.40over head gasket on .20over block?

[dsmcurse]

well heres my situation, FINALLY got the fully built motor done and in the new car. 6bolt block and head, block twenty over, ross 8.5 pistons and rings, eagle rods, clevite bearings, arp's, micro polished/ballanced crank, BSE kit/mod, head was super low milage never been shaved head. it was straight and super clean. i got new valves from a buddy that only had like 2 or 3,000 miles on 'em.

heres where i went wrong, i slid the valves through each of the guides, all felt good. put the valves in, put new seals on top, put the crower springs and retainers on, lubed and installed the crower 272's, installed head with multi layer metal head gasket(twenty over gasket with copper spray). i had the machine shop very involved and double checking every thing for me on the bottom end befor i installed at home. i didnt have the machine shop double check any thing for me on the head befor i installed at home. owch!

i get the car put together, car is low milage(59,000) still VERY excellent condition 95 eclipse, hx40turbo, full turbo header, big fuel system, big intercooler, dsm link v2, pretty much full set of bolt ons you know. all suporting mods, every thing is done right. but car wont start at all. it cranks and cranks and cranks by key with no starting.

ive got 100 miles on the car now, every time it was by a push start. car runs GREAT tho, super fast, awsome oil pressure, perfect water temp, no check engine light, boost comes on faster than i thought it would, but still wont start by key...? i thought bad water temp sens, no cold weather start up comunication to ecu right? put new water temp sensor on. still no start by key just cranking.

so i push start and let it run to normal temps, i pull all 4 plugs and disconect all 4 fuel injector wires, do a compression test, not good guys, two outer pistons 90psi, two middle pistons 50psi! i was shocked! so right away i pull the head to look at the guts of my engine.

five hours later i have my cylinder head on the work bench and im shining flash light through the intake ports and seein light through in my combustion chambers! crap! head isnt even close to bein air tight! it wont start by the key because when its cranking it wont build up enough air pressure to compress during a combustion cycle.

so the head is at the machine shop gettin a three angle valve/head grind. he promised me the valves will close in there air tight so... heres my question. i have a never before used cometic brand multi layer metal head gasket. its 40over tho and my block is 20. whats gonna happen? nothing? its like half a mm right? also i sprayed my old metal gasket with copper spray and the machine shop guy told me dont do that, its worse than goin perfect clean and shiney. is that true?

another question is the head should fix all my low compression issues right? when the car was running it didnt have huge amounts of air pressure coming out from the valve cover when the oil cap was off, and there was no pressure from the dipstick tube so... i just wanted to share my experience and ask for some insightfull advice from some of you experts. thanks and sorry for so long.

any thoughts....?

 

[BogusSVO]

were the cams in the head when you shined the light down the runners?

How are they doing the 3 angle Vjob? with stone seat grinders or a carbide cutter?
is the head getting surfaced?


Btw its .020 for a twenty over bore, not .20 that would be two hundred or over a 1/8th of an inch....

 

[2qik4u]

dont use a head gasket that doesnt fit!!! would you use .02 over rings on a .04 over motor???? NOOOOO!!! if it doesnt fit perfect dont use it! this will cause undo things to happen to your combustion chamber edges where your squish area is!! the area around the outer edges of your combustion chambers are designed to force your fuel and air towards the center of the combustion chamber as your cylinder comes to top dead center and this is a big part of burning fuel properly. if you mess with that and give it more room it will not work to peak performance and cause undo temp increases at the edge of your combustion chamber possible causeing it to burn the edge off!!!

 

[BogusSVO]

most all head gaskets have a larger bore, than the engine that is going on,

did you order a specific .040 over HG?

 

[spoonman]

Some machinists debate this but I believe that both MLS and pure copper gaskets should be used with head gasket sealer (copper spray). Composite head gaskets (OEM) should not be used with gasket sealer. The valves should have been lapped before they were installed. If the camshafts were installed when you checked the head, the valve stem height could be way off or the cams are not properly timed.

I am not picking on you but it is always wiser to have an experienced machinist assemble the engine. Even if you know what you are doing, you may not have the proper equipment or knowledge to check for the proper the clearance measurements.

 

[dsmcurse]

of course i had the cams removed when i shined the light, if they were bolted in tight some valves would be open. no cams means springs were closing valves as hard as they could and i could still see light through. yes i know the differance of.20 and.020. type-o. the debate of copper spray and no copper spray goes back and forth back and forth. seriously im lost as to what to think. and as far as .040 overgasket on a .020 block the differance is half a mm. theres 25.4mm in a inch, as in one mm is way way smaller than a 1/16th so now take a half of a milimeter. very small.2qik4u had a interesting point tho that makes me wanna check into it much more. machine shop man told me that 99percent of all head gaskets are stock bore only. larger bore blocks and stock gaskets all the time is what he said....? any more thoughts guys?

 

[spoonman]

Yes you can use an .040 over bore head gasket on a .020 bore engine. There will be no adverse effects.

This is experience from a real machinist, not a guess or what I think. Heck Flepro MLS gaskets only come in 86mm bore.

 

[dsmcurse]

so any thoughts on copper spray or dry?

 

[spoonman]

There really is a debate with machinists about using head gasket sealer, I am for using it on any gasket that is MLS or Copper. Composite gaskets do not require sealer.

Most people that are against using sealers and sprays argue that it does not allow the head to move or shift. This is insane because you do not want the head to move at all, that is why there are dowel pins in the block.

Trust me on this you want to use copper spray, it fills in small imperfections on the head and block surface to create a better seal.

 

[BogusSVO]

Most people that are against using sealers and sprays argue that it does not allow the head to move or shift. This is insane because you do not want the head to move at all, that is why there are dowel pins in the block.

thermal expantion... an alum head will grow and shrink faster than a cast iron block.. so all eniges move some... that is why the surface finsh has to be so smooth with a MLS gasket so the head can slide on top of it.

I am installing a factory MLS HG on a turbo sicon today, and will be using copper spray