V8 twin carb down on power.

Hi, I'm fairly new to the Rover V8 engine. I have installed a 3.5 SD1 engine into my Volvo 740 (it seemed like a good idea at the time). It was a very tight fit and I was forced to retain the cast iron exhaust manifolds due to space issues. It's up and running now but low on power and thirsty on fuel. I have fitted an electronic distributor and the timing seems okay. I have cleaned the SU's and set the float heights etc. It runs a bit rich but idles okay. There is no smoke from the exhaust and it does not seem to be using oil but there does seem to be a bit of crankcase back pressure (in fact it's giving me a bit of a headache due to the fumes). It will rev up but there's just not much power there. I'm trying to locate the correct top end gasket set so that I can check the camshaft for wear and clean out the rocker covers etc (but even this is proving awkward to confirm the correct gaskets set to obtain). Any ideas? Chris

Since the last post things have progressed a little. The cooling system is starting to pressurise after very short periods (and before the engine temperature has reached operating temp). I'm convinced there is a head gasket issue (where else could that much pressure come from so quickly?). I have conducted a compression test and all 8 cylinders are between 150 and 160psi.

So, yesterday I removed the cylinder heads. There are signs that the head gaskets were leaking between the rear cylinders and the water jacket. Unfortunately 2 inlet manifold bolts snapped into the left hand cylinder head around the front water transfer port while dismantling.

On the plus side the bores are in good shape and the engine internals are clean and free from sludge or other deposits (apart from the right hand rocker cover breather plate which has dried crud in it...this will be cleaned before refitting). So far nothing that would cause the lack of power I have been experiencing.

I then removed the valley plate to inspect the camshaft. I doesn't look that worn. One of the hydraulic tappets has uneven wear but not excessively so. It is also clean in that area. I then removed the front timing cover. This engine has been fitted with a duplex chain and some kind of fibre camshaft sprocket. It is all clean but there seems to be a lot of freeplay in the timing chain. I can rock the camshaft back and forth by about 5 to 8 degrees! Is this normal? I'm used to engines with some kind of tensioner on the chain. This one seems very loose.

The camshaft is now removed and I'm considering which unit to fit. I want low down torque and a good idle with reasonable fuel consumption. Not too bothered about top end power as I don't tend to rev that much and in any case with cast iron manifolds it is not exactly set up for high gas flow.

I'll be starting the rebuild during the coming week. Any advice?

Chris

...also forgot to mention that there seems to be a lot of end float on the camshaft. I presume it is held in place by the timing chain and perhaps the timing cover?

I have managed to drill out one of the snapped bolts and re-tap ready for the rebuild. Will tackle the other one after work tomorrow.

I have no idea which camshaft has been fitted to this engine as I bought it as an un-needed cobra kit car project. The engine is marked as feb 1984 (which would be consistent with what I thought) but I imagine it left the factory with a simplex chain and steel sprockets?

How much freeplay should there be in the chain? Which are the best chains and sprockets to fit?

Update. I have spoken to the very helpful people at 'Real Steel' and ordered a new camshaft. A standard P5B camshaft with new followers (they advised me that Rover had 8 different camshaft profiles which would all fall under the banner 'standard'. The later SD1 cams had milder profiles for emission regulation as did Range Rover/Land Rover cams). I'm also replacing the chain and sprockets for a duplex double roller all steel timing set and fitting new valve springs. In the meantime I have stripped one cylinder head and am ready to lap the valves in, although to be honest they only need final finish as they are pretty good already.

Might be a few days before I get to work on it again due to work commitments etc...

Well...the beast is up and running again Seemed to take an age working for an hour or so each night after work. Both cylinder heads stripped and decoked (although they weren't that bad to be honest). Valves reground and new springs and valve stem oil seals fitted. All torqued down with just a tiny smear of blue hylomar on the gaskets.

P5B camshaft fitted and coated in cam lube paste. Duplex chain kit fitted and no freeplay on the cam now! (happy days). With everything back together (eventually) I drained the oil and replaced it with break in oil from Real Steel, together with a run in additive. Cranked the engine with the spark plugs removed until oil pressure obtained. The engine then started without much fuss and I took it on a gentle drive to run the cam in.

Now that the timing has been set and the carbs balanced and set, it seems to be running much better. Still can't say that there is an abundance of power but this is a heavy car with an automatic gearbox.

Next job is to modify the air filters. I did have a pair of low resistance cleaners which just about fitted under the bonnet but now that I have replaced the engine mountings, the motor sits fractionally higher, so I have ordered some flexible tubing and will relocate the filters behind the headlamps where the air is cool.

Okay...so here's where I'm up to. I now have the air filters fitted near the headlamps where the air is cooler. As an added bonus it also means that I'm not getting crankcase fumes coming into the car anymore as the trunking is too long for that. I have set the carbs as best as I can as it turned out that one was running slightly weak and the other even weaker. Now running better and when the engine speed has settled it seems to pull okay. The problem I'm still getting is whilst accelerating. There seems to be a reluctance to develop very much power as though it is running very lean (if this were a fixed venturi carburetor I would say that the accelerator pump wasn't working. I have tried changing the viscosity of the oil in the dampers and adjusting the mixture...this helps a little but something is still not quite right). I have BAK needles fitted in HIF6 carbs. The float heights are correct and the carbs are clean. I'm running the ignition timing at 8 degrees BTDC at idle and it is advancing with revs. There is no pinking and the idle is smooth. Any advice please? Chris

I decided to try a few more adjustments today. The engine is running okay'ish but still down on power when accelerating. I tried advancing the ignition timing to see if it influenced the issue. I set it to 15 degrees BTDC and this has transformed performance (although it shouldn't really). Light throttle running is smoother and acceleration is far better. There is no sign of pinking and curiously this seems to have cured the running lean issue. Prior to this I had found that pulling out the choke a bit during full throttle acceleration would improve power output...this is no longer the case. It does seem to be running rich at idle but okay during actual driving. The plugs are coming out biscuit brown.
I have a Power Spark distributor fitted and can see the timing advancing with engine speed whilst using a strobe. The engine is a standard 9.35 to 1 unit with twin HIF6 carbs. Other than the P5B camshaft it is unmodified. So I am wondering if the internal advance settings in the distributor do not advance sufficiently as the revs climb of if the timing marker is incorrect for the crank pulley. I do not know the full history of this engine. I was told that it came out of a Rover SD1 and was then fitted to a Land Rover. Later it was removed for a Cobra kit car build but never used. Is there more than one crank pulley? It seems to fit correctly against the bolt on timing mark. Has anyone else had this issue with ignition timing? Chris

Today I had a final twiddle with the settings of the engine. Ignition timing is now set at 18 degrees BTDC at idle (no pinking under load). Smooth idle and nice power delivery. I can only assume that the pointer and marks on the crankshaft pulley are incorrectly matched because this shouldn't have solved the problem...but it has. Also tweeked the SU's just a bit more using the old fashioned method of lifting the dashpot slightly and seeing if the engine revs changed. Left hand carb slightly rich and now balanced. Running and starting well now.

Hope this helps some one one day.

Chris