help needed 308 running rough

[fcguy]

hey guys ,

just wondering if anyone has had problems with a 308/253 running rough"thong slapping" sound in exhaust after a camshaft/manifold change camshaft is a new crow cams item to suit the motor manifold is a second hand item but not very old  ege little corrosion no cracks etc etc now heres the problem timing is spot on 9 links dot to dot, dissy is at number one had two mates look at it both thought it wound be cam timing but upon closer inspectionits spot on, am considering pulling carby back off manifold removing the carby insulator and putting it back on other than that.....HELP please(p.s its a 308 4pd fc )

have also to add i built the motor to start with so a cam change shouldnt b that hard i spose but we are all human after all
cheers

[Ed]

hey fcguy,

what condition are your lifters, pushrods and rockers in?

could be a rocker about to break.  I have had a pushrod go thru a rocker before.

my motor is making a terrible noise at the moment, a metallic noise "clinking" when it is under load... needless to say it is off the road until i suss it out.  

on the brighter side i picked up a good useable, un-bored 304 bottom end which has been cast with the clearances for a stroker crank and a nice T700 R4 to back it up.

am going to stick the new bottom end in soon and put some roller rockers on to strengthen the weak Holden valve train.



Cheers

Ed

[fcguy]

hey ed..

thanks for your input but lifters and pushrods are new items and the rockers werent stressed or anything all seated up nicely as in nice and snug when they werent
under load no different from any other 08 ive done a cam in the only conclusion i could come to
which i am in the middle of at the moment is trying another carby as the new redline manifold doesnt have a seperator in the middle where as the original one did  the motor had a minor noise out right hand side b4 i changed cams which is why i sdecided to change cam and manifold and now with no seperator carbys problem could be magnified to both sides  what do you think could be a rochester problem?

[Ed]

hey fcguy,

figured you would of changed those items  

the separator is merely to divide gases into the differnt planes on a dual plane manifold, so your new manifold is a single plane manifold?

from my reading they say the single plane doesnt distribute the mix as evenly at low revs, however they are more suited to higher RPM applications.

have you given the motor a good run thru the rev range under load?

again im not sure of the rocky carbs, as I've changed over to EFI.

Cheers

Ed

[fcguy]

yeah ed gave it a Good run yesterday its just feels like its missing something chronic down low and its smoking possibly a oil/fuel combo it is a single plane manifold but ive got a manual in the care so with the 4 spd ratios and the 3.36 diff its up above 2200 most of the time so it shouldnt come into effect as you can get her to idle but shes got the dt's  but the smoke issue when u rev her on the driveway is of major concern as shes only 10'000km old

ppl ive spoken to cant fault the cam/ignitiontiming its spot on eg top dead center on the new balancer the dissy is siting smack bang on number one cant get much better than that and shes not backfiring but shes hard to start when hot also wich could be manifold leaking internal? eg hot engine into intake runners? more help if you can also i put the spaker back in as the rochester wasnt fully sealing but also am getting a whilstle/whining noise when driving?

[Ed]

did you dial in the cam using a dial gauge etc to measure exactly the cam specs as stated on teh sheet?

I went to this hassle with mine, and hours later found out at TDC with the new balancer everything was OK. piece of mind was what i got out of it.

sounds a bit like my motor... but mine is definitely blow by just from wear on the bores and rings, prolly not yours as you only have 10,000kms.  strangely enough my compression rings are Ok, but the oil rings have just disintegrated.  this was all Repco's good gear too.

perhaps your intake manifold sealing isnt so good?  i got the machine shop to just check out the mating surface on the Harrop manifold prior to installation.

also ive seen some guys use gasket sealant on both sides of the intake gaskets.  I didnt do this on mine and it seems fine.

what's your static timing? is there a vac advance?

Cheers

Ed

[Ed]

when did you last do your valve seals etc?

[fcguy]

didnt dial im the cam as its a hard task to remove head on drivers side to do it plus when im only running a doulbe row chain with no multi keyways cant really get it wrong the chain is 9 links (11pins) spot on smack bang in the center where its supposed to be, because of the smoke im leanign towards inlet manifold not sealing down low got no coolant leaks but it may not be seating  properly round two of the runners thus causing the problem im goin to put a vac gauge on it check manifold vacuum if its low ill pull the mnaifold off ditch the gaskets use loctite copper gasket in a tube and should be the end of it fingers crossed unless you have any other ideas?

[fcguy]

valve seals were done when heads were rebuilt when motor was put together wasnt gettign any tell tale signs of those leaking

[Jockster]

Hi FC Guy
Is the manifold you have the correct one for your model engine and if it is did you check to make sure it isn't warped along the manifold faces. HX-HZ manifolds had a bad habit of warping allowing manifold vacuum to draw in oil from the lifter recess with consequent smoke and idle/misfire problems.
Cheers
Jockster

[fcguy]

hey jockster hey ed yes the manifold is a pre pollution style to suit the pre pllution heads and motor i have so on to the next thing ive pulled the intake off looks like it wasnt sealing down below casueing oil to enter runners between head and manifold and also now have 4 bent pushrods and i mean bent can anyone shed some light on this?

[fcguy]

hey guys just an up date its 8:30 qld time just came inside from the garage shes up and running again after fixing the oil leak into the intake by removing gaskets and using permatex copper gasket glue she sealed up first go no ol leaks no thong slapping sound purrs like a kitten just need to fine tune the timing still pingin a bit might be a cog out on the dizzy will wait and see thanks to everyone for their input