2.6 head on 2l

[4g54gemi]

Can you put a 2.6l head on a 2l. Im looking at doing this to lower the comp in my 2l to around 7.5:1 (which the 2.6 head I have would do that). Are the 2.6l valves bigger? (astron 2 sigma head). If they are would they clear the smaller bore? Thanks

[rob020]

astron 1 and 2 heads are identical apart from the cams (or so i believe) putting an astron 2 head on any astron 1 (2l or 2.6) should lower its compression to about 6.5:1 (its actually the dished astron1 pistons that do this, swap to the magna flattops and youll get standard compression)

valves and ports in the astron 2 head are bigger, i think ports are 42 compared to 37mm?? cant remember about the valves...
the head will fit fine, i run a magna head on my astron 1 2.6, it loves it

[webby]

2L should already have flat tops, or at least the import ones do. Never seen the insides of an ADM 2L so I wouldn't really know about them.

[4g54gemi]

Yeah Id say it would have flat tops as they have 9.5:1 standard and without machining alot off a standard 2l head you wouldnt get that much using dished pistons in a 2l. The 2.6 head I have has a 73cc chamber so it should end up with 7.5:1 . Im just more worried about valve clearances to the bore?

[rob020]

try a 2l head gasket against a 2.6 head, see if the valves touch it
im sure ive heard of magna injection on original turbo blocks (2l) though

[81GL]

astron 1 and 2 heads are identical apart from the cams (or so i believe)

Quite a lot different actually.

As you have already found, the chamber is a bit bigger on the astron 2's (and this will vary again depending on which casting of the head you have, above exhaust port 2 there is a casting like M6 or M9 etc)

Valves will be fine. I'm running an astron 2 head on my 2lt no troubles, & thats with 3mm removed from the head!!! Before I did this, cheaterparts was playing with a similar set up with out issue.
Naturally, dummy fit the head and turn the engine over by hand to ensure things are as they should be.

You will also need to use a 2.6 head gasket, the 2lt item will not seal.

[DanTurboLancer]

Ive never seen a 2litre and a 2.6 head side by side so i could give any comparison.
But i know that the factory 2Litre Turbo engine, speified that they used a 2.6 head...

So i cold only assume there would be some comparative differences?

Combustion chamber cc, cam profile...??


7.5:1 is pretty low, 6.5 is very low any reason you want to make it that low?
It will make it abit sluggish off boost

[4g54gemi]

The 2.6 head I have is off a GN so it has got bigger valves. I sat the 2.6 head on the 2 litre with no gasket and opened the inlet valve and it tapped the bore so I had to die grind the bore a lil bit for the valves to clear the bore.



The 2 litre head was 49cc and the 2.6 is 70cc. Comp was 10.2 now at 7.7 . Comp was high as pistons are out the bore 0.5mm.

[81GL]

The 2 litre head was 49cc and the 2.6 is 70cc

Keep in mind... that your technically not comparing a 2.6lt Vs 2lt there, its more an astron 1 Vs the astron 2.

& yeah... i have a similar modification on the bore