17 replies to this topic

[The Portly Knaresbruffian]

I've recently changed from an LCB to a Manifow Cooper freeflow as the wider lcb clouted the underside of the car. However on putting everything back together, the car almost refuses to run, sounding as if its on 2 cylinders and not idling below 1700rpm.

I've checked the carb, compression, and sparks and everythings there, but can't find anything wrong.

Can the shorter centre branch of a freeflow cause poor running on a larger bore engine?

1293 A+
Stage 2 head
Hif44 with BDL needle + k&n

[nicklouse]

In a word YES

but it all comes down to the details.

 

what was the LCB make and pipe size. What is the Freeflow. Make and pipe size?

 

the Freeflow is normally just fitted to the small block engines while the LCB works better on the big block ones.

 

I would not have fitted one to an engine spec you mention but you do not mention the CAM.

[Ethel]

First thought is if it's affecting the fit or your inlet manifold.

[The Portly Knaresbruffian]

Good suggestion but Inlet manifold sits ok. Nothing touching or keeping it off the head.

[The Portly Knaresbruffian]

In a word YES
but it all comes down to the details.

what was the LCB make and pipe size. What is the Freeflow. Make and pipe size?

the Freeflow is normally just fitted to the small block engines while the LCB works better on the big block ones.

I would not have fitted one to an engine spec you mention but you do not mention the CAM.

[The Portly Knaresbruffian]

Cam is pretty standard. Lcb was a large bore stainless one, and freeflow is a standard bore maniflow one.

[PoolGuy]

My first thought is an air leak, spray wd40 around the inlet

[Tones61]

Defo an air leak,
Probably at inlet mani

[Icey]

Having swapped an LCB to Freeflow on a 1275 ourselves, I’d be very surprised if it made any notable difference to running. Like others, I’d double check everything is present and correct.

[The Portly Knaresbruffian]

At the risk of this becoming a 'why won't my car start' thread, I can report the following.

WD40 all over the inlet manifold, gaskets, abutment plate etc resulted in nowt. However dripping WD40 on the exhaust manifold showed that the exhaust port from cyl 4 was cold. A timing gun showed all 4 plugs were firing, but pulling the ht leads off whilst it ran showed 3 and 4 were not burning any fuel (no difference to running with them removed).

I can only suspect something blocking the inlet manifold to 3 and 4 to make it too weak to run. I'll take it off tomorrow and inspect. Thanks for the advice so far.

[PoolGuy]

 A timing gun showed all 4 plugs were firing, 

That will only show that the leads are getting a spark, it doesn't show that the plugs are actually producing a spark. Swap the plugs around.

[The Portly Knaresbruffian]

Good point. Have swapped them round and still nothing from 3 and 4. All plugs must be good.

[PoolGuy]

Rocker cover off, check the clearances, valve stuck?

[cal844]

I'd go with the basics, remove the dizzy cap and check for cracks or general damage.

Change or clean the plugs (Id also say to try get some heat into the electrode and refit the plugs hot, refit plug leads and get it started as quick as you can.)

In the past I've cleaned the soot off and used a flammable fluid on the end of the plug and lit it with a lighter to burn the soot and rubbish off.

[The Portly Knaresbruffian]

Thanks all for help on this. I've found the problem and it was an air leak on 3 4 inlet port. My inlet manifold stud holes have been slotted vertically by a past owner to allow the manifold to be lifted off easily (great if you're stuck for space). I just hadn't aligned the inlet with the port properly. I'm an idiot.