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The mkiv Supra Owners Club

Head gasket replacement - some questions.


herbiemercman
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Hi Guys, There must be some of you who have undertaken this job, at this point in time i feel it is one of the most daunting jobs i am about to carry out.

 

Q1. Is it easier to take the engine out, and why?

Q2. Do you need to remove the camshafts to expose the 14 head bolts?

Q3. What is the maximum 'skimming' you can take off if you are applying a stock gasket?

 

I am aware that there are four critical factors in the job:

 

1.You have to loosen the 14 bolts in a certain order, and it has to be done in three stages, loosen a bit, then a bit more, then full loosening for removal.

 

2.Tightening the head bolts is the same sequence and procedure as 1. above.

 

3. Checking the 'flatness' of the head with a engineer's straight edge, and feeler gauge, max warp 0.1mm (.0004.inches).

 

4. Resetting the valve timing.

 

Any info will be much appreciated. Herbie.

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No 3 is 0.004" :) i'd also check it on a milling machine with a DTI or Verdict clock, and after reading

info from CW i'd run the clock along the cam journals as thats the critical part that needs to be inline

to 0.1mm or 0.004"

 

If i was taking the head off i'd be doing a full re fresh on it, valves, seats, guides, seals and re shim

 

CW also hardness tests the heads as well as far as i'm aware

Edited by Dnk (see edit history)
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Q1

On an NA it's just as easy to leave the engine in when removing the head, it's more the TT where it's easier to remove the engine as the turbo side is a pain to get to, especially if doing it on a driveway and no access to a ramp.

 

Q2

Yes, the cams need to be removed before you can gain access to the head bolts.

 

Q3

As dunk says, whilst the head is off get valves re cut, valves guides checked and new stem seals etc. Daft not to while head is off.

 

For your other questions;

 

1. Yes, head bolts need to be loosened in several passes in a particular order, you also need to do the same on the cam cap bolts when removing the cam shafts.

 

2. Yes, tightening is the same as removal in that there are several passes to tighten up to correct torque, then after that you have to turn bolts in order 90 degrees, then another 90 degrees.

 

4. I'd change cam belt and idler pulley whilst you're at it and also water pump.

 

 

I'd recommend downloading the TSRM app for your phone which gives the entire procedure.

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Hi Guys, Many thanks for your info especially, dunk and Jim, great diags etc. Mellonman yes that may be a good idea?

Do any of you have any advice on the actual type of gasket? i purchased the OEM standard kit for the NA.

I think owning a Supra would be a 'balls ache' without this club and its members. Herbie.

Edited by herbiemercman (see edit history)
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Hi Style, I have just ordered the tt gasket it is thicker and has more width surrounding the cylinders, it should drop the compression ratio from 10 to 1 to 9 to 1, i am hoping a remap is not required? This is not something i had thought of, do you know how it would afect the performance and any engine damage? Herbie.

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Hi Style, I have just ordered the tt gasket it is thicker and has more width surrounding the cylinders, it should drop the compression ratio from 10 to 1 to 9 to 1, i am hoping a remap is not required? This is not something i had thought of, do you know how it would afect the performance and any engine damage? Herbie.

 

I’m not 100% sure mate, was kind of wondering myself. It will definitely be less responsive off boost with the lowered compression and thinking about it logically, it will make less power on boost as well. If the air fuel mixture hasn’t changed and is being compressed less than before, I’d say that will result in less power. Getting the car remapped does mean you can up the boost though so you would make a lot more power safely...but only after a ££ remap

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