[kingjnr2677]

Hi All,

I would greatly appreciate any advice on what the piston to cylinder clearances should be on a Suzuki Lj80v f8a engine.

A little background to this request is as follows:

I purchased a 1981 Suzuki Lj80v last year and after driving it for a few days realized that the head gasket was gone and eventually bit the bullet and decided to rebuild the motor (once to many at the side of the road waiting for it to cool down to add water).

Upon striping down the engine I found that the head gasket was blown between the water gallery and cylinder 4 and had been for a long time as the bore had become pitted due to water sitting on top of the piston when not running.

Therefore I decided to go the full hog and strip the complete motor down for a complete overhaul e.g. New shells, pistons, oil pump, water pump, timing belt, fan belt, carb rebuild kit, distributor points/cap/rotor arm/leads etc along with sandblasting and painting all the parts prior to rebuilding.

The cylinder head and block were sent away and had the following work by a machine shop carried out:

- Cylinder head resurfaced
- Cylinder block gasket surface resurfaced
- Cylinder block rebored to suit +1mm oversize pistons (I supplied a new piston to the machine shop to allow them to rebore to suit)

This now leads me on to the situation I am currently in.

Upon cleaning and preparing all the parts I decided to measure all the equipment to ensure they were all within manufactures tolerances and if any were out I would replace them (found the valves and valve springs to be out with tolerances).

When I measured the bore and piston diameter I have found the piston to cylinder clearances to be out with the stated specs in the original service manual.

The standard specs state piston to cylinder clearance to be between 0.040-0.050mm

My calculations were as follows:
(One cylinder but all were about the same)

Piston diameter = 62.96mm
Cylinder bore = 63.903mm (average of 6 readings across the full bore)

Cylinder bore-Piston diameter = 63.903-62.96 = 0.943mm (total clearance)
Divide 0.943 by 2 to get the clearance gap between the piston and cylinder wall = 0.4715mm

0.4715-0.050(maximum specified clearance stated in manual) = 0.4215mm OVERSIZE!

Therefore I assume the machine shop would know what they are doing so am I missing something or are my calculations above correct?

Just wanting some advice on this prior to proceeding to build my engine.

Thanks in advance and Kind Regards,
James

[MacDaddy]

You might get more help if you ask your question here -

LJ50 & LJ80 Picture-Tech-Chat thread
http://www.auszookers.com/forum/viewtop ... =1&t=13051

And direct them to your thread here...

[losfer]

If your measurements are correct then the machine shop has made a huge mistake . Ive built a lot of engines and the general rule of thumb is .001" of clearance per inch of bore.

[losfer]

one other thing , the piston to wall clearance is total clearance so dont divide it by two !!!!

another thing you may want to check since you are doing a full rebuild ... ive seen a lot of gasket failures particularly in older f8's and f10's over cylinder 4 caused by the advance in the distributor not working , so once you get it up and running check the mechanical and vacuum advance . the distributor not advancing causes higher cylinder temps and eventual head gasket failure...

[kingjnr2677]

Thanks for the replys guys,

That's a major concern for me now as the measurements I have taken were checked and double checked and are definitely correct.

I very much appreciate your help on this losfer. Thanks for sharing your knowledge on this subject.

Using your advice I have calculated that the total clearance (thanks again) should be 0.002515" which ties in with the stated 0.0016" - 0.0020" in the original service manual.

The engine is now rebuilt and awaiting a new (old stock) distributor so this should eliminate the head gasket failure due to not advancing.

I guess all I can do now is check the compression readings and take it from there!

What you guys think?

Cheers, James

[losfer]

so the engine has been rebuilt ? with what clearances ? if it was rebuilt with the bores bored to those specs expect some huge piston slap and piston skirt failure not long after.. not to mention the ring end gaps would of been out of spec..?

[kingjnr2677]

Hi losfer,

Yes it is together as this was done before your reply thus I assumed that the machine shop would know the clearances required as I also supplied the piston for them to measure. I guessed that I must of been wrong with my tolerances.

I guess that's my big mistake assuming I was in the wrong. I did check the ring gaps and they were all within tolerances as specified in the original owners manual (bang in the middle of the allowable limits specified).

Therefore could it be the bore dial gauges and micrometer set I bought that is out of spec that is giving me false readings?(bought from Hares & Forbes).

I assume it would be obvious when started who is wrong, either me or the machine shop.

Definitely hope I'm in the wrong!

As if the bores were that far out should I have had issues with the rings as well!

Cheers for your advice with this one mate.

Very much appreciated!

Kind Regards,
James