Lacking Ooomph, where to start looking ?

[MRGT]

A little while ago I had my 944 S on the rollers at Allan Jeffries in Plymouth and was a little disapointed to find it was only putting out 158 BHP (max) and around 125 lb/ft as opposed to stock figures of 190/160, I appreciate that the car is getting on a bit (116K miles) but that seems a bit too low for the mileage. Allan suggested getting a leakdown test done which I have finally got around to doing, and its losing around 20-25 % across cylinders 2 -4 with a substantial 35 % on cylinder one. Adding a little oil to each cylinder produced no noticable change so it looks like the piston rings are OK (at least if I understand the process correctly ! ). So the question is, where is the best place to start looking for the power loss?

On a slightly different topic, when I first purchased the car I had the belts etc changed straight away but was advised by my Indie that the cam sprockets were showing signs of the dredded 'hooking'. I have recently managed to acquire a spare set of cams which are in far superior condition for a bargain price (given they are approx £500 each when new ! ). Now the question is, is it worthwhile/possible/foolish to have the cams reprofiled to provide a bit more push lower in the rev range, as having to wait until 4000 revs before anything happens makes me look like a boy Racer !

All advice gratefully received

Howard

 

[Mike_Pollock]

Hi Howard
Your figures do look a bit low, ny 8 valve got 148 / 158 recently with lots more miles.
Is the hooking of sprockets altering the timing and is it timed correctly?
Bores can get scored but that produces smoke at high revs, so the valves would be the obvious place to start, hopefully a sticking one.
As for whether to get the new cams reprofiled, I've no experinece.
Mike

 

[ChasR]

Cam timing is something EMC and JMG told me about. They said it can account for as much as 15-20BHP power loss from one of the higher powered N/A 944s. To be fair, my 944 with the engine engine timed up does shift quite nicely (the engine is said to have done 90,000 miles).

If you are losing compression, I'd check the basics before doing anything drastic. I'd start at the cam timing so as to see what that brings up, and then move onto looking at maybe having the head refurbished at the same time as when you change the cams.

It sounds like the garage did a compression test, not a leakdown test. With a leakdown test you can normally trace the leaks (a hissing from the inlet manifold (using a stethoscope) or exhaust will show you the source of the leak, or using the dipstick tube etc.)

There is another way IMO to make your S quicker and to make use of the higher power band. Stick an 8v 2.5 gearbox on it. If the car is a daily driver on motorways this could be detrimental to your MPG and cruising ability (I believe the 2.5s rev at 3800rpm in 5th at 70mph on the motorway (maybe one of the others will confirm this), but it will allow you to take what was said to be an overgeared gearbox into something that is more drivable and utilising more of the power in addition to helping the lack of low end grunt thanks to shorter gearing.

Failing that, I'd look into the gearing of a 2.7 but those 'boxes (let alone cars!) are quite rare these days.