Can someone help me understand why.....

[thewave]

my car runs the way it does?

I don't pretend to know anything about engines, basically because I don't. But I like to understand, and want to learn.

I have a 3 litre straight six MGC. It's running triple 45 webbers, lightened flywheel, balanced long duration cam etc.

However, what I can't understand is why it is so difficult to drive the sodding thing from standstill? At tickover after starting, it's around 1,000rpm. When pulling away from standstill I have to VERY carefully press the accelerator, and find it VERY difficult to get the revs up, in order for the car to get going, this usually involves riding the clutch, which obviously isn't good.

However, once on the move, revs up slightly, I can plant my right foot and it'll scream to 7,000 rpm and go like the clappers. Why isn't throttle response there when pulling away?

Answers on a postcard please?

Thanks

[thewave]

Thanks for the responses chaps.

So I understand why it's easy to stall, but what about the throttle, why won't the revs just shoot up when I touch the throttle in neutral, instead of just popping and splodging about?

[thewave]

ewenm said:

thewave said:

Thanks for the responses chaps.

So I understand why it's easy to stall, but what about the throttle, why won't the revs just shoot up when I touch the throttle in neutral, instead of just popping and splodging about?

Does it idle smoothly (so no throttle)?

I suppose for quite a highly tuned engine IMO it does idle fairly smoothly, but then I have nothing to compare it to. Sometimes the revs drop below 1000rmp and oil pressure then drops, so when I was in traffic last night (not easy!) I had to sit with my foot gently on the pedal, then revs increased and it seemed to stay back at 1000.

[thewave]

I've been told it was rolling road set up, but not sure, will find out.

Thanks

[thewave]

I don't have any print outs from the rolling road. Can anyone recommend me a specialist who can sort this out please.

Bear in mind I'm in Suffolk.

Thanks

PS I'm going to a clients soon and will take the MG (As it's a bit of a run), I'll try and get some more info.

[thewave]

Will look into it.

Appreciate the responses

[thewave]

zac510 said:

Don't go to a rolling road - they mainly test heavy load conditions (precisely as Pork-n-Beem said). They can do more but the operators don't usually bother. It's easy to claim that a rolling road might help you if you've never had carbs or bespoke induction before so at this stage just save your money.

If mechanically all your linkages are in order then it sounds like you have a problem with the idle circuits on your DCOEs. These are also important in the transition between idle and the main circuit. (also what Pork-n-Beem was saying )

What you need is a good patient tuner who will take the car out on the road and tune it in the precise condition you are complaining about. You might even want to demonstrate it to him.

Then again, he may just say it's the nature of the beast But a rolling road won't replicate your problem as well as just doing it on the road.

BTW, what's it like when you crack open the throttle in neutral? what's it like when you crack the throttle when the engine's off?

Edited by zac510 on Wednesday 24th October 21:22

When I plant my right foot in neutral the car basically tells me to sod off
To get the revs up in neutral requires a very gentle movement, and playing around a bit, it's really not easy. When underway, if the revs are over 3000 and I crack open the throttle, it goes like a train.

[thewave]

Sorry to drag this back up, please be patient

Decided it might be worth further upgrading the engine before tuning webers. So I will be taking the bottom end, and putting in forged pistons, conrods and a balanced steel crank.

After these mods, I think I'll be safe going for the larger jets on the 45s. Will any further remedial work be required on the top end after these additions?

Currently the engine is as follows:-
Gas flowed, lead free Peter Burgess cylinder head, block re-bored with new pistons and valve cut-outs in top of block. Cam re-profiled to high lift long duration, with Vernier cam gear, all moving parts balanced.

Now I'm foregoing the weber tune at the moment, anyone want to recommend where this (expensive) work should be carried out.

Only two I know at the moment, MGMotorsport and Denis Welch.

[thewave]

Racefan_uk said:

I'd have thought that getting all the expensive work done will be a waste of time until you get the carbs sorted anyway. You may well find that once you've got them checked and working properly you don't actually need to have all the work done anyway.
Just a thought. But you've had plenty of advice from people in the know on here already.

I'm just fed up getting left behind on the track days

[thewave]

I appreciate the mods are expensive, and won't on their own make it any more powerful, but I can use the bigger jets in the webers then, at which point they'd need tuning again anyway.

I think the engine needs to be stronger, it's only used primarily as a track day car and shows, so need it to last.

[thewave]

JP_Midget said:

thewave said:

I appreciate the mods are expensive, and won't on their own make it any more powerful, but I can use the bigger jets in the webers then, at which point they'd need tuning again anyway.

I think the engine needs to be stronger, it's only used primarily as a track day car and shows, so need it to last.

Changing the jets is tuning, and these things don't wear as I understand it. So, if the car was set-up correctly when the mods were carried out, it should be running correctly now. It does some like an accelerator pump issue (but I'm not an expert on carbs).

I take it that you're getting some info from somewhere else as to the need for a stronger bottom end? Since it's a Pete Burgess head, get him on the phone and ask him whether the power gained from it would require upgrading the bottom end, he ought to know the type of other upgrades people that fit them do. He offers free rolling road time to set up his work usually, so might remember or have records of your car; or even offer to have a look over it for you.

I'd try to see if I could find the problem with the current set-up first before I went to the expense you're contemplating, rather than upgrading the bottom end and still having to find the original problem.

I've contacted Denis Welch, and will contact PB aswell, to see what they recommend. Thanks