Let's Talk 1.8L head and 2L block

[RRoller123]

I am curious about using the 1.8L head on a 2L block. It apparently will raise the CR about 0.5 or so, which is advantageous, an easy way to get a little increase in CR. Go from 8.1 to maybe the upper 8's?

First, Has anyone done this, and can comment upon the result?

Secondly, what about doing the large valve conversion on a 1.8L head, and then putting it on a 2L block?

I know that the 1.8L in stock condition IS an interference engine, and the 2L in stock condition is NOT an interference engine.

ALSO, the large valve conversion turns a 2L INTO an interference engine. I have done this on the engine in my car presently.

Who has experience doing this sort of thing and can comment upon actual results?

Thanks,

Pete

[chrisg]

I have not done it with any big valve or otherwise different head, but I've done it a few times, have a car with this setup & will certainly continue with this & others. The old thinking (based on what?) was that it was a better increase in CR than the math says it is, but for basically resurfacing a head, a new gasket & the work, it's fine at 0.5:1. It used to be an excellent recipe for a '79 mixed with a '74....slight CR, better manifold, maybe the 34mm carb, etc. If someone is building something completely with all of the cool machining, new pistons, etc., I guess the 1.8 head is a wash as anything will end up being rather highly worked & I think the builder will need to do the math to decide.

With regard to interference, I have always heard & even said that about the 2L, but it's a bit of a misnomer as I can assure you if the fuel pump lobe hits #2 piston there is interference. And, recently I had the experience of working with a 2L that had crashed valves due to cam pulleys being swapped. So, that's all to say I can't imagine - for myself - letting this particular point being a factor at all in considering a 1.8 head.

Being a little old school i guess, I still have some 2Ls and 1.8 heads lined up as spares for my own cars...but the reality, is their use will likely end up much more complex when the time comes.

[RRoller123]

Thanks for the input, that is very helpful. I was talking specifically about valve interference, but yes, that lobe on the Aux shaft will interfere in either engine if set incorrectly! I actually just had this happen, where I set the Aux shaft yesterday while fitting a new timing belt, pointing the hole to the TENSIONER bolt (that mounts the tensioner itself). NO! It interferes even here. Slight tick. Moved it over a little CW so that the Aux pulley hole points to the SPRING mount bolt, problem solved. I had no idea that it was that sensitive, but it is!

Pete

[MattVAS]

Countless people have done this conversion and yes the larger valves as you noted do make for interference.
However, it is still worth doing if you want to do it.

What I would throw out is that people claim to "feel" a difference when they do the 1.8 head onto a 2.0 block, but I don't think that is true.
I would say what they "feel" is a fresh valve job. People have no idea how out their valves are and then you go and do this and presto you "feel" more power or "runs better". But this IMHO is all due to a valve job that the original engine so desperately needed but never got.

But if you have the 1.8 head then I can't see ANY good reason not to do the swap. I mean you have the head

[RRoller123]

If it raises the CR from 8.1 to 8.53, there should be an actual performance increase to go along with that valve job?

[chrisg]

Yes, though compounded with a few dozen other potential factors, how much one "feels" it is questionable. I tend to go with the math & feel & folk knowledge, then weigh them all in to make a decision. Oh, also, practicality, so with all other factors equal & the 1.8 head in hand, that's good unless it's mated with largely domed pistons, right? In the past, it was often the choice between a rather "clean" 1.8 head and the ugly, mess 1979 2L head, so that was also a factor.

[RRoller123]

Here is a copy and paste from a prior post here on the forum, "budget 2.0L build" or something close to that:

"Jon Logan (Midwest124.com) had an excellent write up on this in the Summer 04 edition of Ricambi, the bi-monthly publication of FLU. In the article he calculated and compared the Static compresson ratio of all combinations of stock 2L pistons, stock 1.8 pistons, Kobenschmidt pistons (1.6mm domes), Mondial pistons with 4.5mm dome, Mondial pistons with 8mm domes, 2L and 1.8L heads, and 2L and 1.8L blocks. You may be able to get reprints from him or FLU, or I could make a copy of the article to send to you.

Here is a list of his calculated compression ratio results:

2 Liter Block and Head and Stock 2L Pistons---- 8.1
2 Liter Block and Head and Stock 1.8L Pistons---- 8.17
2 Liter Block and Head and 1.6mm Dome Pistons---- 8.85
2 Liter Block and Head and 4.5mm Dome Pistons---- 9.93
2 Liter Block and Head and 8mm Dome Pistons---- 10.75
2 Liter Block, 1.8L Head and Stock 2L Pistons---- 8.53
2 Liter Block, 1.8L Head and 1.8L Pistons---- 8.61
2 Liter Block, 1.8L Head, 1.6mm Dome Pistons---- 9.37
2 Liter Block, 1.8L Head, 4.5mm Dome Pistons---- 10.62
2 Liter Block, 1.8L Head, 8mm Dome Pistons---- 11.57
1.8 Liter Block and Head, Stock 1.8L Pistons---- 8
1.8 Liter Block and Head, Stock 2L Pistons---- 7.93
1.8 Liter Block and Head, 1.6mm Dome Pistons---- 8.75
1.8 Liter Block and Head, 4.5mm Dome Pistons---- 9.96
1.8 Liter Block and Head, 8mm Dome Pistons---- 10.91
1.8 Liter Block, 2L Head, Stock 1.8L Pistons---- 7.58
1.8 Liter Block, 2L Head, Stock 2L Pistons---- 7.51
1.8 Liter Block, 2L Head, 1.6mm Dome Pistons---- 8.24
1.8 Liter Block, 2L Head, 4.5mm Dome Pistons---- 9.29
1.8 Liter Block, 2L Head, 8mm Dome Pistons---- 10.1

Of course, if you have modified combustion chambers, shaved heads, decked engine block, different thickness head gasket, etc. then the numbers will be somewhat different. His article includes the dimensions for his components."