Possibilities

[Anton GX K]

Datsun gx coupe 1975

 

Hi can someone please tell me which piston to use that will give me a lower combustion ratio Im looking to get 7.5-8. I currently have an a14 engine that I am repairing. I hit big end bearings on 1 an 2 piston because of oil pressure

[datzenmike]

If you measure the bore and it is within specification then just hone the cylinder and replace with stock rings on the pistons that were removed when replacing the damaged parts. (rod and crank) If the engine is tired and you are rebuilding it, have the block bored out to the next over size and replace the pistons and rings with the next over size to match

 

Lower compression is less efficient and you will loose some power. There's no advantage to this. The A14 is 8.5 keep it that way.

[Draker]

Welcome to Ratsun!

 

Cool to see new members from around the world.

[Anton GX K]

Sorry i left out the part of turbo charging the engine. I thought the stock 1400 c/r was 9.5:1 but cool anyway, Can I put two standard head gaskets ontop of one another to drop the c/r?

[datzenmike]

I'm not a fan of reduced compression ratios for a turbo. It will be a pig anytime off boost, which will be most of the time. There is an increased risk of detonation true. The engine self ignites the fuel simply from the heat of compression, just like a diesel. Simply lower the heat inside the combustion chamber.

 

Oil cooler will remove internal engine heat and take a load off the rad.

Larger rad will prevent heat spikes from turbo use.

Draw your intake air from in front of the rad... avoid hot rad air from behind it.

As the turbo compresses the air, the heat in it is also concentrated so an inter cooler can be used to remove some of it.

Run cooler range spark plugs so they don't glow from the heat and become an ignition source.

Run higher octane gas. Increasing the octane level makes gas harder to ignite. It becomes less sensitive to dieseling.

Add a water alcohol injection system. Alcohol absorbs heat as it evaporates dropping the intake air temperatures.

Invest in an ignition retard system under boost.

[Anton GX K]

Thanx mike I'll see to it to definitely take your advice I'll post updates as I go and what route I chose. B.t.w are you some sort of mechanical masters engineer? Or just a datsun engineer cause it sound's like you know alot!!

[datzenmike]

All the above mentioned will apply to any gas turbo engine. I read a lot too.

[Anton GX K]

Hi Mike i've got a question. Im busy with my H72 head now and I have a worry about play on the exhaust valve guide's. Sould I replace the guide's?

[datzenmike]

They should be measured. Usually (with spring removed) the valve tip is pushed side to side and the 'wobble' measured with a dial gauge. I don't have this spec for an A series head, but someone here might.

 

For example... on the L series exhaust, the amount of deflection is 0.008" or more, it exceeds the 0.0039" clearance between the valve stem and the guide. This is an example and for an L series. The A series may be different 

[Anton GX K]

Hi can some please tell me what the preload is on a datsun b110 gx?

[Anton GX K]

Hi I started wondering about boring out the block of my a14 to 79 mm per piston. Do you get a oversize piston for that or can you get it for the a15 or what other pistons can be used with the same connecting rod? Or what piston and connecting rod combination can be used with the least amount of special modifications?

[Anton GX K]

I also want to know which oversize valves can I use, do you get a14 aftermarket oversize valves?

[Anton GX K]

Hi Datzenmike, what other rings do you get for a nissan vq20 motor

[datsunfreak]

Hi I started wondering about boring out the block of my a14 to 79 mm per piston. 

 

FYI, we bored one to 78mm and couldn't get it to stop overheating. The machine shop theorized that a 2mm oversize bore is probably too far and made the walls too thin.