20v silvertop mild build. Stock Bottom End.

[Brendan]

So basically am looking at building a warm 20v with a stock bottom end.

Realistically i'm aiming at around 170-180hp, or a bit over 100rwkw. I'm mainly going off bill sherwoods information on the 16v so far and trying to apply it to the 20v

I'm having some trouble finding information.

Rev limiter stock seems to be 8200rpm from what i read. But what could the stock bottom end do safely without the limiter? 8500? 9000?

How much lift could you run on the cams without having to modify the stock valve springs?

How aggressive can the cam duration be before modifying to shim under buckets?

"A quick note - the 4AGE that I have in my AE-86 Sprinter has 288° cams, an aftermarket computer, 10.5:1 compression, and a small amount of head work done. It makes about 160hp with a completely stock bottom end. It runs to 8,500rpm without any worries. (so far!" from bill. Don't spose you know how well that held up? haha.

how much can you safelt increase the CR by using a thinner headgasket and skimming the head?

After i find a safe rev limit and set of aggressive cams that wont require much modifying of the head then i think i'll be able to work out tuned length trumpets to suit the rpms.

Sorry so many questions. I'm assuming some are known as the 20v's seemed to be a popular race engine but little is documented via google. lol

Appreciate all input, comment or opinions.

[-GT-]

I've heard from a few people (mainly firsthand experience) that 8500 will be no problem on a stock bottom end. Will you be rebuilding it? I think it's worth lightening and balancing it and checking tolerances etc, and then you'll be fine, with even a little more than that. For example, Takai has been doing 9000, i think 9500 now in his track car on a stock (smallport) bottom end.

Lift: I think the silvertop spring binds at up near 10mm; i have some info from a Dutch(?) cam company for blacktops that states max lift on stock valvetrain of 9.5mm and bind (well, "lift at spring coil collision") of 10.3mm. They also recommend replacing the lower retainer with a 1mm shim to gain more lift out of springs, with this, their upper retainer and spring (requires machining) they state max lift of 11.5 (bind 13.0mm). Anyway, point was, i think the silvertop factory valvetrain limits are a bit less than the blacktops. From my searching 9.0 seems to be acceptable lift on stock springs but the ramp rate and revs are going to be factors in that as well.

I thought the 20Vs were shim under buckets??

Safely increasing CR by HG and skimming comes down to valve clearance and tuning - hopefully all this will be run by a decent programmable ecu, so check your clearances with your new cams and go from there.

I'm also subscribing as i'm hoping for some good info too, sounds like we're looking to head down similar paths.

[Brendan]

haha thanks for your input garth, it seems our 20v's were pretty similarly matched at Wakefield in the wet lol.

The more i read the more confused i get. However thats good news about the RPM side of things and ignorance on the shim under buckets it seems but still good.

Most streetable cams are 9mm max lift anyway, so shouldn't be too big of an issue from what your saying, and changing valve springs isnt too bad, and shims isnt too bad either i think...

At the moment i have a silvertop im somewhat willing to do some testing on thats in the car atm, b4 i rebuild an engine to last a little bit.

If someone can help me find the dynamic compression ratio of a 20v that would be greatly appreciated. Or has a metric DCR calculator instead of all the american ones i've found so far.

And what DCR do people recommend witht he use of 98 RON? 8.5 seems to be that magic number at the upper end of the scale but would love to see what some other engines are stock. Anyone have calculations for street engines on 98 RON?

any way to calculate valve clearances without having the cams? lol

[Sam_Q]

theres quite a few stories around on how high a lift can be run before the cam lobe starts to want to push the bucket sideways out of the head.

You shouldnt need big cams for the power you want anyway.

Many people have reported to have run a constant 8500 all day without breaking a rod, dont try it in a blacktop though.

I dont know anything about it personally but I also have heard reports of retainers failing with heavier valve springs and also valve float at 8500rpm onwards, neither of which is a relevant issue to you I think

[shelldrake]

Aim for 11.5 compression. i'm pretty sure this is achievable with a blacktop by just replacing the standard hg with the trd .8 mm one. If you do it to the silvertop, you'll end up with roughly 11.1. Either way, go for 11.5.

From memory, the cams I'm running are around the 270 degree mark, 9.5mm lift.
I'm running toda valve springs too though.
Wolf 3d v4.
Some porting
Bottom end balanced
ARP rod bolts
Standard pistons and rods - chrome rings though...
Blacktop quads

My cams seem to pull from 3500-7500 then trail off. The dyno charts indicate it's still making power, but not that much after... Max torque is at 5500. VVT is still functional. Once you use cams bigger than 270 the vvt is useless and adjustable cam gears would be best.

