7age Conversion Problem

[OriRacer]

ok as you know i'm doing a 7age conversion. ideal of putting the 4age head on the bottom end getting the nice and torquie 7age engine. So the conversion is all going fine and tonight it was time todo the piston swap since everthing else is striped.

So having pushed both sets of pistons off the conrods I was deciding which piston pins to use with the 1.8 rods so i measure up the pins and both sets are 20mm. I remember reading that you use the 1.6 pins and that would make sence since they are held in with sir-clips and that would match up with the pistons.

But when testing how it would all fit, it all seams a bit tight but after consulting my guru i bash on with pressing the 1.6 piston pins and pistons on to the 1.8 rods.

AND I CRACKED THE PISTON.....

So anyone out there who has done this kind of conversion PLEASE HELP what have I done wrong!

:ffs:

[fouraygeeee]

Oriracer,

Hard luck mate.

The 7afe rods+pins are an interferece fit (the pin being larger than the hole it fills), while the 4age ones are a clearance fit (hence the need for circlips to stop the pin moving sideways and scoring the bore). Captive pins do not rotote in the rod while floating ones can rotate in rod and piston. Standard procedure is to have the 7afe rods (the bushes) honed to the same spec as 4age ones to give the correct running clearance. Strictly professional engineering job, bit fiddly/tricky.

Easy enough fitting 4ag pistons if they are warmed up first(expansion), but always tricky with captive pins. Everything needs to be absolutely true and square to each other and even then a fair bit of welly applied.

Curious about your plans for fuelling your 7ag. What ECU will you be running? 4age/7afe/aftermarket??

Sorry waffling on a bit..... :)

Rgds

Andy

[OriRacer]

Thanks for that andy. As for fueling I've get some quad throtle body on order if they ever turn up, it will be a custom ECU (motec) and bigger injectors.

But back to the pistons it was the 1.6 pins that cracked the piston didnt even get to the con rod thats whats got me confused will I have to heat the pistons even after getting the conrods honed?

[Jones~32]

sorry to hear that OriRacer, sure you'll get it sorted

You gonna dyno it afterwards to see what HP gains you actually get? :bookworm:

Mike

[Treuno]

Umm, well my mate who done a 7AGE for his AE86 just bolted the 4AG head onto the 7A bottom end, with out swapping pistons over! :P

Not sure if he scoloped the pistons out slightly for valve clearance, but as far as i know he didnt do anything else!

[OriRacer]

sorry to hear that OriRacer, sure you'll get it sorted

You gonna dyno it afterwards to see what HP gains you actually get? :bookworm:

Mike

←

na mike i'm just gone to run qtr miles to gauge my performance, I dont know any dynos I can use for free

[s_mccullie]

GOT YOUR T-BELT YOU WANTING THEM GASKETS FOR THE BOTTOM END THIS

WEEK ??? SCOTT

[OriRacer]

I gives the gaskets & I need that other piston as well. Looks like I'm going to have to get the con rods adjusted as might just get them all hardend along with crank. How much were thery going to charge for that again ?

[Jones~32]

na mike i'm just gone to run qtr miles to gauge my performance, I dont know any dynos I can use for free 

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Haha, fair enough, have you run the 1/4 with the standard 7AFE? if so what times did you get?

[s_mccullie]

na hes no done that yet but crail is on the 27th so what you say take it down then??? oh tyres 43inc vat each just sent me the money via paypal ta cant remember how much for the rods will have to phone him again see what he

said might try another company that had done some head work for us this week and see what they say

[OriRacer]

na hes no done that yet but crail is on the 27th so what you say take it down then??? oh tyres 43inc vat each just sent me the money via paypal ta cant remember how much for the rods will have to phone him again see what he

said might try another company that had done some head work for us this week and see what they say

←

Sweet I might go get the pistons on my lunch and bring them up at the weekend. As long as the weather is good i'll be there at crail. Remember the soarer owners club is having a meet there on the 27th too, should make to a good days racing