The V8 Owners Forum -

Hey,

I bought Andy's old MX5 V8 last October and after a couple of running issues Andy told me about this forum.

The car is a mk1 MX5 which a JRV8 3.5 Rover engine. Just had it on the rolling road today and it made a measly 164bhp. Every fuelling/ignition reading was perfect, any suggestions will be really welcome!

southernd wrote:Hey,

I bought Andy's old MX5 V8 last October and after a couple of running issues Andy told me about this forum.

The car is a mk1 MX5 which a JRV8 3.5 Rover engine. Just had it on the rolling road today and it made a measly 164bhp. Every fuelling/ignition reading was perfect, any suggestions will be really welcome!

What is the spec of the engine? 164 bhp is more than many, but less than some.

Note that RV8 cams - especially 'wild' ones - can have a pretty short life. And the engine can appear to run ok, but be well down on maximum power.

Hey Dave,

It was option 3:

http://www.jrv8.co.uk/engines/

285 cams if I remember and a pretty extensive rebuild. Built for around the 200bhp mark. It's done very few miles since rebuild, less than 10k from what I can see. I've yet to do a compression check but there's zero that sticks out as an issue. Torque wasn't that high either.

Here's a short vid on the rolling road:



This was after the ignition was advanced a little too much but gives an idea of the running

If engine built for 200bhp at fly, I'd expect to see 168bhp at rear wheels c/o transmission losses. So may be the engine/car is on tap at originally planned?

Pretty sure he said flywheel, I'll post a pic in a second.

southernd wrote:Pretty sure he said flywheel, I'll post a pic in a second.

what was their engine correction set up factor? or, could they have a print out error where the reading is at rear wheels?

To be honest I don't know, it's the first rolling road I've been too. I did try and get to Austec but 3 phone calls not returned I gave up with them!

Most likely I'll try and get hold of an experienced Rover V8 mechanic. If the engine proves no good I'll look at getting a 4.6 short block, a bit of work but more powerful from the start

What's the tolerance on that reading? They are 'compensating' for the transmission losses somehow, and although they always reckon they are spot-on, I would hope they could give you a +/- on the reading.

Chris.

southernd wrote:Most likely I'll try and get hold of an experienced Rover V8 mechanic. If the engine proves no good I'll look at getting a 4.6 short block, a bit of work but more powerful from the start

Does it really feel short of power on such a light vehicle? I know we all want more.

If the heads are stock and unmodified you can put as much cam, carb and compression as you like on it - It will not do 200BHP - for stock heads 168BHP is about as much as you could ever expect.

ETA

Graph shows as expected with stock deads - flow stops after 5500. Lift the valve as much as you like and put as much carb behind it as you please - the air will not get past the restriction in the throat.

Spend £4-500 having the throats opened up and some decent seat cut and it should see 225BHP.

ETA +

The torque increase from 2500 would be what you would notice most with the head works.

Andrew

They didn't tell me much to be honest, I got the print out you see

If anyone remembers the MG Maestro, it feels like that. Yes it's nippy, it will move if you spank it but nothing like a V8 should. I'm not a BHP snob, it's not something I normally chase but for a V8 it just doesn't have much umph.

They are Vitesse cylinder heads, I'll Google them in a mo. Looking at the invoice/list of work the compression was raised to 9.75:1 and a hurricane camshaft, the rest was pretty much a full rebuild.

Thanks for the head info, that makes sense. The Vitesse do seem to have bigger valves etc, would they be classed as performance?