My setup is perfectly streetable and still pulls well up top - I still think there is tweaking to be done so it keeps pulling hard to 8500ish... I think the guy who tuned it was scared to make it rev.

[Sam_Q]

11.54 for the blacktop and 10.9:1 for the silvertop by memory I think eddie.

So whens the next tune happening eddie? I remember a big discussion so many years ago on the old toymods when a 4age owner wasnt making the power and he found it was because the tuner was an old V8 guy and the thought of a stock bottom end revving to 8000 was beyond him.

[shelldrake]

11.54 for the blacktop and 10.9:1 for the silvertop by memory I think eddie.

So whens the next tune happening eddie? I remember a big discussion so many years ago on the old toymods when a 4age owner wasnt making the power and he found it was because the tuner was an old V8 guy and the thought of a stock bottom end revving to 8000 was beyond him.

How about next time you come over we road tune it a bit between 7500-8500. Altertnatively, when I can afford some more dyno time... My money priorities lie elsewhere at the moment.

(For reference my setup is making around the 100rwkw mark at 7500)

[-GT-]

And for reference to that my previous stock silvertop was still making power all the way to the 8k limiter. It was balanced when it was rebuilt and that's it. Made a best of 86.3kw. The current one is unopened and getting a little tired, last dyno run power dipped just before the limiter (the afm wavered too). There should definately be more revs in that engine! And i can't see why there's not more power - if that was my engine i'd be spinning it to 9000...

In fact, it's pretty well making what i'd hoped for from a similar build, but at least 1k rpm lower than expected - hmmm, i was considering going bigger on the cams and dealing with ditching the vvt, but really want to keep it if i can; are you running an adjustable exhaust cam and (modified?) factory intake cam? And is that a silvertop or blacktop?

Mind giving some more details on the cams and what limits the vvt usage beyond them? I've found reference to 270-ish being the limit to retaining vvt but nothing detailing why or how to verify. It seems to be the accepted limit, and i've read it's to do with the engagement not dropping off the lobe by the time the next one is lifting but that makes no sense to me, it's all in the gear on the front of the cam?? Perhaps at a combo of lift and duration it becomes interference, but it seems to be duration alone that is the limiting factor? I've never found anything explaining what the issue is, only vague recommended maximum durations.

Anyway, basically i'd like to maintain vvt for what little mid-range i can salvage and run the biggest cams i can. Obviously not expecting them to be huge anyway so somewhat streetable, and maybe 105-110kw?? 100+ ideally.

[Brendan]

Hmm emailed adrian and toda australia and he was extremely helpful.

His opinion to make 180hp:

"To make 180hp at the flywheel with 10.5:1 C/R

For AE101 use 264deg intake @ 9.0mm + 256deg exhaust @ 9.0mm together with TODA valve springs & 0.8mm head gasket

+ TODA intake trumpet kit.

For best results an aftermarket programmable ECU should be used."

So very mild build really but he thinks it would be enough.

The next step to run higher duration cams is to increase the CR as the DCR will drop significantly.

But that then requires high compression pistons at extra cost. So it depends on the budget.

Adrians recommended fo max street/circuit:

For a maximum output street/circuit engine, please consider the following combination.

"Aftermarket ECU +

288deg intake @ 9.0mm + 272deg exhaust @ 9.0mm + TODA valve springs + TODA cam pulleys + 0.8mm head gasket

+ TODA intake trumpet kit.

+ 82.00mm high compression forged piston kit (New capacity = 1627cc)

Together with head machining & light skim of block deck surface, compression ratio of 12.0:1 is easily achieved."

I should be getting some better detailed pdf's about the cam profiles and have fired off some more questions regarding max CR with 98 RON as those figures were for 100 RON i think. Also what rpm ranges what cams should be used for.

What are your opinions?

[Sam_Q]

that sounds interesting, it would be theoreticly possible to put blacktop pistons in a silvertop, but the compression would be seriously high, I can work it out?

[Brendan]

if you could thatd be grealy appreciated as i assume blacktops would be more affordable than todas

[-GT-]

Did he give any explanation as to the reasoning behind staggered cams?

Interesting idea with the blacktop pistons - are the valves in the same place and angle in the head? Any reason the flycuts won't match up? Combustion chamber shapes are different... squish won't be great i don't think. Still, if it's a budget option...