20V Blacktop/Silvertop hybrid

[Sam_Q]

I am interested in building up a hybrid engine the has a blacktop head and a bottom end of a modified silvertop. Now I dont have any of the intake gear so I would have to use the silvertop intake manifold.

Now the question I want to know is what silver/blacktop differences will affect me?

heres a few I thought of:

-timing belt, I have a new timing belt for a silver but apparently a blacktop requires something different.

-compression ratio, I know that a blacktop has a different squish area shape than a silver so therefore I would think that the head CC's are different resulting in a different compression ratio.

- intake manifold, I know blacktop manifolds are a different shape but would a silvertop manifold bolt onto a blacktop head?

- gaskets: are they the same?


if anyone asks why I would want to do this its because of the following:

- blacktop heads are cheaper than longblocks
- I have a good nick silvertop bottom-end
- I have already have some cracktested and shotpeened silvertop rods which are nice and thick unlike a blacktop

[Toycrash]

For manifolds, bolt pattern is same, they will bolt on.
But port size and shape is quite different, dunno if there is even enough alloy to be grinded in silvertops manifold.
Heres a pic, abowe is ST and below BT
http://www.koti.phnet.fi/crash/Flame/QTB/PICT2206_1.jpg

You would have to use BT intake gasket or make your own.

[Vios-GT_07]

my understanding is that their timing belts are a few teeth different as well but then again i could be wrong... this is from part numbers a while back.. would like to have someone confirm them for me too..

a few people have done blacktop to GZE bottom ends... which still confuses me how it's possible.. are the BT and ST heads interchangable... with 16V blocks as well?

[S.W.A.M.I.]

timing belts are different.
so crank & cam gears will need to be used from either model...

if ur using a blacktop head......just get all blacktop gaskets....
the intake manifolds are different, intake ports are different between silvertop and black.
yes there is enough material to grind away, but its not worth it to do so.

exhaust manifolds can be interchanged.

silvertop rods are heavier & are not really a plus like you make it sound if your intensions are to build an N/A motor.

[johnny]

timing belts are different.
so crank & cam gears will need to be used from either model...

if ur using a blacktop head......just get all blacktop gaskets....
the intake manifolds are different, intake ports are different between silvertop and black.
yes there is enough material to grind away, but its not worth it to do so.

exhaust manifolds can be interchanged.

silvertop rods are heavier & are not really a plus like you make it sound if your intensions are to build an N/A motor.

We've gone the other way around, B/T bottom end, S/T top, with B/T cams manifold etc. ATM it needs a tuning as it was only put into the car last week, but this feel a lot more willing to rev than any S/T I have driven so far. The Jap's have been doing this combo quite regularly now and seems the best HP out of the Silver/Black combo, and the reason why? higher comp+ more revs= more HP!! Well that's the theory and only after a tune can I say yes or no if it's true.

[Vios-GT_07]

ah thanks for the info..

the BT has lighter but stronger bottom end from what i gather, which explains the compression and HP.. i wouldn't necessarily say it's weaker though considering it's being used as a race engine in the "stock-car" races...

johnny - good luck with it and when it's all done, make a new thread share the info ehh! Cheers

[Ben Wilson]

For manifolds, bolt pattern is same, they will bolt on.
But port size and shape is quite different, dunno if there is even enough alloy to be grinded in silvertops manifold.
Heres a pic, abowe is ST and below BT
http://www.koti.phnet.fi/crash/Flame/QTB/PICT2206_1.jpg

You would have to use BT intake gasket or make your own.

Has that silvertop manifold been ported? That looks very different to mine (pics not working right now)

[Toycrash]

Has that silvertop manifold been ported? That looks very different to mine (pics not working right now)

No it's not ported from head side.. But i assume you have early silvertop manifold.
On that the injector nozzles boss has sharp corners, not round like that late ST manifold.

Alltho the manifold is ported to mate BT throttlebodies..

