Hiya, just blown the head gasket trying to race a mondeo st24, i already have a ported and flowed head but never got it skimmed how much can i take off to improve performance and to leave room for another small skim in case needed, and to eventurly run kent cvh21k cvh22k or cvh32k or simular lift piper, also any bad side effects., its 1.6 CVH Xr2 engine with a lean burn head. Cheers BAZ

 

just take it to a head specialist mate,why not try the place thats done a feature,in this mths performance ford! they look good!!

 

Cheers i live down in devon so they're arn't that many around i'll have a look in the yellow pages, i kinda had a garage i plan to use but they don't do engine tuning just rebuilding. so i was hoping to just to tell him the figures since it needs skimming anyway. Thanks Again

 

i had a 40 thou skim on my xr2 running a piper 285 cam and get your self a webber carb off a b or c plate xr2 they are alot better than the lean burn type carbs

 

Hiya thanks for your reply when you had 40 thou taken off was this for road use, or track, did it mess up idle, starting and did it have any other bad side affects also, did it improve performence much, say 2 - 4 hp or more, Cheers BAZ

 

Also whats the main way of telling weather a heads been skimmed before i think it was still on its original gasket when i replaced the stem seals about 3 months ago and i didn't have it skimmed then, would any 1 no what the thickness off the head is, or would you measure the Combustion Chamber deepness!. Cheers

 

You will NEED to bearuette it first to check the chamber volumes, it could have had a big skim already.

No good copying what someone else did when their head could of been unskimmed to begin with and yours might already be down 40 thou.

also you need to set the CR up specific to the cam if you are doing it properly, the hotter the cam the more CR you can get away with, so you need to make a final decision on that first too.

 

Thanks for your Reply, um Whats BEARUETTE mean,

I will aim to use the Kent cvh22k Sports R CAM (Power Band 2000>6500 rpm. Valve Lift .437" inlet / exh. Duration 274 inlet / exh) but won't get this for a month or two after the skim would it be ok to run the standard cam for a while, i don't want to go over the top so the car will hardly turn over or idle shit, just ok'ish idle and better performance. Cheers BAZ.

 

you use it to measure the volume.

if you get the CR raised a fair bit in preperation for the new cam and having it re-setup you shouldnt drive it till then, it could pink baldy otherwise because the timing will be too advanced.

Saying that, on a mildish cam like that you wont want much extra CR anyway, so on decent fuel you will probably get away with it.

Ask the cam manufacturers what CR they recomend

 

Thanks for your Help. i'll try and get in touch with them. how would i work out the CR, also i can always adjust the Ignition timing and i always use optimax.

 

To calculate the Cr you need to know:

The Bore and The Stroke (to work out swept volume)

then for unswept volume you need:

The compressed volume of your gasket
The volume in your head (the bit you are changing)
The dish of the piston
The deckheight of the piston




CR = (Swept + Unswept) / (Unswept)





If you can retard the timing you can make it safe to use mate

 

Cheers

 

U might have already done your skim m8 but as a guide, Ford put 2 half moon shape castings about 5mm below the head face. This is apparently the maximum a head can be shaved by without valve contact.

I have had an XR2i Hemi head skimmed down to those half moon indicators without any problems. New standard cam, lifters and a weber DFT carb make the Mk2 Fezza fly.

P.S. I use mine for racing, permanently around 7000rpm and have no problems hot starting although I think I need a motorssport head gasket to cope with the extra compression.

 

Cheers i already done it, now i only had 30 thou taken off since i wanted to save a bit extra incase i need another skim.

It goes better at higher RPM and doing motorway work but i find it make's it a bit more sluggish around 1,000 say when pulling away. and seems to make it labour a tad more under accerlaration in higher gears.

But it seems to hold it's gear for longer now so it was worth it a lot better on the motorway seems to pull on a lot better. im not that bothered to be honest since i will just put a different cam in it, and leave it at that untill i get a 2 years no claims and i'll stick in a FRST engine and spend my money doing that up.

Thanks for ur help anyway.