New rally engine advice

[Mr Revhead]

why would you recomend a silvertop over a blacktop.

Guessing conrods?

Yep. Plus once you sort the tune the silvertop goes pretty much as good as a blacktop. And are cheaper.

[RobertC]

here is a little comparison

Green factory blacktop (Rhys)
Blue (AceSniper) Med size cams
Pink (Daniel)

Everything is the same till about 5000 rpm.

So build something like either of the above with a close ratio box and keep it between 6 & 10 000 rpm will have plenty of power

[shihad]

why would you recomend a silvertop over a blacktop.

Guessing conrods?

Yep. Plus once you sort the tune the silvertop goes pretty much as good as a blacktop. And are cheaper.

ahh the rods well personally i believe the blacktop rods are better for na as i dont believe they break unless you run the bearings first (im refering to factory rev limit here).One person has said on here they have seen the rods break with out run bearings but i find it hard to believe.anyway the guy said he has around 5k to throw at the motor so i would imagine hes gana rebuild the motor so why not put silvertop rods in blacktop if your not a fan of the rods.

anyone got any dyno sheets of silvertops that make decent power?
didnt barry flow bench all or most of the 4ages and blacktop was best stock?

i guess silvertop is the new bluetop a dime a dozen but why throw 5k at a silvertop when with a little bit of searching you could find a cheap blacktop.

[Mr Revhead]

I've personally seen black top rods broken with no run bearings. In one case twice in the same car. A rally car funnily enough.
The stock tune is what gives the silvertop a bad Rep.

There is much much more to HP than a flow test on the heads.
IMO if you are not opening the engine up the silvertop would be the one to go for.
If you are opening it up. Well what advantage does the black top have? A head that flows more but with what a lot consider to be an inferior combustion chamber.

And then there is the blacktop oiling issue with the run bearings.

[Boost_4_Life]

thought it was time to update this. the plan is underway, silvertop engine is currently being rebuilt by my wizard. Decking the block, balancing bottom end etc, getting rid of the terrible casting marks in the head, and nice valve seat job. There was a cast testicle hanging down in the middle of no3 inlet, couldn't beilieve how bad it was! G4 Atom will be arriving this week, so with the minor head work, trd headgasket, assholing the airflow meter, and a good tune it will be good to see what a decent otherwise stock engine can make. I couldn't quite afford cams, otherwise i would have stuck kelfords 194B cam in. Am putting in their valve springs tho, so doing cam later should be easy.

Watch this space for dyno results. I'm not expecting huge gains, but the factory ecu had been running it bastard rich, so it should be noticably better out on the gravel, driveability and torque is the name of the game for me.

All this is readiness for rally extreme series http://www.rallyxtreme.co.nz/

[Mr Revhead]

A good tune alone will make it feel like you plugged in a extra cyclinder

[Boost_4_Life]

so, engine is done and tuned. Power figure much what you'd expect for a stock motor. Runs heaps better than it did tho for sure, pulls hard through 5k - 7500, which is what i wanted. It did a few silly things above 7000ish, they had to muck around with the turn off point for vvt a bit. Otherwise happy tho, remember that this is a gravel car so outright power = not relevant!

Next trick would be sorting out my crap intake, and maybe the kelford rally cam. We did use the kelford valve springs, so doing the cam should be easy. Got a good base to work from now anyway.

[Dell'Orto]

Good power for a silvertop! Quite smooth too
For comparison sake, my cars plot on a rolling road dyno

[Lloyd]

If its a smallport, you can get good power out of them - even stock they have more low end torque than a 20v. Go smallport 16v with big lairy cams and millions of compression

+1

[RomanV]

So start with a smallport because it has more torque down low, and then modify it so it doesnt anymore?

[rollaholic]

i would like to see a 16v thats been modified to the point of those blacktops that were posted above, just for a comparison.

[Boost_4_Life]

methinks my torque figures might be a bit suss brad lol. Compared with another engine up here too, especailly so! ah well, the thing pulls fine, feels bloody good on the road so bring on the gravel

[Lloyd]

No one has managed to stretch valves in a 20V?

[Dell'Orto]

methinks my torque figures might be a bit suss brad lol. Compared with another engine up here too, especailly so! ah well, the thing pulls fine, feels bloody good on the road so bring on the gravel

Different final drive etc will change those figures, was more a comparison of how smooth your curve is vs mine.

[nzae86]

I had my rally car on the dyno recently , smallport with wisco pistons , standard rods , a bit of head work by Franklin's ,still with standard valve sizes and shim over bucket , quads and an old link computer .



Produces good power and torque from down low to the rev limiter,

In comparison here is my circuit car with every TRD part made thrown at it , it seems that when you get to a certain horsepower point the each additional horsepower costs about another $1000 -1500 !!

[Boost_4_Life]

Thats interesting Steve, the old girl makes good power... Do you run trumpets with your quads? I want to try trumpets next, then it will be the kelford cam. Motor is otherwise bog stock so I'm pretty happy. Need a bit more to get closer to that certain bloody honda at wairarapa rally tho...

[Boost_4_Life]

So, plans for the offseason...

I scored a complete blacktop motor, so do I..

a) Just throw some Cams and trumpets on the silvertop and see how it goes.

b) put the blacktop head onto my silvertop bottom end

c) Blacktop head on silvertop bottom end + cams/trumpets

[jacobrjett]

maybe put the blacktop pistons in? think it would yield slightly more compression?

not that id know but...

[Boost_4_Life]

not more options!

[Dell'Orto]

A.