[matty kirk]

Hello.
I am thinking about building a solid lifter head for my 90 Cabriolet, but wondering of this will cause a problem if run on Digi2 EFI.
The head in question was pulled from a 1985 Cabriolet. I would be looking to run 42/35mm valves if possible and a bigger cam.
I am currently running an ABA block with the 2H hydro head and a TT 270 Street cam. I have re built the head with a TT hi-flow kit.

Interested in trying to get a bit more, and don't mind spending money and doing work to see what I can do.
Thanks for any information.

 

[Butcher]

I doubt it, the EFI system would not care. Maybe the knock sensor would 'hear' more noises, but I doubt it.

 

[matty kirk]

I doubt it, the EFI system would not care. Maybe the knock sensor would 'hear' more noises, but I doubt it.

Great. Thanks for the reply.

 

[matty kirk]

So my next question is would/should I actually expect to get much gains from bigger valves.
In the VW performance handbook by Greg Raven he gives an equation for determining ideal intake valve sizing.

It is basically the square root of (rpm x S x B x B/2,286,000)

Using this equation with an rpm number of 6000 with bore and stroke of an ABA block renders an ideal intake valve of 40MM, which of course, I already have.

So at what point is a 42MM intake valve warranted??

 

[Butcher]

I'm not into that much science but bigger is better. There is no bragging rights when you say you got stock size valves.

What I normally do when I 'rebuild' a head is replace the valves with 7mm stems [ABA] and install the 41mm intake valves since the stock ABA valves are really 39.5mm.

Not certain what options you have since you want to use a solid lifter head. For my driving style, I see no gains with a solid lifter head. I like the idea of a set it and forget it type of valve adjustment.

 

[matty kirk]

I'm not into that much science but bigger is better. There is no bragging rights when you say you got stock size valves.

What I normally do when I 'rebuild' a head is replace the valves with 7mm stems [ABA] and install the 41mm intake valves since the stock ABA valves are really 39.5mm.

Not certain what options you have since you want to use a solid lifter head. For my driving style, I see no gains with a solid lifter head. I like the idea of a set it and forget it type of valve adjustment.

Well, OK.

I do my best to understand science and do the math. I'm far from brilliant, but I try.
It would seem that bigger is definitely not always better. There are many things that will only help you in the high RPM ranges and actually hurt you down low.
If fitting 42mm intake valves will only help you above 8000rpm, and you lose low end torque, then what's the point?
Unless of course you're doing hot laps on an actual race track, which I am not.

When I built my ABA I thought it would be really slick to use fully slotted RACE main bearings.
They work really great except that my oil light blinks at every stop light. Ooof.

My interest in solid lifters is that they provide much better valve engagement in my understanding. In actuality, they may not do anything for me in my specific application.

At the end of the day science is what will tell you if all the performance stuff you're spending money on is actually doing anything. I'm also not interested in bragging to anybody.

Thanks for the reply just the same.

 

[Muldermutt]

I'm also heavily into solid lifters on diesel and gas. They have such a "real-world" music to them when they run. I have always hated hyd. lifters on this era of VW engine. Setting of the solids takes some time and getting all the shims one needs. But, they actually rarely need attention once the engine is broken in and the new valves settle into their properly-lightly-cut seats.

 

[Butcher]

I'm just sharing my thoughts. There is no way I'm saying I'm right.