20v Silvertop Turbo Vs Blacktop Turbo Flow

[s-twig]

Hi

I'm about to acquire a 20v Silvertop, and was told that they don't flow too much more than a smallport 4AGE and to go Blacktop.

I want to turbocharge the Silvertop but was wondering if I should be looking for a blacktop head, or if there is little difference when using force induction?

Thanks

[IH8TEC]

use blacktop as they flow better std, only thing to do to it is put heavy duty valve springs, i was in my mates levin with 7agte running 27psi when we boosted onto the motorway and had valve float and bent two valves, now with heavy duty springs, no problems.

[blacktop]

I'm currently turboing a silvertop 20v, and as far as i can tell its all minor! If you're gonna turbo what does it matter if one flows a Little bit more than the other!

I have herd that the bigports flow just as well as the 20v's when turbo charged, but i have seen no evidance.

Just jam a turbo on and worry about the important things, like what's going to brake when you turn the boost up.

This is just my personal opinion, so you don't have to take it as gospel

[-GT-]

It depends what sort of 'flow' you're talking about, and how you plan on using the head. Flow bench figures for arguements sake, or which stock head will make more power in a given setup. The blacktop will flow a little better, due mainly to the larger throttle bodies and slightly bigger (and longer) cams.

If you're just going to get a head and strap a turbo to it, i would expect, all else being equal, the blacktop head to produce slightly more power. How much? Can't say, but it wouldn't be heaps. Now, is that difference worth the extra cost to you?

Then, what else are you planning to do to it? Are you going to change the cams? Port the head, even just clean it up a little? The more you do to it, the more of the blacktop advantage you negate, and the more insignificant the original power difference was anyway.

The larger thottles are one advantage likely to make a difference once power levels get up there, but once again you can always bore silvertop throttles (you're spending a bit by this point anyway). And they're not necessarily the restriction either.

What i'm trying to say is, yes, but not a big difference, and is it worth it to you for the increased cost and maybe finding one?

What rods are you planning on using?

[s-twig]

I'd be looking at aftermarket forged rods and pistons (will 4AGZE pistons work well?).

I was just interested in knowing about the silvertop/blacktop difference, as I had the impression that the blacktop was a much better attempt at the 20 valve engine and that the silvertop wasn't so great.

I'd probably be ditching the quad throttles too.

Thanks for all the advice.

[-GT-]

The silvertop isn't that bad at all. There are differences/improvements, but it sounds like you'll be ditching most of them anyway. 4agze pistons will work (ie fit in the bore, work with the rods, and don't hit the valves, no idea on comp ratio but calculable), but nowhere near as well as some good aftermarket 20V equivalent compression pistons (ie ones actually designed to suit the combustion chamber and valves).

You're ditching the quads, how much power are you aiming for? The stock silvertop rods are the same as ae101 gze rods, they can take a fair bit. Is this a budget build? If you've got a spending limit i'd be going for a silvertop, getting aftermarket pistons and running the standard rods. Spend a little on some headwork and valvesprings.

[thanhngo]

With ST you get thicker rods than the BT, lower static compression 10.5 vs 11.

This would be enough to convince me that the ST is better suited for FI applications in stock form.

[KARNAGE]

with using either generation of the gze pistons the compression ratios are very similar to what they are when used with a 4agze head. the early gen pistons are normally 8.0:1 and when used with a black top head and standard thickness hg mine was measured at 8.14:1with a 0.8mm head gaskit it was 8.19:1 and when i last checked a customers car that was using the 8.9:1 comp pistons the comp is around the 9 mark so very good for a turbo build. as long as you spend some money on a very good timing belt so no big engine failures happen down the track.

[blacktop]

With ST you get thicker rods than the BT, lower static compression 10.5 vs 11.

This would be enough to convince me that the ST is better suited for FI applications in stock form.

Exactly why i didn't buy a blacktop

If you even have a budget, stick with a ST, as budgets and turbocharging don't mix, i'm currantly $2K over budget and i need to spend another $1k to finish it off.

or you can buy Beau Yates BT turbo setup for about $12K
http://www.driftaustralia.com.au/for...?TOPIC_ID=1388

[Sam_Q]

GT: sopposedly the only difference in cams between the heads is that the blacktop intake cam has an extra 0.2mm of intake lift. I would of thought the blacktop would flow a bit better purely on how much better the port design is.

s-twig: fitting 4agze pistons isnt a bad way to go, what karnage worked out sounds right but with a silvertop the compression would be higher again. If you like I can work it out. It all comes down to the revs and the boost you want to run. If you are prepared to spend the extra cash and time then I personally think you will get a bit more out of the blacktop purely because of the better port design and larger ports.

karnage what head CC's did you use to work out what you did?

[Sam_Q]

just worked it out: using the original smallport 4agze pistons with its quoted 8.9:1 compression with a 39cc chamber (from the arias pistonswebsite )when installed into the 20V engines works out according to me to the following:

Silvertop - 35cc chamber (according to arias) = 9.58:1
Blacktop - 37.8cc chamber (measured it out myself) = 9.09:1

[The Real Roadrunner]

more compresion with a bigger chamber? how does that work? might want to redo the calcs again.

[s-twig]

Will a blacktop head bolt straight on to the silvertop bottom end?

[-GT-]

Sort of. Depends on your definition of 'straight on'. Have a search, there was a thread about it recently, from memory consideration is required of the timing belt, tensioner, and head gasket.

[Sam_Q]

roadrunner: oops! thanks for the correction I was in a rush this morning and I got it back to front.

s-twig: heres a basic run down: Timing belt depends on which oil pump+tensioner is used, ie if the blacktop oil pump+ tensioner stays with a silver head then a blacktop belt is needed. Gasket is the same but there would be a signifiacant increase in the compression, so silvertop pistons would probably also be needed. other than that its all good if your using the appropriate intake and exhuast.