Block Prep

[SpoonyDC5]

just wanted to get you guys opinion on best way to prep the block to get mated up with the cylinder head again. cylinder head got back from the machine shop and wanted to kno if a high grit sandpaper could be used to get all the shit off the block or what prior to installing new HG and fresh CH. thanks in advance

-Justin

 

[IJ.]

What type gasket?

 

[SpoonyDC5]

hks mhg 1.2

 

[IJ.]

Block really needs to be surfaced if you want it reliable.

 

[SpoonyDC5]

and if thats out of the question?

 

[IJ.]

Sell the HKS and buy a composite.

 

[SpoonyDC5]

lol oh gosh, im new to the supra world whats the reasoning for this and where can i find a good composite?

 

[IJ.]

Unless the block surface is smooth/flat/true it will fail with the HKS, "some" people have rolled the dice and had success but the vast majority fail and end up redoing the jpb properly and at worst end up doing a full rebuild after the Coolant/Oil mix trashes the bearings.

Toyota HG is quite good quality, or any kits that use "Stone" HG's (they make Toyota's gaskets)

 

[92nsx]

EDIT: Ian, with his lighting fast typing beat me to it.

OEM toyota HG for composite.

 

[thorpedo]

-Scrape the block being very careful not to scratch the surface AT ALL
-Wet the surface with wd40
-Pick up some 400+ grit emery cloth and sand using a sanding block
-Examine the surface for any nicks, gouges, pitting or wear around the cylinders. Anything you can catch your fingernail in or feel will likely cause the gasket to fail.
-If there is any way you can get your hands on a straight edge and feeler gauges verify that the block is perfectly flat.


If you are dead set on using a MHG this will maximize your chances of being succesful without getting the deck machined.

 

[IJ.]

-Scrape the block being very careful not to scratch the surface AT ALL
-Wet the surface with wd40
-Pick up some 400+ grit emery cloth and sand using a sanding block
-Examine the surface for any nicks, gouges, pitting or wear around the cylinders. Anything you can catch your fingernail in or feel will likely cause the gasket to fail.
-If there is any way you can get your hands on a straight edge and feeler gauges verify that the block is perfectly flat.


If you are dead set on using a MHG this will maximize your chances of being succesful without getting the deck machined.

Do all of the above then report back here after you wind the boost up and it fails.....

Keeping in mind that the engine may fail well before the HG from the crap you've introduced after sanding the deck and not plugging the Oil galleries/ drain passages or sealing the pistons to the bores so the iron/gasket crap can't find it's way into the top ring land..... :nono:

 

[suprarich]

I second the fact that if the block can not be removed from the car then MHG is just not a realistic option.

 

[IJ.]

Thanks Rich!

Appears I've stepped on a few toes with this subject, my advice is given to provide the best chance for success as I tire of the "Built a 7M and am having xxx issues" resulting in part outs a few months after kids have dropped ALL their coin into a car that "could" have been fine if they hadn't skipped a few essential steps... :nono:

 

[Dirgle]

The OP hasn't gotten back so I'll give him the benefit of the doubt and believe he is weighing his responsible choices.

As far as the original question goes Metal head gaskets require an extremely low RA (roughness average) HKS is usually in the 10 to 20 area depending on HG type. These are mirror finishes. Incredibly smooth. The surfaces also have to be completely flat, something unachievable with simple sand paper at minimum a lapping block is required. After all this is done you need to figure out how much material has been removed from both the head and the block, and use this to choose your MHG thickness. That is why most people wait until after the machining has been done to purchase the head gasket. Done correctly the MHG is extremely durable, but it's reliability is exponentially influenced by the amount of prep work that went in before hand. The OEM Toyota HG is fairly durable for mild to modest power goals, as long as considerable attention is paid to proper and safe tuning. It's installation requirements are far more forgiving than a MHG, but preparation is still key to reliability.

 

[kneedragger85]

If you are dead set on using a MHG this will maximize your chances of being succesful without getting the deck machined.

Maximizing his chances is not worth skimping out on doing it right. I prefer leaving nothing to chance on these engines. Slap on a stock gasket and ARP studs or shell the money to deck both surfaces to an acceptable RA for the MHG and add ARP studs.

 

[89supra7mgte]

The po of my car had installed a jdm engine along with arp and mhg (hks 2.0 i believe, thicker than my 1.2 i purchased) anyways i bought the car with a bhg coolant in oil, but no signs of how it got there? Anyways i replaced the mhg with a toyota oe cause i could not get the block out at the time. When i pulled the head off there were no signs of where it was leaking, and he did take the proper steps in having block prepped, can i still reuse this gasket for my spare block, and what is required to use it again? Also what is the max that the oe can handle? (hp, tq, boost) I am in the process of building my other engine but wanna get the most i can out of this one. sorry for the attempted hijack.

 

[WhtMa71]

I have a Cometic MLS gasket sitting the corner of my room for when my composite gasket blows again. Notice I said WHEN..I'll be doing a full rebuild when that time comes.

 

[hvyman]

WHEN only comes to mind when exceeding the limits of the composite hg. doing it right with stock power levels and no abuse it will last for a long while.

 

[89supra7mgte]

What are the power levels of the composite, with arp studs, and proper installing and cleaning?

 

[suprarich]

Thanks Rich!

Appears I've stepped on a few toes with this subject, my advice is given to provide the best chance for success as I tire of the "Built a 7M and am having xxx issues" resulting in part outs a few months after kids have dropped ALL their coin into a car that "could" have been fine if they hadn't skipped a few essential steps... :nono:

We just see alike! And your advice should be taken as the rule because you really don't give an opinion unless it has been tried and true.

What are the power levels of the composite, with arp studs, and proper installing and cleaning?

There really is no threashold. Each make of composite gasket will fail at a different level than the next. Also, it is really not the amount of power, but the cylinder pressure either from the amount boost, nitrous, or detonation that causes the gasket to deform and push out. At least in cases where the gasket is over powered.