AMC heads for a 2056 build

[saggs]

I'm looking to build a 2056 motor for my split camper. I'm looking to get new heads and the question is, do I need 2.0 heads or can I bore out a set of 1.7 AMC heads? Will they flow any better or worse than a set of 2.0 bus heads? Not sure it's worth the extra coin for the 2.0 914 heads? Maybe it is. Not looking for a high revving motor just something with good torque and power.

[Andy Somogyi]

For a bus, the smaller valve heads will produce more torque at lower RPM.

Head port design is a delicate balance between flow velocity and volume. High CFM heads are important at higher RPMs, you have fast piston speed pulling air in at a good velocity, so you get good cylinder filing.

However large port sizes and valves typically hurt low rpm performance.

I’d save your money on heads and go with a longer stroke crank to push the engine closer to a square bore.


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[saggs]

I understand what you're saying as far as port size and intake velocity. That being said I may need a new set of heads and don't want to rebuild a 40yr old set of heads, do you think the 1.7 heads bored to 96mm would be a good fit or can they be opened up to 96mm with no issues?

[H2OSB]

Along these same lines, do the 1.7 AMC heads on the market have the same fast ports of the original 1.7 heads?

[Clatter]

I'm going to buy a set of 1.7 heads next time,
And open them up for the 94 bore.

Unless you are 100% stock, and mostly lug in traffic, no reason to not get the bigger valves, better ports and better chambers.
Only 'con' is having to get the heads opened up.

If you are already in a lighter early bus, and up to 2056, it's an easy choice.
Moreso if you go for a free flowing exhaust, and especially with a bit more cam.

Remember that Jake's Camper Specials were 1971cc and had 42 x 36 valves..

[saggs]

Thanks for the input. So can the 1.7 AMC heads be safely opened up to 96MM. I already have the pistons and cyls. And do the new heads come set up with a set of valve springs that are safe with stock crank rpms? Probably not worth spending any money on a cw 71mm crank, I'm robbing parts from a 2.0 914 motor I have. I bought a cam and lifters from EMW a while back but lost the slip so I don't know which grind I have, I'll have to call him.

[saggs]

I have spoke to Len at HAM and he suggested a set of his blueprinted 2.0 bus heads, they have 33x39mm valves. That seems pretty small but with a set of 36 Dellortos and the proper cam it should make good low end and mid range power. Can anyone recommend a good cam for this size valve setup? Was looking to run around 9-1 comp ratio. These heads already cost a fair amount and I'm not sure what a jump in valve size will cost? maybe nothing?

[Clatter]

Cam will determine CR.
Usually a heavy camper will be around 8:1 with a Web 73 or something similar.
Might figure out what cam you have first - Measuring lift might help.

I'm guessing that if Len does a set of heads, they will get new seats/valves regardless..