[psychofox]

We've gone the other way around, B/T bottom end, S/T top, with B/T cams manifold etc. ATM it needs a tuning as it was only put into the car last week, but this feel a lot more willing to rev than any S/T I have driven so far. The Jap's have been doing this combo quite regularly now and seems the best HP out of the Silver/Black combo, and the reason why? higher comp+ more revs= more HP!! Well that's the theory and only after a tune can I say yes or no if it's true.

So does this mean that Blacktop AE111 pistons don't hit a Silvertop AE101 head? Roughly what Comp Ratio do you end up with?

[Ben Wilson]

No it's not ported from head side.. But i assume you have early silvertop manifold.
On that the injector nozzles boss has sharp corners, not round like that late ST manifold.

That sounds like the one, thanks. I think I might be doing some work in mine with a die grinder if I ever use it again....

[Sam_Q]

I dont understand how would it be benaficial to have a silvertop head onto a blacktop block? doesnt the blacktop have significantly better ports? also why wouldnt it be worth it to adapt a silvertop manifold.

Also I have condfirmed I will go ahead with this. I think it is a good idea to use silvertop butterflies because they are smaller and while still big enough to not be a restriction it will give me more of a vacume signal. Am I right with my theory or way off?

[psychofox]

I assume it is beneficial because the silvertop head has better squish areas in the combustion chamber whereas the blacktop has a more open style, with higher crown pistons. When you combine the 2, you get higher compression. If you use a Blacktop head on a silvertop bottom end, you will end up with lower compression.

I think the blacktop having significantly better ports is a bit over-rated, they are slightly bigger both inlet and exhaust, which probably reduces low end response more than anything (sounds like bigport vs smallport all over again...) In reality what is going to make the biggest difference between the AE111/AE101 heads are the cams (bigger inlet lift on AE111) and the quads (45mm vs 42mm), both of which can be fitted to either head with relatively little effort.

Why I am interested in the silver head/blacktop piston combo is that I want to run the blacktop pistons in a 7AGE 20V NA motor, and I already have an AE101 Silvertop head.

[psychofox]

Oh and the timing belt difference is in the belt tensioner, AE111 has one of those hydraulic ones, whereas AE101 is the same as all other 4AGs. If you use the AE111 head on a AE101 bottom end you should use the AE101 timing belt (111Teeth)

[3sgte]

I'll vouch for the tensioner thing too. I bought a belt for mine, and got a little surprise when I started pulling it down!

I never expected to see that on an "A" series engine!

Edit:
Some AE101 carried the blacktop, for example an AE101 wagon, circa 1996 MY.

[Dimitri]

Oh and the timing belt difference is in the belt tensioner, AE111 has one of those hydraulic ones, whereas AE101 is the same as all other 4AGs. If you use the AE111 head on a AE101 bottom end you should use the AE101 timing belt (111Teeth)

you nailed it on the post above the one i am quoting re chambers and CR. but youre wrong about the belt.

the tensioners are diffferant yes. but so is the tooth profile.

i have only heard of anyone ever choosing ST rods over BT rods once. was mentioned in TAKA's spec's.. he was running toda forged pistons though. possibly the extra weight warranted the choice.

[3sgte]

How is the profile different?

Mine (blacktop) had a rounded profile, it looked close enough to a "normal" 4AG one that I didn't notice anything different.

Clearly nothing like a 4AFE one, but I think that is understood...

[Sam_Q]

this might make you guys squirm but I was thinking of shaving the block to raise the compression. It looks like I will have to CC the heads to work it out mathematicly, something I really wanted to avoid, oh well.

the head gasket is the same right?

[Dimitri]

gasket is the same.

tooth profile is definately differant. look at 2 side by side.

[AE86slut]

i have only heard of anyone ever choosing ST rods over BT rods once. was mentioned in TAKA's spec's.. he was running toda forged pistons though. possibly the extra weight warranted the choice.

It's actually pretty common, especially in high comp or turbo motors, because while the blacktop rods are thinner and lighter, they silvertop ones are quite a bit stronger. Of course, going to a set of Eagle H-Beams or something would kill both birds with one stone!

[Sam_Q]

whats the weight of some eagle rods compared to silvertop ones? also where do I buy some and what might they cost?