flow?
Its something people did years back.

[Iain]

Thanks, did you notice any change to the exhaust sound/performance with the Gravity manifold? Also what made you go for the gravity rather than decatting the original please?

Yes gave it a bit more sound (burble is a good word) and releases a touch of power in the low to mid range. 

As Scotte has mentioned decatting the original is not a good option. Will actually hurt performance and not to mention its a messy job.

The gravity manifolds come on offer now and again, i got mine for about £140 so well worth changing it for a stainless one.

[Gaz mr-s]

At the time when a few people were buying the Zero manifold, the maker of them said that modifying the o/e one was bound to be detrimental to flow.

[shnazzle]

Or keep the stock one. A big dump and a haircut will gain you more performance.

[Joesson]

I decatted the OE exhaust on my 2 in 2011, it got me under the car to have a good look around, important in itself,  I polished the heat shields on the main cat and replaced the broken welds with stainless machine screws and nuts and refixed the broken weld near the Flexis with proprietary exhaust clamps. I wore a 3m mask and eye protection when bashing out the precast and finished off with a pressure washer.
No requirement for lagging the pipes the OE manifold heat shield was painted and replaced.
Ten years later, no cat rattles, no noticeable gain or loss in performance, the heat shield paint is still good, the cost was for replacement gaskets which are necessary with aftermarket manifolds. So perhaps I am £140 in pocket.
A supplier of an aftermarket bolt on is hardly likely to advocate keeping what is OE.
Historically that was the thing to do. However time changes many things, particularly opinions, but not mine.

[Call the midlife!]

One of the deciding factors for a lot of people currently is the standard manifold while intact carries at least half the cost of a replacement s/s tubular manifold in scrap value.
Whereas I, like many other people just bashed mine out a few years ago and responsibly binned the contents 😆

[BARNPOT2000]

One of the deciding factors for a lot of people currently is the standard manifold while intact carries at least half the cost of a replacement s/s tubular manifold in scrap value.
Whereas I, like many other people just bashed mine out a few years ago and responsibly binned the contents 😆

Good point, worth investigating the value at the local scrap yard before I decide what to do. I did the same as you years ago 🙄.

[BARNPOT2000]

I decatted the OE exhaust on my 2 in 2011, it got me under the car to have a good look around, important in itself,  I polished the heat shields on the main cat and replaced the broken welds with stainless machine screws and nuts and refixed the broken weld near the Flexis with proprietary exhaust clamps. I wore a 3m mask and eye protection when bashing out the precast and finished off with a pressure washer.
No requirement for lagging the pipes the OE manifold heat shield was painted and replaced.
Ten years later, no cat rattles, no noticeable gain or loss in performance, the heat shield paint is still good, the cost was for replacement gaskets which are necessary with aftermarket manifolds. So perhaps I am £140 in pocket.
A supplier of an aftermarket bolt on is hardly likely to advocate keeping what is OE.
Historically that was the thing to do. However time changes many things, particularly opinions, but not mine.

You got me thinking, doesn't happen often 🤔... in the future, or maybe now, as with many other "classic" cars it's all about originality. Would stalwart enthusiasts be looking for the original shaped manifold whether decatted or not do you think?

[Topdownman]

Nothing to stop you keeping the old manifold in case its wanted. This is assuming that your car is otherwise completely stock and a superb example though as that would be the only type of car where it may make a difference.

For people who want to drive the car though, I cant see it making any difference or even being a plus that you have an aftermarket manifold which should save weight, reduce the fear of the pre cats breaking up and maybe? give a little performance gain. They also look better to most I would have thought.

[Joesson]

Today's World market price (in US $) at today's exchange rate is £332.50/ tonne. Or £0.3325/ kg. At that rate the OE manifold would need to weigh in at 210 kg to fetch £70 ( half the price of a tubular manifold).
Of course it doesn't weigh that and also you would be unlikely to get the World rate/ tonne at your local scrap yard for an OE manifold.

As for keeping the old one in case a classic collector in the future wants to pay a small fortune for an unmolested OE model, that simply depends on how much space there is at the back of the shed.

For clarity about performance gains look no further than post #7.

[Iain]

Id change from the stock one simply to know the fact that my engine wont eat itself anymore.

Add in the small performance gains, less weight, more noise and a nice looking pipe, its a win win.

[Beachbum957]

There are a lot of cheap clone headers on eBay that are copies of the original TRD design and can use the original heat shields.  The Gravity header has awfully short primaries, which is the complete opposite of the Zero which has primaries longer than the TRD design. Neither can use the original heat shields.

Some places in the US have laws that require emission components (such as all cats) to appear visually stock, or be approved replacements.  That is one reason many people decat the original manifold or run a header that can use the original heat shields to hide the header.  It still "looks" stock.

We have run the cheap clone headers for years with no issues.  Not only was that easier that messing with removing the cat material, the headers do seem to give slightly better midrange, and we still have the original manifold on the shelf.

[Iain]

There are a lot of cheap clone headers on eBay that are copies of the original TRD design and can use the original heat shields.  The Gravity header has awfully short primaries, which is the complete opposite of the Zero which has primaries longer than the TRD design. Neither can use the original heat shields.

Some places in the US have laws that require emission components (such as all cats) to appear visually stock, or be approved replacements.  That is one reason many people decat the original manifold or run a header that can use the original heat shields to hide the header.  It still "looks" stock.

