Building 1835cc engine - need some advice

[Corwin]

Hey all. I'm building a new engine and I need some input/advice on it. Especially if any pro engine builders out there can tell me that this will in fact work and that I will end up with an engine that will run on pump gas (premium is okay). And before you burn me, yes, I'm a novice and no I'm not building the engine by myself. Don't hate!

It's a 1600cc bug block. Here's what I want to do:

AA 92mm pistons/cylinders
Engle 120 cam
Performance crankshaft (not sure what stroke I'll need...)
1:25 ratio rocker arms

The heads will be sent down to AJ Sims at lowbugget, along with the manifolds to all be ported/machined and set up with dual springs. I'm also having them rebuild the dual 40mm Kads at the same time. I know I'll need chromoly pushrods and assorted other goodies, but these are the basics.

I'm having the head tapped for full flow and am going with an upgraded oil pump.

Can anyone tell me if they see any problems with this or suggest a crankshaft to go with all of this? Thanks ahead of time.

[Rome]

I'll start with your easiest question. For an 1835cc engine, if you use the 92mm pistons, then the stroke works out to be 69mm. That is the same stroke as a stock VW 1600cc type 1 engine. The 1600 uses 85.5 pistons with the 69mm stroke to get an actual 1584cc.

Your cam, heads and carb choices will allow the engine to easily exceed 5000rpm, generally regarded as the safe upper limit for a stock factory crankshaft. Such cranks that came in the engines in Beetles made in Germany (all those officially imported to the USA) were forged steel, had 4 dowel pins to hold the flywheel (also forged), and the crankshaft was not counterweighted.

Most people would strongly recommend that you buy a crank that is forged, counterweighted and has 8 dowel pins. The counterweights come into play at higher engine revolutions to balance out the mass of the connecting rod ends and the crank itself. Some companies can weld steel counterweights onto a stock factory crankshaft; this is called a "welded forged counterweight crank". Any stroke beyond the stock 69mm would be considered a "stroker crank". Both 69mm as well as some stroker cranks are available as CAST steel which is not as strong as FORGED steel. So read the crank descriptions carefully.

[Corwin]

Thanks - that definitely helps.

So the Scat Volksracer crank (forged/8-dowel) is a 69mm - I'll search to find out opinions on it. So is it not possible to run a stroker crank then with the 92mm pistons?

Other than that do you see anything else I am missing or need to consider? Thanks guys. I'm not an idiot, and I'm not new to VW's, I just haven't built an engine before.

[krusher]

just ask AJ for a full combo to go with the heads , he knows how they flow and what they like.

[Rome]

"So is it not possible to run a stroker crank then with the 92mm pistons? "

Umm, a stroker crank has nothing to do with the size of the pistons; you can run a larger stroker crank like 82mm with stock 85.5 pistons. But there are lots of factors to consider. Stroker cranks for VW type 1 engines are currently available in 74mm, 76, 78, 82 and even larger. the larger the stroke, the more leverage you are adding to the crank every time the spark plug fires, so that you are producing more torque on the crankshaft.

Larger pistons like 90.5, the 92's and 94 come with 2 different wrist pin dimensions; those for larger stroke cranks are generally referred to as "stroker" piston sets or "B" pistons. The wrist pins are about 1/4" closer to the top of the piston surface on those than on the "stock" set or "A" pistons. This is done so that when you choose a stroker crank that has about 6-8mm (about 1/4") longer stroke than stock, the engine is not too wide when fully assembled.

For your first engine, I suggest to keep your 69mm stroke. Build it carefully, plan your desired compression ratio and build the engine accordingly. Pay attention to your rocker geometry and upgrade your valvetrain as needed. Once the engine is together and running (tremendous ego boost), then consider your next engine as a stroker.

[Corwin]

Thanks - yeah, I got the difference between a stroker and regular crank. Just wasn't clear on what he was saying in the above post.

Anyhow, I appreciate it - been a lot of help.

I went with:
Scat Volksracer 69mm forged counter-weighted crank
Scat Pro-series forged 1:25 ratio rocker arm kit
Engle 110 cam
AA 94mm (1914cc) cylinders/pistons

[bugnut68]

I was going to suggest going up to 94 P/C's, but it looks like you beat me to the punch in your last post, there.

[Corwin]