Lost Vegaz

Cruising around MSA's sit, came accross 2mm head gaskets. How much would that lower the compression ratio?? And what else do you need to do, to use it?? Longer bolts, chain, etc, etc

jfairladyz

I dont know how much it would off set compression ratio (you'd have to know the installed thickness of the stock head gasket to figure that out). As far as head bolts go: No you dont need to change those out for longer ones. They're plenty long. You should however replace them. Reusing head bolts are a big no no and shouldn't be done. They stretch when you use them and that throws off torque readings. So definitely swap them out for new ones. Stock are fine.

Timing chain will be fine. Typically you only have a problem when you shorten the distance between the cam and crank sprockets because this causes too much slack for the tensioner to pick up and also misaligns it. Installing a thicker gasket (raising the cam sprocket) will take some of the slack out of the chain. This isn't a problem cause it's slack the tensioner would've taken out anyways. So the tensioner just doesn't havent to do so much.

Other than that it's straight forward. When you move the head away from the block you really don't have anything to worry about like you do when you move it closer. Then you have to shim the cam towers, check for valve to piston clearance and stuff like that.

lifegrddude

Stock headgasket is about 1.2mm if memory serves me right.

NismoPick

I swapped out my goofy *** stock AutoZone headgasket for the MLS 2mm... Lowered the CR about .2 if I remember correctly. Tho now I wish I had gone w/ the 1mm. I've got a link to an L28 design website @ home... I'll post that link later tonight. You can change the headgasket thickness & see the change in CR.

Bleach

Chaning for new head bolts is optional. I have reused head bolts a couple times on the same engine with no problems. (non turbo) Although these L-series bolts do stretch due to the physics of metal, they are not the 'stretching' type of head bolt you sometimes find on other OHV engines. (vs. the Nissan OHC) Those 'stretching' bolts can not be re-used even once or they snap. (most of the time)

but many people rebuilding an engine or doing a good teardown of one choose to buy new bolts because it is just a better quality build. Especially on a modified turbo engine.

NismoPick

My next L28ET will be using ARP studs all around! Yummah!

SHADY280

I Had The Machine Shop Calculate Mine From When I Had A 1mm To A 2mm, The Change Was 1.2. P79 Head Decked 80 Thou With Flat Top Pistons 20 Thou Above Deck.

NismoPick

here's that link:

http://www.ozdat.com/ozdatonline/enginedesign/

jfairladyz

Thats definitely bookmarked. Cool link.

NismoPick

So using that link I posted... Stock CR is 7.353. With a 2mm MLS: 6.983.

I ended up shaving my head .020... so a 2mm evened it back out for me. I wish I had used a 1mm to raise the CR a lil.

jfairladyz

OUCH if you're running stock compression ratio already and installing that sucker on an L28ET. On a F54 non turbo block that would be a good idea if you wanted to add a turbo without the expense and work of installing dished pistons though. Or if you shaved your head the way Nismo did.

jfairladyz

Here's an awesome link I came across. You don't have to know any parameters. Alls you have to know are what parts you're using and it calculates everything for you. It has the 1 and 2mm head gaskets programmed into it too. It's not quite as in depth as the one Nismo posted but it's nice for some quick and easy info.

http://www.atlanticz.ca/zclub/techti...der/index.html

According to their calculator adding the 2mm gasket to an L28 will net you 7.84 on an NA motor. L28ET will get you down to 6.88. So basically, if you've got a turbo then DO NOT USE THAT GASKET. If it's an
81+ NA and you're looking at turbo motor type compression ratios.

nismo619

so if some one with a turbo car wanted a performence head gasket what size mm should they get ? hehehe im wondering for my car...

NismoPick

It depends on what else has been done to the engine & head. I had shaved the head .020, so my CR would be up a lil. I bought a 2mm to even it out, but I think a lil higher CR would have given me a bit more power.

The major variable when building an L28ET... is how much boost you will be running. The higher the CR (high CR = less combustion room), the less room for + boost (tho the #'s might be small, they do add up). So if you want to up the boost a lot w/o detonation, keep the CR lower. Newer cars have higher CR's due to better ECU's & different engine designs.

hopefully that all made sense... if not, someone can add their 2 pennies.

For a stock L28ET... a 1mm might be best, as it will increase CR, just enough... but I wouldn't take it over 12 or 13psi stock.

jfairladyz

The 1mm gasket will raise the compression ratio by a negligable amount. The 2mm will lower it enough to the point that you'll wish you hadn't gone that route (unless you've got a situation like Nismo's). The stock gasked is in between but a lot closer to the 1mm. I think it's 1.2 like somebody mentioned earlier. A head gasket isn't going to do much in this case to help performance. But a 1mm would be the best choice here as its going to handle more boost then the stock one and still wont raise C/R enough to cause any problems.