mx5cartalk.com

Hi all,

I cooked my motor at the start of the year and blew the head gasket. Compression was down and there was steam coming out of the exhaust and cam cover breather/catch can.

I changed the head gasket thinking that would be quick fix and i could be on my merry way! Wrong!

As a result of the overheating it also made the alloy head "soft" and i had little or no compression in any of my cylinders. So off came the head and down to B'n'B Engines on westal road. They did a hardness test and some sort of valve seat seal check and turns out the head had gone soft and none of the valves were seating properly! = no comp

So i got my hands on another head and took it straight there to get checked (apparently soft heads are common on the BP motors ). They tested it and all was good so i had them "deck" it and re seat the valves and install new valve stem seals.

I got it back and proceeded to re-install it using a KP brand gasket kit made in Osaka Japan (uni torque). I sprayed the holymer spray stuff on each side of the head gasket and put it in, head on , then tightened the ARP head studs down in 3 stages. working my way out evenly from the centre...... Torqued to 74 foot pounds.

Anyway all back together and she had 190 across all 4 and fired up in the key turn. i was happy

The only other thing i had changed while the head was out was that i took off the water lines that heat the throttle body and oil filter mount thingy ( i have after market oil cooler) and blocked the two 8mm outlets at each end of the head!
Anyway.......car was blazing and it was all smiles!.....until ! One of the new 8mm water line blockers split ! I only notice when steam started to come out on the drivers side of the bonnet. I looked at my temp gauge and it said 85.....i headed straight for the pits and by the time i got there the temp said 120 ! Oil temp was 80-85 deg max the whole time !

I fixed the split blocker and tried to start it after it had cooled..... it just cranked over and not firing at all ! seemed to be same as last time....no comp so no fire! I pulled out the spark plugs and saw my reflection in the surface of the coolant sitting on top of my pistons (1,2). Day over for me

So i drained the coolant to pull the head off and there was still 4.5 litres that came out of the radiator drain plug (meaning there should still be a little in the re-route hose etc) so i figure it didn't get that hot and the 120 deg i saw was probably a steam temp because the temp gauge sensor is in the top of my rad and would have been out of the actual coolant level.

So really the head gasket should not have blown..... ?????? Did i torque it down wrong ? am i using the wrong head gasket ? (its the correct one for my model) Is the SE / SP model head gasket the same style multi layer with no ring around the bores?

Im running 19 psi boost and e85..... These multi layer metal head gaskets dont have a ring around the bore like most other head gaskets ive seen....wondering if high boost causes them to blow through ??

The perils of racing ... Bad luck.

Torquing sequence is:


You should not use any gasket compound on a head gasket, just a thin smear of oil on the block, gasket and head surfaces.

You need to check that a new head gasket is exactly the right one for your engine. Not all BP gaskets have the same perforations, even Mazda can supply one that's not right. Basically you need to check that every matching pair of holes between the block and the head has a matching hole in the gasket. I've seen some gaskets which don't have all the holes around the exhaust side of the combustion chambers and these are the most critical ones for high performance usage.

You realise you'll need another hardness check on the head, a head shave and a check of block straightness, don't you?

He may find the head and block are straight and fine to reuse.

Dann

Just got back from the engine shop. They said the Head is stuffed! gone soft again ! yawn.... was 59 and 64 on exhaust side of pistons 1, 2

So i need another head..... Can i use a ford laser one ? what other BP heads can i just get from a pick apart and throw on.

Yeah Dann i read a couple of threads on the head gasket hole a while back...... the one i put in was same hole layout as the oem that came out.

Hi.
If you are running 19psi you should use a steel head gasket maybe Maruah.

wazman wrote:Yeah Dann i read a couple of threads on the head gasket hole a while back...... the one i put in was same hole layout as the oem that came out.

Wrong test, when you change heads you don't check if the new one is the same as the old one you check that the new one matches the holes in the block and the new head.

Waz
Have a read,some very good stuff here.
http://www.enginebuildermag.com/Article ... ishes.aspx

Im off to the pick-a-part to see if i can use a ford laser/protege/kia head...... my budget for racing is blown this year already so now i have to do what ever i can for a couple of laps!


whats the definition of addiction again ? lol

I thought i read in one of those head gasket threads that some of the hole may be ment to be blocked to create the correct flow for that particular head ?