Head gasket

Submitted: Friday, Sep 11, 2015 at 08:55
ThreadID: 130261 Views:5910 Replies:5 FollowUps:5
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Hi I'm replacing the head on my 92 model landcrusier ute 1hz motor. The old head had a 3 notch 1.35 gasket. The vrs kit I've order has the 5 notch 1.45 gasket in it. I was wondering if I was to use this gasket would it being thicker affect the performance ect of the motor.
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Reply By: pop2jocem - Friday, Sep 11, 2015 at 10:47

Friday, Sep 11, 2015 at 10:47

From memory the ex factory gaskets came in 5 different thicknesses. For whatever reason the spare part replacements only came in 3 different thicknesses. Once again from memory it was something to do with piston protrusion above the block deck. When I replaced the head on the original engine in my 91 model I went for the next available thicker one. I can't remember what notches were involved but I thought the replacement gaskets came with 1, 3, or 5 notches but way too long ago.
I don't remember being able to detect any difference in performance or starting.

AnswerID: 590253

Reply By: Erad - Friday, Sep 11, 2015 at 11:42

Friday, Sep 11, 2015 at 11:42
Performance will affected. By having a thicker head gasket, this would give more clearance and reduce the comrpression ratio. How much drop in output is difficult to say, but there will be some drop. Compared to a blown head gasket, the difference will be huge anyway and you would not know if it could have been better or not.
AnswerID: 590254

Reply By: Ron N - Friday, Sep 11, 2015 at 12:57

Friday, Sep 11, 2015 at 12:57
Yes, it will affect the performance of the engine - only moderately - but the greatest potential for change in performance will be in starting, particularly on cold mornings.

Diesels rely on several things for good, easy starting - the primary one being adequate cranking speed by the starter motor.
The next most important thing is adequate compression pressures when cranking, which is affected by compression ratio and proper valve sealing.

A thicker head gasket will reduce the compression ratio by enough to change starting characteristics from easy starting to hard starting.

The recommendation from ACL is to utilise the same number of notches (thickness) in the replacement gasket, as in the original.

Possibly more importantly, is that you do a piston protrusion check accurately on all pistons, and fit the thickness of gasket as indicated in the ACL chart.

ACL chart

Cheers, Ron.
AnswerID: 590256

Reply By: pop2jocem - Friday, Sep 11, 2015 at 17:11

Friday, Sep 11, 2015 at 17:11
Original factory engines came with a selection of 1 through to 5 notches.

The replacements from memory and according to ToyoDIY gave a choice of 1, 3 or 5 notches.

So supposing you found your gasket had 4 notches.

Would you use the 5 notch and lose all that compression, as others seem to think will happen, or go to a 3 notch and risk the pistons getting up close and personal with the cylinder head??

In your case Nick, I would chase up a 3 notch as per original if possible. If not the choice is yours.
AnswerID: 590260

Follow Up By: Ron N - Friday, Sep 11, 2015 at 20:11

Friday, Sep 11, 2015 at 20:11
Pop, to answer that question - a lot depends on the general engine condition!
I haven't seen Nick mention if he's fully reconditioning the engine or just doing a top overhaul on a 500,000 km engine - and leaving the rest, as-is!!
In that case, you're best advised to leave a bit of room for gudgeon/big-end bearing slop! [;-)

Pulled an ancient Caterpillar RD-4 engine apart, a while back - some of the big-end bearings had between .030" to .050" clearance!
I wonder why she had a broken crank! LOL

Cheers, Ron.
FollowupID: 858258

Follow Up By: Slow one - Saturday, Sep 12, 2015 at 07:11

Saturday, Sep 12, 2015 at 07:11
That is one very old tractor. I remember we had one on the property in the late sixties and we stiff used it on occasions for general light work.

I remember it also had a logging winch and a small spear on the bull blade.

FollowupID: 858267

Reply By: howesy - Friday, Sep 11, 2015 at 19:37

Friday, Sep 11, 2015 at 19:37
Head gaskets were made in 5 grades
1 - 1.25mm
2 - 1.30mm
3 - 1.35mm
4 - 1.40mm
5 - 1.45mm

only grades 1, 3 , and 5 are used in rebuilds based on the piston protusion as measured.

Gasket 1 is used for protrusions under 0.525mm
Gasket 3 is used for protrusions from 0.526mm to 0.625mm
Gasket 5 is used for protrusions over 0.625mm

DO NOT re-use head bolts on a torque to yield engine. Buy new bolts and from memory its about 38NM (check that) then 2 times 90 degree pulls in sequence on about 28 head bolts and your arms will feel it I had a guy pulling the bar as i was pushing on the last pull.

Hope this makes it clear and helps you.
AnswerID: 590266

Follow Up By: howesy - Friday, Sep 11, 2015 at 19:42

Friday, Sep 11, 2015 at 19:42
just as a tid bit at cranking you should be around 526psi in a perfect world and no lower than around 380 for servicability, and perfect compression is 22.4:1
FollowupID: 858253

Follow Up By: howesy - Friday, Sep 11, 2015 at 19:44

Friday, Sep 11, 2015 at 19:44
permaseal part numbers for grades 1, 2, and 3

Grade 1: 1.25mm S2033SS
Grade 3: 1.35mm S2034SS
Grade 5: 1.45mm S2035SS
FollowupID: 858255

Follow Up By: howesy - Friday, Sep 11, 2015 at 19:51

Friday, Sep 11, 2015 at 19:51
OOPS !!!!

Sorry that was 1HDT protrusions


1HZ Engine piston protrusions for gaskets

less than 0.455 mm use Grade 1
0.456 to 0.555 mm use Grade 3
more than 0.556 mm use Grade 5

Thicknesses are as quoted

FollowupID: 858256

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