Stock 4AGE Smallport Turbo Choice please

[oldeskewltoy]

OK - I'm just chasing a little more advice from those who know .......

Late model GZE pistons in a 20V head with a standard 1.2mm Head gasket will give me 9.4:1 - so a little bit more once the block and head have received a tidy up. Trouble is - I can't find any standard bore late model pistons.

I've cc'd the dish in the early model 8:1 GZE pistons I found at 13.2cc - quite a bit more than the 10.4 the www tells me. With these, an 0.8mm head gasket and .1mm off both the deck and the head, I'll get around 8.7:1.

Not sure where you got 9.4 to 1... 20V head is 37.8cc*, 16V head is 36cc... so any 16V piston under a 20V head will drop in compression, not rise.... (allowing for all other specifications being unmodified)

* - http://www.toymods.org.au/forums/tec...ad-volume.html

std bore, std stroke, later version 4AGZE pistons will deliver a 8.6 to 1 static CR under a stock 20V head.

[mr2360]

for not much more than beer money Amayama have new GZE pistons at the moment apparently.

[rick q]

Oldeskewltoy

I got my figures from a lengthy thread on Club4AG [ http://forums.club4ag.com/zerothread?id=55003&page=2 ]

Engine-----------OEM CR-----headCC--------Piston heigth-------------piston dome:
4agze (BP)---------8:1---------36cc---------------30mm----------------------- -11.9
4agze (SP)-------8.9:1--------36cc----------------30mm---------------------- -5.45
4age (BP)--------9.4:1--------36cc----------------30mm----------------------- -2.5
4age (euro)------10:1--------36cc----------------30mm----------------------- .65
4age (SP)-------10.3:1--------36cc---------------30mm----------------------- 2.1
4age (ST)-------10.5:1--------34.5cc ------------30.5mm--------------------- -1.1
4age (BT)-------11.1:1--------37.8cc ------------30.5mm--------------------- 4.7

Sounds like I should cc the Silvertop and smallport heads in the shed and report back - who'd have thought something was wrong on the www

Thanks for the help so far - some more research required methinks!

[oldeskewltoy]

Oldeskewltoy

I got my figures from a lengthy thread on Club4AG [ http://forums.club4ag.com/zerothread?id=55003&page=2 ]

Engine-----------OEM CR-----headCC--------Piston heigth-------------piston dome:
4agze (BP)---------8:1---------36cc---------------30mm----------------------- -11.9
4agze (SP)-------8.9:1--------36cc----------------30mm---------------------- -5.45
4age (BP)--------9.4:1--------36cc----------------30mm----------------------- -2.5
4age (euro)------10:1--------36cc----------------30mm----------------------- .65
4age (SP)-------10.3:1--------36cc---------------30mm----------------------- 2.1
4age (ST)-------10.5:1--------34.5cc ------------30.5mm--------------------- -1.1
4age (BT)-------11.1:1--------37.8cc ------------30.5mm--------------------- 4.7

Sounds like I should cc the Silvertop and smallport heads in the shed and report back - who'd have thought something was wrong on the www

Thanks for the help so far - some more research required methinks!

The STOCK 16V chamber @ 36cc is pretty much no longer debatable... besides many measurements by me, and others... the TRD Bible shows the chamber volume in the AE92 manual for 9.4 to 1 compression as 36cc - http://i79.photobucket.com/albums/j1...nfirmation.jpg

As far as the 20V I referenced... it was based on SamQ... and as I referenced he seems to know what he was doing.... (never hurts to re-confirm)

I recently designed a piston with JE piston... I sent them a 9.4 to one, a 10.3 to 1 and an old TRD. I asked him to get me crown volumes on the 9.4, and the 10.3....

9.4 crown volume = 3.8cc dish
10.3 crown volume = -.25cc dome

[rick q]

Oldeskewltoy

I've just cc'd two of the combustion chambers on the Silvertop head in my shed using a lightly greased perspex plate, and a light smear of grease around the valves [I scrubbed the excess grease out of the chambers leaving just a thin film in the gap where the valve head meets the valve seat].

Volumes were measured with a syringe and hydraulic oil. I did both chambers twice, and both pulled up at around 34.5cc. I don't know whether this head has been skimmed during its life, but I understand the engine hadn't been opened previously.

So, for now, I'll stick with the chamber volume of the Silvertop as being less than the 36cc of the Smallport - which would mean the CR would be higher in the Silvertop than the smallport with the same pistons.

I also acknowledge there'll be manufacturing differences between engines - but for my purposes, I'll stick with my earlier figures since that's the actual head I'll be using.

It's a bloody minefield this stuff!

[oldeskewltoy]

Oldeskewltoy

I've just cc'd two of the combustion chambers on the Silvertop head in my shed using a lightly greased perspex plate, and a light smear of grease around the valves [I scrubbed the excess grease out of the chambers leaving just a thin film in the gap where the valve head meets the valve seat].

Volumes were measured with a syringe and hydraulic oil. I did both chambers twice, and both pulled up at around 34.5cc. I don't know whether this head has been skimmed during its life, but I understand the engine hadn't been opened previously.

So, for now, I'll stick with the chamber volume of the Silvertop as being less than the 36cc of the Smallport - which would mean the CR would be higher in the Silvertop than the smallport with the same pistons.

VERY cool! nice to have someone actually check! I have a silvertop head here... if I can find the time... I'll also get you a chamber volume....

[rick q]

It's be great to have a comparison - thanks for that. I look forward to your results.

I know when I measured the bowl on the early GZE pistons I have, I got significantly more volume than the www stated [IIRC I measured 13cc, whereas the www indicated 10.45cc] though I only did one, and did it in a rush as I was just looking to confirm they were the early version rather than the late version which I was wanting.

For anyone who's interested, SamQ managed to find a manufacturer for late model GZE pistons - there's not much he can't source!

[trdee]

For anyone who's interested, SamQ managed to find a manufacturer for late model GZE pistons - there's not much he can't source!

you mean like...... toyota? they are still available off the shelf