building 7a with 20v head....

[shelldrake]

Hey guys,
Just thinking about the 20v's using the 7a crank and rods...I've only really head a little bit about these. I have some questions though. What is the combination exactly? Are custom rods and pistons required? Or is it 20v pistons with 7a rods and crank? Are the 7a blocks the same as teh 4a? Is the rod ratio ok in this format(if it works)? Is it worthwhile going this direction instead of a worked 1600 20v? (aS far as bang for buck is concerned) (If custom rods and pistons are required I prolly wont go this way) Would really like to hear from a few people who have built these.....

[Javal]

You use the standard 7a block / crank / rods / pistons with the 4A head.

20V head will fit no problems if it is already modded for RWD.

7A blocks are NOT the same as 4A ones, hence why the block is used, not just the internals

7A rods do NOT like revs too much, so a circa 7000rpm limit should be used. Otherwise you'll have a nice hole in the side of your new 7AGE.

More info here:

AEU86 7age guide (http://www.aeu86.org/index/engine-4age-to-7age-conversion/cat/9/topic=4156/post=60902)

Javal

[dr1ft-pig]

from memory, building a 20v 7age u SHOULD use 20v pistons (5 valve as opposed to 4) and as javal has said use 7A block, crank and i advise get good rods if you want to rev it.
the 7afe block is a bit higher than a 4age block (16or 20v) so with the 16v u must use the timing belt from a porsche 944, or in the case of building a 20v 7age u will use the timing belt from a 16v, the reason for this is that the extra 7-8mm on top of the the block will make head sit higher and obviously need a longer timing belt, and the timing gears on the 20v head are closer together than 16v so u can just use a 16v belt which makes things really easy

unsure on comression ratios once this conversion is done, there is info on it with the 16v head but not the 20v from what i have read

should be a descent ratio if using 20v pistons

[Javal]

from memory, building a 20v 7age u SHOULD use 20v pistons (5 valve as opposed to 4) and as javal has said use 7A block, crank and i advise get good rods if you want to rev it.
the 7afe block is a bit higher than a 4age block (16or 20v) so with the 16v u must use the timing belt from a porsche 944, or in the case of building a 20v 7age u will use the timing belt from a 16v, the reason for this is that the extra 7-8mm on top of the the block will make head sit higher and obviously need a longer timing belt, and the timing gears on the 20v head are closer together than 16v so u can just use a 16v belt which makes things really easy

unsure on comression ratios once this conversion is done, there is info on it with the 16v head but not the 20v from what i have read

should be a descent ratio if using 20v pistons[/b]

I would be very careful if you decide to put the 20v pistons on the 7a rods just to make sure it doesn't become an 'interference' motor, but that'd be my only concern.

There's alot in that page i linked, have a read.

[dr1ft-pig]

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from memory, building a 20v 7age u SHOULD use 20v pistons (5 valve as opposed to 4) and as javal has said use 7A block, crank and i advise get good rods if you want to rev it.
the 7afe block is a bit higher than a 4age block (16or 20v) so with the 16v u must use the timing belt from a porsche 944, or in the case of building a 20v 7age u will use the timing belt from a 16v, the reason for this is that the extra 7-8mm on top of the the block will make head sit higher and obviously need a longer timing belt, and the timing gears on the 20v head are closer together than 16v so u can just use a 16v belt which makes things really easy

unsure on comression ratios once this conversion is done, there is info on it with the 16v head but not the 20v from what i have read

should be a descent ratio if using 20v pistons[/b]

I would be very careful if you decide to put the 20v pistons on the 7a rods just to make sure it doesn't become an 'interference' motor, but that'd be my only concern.

There's alot in that page i linked, have a read.
[/b]


it does become an interference motor, if u change timing belt every 50 thousand there little to no chance of the timing belt snapping