rebuilding silvertop 4age

[20v FX-GT]

Sorted then, catch me if you can!

consider yourself run down and passed

OK then, you've got a 200cc advantage before we have even started though! I'm still keen

[Phat Stu]

I got a Blacktop workshop manual off the web that covers all the engine and electrics. Its only a copy but the quality is good if you can get a printer to print it at a good size for ya.... go to http://locost7.info/mirror/4age_blacktop.php

Cheers

[neo]

I found an extra 1.5 L of 10w30 made mine run alot quiter .. (hadnt looked at the dip stick in 5000k, and it had no oil at all on the dipstick)... oopse

shims -==
t = thickness of used shim
a = measured valve clearance
n = thinkness of new shim

n = t+ (A - 0.24mm) intake
n = t+ (a - 0.44mm) exaust

shims come in 3 sizes

0.02mm ~ 1.7 - 1.9
0.01mm ~ 1.9 - 2.1
0.02mm ~ 2.1 - 2.3

[20v FX-GT]

Thanks Neil

[iplen]

Wiseco forged pistons to the trick nicely, we are running the same crown size as standard, but slightly skimmed head, still using 98 ron fuel, and with the bottom end balanced, but standard apart from arp rod bolts, some cams we are revving to 8800. This is a "safety" setting, as the car is a rally car we are after torque, not horsepower, but that setup would apparently be good for 9500, so call it 10,000. There is a rumour that if you take the ZE crank and rods that you can make 20v rev to 11,000+ with a really light set of pistons. Although this is true, you may as well use the standard crank+ rods, because they are the same anyway. Standard crank is nitrided from the factory, as an example, so the bottom end is not too much of an issue. I would be tempted if I was not limited by rules to take the 20v bottom end and bore it out by about 1-1.5mm(+?) (the pistons are available so I am guessing it is possible) they can go out to 1800, and by running forged pistons there is no reason why it should not still rev just as hard, if not harder, because I doubt they would weigh any more. give comression a bump, to 12-12.5:1, and use an octane booster, unless NZ fuel is better than AUS. use some blacktop throttle bodies, to go with increased capacity. Get as set of "reduced vortex" extractors made (using standard ones as a base) A good computer, and some headwork and you would be looking in excess of 110kw at the wheels, and na 20vs are one of the best sounding engines you will EVER hear at full noise!

[neo]

damm where did all the info come from?
got ne more?

[RedMist]

IPLen, the Blacktop throttle bodies taper in the body itself. You would have to construct your own cast manifold to match the TB to the head. Silvertop ones are 2mm smaller in the butterfly and I think better suited to a 1600cc race engine. Remember you are after an increase in velocity over any equilivalent increase in flow.
The Bore can be taken to 83mm, however this is pushing the bounds and most engines run a max bore of 82.5mm. With standard stroke this gives you (83mm) 1666cc or (82.5) 1646cc. The 1800cc conversions are made by converting a larger FE engine block with custom rods and pistons to suit the 4age 16 valve head.
In regards to compression 12.5:1 is a little hard for 98 octane. We could get into the merits of an octane booster here, but they don't work consistantly and I won't touch one. AvGas or a dedicated race fuel would have to be the way to go.
Wiseco make a good piston, however they are known for being on the heavy side. I run Aries, again a good piston, not as sturdy as Wiseco but lighter. Gapless rings are a must, as is a high torque starter!! Found that one out deep in a forest with a stall. Tried the starter and just got a click. Once the engine had cooled the car started beautifully.
I noted the restriction in regards to money so I didn't pipe up about serious race modifications at that point.
The best bang for your buck is aftermarket induction box ($450) some TOMS trumpets (not made anymore but you may be able to replicate them for about $300) A custom made race header based upon a 4-2-1 configuration with very long primaries (29inches) and short (10inch) secondaries. (I paid $450 for mine)
Port work is very hard as they are a very good head. There is an area in the port roof about half way between the manifold face and the valve guide that can be taken up a smidgen to clean up the flow. Inlet valves 1 and 3 can be deshrouded to give better flow however this may decrease swirl (the bench I used didn't have a swirl meter). This is worth possibly five HP at best.
The post facelift inlet manifold will be worth a few HP as it mates to the head better.
The CAMS can be increased in both duration and lift to give more horsepower at a higher RPM. However both lift and duration are limited by the small shim size.
Vernier cam wheels will be needed for initial setup, however CSL Cams in Hamilton are able to reprofile the VVT pulley once you inform them of two good intake cam settings that will allow you to increase mid range torque. The vernier on the exhaust side will need to remain. The one on the inlet side is custom and the only manufacturer I know of that manufactures them is TRD. IPLen may be able to point you in another direction.

I agree with IPLen in regards to the silvertop 20 valve bottom end, it is very good. I however don't think that the ZE rods would work well in the 20 valve situation. The ZE rods are substancially heavier than the silvertop 20 valve. You want light weight rods to lower the rotating mass and allow the engine to rev. Imagine the stresses on a heavy rod attempting to change direction 16000 times per minute (8000rpm).

Saying all that, it will cost you half as much to develop a 16 valve (as it's all been done before) and you'll end up with more power for your buck.
Minor mods = 20 valve all the way
Full out race engine = 16 valve. (unless you have a tonne of money)

I've played with all three of my silvertops and a single blacktop.... I now run a 16 valve beast. 130kw at the wheels.. and still a bit more to come. Those of you who have run on the old Columbus Car Clinic Rolling Road Dyno know that it tends to underread. Just waiting for the box to come back with the new ratios to do another run with the new airbox, Nevo crank pulley on Brett's digital dyno.

One thing to note with any high performance engine. The more you spend on the motor, the more you spend in maintenance.

Daniel.

[RedMist]

In addition if your going to rev to 11000 rpm are you going to do so through a new custom made gearbox / diff? As it either won't handle the power or will be geared stupidly. Say your geared to do 3000 rpm at 100kph. Thats over 390KPH at 11000 RPM!!! If your going to be doing anywhere near that speed, you'll also want a wind tunnel, some specialist tyres (possibly custom made) a good aerodynamics crew, some fabricators, AP or similar racing brakes, a cage, a big expance of straight road, a fuggin big chequebook and of course your brothers drivers licence.

Daniel.

[ChaosAD]

bump

[vvega]

Ace is right. The TOM'S trumpets extend into the throttle body. I haven't seen another set that does this.

i have
its how most high quailtiy trumpets work :S
i guess motor bike parts are just better

v