FE-FC Holden Discussion Forum

just had head done,running unleaded with additive.
tappets done plugs,new...new leads coming.points,dis cap ok.
carby done.
now
runs great up to 55mph.
then pops in the exhaust :- & makes no more power.
flushed out radiator,was dirty as.
any ideas would great...

Exhaust valves are too tight, recheck them.

did the clearances 12th exhaust,8 th on the inlet...

Sounds like a timing issue as its not low down in torque range where you would expect spark to be an issue. Does it make the same sound when reconfigure at same recap stationary it just under load

Sorry. Does it make same sound when stationary it was supposed to say. Is your distributor advancing. Put a timing light on and rev it and see if its advancing. A quick and easy test to do. Does it only happen in top gear or all gears at same revs

only in top gear.
idles great.
goes good till about 55mph...

zl296

Assuming the valves are adjusted correctly and if the timing and centrifugal and vacuum advance check out OK and even though you have had the carburettor done it may be a low float level or incorrect main jet which is starving the engine of petrol or possibly a loose baffle in the muffler/s or bent tailpipe etc that are causing a restriction. Also check that the exhaust manifold is sealed at the gasket area/s.

Cheers Wayne

thank you for that info...
up early to try..
dave. ;)

I think wayne is on the money with that extra info because if it was valve adj it would pop even at idle or on deceleration from idle but if its fuel starvation it happens under full load high speed conditions. a crude method to unblock a jet is to rev it hard and while throttle still full quickly choke the top of the carby with a rag (cotton) and this can unblock it. a crude method that get a lot of people out of trouble  ;)

If you have rechecked valve clearance, then its got to be electrical eg. 1/ ignition timing - ajust it by hear, take it for a run a few times. 2/ Condensor or Points are shot, new ones can be rubbish, check earth wire in dizzy too. 3/ Wrong Coil or wiring loose or wrong voltage to coil ? Fuel 1/ blockage ? take it for a drive and when it plays up, stop engine, remove top of carbie and check fuel level, if its low Bingo! 2/ Bad fuel ? 3/ Blocked Air filter or choke is partly on, check cable is not loose 4/ Power by pass is jammed off ? or Main Jet has huge blockage ?

My first thought is electrical also. If points, condenser and cap are are in good condition along with correct timing, I would be checking the distributor shaft for wear. At higher engine speeds there is more chance of movement in the shaft if there is wear causing erratic points opening / closing. My next bet is incorrect float height as previously mentioned.

Have a good one.

Rod

I want to emphasize a point Hobbo made

The choke.

FE and FC have a peculiar choke butterfly system which allows the choke to be partly on if the wire is not set correctly. It is possible that the wire can be set in place and it appears that the choke is off but it will spring to partly on when the car is running. I don't know how to describe it better than this.
When you set the choke cable wire, make sure that the butterflly is vertical and the lever is forward as far as possible then do up the bolt to attach the wire.

Ken

So basically it can just about be anything lol  :D

9 times out of 10 if the car was running ok ( faster ) before the head work, it will probably be something you changed or ajusted during the headwork eg. fitted new points or coil etc. Another thing to check with a timing light is to see if centrifugal bob weights inside the dizzy are giving you proper advance timing at high speed. If I was local I'd have a look at it for you.

With the extra compression it takes more energy to ignite the fuel.

thank you for all your help.
just picked up new points,leads,etc,
will go over the lot over xmas...
owe you all a beer...
thanks again.
let you know.... ;)

Also with extra comp it will pre-egnight, another way to check is to rev up engine with timing light on and check timing at it's max, on mine I don't run the vac advance,