We have run the cheap clone headers for years with no issues.  Not only was that easier that messing with removing the cat material, the headers do seem to give slightly better midrange, and we still have the original manifold on the shelf.

The heat shields problem is the only issue with the gravity one that i have come across. Im going to be brave soon and wrap it, heat in the engine bay is alot higher without the shields on.

The zero header is the proper one, but it costs alot of money. If you're tracking or racing and need every gain possible its the one to buy, other than that the clones do a decent job.

[BARNPOT2000]

There are a lot of cheap clone headers on eBay that are copies of the original TRD design and can use the original heat shields.  The Gravity header has awfully short primaries, which is the complete opposite of the Zero which has primaries longer than the TRD design. Neither can use the original heat shields.

Some places in the US have laws that require emission components (such as all cats) to appear visually stock, or be approved replacements.  That is one reason many people decat the original manifold or run a header that can use the original heat shields to hide the header.  It still "looks" stock.

We have run the cheap clone headers for years with no issues.  Not only was that easier that messing with removing the cat material, the headers do seem to give slightly better midrange, and we still have the original manifold on the shelf.

Useful info. thanks. So your header can accomodate the original heatshield? Which make did you go for?

[Beachbum957]

Useful info. thanks. So your header can accomodate the original heatshield? Which make did you go for?

We bought the headers many years ago, but there are a lot on the US eBay site. 

Example

Note that prices vary a lot, but most are the same part from the same suppliers in China

[BARNPOT2000]

Thanks, probably wouldn't get it from the us simply because of the cost of postage and import duty. BTW probably a daft question but what are those two straight lugs that stick out near the "amigo" end, on some of the after market ones?

[Beachbum957]

Thanks, probably wouldn't get it from the us simply because of the cost of postage and import duty. BTW probably a daft question but what are those two straight lugs that stick out near the "amigo" end, on some of the after market ones?

Lower mounts for the inner heat shield.

[BARNPOT2000]

Thanks, probably wouldn't get it from the us simply because of the cost of postage and import duty. BTW probably a daft question but what are those two straight lugs that stick out near the "amigo" end, on some of the after market ones?

Lower mounts for the inner heat shield.

Thanks 👍

[BARNPOT2000]

Well, I went for a swap of standard manifold for a Malian straight through manifold in the end. All went well with operation with all head nuts coming free with studs remaining in the block, and the three amigos played ball although one stud decided to leave with the nut, no problems.
One small issue was the offside O2 sensor wire being a tiny bit too short to reach the connector on the engine block near the dipstick. Resolved by purchasing the rear Denso sensor with the long cable attached.

My question for members, who may have also experienced this, as the original heatshields associated with the original manifold are no longer in place, I wrapped the manifold in titanium wrap to help retain the heat. Despite this the engine bay and engine lid seem to be getting very hot after a "normal" journey (not a spirited drive 😉). Has anyone noticed this and is it or could it become a problem? Hoping its not an issue and am I worrying unduly 🙄?

[Dev]

Well, I went for a swap of standard manifold for a Malian straight through manifold in the end. All went well with operation with all head nuts coming free with studs remaining in the block, and the three amigos played ball although one stud decided to leave with the nut, no problems.
One small issue was the offside O2 sensor wire being a tiny bit too short to reach the connector on the engine block near the dipstick. Resolved by purchasing the rear Denso sensor with the long cable attached.

My question for members, who may have also experienced this, as the original heatshields associated with the original manifold are no longer in place, I wrapped the manifold in titanium wrap to help retain the heat. Despite this the engine bay and engine lid seem to be getting very hot after a "normal" journey (not a spirited drive 😉). Has anyone noticed this and is it or could it become a problem? Hoping its not an issue and am I worrying unduly 🙄?

It can get very hot back there and it is completely normal. The reason why it seems to be very hot is primarily because the exhaust side components are rear facing. With the same engine in the front engine configuration the exhaust header is against the fire wall and the cat under the car where the radiated heat is shielded. Our configuration is better because the area of the fire wall with all of its components and wiring stays cooler because there is no radiator in the engine bay.  When the car is in motion most of that radiated heat goes out the back.
 

[BARNPOT2000]

Well, I went for a swap of standard manifold for a Malian straight through manifold in the end. All went well with operation with all head nuts coming free with studs remaining in the block, and the three amigos played ball although one stud decided to leave with the nut, no problems.
One small issue was the offside O2 sensor wire being a tiny bit too short to reach the connector on the engine block near the dipstick. Resolved by purchasing the rear Denso sensor with the long cable attached.

My question for members, who may have also experienced this, as the original heatshields associated with the original manifold are no longer in place, I wrapped the manifold in titanium wrap to help retain the heat. Despite this the engine bay and engine lid seem to be getting very hot after a "normal" journey (not a spirited drive 😉). Has anyone noticed this and is it or could it become a problem? Hoping its not an issue and am I worrying unduly 🙄?

It can get very hot back there and it is completely normal. The reason why it seems to be very hot is primarily because the exhaust side components are rear facing. With the same engine in the front engine configuration the exhaust header is against the fire wall and the cat under the car where the radiated heat is shielded. Our configuration is better because the area of the fire wall with all of its components and wiring stays cooler because there is no radiator in the engine bay.  When the car is in motion most of that radiated heat goes out the back.
 

Thanks Dev, that's good to hear, I was thinking some heat reflecting insulation above the engine fixed to the engine lid might help?