Perfmr2

Hi,

Ive been having some compression issues of late on my 90 spec. Everything pointed to a duff head, so I purchased the NMS head in the for sale section at the weekend. Im not doing the engine work till over the winter, but curiosity got the better of me, so I put the new head on, and now Im more confuzzled than ever.

These are all the results over the last few month;

(PSI);

4/6/14 124948 miles 140 145 145 148 (original head)
12/10/14 125812 miles 123 130 87 130 (original head)
30.10/14 125812 miles 58 108 21 58 (new head)

As you can see, Ive done no miles since changing heads, and my compression has gone right down while standing still.

Im now more inclined to think Ive blown all my rings, but that would be a unfortunate coincidence.

Im now calling on my fellow ford nuts for help and advice. Is it time to pull the block and do a full rebuild?. What else could I be looking at?

Any suggestions, great, small weird and wonderful welcome.

Thank you

Wayne

Piston Broke

Hi mate were all three readings taken cold ??

gup

iTrader: (1)

Have you tried it with a little bit of oil down the bores
Also what grade oil are you using

Perfmr2

Hi,

All results were cold.
I use Mobil 1 10-40, but there is no fluids in the car at the moment. Also no manifolds on etc. I just wanted to see if Id cured the problem, but it looks to be worse than ever.

Im stumped now, as the car was performing perfect on the drive home after the compression loss on cylinder 3.

Tomorrow, im gonna take the head off, remove the rockers and try the petrol test. not that Im doubting the head, but gonna cover all bases to be sure.

botters

iTrader: (2)

you need to do a leak down test, compression tests will only tell you compression is low, a leak down test will show you why

Piston Broke

As above mate it will show ring problems etc, worth doing or buying the gear as not expensive !

Karlos G

iTrader: (4)

Comp test should be done hot, with all four plugs removed and your foot flat down on the throttle.
Also make sure the o-ring is in good condition.

Perfmr2

Front end of car wont be getting put back together till new year, so will have to wait till then to warm her up.

Is it worth popping a rod/piston out through the top of block for a look see in the meantime?

Piston Broke

To be fair mate if the case is your not using it i would re-ring the pistons or look at if it needs a .5 oversize instead of chasing nightmares with good money

Perfmr2

Yeah, car is off the road till april/may now, so have nothing but time.

Whats involved in doing a .5 oversize, rehoning etc?

Piston Broke

to be honest it would be good to remove the full engine take the head off, crank out, piston/rods out and bits with them then take the block to a machine shop and ask for a re bore a .5 and get pistons and rings to suit and other parts as needed to fresh up. When you do it buy the best you can when it comes to parts as its easy to do it once right, twice is shite lol us a machine shop recommended i have used the same bloke for YEARS and always does a spot on job.

Perfmr2

Looks like the new head is at fault.Poured petrol in, came gushing out of 7 of the ports. Ive just stripped cylinder 1 down and the valve seats are a mess. Gonna require some work. . Gonna strip it right down now, and inspect everything.

haz87

You did a comp test on a dry engine? Not exactly a clever move!
You also don't say what made you believe the initial comp issue was deffo head?
I take it you've done the petrol on the new head with springs etc in?

Perfmr2

Original head had a sticky lifter on No3 inlet. It was oversized on bottom edge by 2 thou. Instead of repairing and replacing on my original head, I decided to buy a already uprated one instead.

Did petrol check by just removing the rockers so valves sat tight, petrol gushed out. Ive got head stripped, and have 2 bent valves, and seats all need work.
Should just repaired mine, but you live and learn.

gup

iTrader: (1)

Can you not get a refund on it dude
That was a fair bit you paid for it too

Perfmr2

Never really considered that matey. Im just gutted I cant get my car running for a few month until I can afford to replace the valves and seats.

In hindsight, maybe I should of worked mine, or bought yours.

Perfmr2

Quick update,

Ive had the head penetrant tested, and have found a multitude of cracks around the seat to spark plug area. The worst being where the 2 valves are bent.

Canada1

Who did you get your "new" head from?
It sounds like it was/is a piece of poo.
Might be one of those "home built" rebuilds. Maybe even a stage 1,2, 3 or 4 or 5?

Karlos G

iTrader: (4)

That's a nightmare mate, was an expensive head when I first bought it from NMS, shame to hear it's in such a state
But yeah whoever sold it to you needs a phone call/visit and to be returning your money for sure.... unless they somehow didn't know, but still.

Cracks around the plug threads is very common on CVH heads and often cause no problems (not ideal obviously but many run like this), but yeah bent valves and damaged seats are no good.

Perfmr2

It was the one for sale in the RS Turbo section. You can see its been expertly put together, and had some money spent on it, but unfortunatly it wont hold compression now

Both myself and the seller have come to a arrangement we are both happy with.
In fairness to him, you wouldnt know there was a problem without stripping and cleaning it, or putting it on the block to do a compression check.
Ill post some pictures up tomorrow of the head.