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V8 rebuild- which camshaft?


Quagmire
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I know its not for a Rangie, but it is a V8 so figured most of the relevant knowledge would be in here.

I have a top notch block that i am going to be using as the base for building a new engine for my 90. The block is a 9.35:1 from an SD1.

I am aiming to build a nice reliable unit that will make my 70mile a day commute more bearable/fun.

With that in mind, which of the standard cams would you suggest i go for? What are the differences between the 3.5 carb and 3.5 efi cams- if any? And how do the different compression ratio cams compare- say the 8.13:1 vs, the 9.35:1?

I dont have megabucks to spend hence the reason i want to go for a standard LR cam. ;)

cheers in advance.

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Whats the fukll spec of the engine 1st ?

I'm guessing 3.5, but carbed or EFI as the finished product, are there any other mods to it.

Then the key Q is what else (if anything) are you planning to do to it on rebuild tuning wise ?, this then helps narrow further, and lastly what are yoiu looking for from the finsihed engine,massive lo end grunt - low mid powerband, or a high rev screamer, all 3 will have different cams.

There are IMHO some very basic tweaks you should consider for rebuild on reliability / sterength

ARP Stud kit for bottom end

ARP Head stud kit

Solid Steel timing gears with duplex chain - NOT VERNIER

Composite gaskets for Heads and inlet manifold

Stuck on sump (no gasket)

Drill holes in front of valley of block for lubriction / drainage from lifter gallery

IN answer to you question re Compression, with V8s the compression is done vai the pistons, cams are often the same or similar as such lower comp engines tend to just be flat powerwise but can run on poorer fuel and generate less heat

Post up re the above and also do a search I have posted stuff in on LR4x4 re cams etc previoulsy - somewhere :blink:

Nige

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Nige,

The block i am using was given to me free by someone from the v8 forum, was in a guys AC replica having done only 5000 from its last major overhaul. He took it out to start improving the performance when he was offered a good 4.6 at the right price and so the 3.5 sat on the bench.

The crank has been nitrided, and has new main bearings fitted, the bores are all spot on and honing marks are still visible. I was also given the solid steel timing gear and chain, which was new when the engine was rebuilt- and the guy has some unused ARP bottom end studs he said i could have (when he finds them)

The engine will be running on SU's not EFI. :ph34r:

I do have a P6 engine that i could take the pistons out of, but am not sure i want to go as high as the 10.5:1 comp. However i was thinking I could stick those in and use a comp gasket to lower the overall compression slightly and benefit from the better gaskets. I guess i would need to do some buretting to figure out what the compression difference would end up being.

As i spend most of my time running on the motorway i ideally am after some mid-range overtaking type grunt, not stupendously high revs.

As i run on LPG 95% of the time, running the more advanced efi cam would be a benefit i guess?

Thanks

Jamie

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Nige,

As i run on LPG 95% of the time, running the more advanced efi cam would be a benefit i guess?

Thanks

Jamie

I would think the 10.5:1 compression and LPG would be a good match ... pink like hell on unleaded unless you chuck some decent additive in it but that wouldn't be a major issue if you're not using it much ...

AndyG

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I'm pretty sure the Rover P6 engines weren't 10.5:1 comp ratio, that was reserved for the earlier P5B vehicles which needed 5 Star fuel (100 Octane :o ), so don't go pulling apart two engines only to find one is a 9.35 and one an 8.13 and you are no better off...

LPG does like a higher compression ratio, I have heard 12:1 in some technical document somewhere, although I can't find it now -but you will break things if you have to run it on petrol...

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I'm pretty sure the Rover P6 engines weren't 10.5:1 comp ratio, that was reserved for the earlier P5B vehicles which needed 5 Star fuel (100 Octane :o ), so don't go pulling apart two engines only to find one is a 9.35 and one an 8.13 and you are no better off...

LPG does like a higher compression ratio, I have heard 12:1 in some technical document somewhere, although I can't find it now -but you will break things if you have to run it on petrol...

I have checked the engine number against several different listings and it shows as a 10.5:1 P6 engine. The pistons also have much less of a dish than any of the other engines i have lying about so am pretty sure that the lists tell the truth.

I think i have decided to go with the 9.35's and get the heads skimmed for comp gaskets anyway, much as i try to run on gas all of the time it is handy to have the ability to run on the expensive stuff sometimes :P

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My commpression is 10.1 and the engine has EFI heads and cam off a 4.6 I think.

It runs well on petrol or gas but really needs to be advanced for gas and then retarded a little for petrol by about 5deg at a guess or it pinks (on petrol)

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All this talk of pratting about with timing, I can't help but suggest MegaJolt or MegaSquirt as a better solution.
I dont have megabucks to spend hence the reason i want to go for a standard LR cam. ;)

I never drive on petrol out of choice anymore- only if i run out. The 2.25 is perfectly happy running with the timing set so that it will just pink under heavy load on petrol, i just have to drive around it on the rare occasions i am running on it. Was planning on setting the V8 in the same manner. My original question was more to do with what differences (if anything noticeable) there were between the different cams listed as standard LR parts on the various sites.

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I've found that standard cams produce the goods in most tweaked engines when using relatively low revs, correct ignition timing is also vital.

There really is no need for big valves and hairy cams if using the standard rev range, that's why most manufacturers have gone 16 valve and variable cam timing to make the engine usable as a plodder and a flyer all in one.

So the answer I suppose is go with the standard cam. :)

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