a20a1 or a20a4 bottom.

[Vector]

my car currently runs 89 efi conversion mod on a a20a1 head and block/internals except for the cam which came out of the 89 as well.
so heres what i was thinking:

1. I put the a20a4 head/block in to my car, and thats good for what? 1-3 more hp due to compression change?

2. I pull my a20a1 head w/89 cam over to the a20a4 block. i was talking to some friends at a machine shop and according to there books, the accord carb head has slightly bigger exhaust valves, and since the 89 cam has little more lift(miniscule i know) it may flow alittle better?

it might be true for the 86-88/89 carb'd to efi but the 88/89 could be the same.
i also dont know if it is posible that the head it self could determine a compression diference(diferent demensions on the inside). if someone knows these heads well, i would like your input

[smufguy]

I found out the difference in the exhaust valve free length about 7 or 8 months back when i was putting my website back together. The differece is around 1mm {120.66 – 120.96 mm ( A20A3 ) , 121.36 – 121.66 mm ( A20A1 )}. The deck height and clearance volume is the same on the A1 and A3 head so u wont see any compression ratio difference or change. the crank shafts are the same so u got the same stroke. As you mentioned, the camshaft lobe height is about 38.477 mm ( IN ) , 38.353 mm ( EX ) for A1 and 38.858 mm ( IN ) , 38.796 mm ( EX ) for the A3. [IN = Intake: EX=Exhaust]. so as you can see, not that great of a difference in length. But its a big difference when they are put together, as in a 88-89 efi camshaft on a A1 head will defenitely provide you with better performance as to the longer exhaust valve and the higher lift providing you with atleast 1mm extra lift on your valve on the EX side and close to the same on the IN side and yes it will be able to flow more at higher rpm.

the valve face dimensions for the exhaust and intake are the same for the A1 and A3 head.

the last difference between the heads is the EXhaust valve seat 1.75 – 1.95 mm ( A20A3 ) , 3.85 – 4.15 mm ( A20A1 ).

[Vector]

thanks so much, i now know what i'm going to do with all the parts i have.

a20a1 head w/a4 cam
a20a4 block/internals.

pnp/matched.

i will see if i can have it done for the 24th and oct 8th, last 2 autox events here.

[smufguy]

yup thats the best combo, i think Alex is running the same set up.