1986 Opel Manta Coupe V8

I believe Blackpopracing is onto something with the juddering when he mentioned it being fuel related.
I was also told to check out the overrun valve at the rear of the plenum chamber so while I was isolating this thought I'd spray some Easy Start around the various hoses and found two major air leaks one being the centre plenum securing bolt and worse the inlet butterfly spindle.

A very good friend of mine has made a sheet to protect the acrylic at the rear of the car so from this -


To this.

Another problem has risen now! The gear lever has got really difficult to select the right gear whilst driving, had a look underneath the car and saw the problem, the nylon/plastic bush that holds the doughnut thingamajig (not sure whats it called) in which the gear lever sits was missing.


Had to take out all the centre dash to get to the top of the gearbox.


Thankfully I had a spare one kicking about so now that's all done and working better although I'm still struggling getting from 3rd into 2nd gear!

Now we come to the fast idling. My current Air Flow Meter which I got second hand did not have a lid to it so I was never sure if it had been tampered with. I've managed to get another unit and on inspection there are differences, firstly the butterfly is much harder to to open compared to mu old unit also there was a spring missing. (Bottom left).



This has definitely made a difference in driving the car.

so i guess you lose self cancelling on the turn signals ?

Well its been a couple of weeks since my last update and this is whats been happening.
Took the car out to test the speedo and it works great no problems there, thought I'd drive it through Winchester town centre it certainly raised some eyebrows! Now on the way home I hit a traffic jam, engine starts getting hot, fan kicks in which keeps the engine at a steady 90 degrees. 15 mins later still stuck in traffic then it stalls starts up fine travels 20 foot stops and it cuts out again! does this three or four times, traffic clears revs hit 1200 rpm and the engine feels like its about to stall / strangled almost like pulling out the choke whilst the engine is hot.

Changed the coil, new spark plugs, double checked the timing still the same, unplugged the ECU to check the connections all seems to be ok reconnected it started up fine problem seem to have disappeared!

Took it out for another spin well I'll be damned if I didn't hit another traffic jam, and it starts all over again managed to pull over to a lay-by pulled the ECU left it 5 mins reconnected and no change, limped home again!
Left it for an hour with the ECU out reconnect and its all hunky dory.

I've now come to the conclusion it an overheating problem - not with the engine directly but the environment its in.
The engine bay is compact with the exhaust manifolds running forward to the front of the engine then under and out with an extensive sump tray, the bonnet is limned with reflective foil, the only air flow is through the radiator around the engine and the only way out is down under the car.
As we all know heat rises and its being trapped in the engine bay the inlet manifold is so hot you cant put your hand on it which I believe is causing the fuel to evaporate.
So the only thing I can think of is to cut a vent in the bonnet and try not to damage the paint work!

Great looking car and nice build! .I did a Rover V8 conversion on an MGB and this is also a tight engine compartment for a V8. These conversions are quit common and lots of these also face overheating problems. Luckily not mine. This summer we were stuck in traffic with 35 C and no overheating or fuel evaporation although it does get hot in there. I used a new radiator and the MGB has 2 electric fans standard. I fitted a Kenlow adjustabel switch for the fans so i can adjust the "kick in"temperature fairly precise which i believe helps a lot. I did the conversion and then drove the car some times and then restored it. During the restoration i also got the exhaust manifold ceramic coated which seems to help also.
Maybe it is worth to install a Air-fuel ratio device to check if it is not too lean or get it on a roling road also to check the ignition timing Its critical but it should be possible to run it without overheating

Good luck and keep posting

Peter

A very busy night last night, cut out the rear section first, this then allowed me to drill a small pilot hole through the rear of the bonnet to get the main section centralised.





Laid out masking tape across the face of the bonnet to mark out the final cut. Firstly got a piece of galvanised sheet steel and made up a hood as low as possible.





This view is the underside of the vent I've given myself an 30 mm lip to secur it to the bonnet.



The next part was to lay it out onto the masking tape and mark out the inside of the lip and very carefully cut it out with a 4" disc cutter and a dremel.



Thankfully there was very little damaged of chipped paint, with this done I repositioned the vent and secured it with mini G clamps and drilled 3mm holes through from the rear with the aim of using self tapping screws. Painted all the edges and hole to minimised any chance of water getting in.



Back on the bench to give it a skim of filler, that'll be a job for friday!

Just love the work you are doing...very nice fab work there.

keeping a car running is one thing...keeping it running in style like this is yet another!

JP

Took the car out friday night in torrential rain definitely not the best time to test drive the recent mods it seems to have cured part of the problem, it runs ok but still it cuts out on idle now and then!
Anyway arrived at my destination only to find the electric radiator fan came on even though the engine wasn't over heating so I had to pull the fuse this didn't look good!





I presume there is a short somewhere which only appears when its raining and to top it all when I flash the headlights the dam interior lights flash too! I must have moved something when the dash was out.