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Whats the BHP


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  • 1 month later...

Ah ………………. So what’s going on here ?.......................... :rolleyes:

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Not as bad as it seems :P ………I just like pulling it apart………….. when I built the engine, the heads were very much an unknown quantity as it is all too easy to get the porting wrong. The original plan was to see how it went and then build up some big valve heads to try and gain the full benefits from the cam, however, the torque band is perfectly placed with the current heads and the engine performance is more than acceptable (the performance has exceed all expectations)………….. so I decided to rebuild these heads to a level that I am comfortable with.

The much increased oil pressure together with the pi$$ poor early stem seals have given me some problems with oil finding its way down the stems …………… also the older type guides sit a little too high for comfort when using a high lift cam, plus it has the downside of pushing the stem seal right up to the top of the valve.

The solution was to either replace the existing guides with the later version, thus enabling the hood seals to be fitted on both inlet and exhaust, or have the existing guides manganese bronze lined and then the tops machined for added clearance and to take the hooded seals. The beauty of the bronze liners is longevity, less friction, and they are also spiral grooved for oil retention.

I decided to take the latter route and the machine shop that did my liners were instructed to,

1) Manganese bronze line the guides.

2) Machine the guide tops level to the head to take hooded seals

3) Recut and blend all the seats

4) Takes another 10 thou off the head face.

5) Take 20 thou from each side of the inlet manifold (to ensure it fits correctly)

So this is the result ………not cheap, but not expensive either………….V8 head porn at its finest :D

Chemically cleaned heads…………

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the machined valve guide complete with manganese bronze liner viewed from the top

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Recut (3 angle) & blended valve seats

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Brand new rock hard valves (satellite)

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I know that Hoss and one or two others are / were interesting in pressing in their own guides, but available info is somewhat confusing ……….. well, here’s the info as I see it.

The later guides are shorter than the earlier guides, so the all dimensions will refer to the later type guides. The early guides are also finished to size, but the later type guides require reaming as they are supplied 25thou under size, however, the outer dimension is 1 thou oversize in order to ensure a good fit.

The correct reamer size (standard reamer) is 11/32 (0.34375) which results in an 8.73125mm hole ……….. if you check this with the published specs, it sits right in the middle of the stem to guide tolerance allowance.

The guide height is measured from the base of the outer spring seat ……… depending on who you ask the measurement is 0.6 to 0.65 in (this will then accommodate a high lift cam)……….. for this info we need to thank Real Steel, Roland Marlow (ACR), and JE Engineering.

I have concluded that unless you have access to a floating head mill, then it would be best to ream the guides before fitting to ensure perfect concentricity, however, the pressing process may cause a small burr on the guide that will need to be removed (a tickle with the reamer.

If you have a lathe then it would only be a few hours work to turn up the removal (spigot tool @ 10thou undersize) and insertion tool (cap tool that is the correct height measurement)……

Don’t forget that the seats must be recut after fitting of the guides …………

:)

Ian

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lots of lovely shiney porn in this thread............hmmm V8

serious question though- do you think that the time/money spent on this engine outweighs the money you could hvae spent on a newer design- say an LS1 or similar? The money works out about the same i reckon based on importing a low miler LS1 v rebuilding a rover V8. I went with the former option, but the latter had merits- would you go the same route again?

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Jim that is an excellent question ………………………

I guess its just self indulgence in a playground that I am familiar with ……………….but yes, I could have got more 'bang per buck' by going down the LS / SBC / SBB route …………

For its age, the RV8 is a finicky bu$$er that is quite difficult to live with at times ………… so I guess I also looked upon it as a challenge …………….

:)

Ian

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  • 2 months later...

Do I get the last word ?……………………Hmmmmmmmm :lol:

A quick play on the rollers today gave some more then interesting results,

At the wheels ……….. 225ft/lbs @ 2800prm…………… 165.3bhp @ 4600rpm

We are pretty sure the air filter is strangling the top end so looking at the curve a more realistic figure would be 180bhp @ 5100…………but that’s pure interpolation.

The LR drive train is not noted for being slick (it’s a 24 year old design) and coupled with the losses associated with open tread MT tyres, I feel 33% is a fair figure………..

So the flywheel figures probably look something like well over 320ft/lbs of torque and 240bhp (ish)

Certainly the driving experience seems to reflect those sort of numbers ……..

However, I am not concerned with top end BHP ……….. it’s the low down torque I wanted and the curve is much the way I planned it…………..

:)

Ian

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