Slow getting through the rev range

[4535jacks]

I recently had my standard 400 on a rolling road. It produced 214 bhp at the flywheel, which isn't too bad, but the chap running the test said it was quite slow to actually move through the rev range, Producing a shallow power curve. The acceleration doesn't seem that great to me at all.

Thinking this could be cam wear with 64k on the clock (my guess), I've book her in for new MC1 or stealth cam.

Any Ideas what may cause this sluggishness through the revs.

Gary

[chrispitman]

If its slow to rev I would look at the Air intake side, are you running a standard system or have you a smooth bore intake pipe and bend. The original pipe has been known to colapse and cause problems. Also as you say it could be a warn cam again less time for the air to enter the cylinder.

[GreenV8S]

4535jacks said:

I recently had my standard 400 on a rolling road. It produced 214 bhp at the flywheel, which isn't too bad, but the chap running the test said it was quite slow to actually move through the rev range, Producing a shallow power curve. The acceleration doesn't seem that great to me at all.

Figures from an uncalibrated rolling road are pretty meaningless. Was it anywhere that is used to dealing with TVRs? If so they should be able to tell you what a good standard engine would be expected to make on their system. At most places, 214 bhp would be a very good figure to get from a standard engine.

Comments like 'a bit slow to move through the rev range' don't make much sense - I would have expected the speed through the rev range to be controlled by the brakes on the rolling road and not any indication of the engine power.

[4535jacks]

The rolling road was a tvr specialist and very reputable, So I believe the figures to be accurate and his opinion to be right.
Any other ideas on what could cause this?

[350Matt]

When was the intake hose last checked? As these can collaspe internally.

Thing is 214 pones from a std 4.0 is pretty good, if its lacking torque but making power I say check the dizzy vacuum advance mech and the then cam timing.

Matt

[GreenV8S]

4535jacks said:

The rolling road was a tvr specialist and very reputable, So I believe the figures to be accurate and his opinion to be right.
Any other ideas on what could cause this?

Almost all problems would tend to show up most at the top end of the power band and affect the peak figures. Blocked induction/exhaust, inadequate fuel flow, worn cam etc would all tend to show up at the top end. I'm wary of taking an unknown person's comments at face value especially when they don't appear to make sense, but assuming that as you say the figures are accurate and the results show a lack of mid-range power I would guess that either the fuelling or the ignition timing might be out in that part of the power band. Did your rolling road operator check either of these?

[4535jacks]

He checked timing and said it was fine. I don't think he checked fueling though. I'm hoping V8D shed a light on it when I drop the car off to them for a new cam.
Would getting a stealth cam or MC1 by a complete waste of money if the cam is good working order?

[GreenV8S]

4535jacks said:

Would getting a stealth cam or MC1 by a complete waste of money if the cam is good working order?

If there's nothing wrong with it, the only reason to replace it would be to change the cam spec. Given the power characteristics you're describing, it may be that you already have a long cam in there; that would typically result in good peak power figures at the top end but less power mid range. So you're looking at the thick end of £1000 to replace something that as far as you know doesn't need replacing. Still, this is all speculative without having seen the power curve or got a description of exactly what the rolling road operator found. For example 'he checked the ignition timing, it was OK' could mean he just checked the static timing, or it could mean he has optimised the timing through the power band. We don't know.