P404 cam, lumpy tick over

[steve-v8s]

I am looking at Griffs and one of them has a 404 cam with solid lifters. Over 2500 rpm, or lower if the engine is under load, power delivery is smooth and strong. Below 2500 it seems not at all happy and it is very ragged at tick over, sounds like a 5 cylinder V8. I know even the standard cam is a little lumpy low down but this is very noticeable. Is it normal for this mod ? The pre cats have been removed ( because they broke up) If the engine is off tune until it gets “on cam” is there increased risk of un burnt fuel getting to the cats ? Any advice appreciated.

[Apache]

This is a road I've been down, see profile. The 500 engines can be a pain in the arse in town due to their intractability at low rpm, some worse than others. Mine dveloped this problem and I went for a P404 with all the trimmings to eradicate it. The mods merely exacerbated the problem, Mark Adams and V8 Developments gave the car a thorough check out and returned, an exceptional for its age, clean bill of health.
I ended up fitting the carbs which totally transformed the car and it now runs beautifully. Before I get flamed I am not endorsing this as a cure all for everyone, but......
This is a common problem and can be cured if all other avenues have been explored, more here.

www.pistonheads.co.uk/gassing/topic.asp?f=9&h=&t=74648

>> Edited by Apache on Wednesday 21st January 14:45

[Marlon]

I've got a P404 and it's not too bad at all. It doesn't much like being below 2,000 RPM on a light throttle - a bit of shunt - but idle is very smooth at 1,000 RPM and it certainly sounds like all 8 cylinders are there!

[Guillotine]

shouln't be lumpy. probs elsewhere.

the fuel maps for these cars are very lean, and chipping etc can help a great deal, but i suspect here that there is a problem with timing / ignition.

either way, tell them to get it sorted before you buy.

good luck

[gerjo]

Marlon said:

I've got a P404 and it's not too bad at all. It doesn't much like being below 2,000 RPM on a light throttle - a bit of shunt - but idle is very smooth at 1,000 RPM and it certainly sounds like all 8 cylinders are there!

ditto; the P404 needs a remap by Mark, this should solve part of the problem. Still remains a bit rough below 2,000 rpm. Fantastic cam though!

[Mark Adams]

If it helps and you have no other way of finding out, I can check from the registration whether it has been seen on the dyno.

The 404 does need a higher than standard idle speed, and idle behaviour will be worse on any car running Oxygen sensors (due to the leaner-than-ideal mixture).

[Apache]

Mine ticks over at 850 ish