How good is a 7AG?

[jezza323]

if sump clearance is an issue......

DRY SUMP

problem solved!

[takai]

Whilst technically making the whole engine taller, since the sump is below the engine mounts (and assuming you keep the standard A-series mounts) wouldn't this NOT affect the "height" (ie for bonnet clearances) of the engine?. Unless it also brings up crossmember clearance issues, the extra sump depth (7A is a 2-piece sump) shouldn't be an issue

Yeah, but from BigPerms experience with putting an AE71 crossmember in a RA23 the height of the sump does make a difference. Hence i was taking it into account.

[Valkyrie]

Hi,
I've got plenty of room from the bonnet with a 4AGZE in my TA22.

I don't think you will have problems with the extra 25mm.

I used 4A engine mounts and cut'n'shut factory 2T engine mounts.

Cheers

[Ben Wilson]

Just found this on another forum, thought I'd add it for reference..

First post:
Compression ratio depends on which head gasket you use. 7a (0.6mm) or 4a (1.2mm)

Stock bigport 4A-GE = 9.4:1
Stock smallport 4A-GE = 10.3:1

7A-G, bigport pistons, stock deck height, 7A-FE head gasket = 10.3:1
7A-G, bigport pistons, block decked .024" (0.6mm), 4A-GE HG = 10.3:1
7A-G, bigport pistons, stock deck height, 4A-GE head gasket = 9.7:1

7A-G, smallport pistons, stock deck height, 7A-FE head gasket = 11.3:1
7A-G, smallport pistons, block decked .024" (0.6mm), 4A-GE HG = 11.3:1
7A-G, smallport pistons, stock deck height, 4A-GE head gasket = 10.6:1

7A-G, 8.0:1 early GZE pistons, stock deck height, 7A-FE head gasket = 8.8:1
7A-G, 8.9:1 early GZE pistons, stock deck height, 7A-FE head gasket = 9.8:1

7A-GE with stock 7A block, silvertop pistons and head, 7A 0.6mm HG = 11.55:1
7A-GE with stock 7A block, silvertop pistons and head, TRD 0.8mm HG = 11.48:1
7A-GE with stock 7A block, silvertop pistons and head, 4A 1.2mm HG = 11.35:1

Second post:
Jeff, my brain is fried. I have been up since half past February. But I believe the 7A block is about 15mm taller than the 4A block.

Uhh wait, I have both 4A and 7A rods in the garage...let me go measure them.
7A: 132.5mm
4A: 122mm
Note that I'm pretty tired, and am eyeballing the 4A rod just a little bit, since it has a piston on it and I can't really get the caliper on it properly. I came up with 122.5mm, but Jun lists it at 122mm:
http://www.junauto.co.jp/products/cy.../index.html?en

OK, might as well do the math...
7A deck height = compression height + 0.6mm (pistons below deck at TDC) + 132.5 + 42.75 (85.5mm stroke /2) = compression height + 175.85mm
4A deck height = compression height + 0 (pistons dero deck at TDC) + 122 + 38.5 (77mm stroke /2) = compression height + 160.5

So I was close. A stock 7A block should be 15.35mm taller than a stock 4A block.

[takai]

Interesting, i have some 4A smallport pistons lying around, and have a 7AFE on the way.