7age: how to?

[Hiro]

I'd be looking for some really light pistons....

Stock pistons are around 300 grams, not sure exactly as the one I'm using for the model is still firmly (a little too firmly, actually, it's surprising the engine was still running) attached to the conrod. The whole shebang (bearing cap, rod bolts, conrod, gudgeon pin, piston) weighed 850g

[takai]

Once i find some good scales ill weigh my AE92 smallport doorstop (piston).

[nick.parker]

Thanks for the info Ben, apparently I don't spread enough rep around

*begins daydream*
How about a 4A crank in a 7A block, with custom rods?
You could end up with a 137mm rod / 77.0 = 1.78 rod stroke ratio which you could maybe rev pretty insanely (assuming light enough reciprocating parts).
I read superbikes sometimes use up to a 2:1 rod stroke ratio . Also you can use your 8-bolt flywheel and GZE pistons...Or maybe create some inbetween capacity by offset grinding the 4A crank a little bit to closer to 1.7L or something and a better rod stroke ratio than a 4A still.....
*stops daydreaming*

Yeah its all crazy I'm just having some fun, I guess I just proved a that having a little knowledge is dangerous...

Does anyone have picture of a 7A block? I am curious to see how similar the block is to a 4A block in terms of the 'ribs' etc and also the mounting holes for SC brackets and so on. I have seen some unclear pics which indicate the holes exist to mount the lower sc bracket just like on a 4A.

Cheers, Nick

[Ben Wilson]

How about a 4A crank in a 7A block, with custom rods?
You could end up with a 137mm rod / 77.0 = 1.78 rod stroke ratio which you could maybe rev pretty insanely (assuming light enough reciprocating parts).

You've got to consider you're adding a fair bit of weight there (extra 15mm of block) as well as having a higher center of gravity, not sure if it's worth it..

[nick.parker]

I guess I almost needn't ask since people have been had some sucess with 7AGZE's and 7AGTEs etc. What are the 7A crankshafts like compared to the 4A? I have heard conflicting things. Some say 7A crank is superior (which I would doubt and I don't know what aspects!), but obviously the 6 bolt flywheel can't be as tough as the 8-bolt. Some say the crank is cast, but then some people extract 300hp with a turbo so what gives? It looks like all you need are ZE pistons and some ARGO/Pauter 7A rods to build something decent. I guess without experienceing the pain I'm hoping to glean whether a 7AGZE will stand up to the odd clutch dump / high load driving with a torquey SC motor etc...

Ben, have you got access to a 7A?

Edit:: Just found this resource on club4ag its got pics of the crank and explanation excellent info!!! http://www.club4ag.com/faq%20and%20t...0Analysis.html

[Ben Wilson]

You must spread some Reputation around before giving it to nick.parker again.

Nice find

[takai]

Nice one bruvva. +rep for you.

[joe90]

Not sure if this is of any help to anyone but I just put one into my sprinter and nearly everything bolted up no probs.The only issue were the 2 bottom bolt holes to the gearbox(the ones the 4ac had a couple of brackets for), the height of (or lack there of) the extractors and the throttle body hitting a bonnet rib (ballpeen massage fixed the latter). It actualy feels realy nice but it dont like cold starts and idles a bit ruff and is very tempremental at light throttle.It has a stock 7a bottom end with smallport head, bigport cams and electrics.I have tried 180/200/250cc injectors and the 200's offer the best all round feel but it still suffers the afore mentiond unpleasentries.
Any thoughts?

cheers joe

[SEXY 16]

next friday night is when john sprinterman68 puts my 7a together
lifting my head from graham wilkins tomorrow..smallport 16v extensive headwork 304 cams 11mm lift cam pullies heavy duty springs underbucket shims custom throttle bodies
toda extractors

block and crank
percision crankshafts 7a special
knife egded and went on a extreem diet lol
heat treated
argo rods
weisco 11.5/1 pistons
arp head and main bolts
custom lightweight flywheel

i know nothing about engines but there will be photos for every stage of the build
hope this will be of use to people
note* this is note a cheap excercise
if i had to do it again i wouldnt
i would fit a 16v 2.0 calibra engine instead

[Matt-AE86]

where is a good source to find 7afe's ?

[nick.parker]

Any thoughts?

Yeah, stop playing Russian Roulette with the your engine and injectors! Get an aftermarket EFI computer system. I guess you didn't want that answer, but once you finally do this you will then realise no matter what you do to the engine you can optimally tune it. And its so worth it to just to have everything working nicely...

[joe90]

Cheers nic. I'm happy to recieve any constructive info and your probably spot on there.Maybe the mix is to varied for the std management to deal with.I hope to go sequential vapour gas injection in the near future (and an sc14) and of coarse aftermarket management.I'm not chasing big numbers, I'll be content with whatever it ends up like. I'm happy enough with it now realy but it was always my intention to fit the blower and gas.

cheers joe

[mullett]

Thread revival! I'm thinking seriously about embarking down this path, although with an SC14 on the side of it, and maybe rev-limited to 6500-7000rpm. Has anyone found a conclusive and good writeup?

RM.

[Poggy]

7afe rods are stronger then blacktop rods and they rev to 8k

[ViPeR_NiPPleX]

stronger... or heavier?