Right, Some of you may have read my drifting thread...

I am rebuilding my cosworth engine following a little mishap!

I have refitted a polished and skimmed head, to a fully built, nalanced and uprated bottom end. I am no mechanic but I had the help of a cosworth specialist mechanic from West Sussex help me.

The car starts fine, oil is getting to the head / hydraulic followers etc but it knocks like a b***h.

I am using 15-50 Sikilone fully synth
had the head caps tightened down to ford spec. I did have to have 4 new valves fitted as the mishap bent 4 valves!

I am wondering what might be wrong? My mechanic cant get to me before the weekend and I am racing on Saturday... well, I should be! I am thinking that maybe when the valves were damaged, the followers may also have been damaged?? Is this possible?

I have just bought new followers and new cam barings, waiting for them to be delivered. Could it be anything else? The noise gets louder as the revs increase. I can only explain it as "sounds like an old style diesel" It sounds like it would be " screwed tappets" if it has any!

All help appreciated.

 

Did you measure the piston "overlap" over the block? It can be 0.6 mm max, mine was 0.65 and was quiet on idle but knocked more the higher the revs. took mine down to 0.2 and now its fine

 

did you time up to the notch rather than the lug for tdc on the crankshaft pulley?

 

http://www.youtube.com/watch?v=6vZWomz4sFM

this was my first start with new lifters, took about 5 mins to pressurise the lifters.

good luck fella.

 

I did not measure the piston overlap..... may be an issue.....?? would this not give more of a bottom end noise.. like piston knocking rather than a clear cam noise??

 

I will take a look at the link when I get home but yes, TDC was timed to the notch.... dizzy lined up and cams spot on...

Just waiting for my new lifters and then maybe I will try again....

 

in answer to your question.... yes, the followers can be damaged when the valve pushes up back through them. you will probably fin that if you change these, you will be ok.

 

the funny thing is it sounded much like empty lifters but a bit "harder". thought it was the lifters at first, had to take off the head due to the gasket not sealing and thats when i noticed the marks on pistons and head.. but this is most likely to happen if the block has been skimmed.

i´d start by changing the lifters, then take off the head and check the guides then you´ll also be able to se if your pistons has touched the head. all this AFTER you´ve checked the cam-belt is timed up correctly, the crank is supposed to line up to the pin by the jacket and not the jacket itself. if this is the case you´ve probably fucked the valves again if unlucky.

 

Hi,
Often, when you have a contact between exhaust valve and piston, you have also a problem with camshaft bearing cap dowel.
Check, one by one, the state of bearing cap.
Sometime it is necessary to repair thread dowel with helicoil system.

Check torque setting :
6 mm. dowel : 10 Nm.
8 mm. dowel : 20 Nm.

Regards.
Claude

 

Cheers for the advice guys. I will check everything later on.

I know the timing is right... thats been set outside of the car, checked and double checked, turned by hand,

Then engine went back into the car and it was checked and double checked again with it being turned again by hand.

Head was purchased second hand but re-machined by Sutton Rebore and said to be fine although they did say it was now on its last skim. I will replace the followers in case they are damaged, then re-time it up and give it a go.... worst case I may need to take the head off and use a spacing plate if the head is over skimmed or just not allowing clearence.

 

But here you stated it was timed on the notch instead of the lug...

 

Opps.... mis typed..... it was the lug on the block which is at about "11 O'Clock" as you look at it.... correct??

 

Did you replace the small end bushes. These sound just like a cam rattle when they go!

 

Small end bushes?? Can you explain?? I dont know what these are?

 

New Cam barings and Followers just turned up!

I will give updates once they are fitted!

I double checked all the timing last night and everything lined up, as per my expectations.....

 

I think the bushes on the small end of the connecting rods...

 

the bottom end of the block has been rebuilt using all new parts...

New block, New Con Rods, New pistons and rings, new gudgeon pins, even as far as new circlips, new barings, re-ground crank to 0.25, new arp bolts, new sump, new baffle, new oil fee, new oil pump,

2nd hand was bought and its been compression and crack tested, skimmed. 4 new valves and springs, retainers etc fitted, the other 12 valves were from my old head. New nylock nuts and stainless washers used on the head cap studs, New ARP head bolts and new gaskets throughout!

The only things that are not new or re-machined are the cams, cam gears and 12 valves!

 

The lug fixed to the block is the timing reference, on the pulley there is a lug and a V close together, the V represents 16deg btdc and the lug is tdc. It does sound like the engine is incorrectly timed. I would bet that if you get a boreoscope and look into the cylinders, your inlet valves will have been hitting the pistons.

I hope Im wrong but I have seen this before...you will be wasting your money on new lifters. When you retime the engine after replacing the lifters, use a dial indicator guage down number 1 spark plug hole to the top of the piston to accurately establish tdc no1,then time the cams from that.

Cheers,

Phil.

 

yay.. its sorted...cheers guys... just packing it up for norfolk lol

 

Hi folks.... All sorted out....

The timing was out by 2 teeth. I had not accounted for the movement when the tensioner pully is tightened!.... no damage done and the car is running as sweat as now!!

I have brand new genuine INA followers for sale now!! unused, only opened and soaked in Silikone 15w-50 oil in anticipation for fitting that was not required. I will post them on ebay.

Just my luck.. wasting money like that when I don't have it to spend!

 

???????????

 

Just a word of advice,

NEVER run a freshly build engine on fully synthetic oil. Basically if you put new rings in an engine, consider it as requiring running in. Use a fairly basic spec oil and run in on upto 3/4 full load for 3-500miles and don't labour it or sit with it at a constant throttle for any length of time.

Pop a new oil filter on when you change the oil. Usally manufacturers oil filters are way better than pattern ones like some nasty Halfords rubbish.

If you have hydraulic lifters Wynns Lifter Treatment works very well at flushing them out and is safe to leave in oil until next change.

We specialise in MG Rover stuff and do a lot of engine/transmission build work but I will admit not know so much on the Ford engine families but some techniques are true what ever you build.

 

thought it was timing .
Kewl well good luck.
and yer dont use synth oil for run in.

 

I ran it in on 10-40 semi synth.... but did not get many miles under its belt before the change. I did not fancy running at high revs on normal 10-40. Maybe that was a mistake.... but I will just have to learn from it.

It was idling for about 4 hours (2 hours sat, and 2 hours Sunday) then only drove about 150 miles before the oil and filter change.

 

I get all my service parts from my sponsors, Opie Oils

 

If you run an engine in on constant revs, or idle it will severely affect performance. You generally find engine run in on idle do not rev well and well down on peak power, when taken to high revs they can frequently be unreliable. 3/4 of full throttle with no position held for too long is general rule of thumb for running in and a low grade oil is absolutely fine, even a cheapo mineral oil is good as it allows all the components to bed in properly. If the oil grade is too good during running in you tend to get an engine that has a heavy oil consumption in future life.

The only reason we don't have oil changes at 1000 miles and running in now is cost, nothing else. manufacturers dance to the fleet tune. Same reason why service intervals were stretched, oil expected to last longer, brakes stopped wearing etc.

 

OK then..... maybe I have screwed up a little......

Just have to pray a little now!!