Cast iron manifolds

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30EK42
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Cast iron manifolds

Post by 30EK42 »

I'm in the process of fitting a hybrid P6/SD1 engine into my series Land Rover.
Nothing special, 9.35 CR with twin SU carbs.
The front half of an exhaust system came with the engine which consists of a pair of RR Classic iron manifolds, and a RR Y pipe.
Just needs a rear section fabricating.
Now I've read that those early manifols with the single outlets are very restrictive, but I'm not sure exactly how much.
Will they affect low to mid range torque much ?
I'm not really too concerned about them restricting power at high revs, because I won't be going there too often.
I suppose that I could convert to tube headers off the later engines, but would I really gain anything useful ?



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ChrisJC
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Re: Cast iron manifolds

Post by ChrisJC »

I've mucked about with lots of different manifolds over the years in my Series Landie.

I found all of the tubular ones noisy.

The best ones were the twin outlet Range Rover EFi ones. They were used up to 190BHP on the 3.9l engines.

But I couldn't put numbers on performance gains.

Chris.
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Series IIA 4.6 V8
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R/R L405 4.4 SDV8

30EK42
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Re: Cast iron manifolds

Post by 30EK42 »

Cheers Chris !

I'd just about given up on this thread getting any useful replies.
Would those RR EFi ones be the cast ones with twin internal outlets ?
Also fitted to the SD1 car I think ?
I've just found some nice cheap(ish) pattern header pipes and matching "Y" pipe to suit those.
Probably worth the extra expense IMHO.
Those early RR things look pretty restrictive

DaveEFI
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Re: Cast iron manifolds

Post by DaveEFI »

The SD1 is reckoned to have very well designed manifolds. But the twin exits cross the starter motor and might make the pipe runs a problem on some other installations.
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ChrisJC
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Re: Cast iron manifolds

Post by ChrisJC »

Yeah, I do mean the cast ones with twin outlets.

As Dave says, the SD1 manifolds with twin outlets won't fit a Landie. The main reason being that the engine is heavily offset towards the passenger side, so the manifold on that side hugs the block to allow the downpipe to fit between the block and chassis. The SD1 engine is central in the body so the manifolds just exit rearwards.

You can't fit P38 manifolds to a Series Landie for the same reason - I know because I tried!!

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30EK42
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Re: Cast iron manifolds

Post by 30EK42 »

Thanks again gents !
Please forgive my ignorance, I'm on a fairly steep V8 learning curve at the moment.
TBH I avoided V8 conversions for years, until I discovered just how affordable the Rover V8 had become.

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Re: Cast iron manifolds

Post by ChrisJC »

They are very affordable. But of course even the newest ones are now 20 years old, so there is plenty of scope for problems to occur. It's also got quite a few quirks, but at least they are well understood now and it is quite possible to build a very good engine.

Chris.
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30EK42
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Re: Cast iron manifolds

Post by 30EK42 »

Just picked up a pair of Discovery V8i cast iron manifolds off eBlagg.
You can see in the photos how the LH manifold tucks in close to the block compared to the SD1 items.
I'm not counting my chickens yet, they've not arrived yet, and I've got to check for cracks/warping and replace the studs yet, so plenty to go wrong yet.
Next step will be to make an exhaust system.
I'm thinking cheapo/pattern front end from a Discovery or Rangy, then start cutting/welding/bending as required.

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Re: Cast iron manifolds

Post by ChrisJC »

Yeah, I always start with pattern downpipes and the y-piece, and then fabricate what comes behind that.

Chris.
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paul c
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Re: Cast iron manifolds

Post by paul c »

I have the 3.9 disco exhaust on my 110 from when I converted my 3.5 to the 3.9 and auto, the disco parts car had a good system on it so just added a 10in piece between the front muffler and y piece. The downpipes are the single pipe with the cats removed, which seem to be a little better for torque than the RR twin downpipes. I am currently making some replacement downpipes in 2in tubing into a 2.5in single system for the 4.6 I will be fitting soon.

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Re: Cast iron manifolds

Post by 30EK42 »

So you reckon the single downpipe design gives slightly better low end torque then ?
Oh well, it looks like I've just wasted my money buying the RR twin pipe manifolds then :(
Never mind though, at least I will have both types now, so I can play at building exhaust systems to my hearts content.
And fortunately bits of exhaust pipe and pre-formed bends are as cheap as chips.
I fully expect the first system I build will be absolute pants, but I will learn from my mistakes

paul c
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Re: Cast iron manifolds

Post by paul c »

the disco and rangey 3.9 use the same manifolds, they are twin outlet, but the RR (non cats) had twin small diameter front pipes where the disco went into a y and single pipe after the manifold, they seem to be the best configuration.

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