Block surface question

[SC61 MK3]

I am fixing my 7mgte which had a bhg. I already got the head machined and I'm going to be using a cometic mhg and arp's. The know the block should be lapped by hand but i do not have access to a lapping tool.

Those of you that had your block surfaced by a machine shop do i have to disassemble the block and then get it surfaced or can they do it with everything still installed??

I would perfer to do this myself by hand is there anything i can use besides a lapping tool??

 

[GrimJack]

They will need to disassemble the block to do it right. The last thing you want is metal shavings caught in the rings - and worse yet, washed into the oilpan and clogging up your oil filter.

You do not need to hand lap the block for a cometic MHG, just make sure the machine shop can provide the Roughness Average (RA) that's required.

 

[IJ.]

Hand Lapping while smooth will rarely ever be flat and this is just as important as the MHG can't deform when installed like a composite HG.

 

[SC61 MK3]

well I dont think getting the block machined is an option I only have a few days to get the car running and the only machine shop around here takes forever.

I will verify the deck is not warped by using a stright edge. but i need to know the best way to remove the stock head gasket crap left over from the bhg. I have to get the block surface as smooth as possiable and pray that my cometic with brake quite will hold.

i've heard of people using multiple grit sand paper, various griding wheels and some stones. what would be the best option??

 

[SC61 MK3]

oh i already have a gasket remover spray and a gasket scraper and it aint doing shit

 

[IJ.]

Go buy a composite HG ....

 

[clifftrail]

If you rush it, you'll only be doing it twice.

 

[GrimJack]

I use a wire wheel to pull off the old gasket material. Just make sure the material the wheel is made of is softer than the cast iron block.

 

[GrimJack]

If you rush it, you'll only be doing it twice.

Agreed.

 

[suprarich]

I use a wire wheel to pull off the old gasket material. Just make sure the material the wheel is made of is softer than the cast iron block.

Yes, brass type small wire wheel in an air die grinder is the best. Fill your cylinder bores up with clean rags to keep any material from entering the bores.

 

[SC61 MK3]

well i managed to get it pretty clean after a few fucking hours. i think i am gonna play it safe and install the stock head gasket and arp's. i should only push this motor to around 400-450whp

i have a another engine to build so i guess i'll have to wait to start making real power (550-600whp)

 

[malloynx]

You shouldn't need to ever lap a block, if the shop can't get it that smooth (RA) find a differnt shop.

FYI shop in my town can cut to an RA of 4..

 

[Ckanderson]

Yes, brass type small wire wheel in an air die grinder is the best. Fill your cylinder bores up with clean rags to keep any material from entering the bores.

good idea... never thought of doing that!

 

[boltz]

The reason you need the motor dissassembled is because to deck(machine) the block surface don't they need the crank out so they can mount the block in their jig via the main caps? it is the only way to machine the deck Perpendicular to the cylenders. (non technical 90 degree to the cyls)

 

[Stretch]

Correct boltz.
eric