Lapping plate for cleaning a cylinder block face in situ.

[dawesy]

Can anyone recommend anything to Lapp the face of a cylinder block in situ ( 4cyl car engine)
Basically I just want to make it smooth and even before fitting a multi layer steel headgasket. These need a smooth finish.
The block was decked about 15,000 miles ago but the headgasket has failed (thermostat failure) don't really want to pull the block. The head isn't a issue as I can have this skimmed if needed.  Block is cast iron by the way.
What is the best tool for the job. Had a look at lapping plates but they seem either too small or to big and expensive. Anything else I can use?

[awemawson]

Sheet of plate glass and some emery paper ? It'll reveal the problems if they exist

[dawesy]

Excellent. Don't know why I didn't think about that

[BaronJ]

Hi Lee,


I use a porcelain bathroom tile as both a surface plate and for lapping on.  Fine abrasive cloth held down with pva (it needs some time to set) works great and washes off with hot water when you need to remove it.  I did try double sided adhesive tape without to much success and its a pig to clean off.


 

[Pete.]

You'll need to come up with a very good idea to prevent abrasive slurry running down your cylinder walls and getting trapped in the piston clearance and ring grooves, or you might be lapping the bore too when it's first run. I suggest plasticine around the edge piston crown for a secondary line of defence followed by a close-cut plastic disc fitted a short way down the bore with bathroom sealant or something similar. You can cut away the sealant later with a stanley/razor blade. Lap using something that is definitely not going to bend with hand pressure or you'll bow the top of the block.

[Fergus OMore]

Personally, I think that you are wrong on several counts.
Frankly, buggering your head gasket from a thermostat fault is questionable. I've done quite a number of heads in the past and the first question that I would raise is whether you removed and replaced the repair with new bolts etc. The next question is whether you 'blued in' the top of your cast iron block 15000 miles ago and whether you have checked the block yet again- on this, the second blow up. As you inform us that you do not possess anything, I would assume to be correct.

You can- or I could- blue in the block and scrape it- assuming that nothing really serious exists but the cheapest and most reliable repair is to have BOTH the block and the head checked and flattened.
Again, at the end of the day- when all is well again, you will need to torque down the head.

Having said all this, the cylinder head might not be strong enough now to stand the weaknesses already created. I've had to be aware of oil ways which are hidden just below the face of the head- and if it is a cast iron block- porosity.
I once skimmed a 12G295 Mini Cooper 998cc block, opened up the ports, reworked and rebalanced the combustion chambers etc for larger valves- and the lot wouldn't turn over. I pulled the plugs, and got an eyeful of glycol from a unseen hole 

Read Pete's comments about 'blowing the block' His views are worth digesting.

Norman

[chipenter]

Why not use the head remove any locating dowels , use a figure of eight motion was standard pratice for racing 50 years ago .

[dawesy]

Should probably give you more info on the engine.
It's a Toyota 3S-GTE but bored and stroked to 2.2 Ltrs from 2.0. It's running over 500hp.
The thermostat failed just before Christmas temps hit a max of 115deg c. Before this it ran absolutely fine. After the stat replacement the temps would rise significantly only on boost. Cruising round they were fine. I expected it to be a cracked block as this is common on this engine and I have had two go in the past.
On removing the head I found the cylinders in perfect condition but a small dark spot on the headgasket suggesting the gasket had been passing combustion.
Head studs are uprated items from ARP.
This engine was fully built 15000 miles ago. Both block
and head were decked and faced at that time.
All I want to do is ensure that the block face hasn't been marred by the escaping gas.
Pete thanks for the suggestions on protecting the bores. It was something I was thinking of ;)

[Pete.]

I expect that what happened was the gasket let by, shooting up the temperatures making you think the thermostat was to blame. Did you use the ultra-torque grease that ARP supplies for torquing the bolts? If not they might have fallen short of torquing spec.

[dawesy]

Yeah I did. It may have been a bit of both to be fair. I tested the stat and it was goosed. I've built countless of these engines ( including this one ) and to be fair the head nuts didn't seem as tight as normal. They were defiantly torqued up to spec so have either stretched or the headgasket has settled causing torque drop off.
I originally built the engine for a friend who after losing his job sold it to me. It had never been in the car. He used a cometic gasket which I had never used. I normally use a HKS one in big power builds. So not sure if it's a gasket issue or not I'll be using a HKS one this time though.
I'll also retorque the head studs after 500 miles or so even though not specified by arp.

[doubleboost]

A small surface plate or a brick with 80 grit emery paper
Put some thick oil down the bores this will keep the bits out of the top ring
Are the head bolts not "stretch bolts" a small initial torque plus a set amount of degrees (use cv grease under the head bolts nuts) gives a nice smoothe torque
The head will be warped if it has been hot but a cast iron block wont move much
John

[Pete.]

I use M12 x 1.25 12.9 socket caps on my bike torqued to 75 foot pounds, those things ain't stretching much I've heard of people taking them to 100 but I didn't have the guts to go that far.

I use a standard gasket but Cometic seem well-regarded by most of the people I know.

[dawesy]

Arp arnt stretch studs. 65ftlbs is all the torque they take ( using arp assembly lube) they are reusable if still in spec   
I have herd of heads lifting but normally only above 2.2bar boost. I'm only running 1.8 so that shouldn't be happening.
Thanks john. Not got round to measuring the head yet. I'm expecting it to be a tad warped.

[doubleboost]

Modern engines are highly stressed before you even start modifying them

John

[dawesy]

This is true john. Tbh if you think about it it's over 200 hp per ltr.

[doubleboost]

We were not getting that 20 years ago with BDAs mind no turbo

[Buksie]

Hi dawesy
Maybe a little late, but I have seen my friend lap his 4AG turbo motor block using a ADE engine cast iron cylinder head as a lap, the engine was removed and stripped to prevent the paste from going between the pistons and sleeves and some serious scrubbing and high pressure cleaning was necessary after the lapping was complete to remove the remaining paste.
It is definitely the way to go if you want to eliminate head gasket leakage and ensure a perfectly flat surface but it is a very slow process and believe me hard work as well.
It is doable but a lot of work and I will not recommend doing it with the engine in place as the crap will enter every oil and cooling channel on the block deck and run down the sleeves, so the engine will require thorough cleaning from inside.
Good luck anyway.
Best Regards
B.