TheSamba.com :: View topic - 1600 AH engine build. Questions. 1641 etc.

Wed Sep 23, 2020 7:43 am

My son and I are in the process of tearing down a 1600cc engine with the following codes.
Engine code AH which shows as a 73/74 1600 w/ 8mm head studs with case saver.

Block number on side = AS41
Heads # = 040 101 375 2

I have a lot of experience building high performance nitrous and supercharged chevy motors through the years but this will be our first time rebuilding an air cooled VW engine so looking for some advice.
Do the balance marks on the crank look factory?
Are these just stock pistons?
Stock cam by the looks of it?

Looking to go 1600 or 1641 with an engle 100 cam unless we can go bigger without spending a lot of money. I am in central Ny and from what i hear most machinists do not want to work with vw machining .
So i realize in the future it may be more efficient to buy a set of heads instead of sending them out etc.

Sat Sep 26, 2020 12:05 pm

What are your plans for the intake system- keep the original single carburetor, or go with dual carbs?

-The crankshaft does look like factory balance drillings.
-Camshaft- the VW and the Audi markings indicate a later, stock replacement cam.
-Pistons: I don't recognize that marking.

You can buy 88 mm cylinders that slip into the engine case with no cutting of the case. The cylinders are "thick-walled" so that the tops are a larger diameter than the original 85.5's. If you send your current heads out for machining, the combustion chambers can be cut to the larger size so that those 88's slip in. Then you have 1679 cc, or almost 100 cc more than the stock 1584 cc with the 85.5's. I've sent several pairs of heads for machining (larger cylinders) to central PA- https://www.v-dubstore.com/Default.asp

Sat Sep 26, 2020 1:06 pm

The piston shown above looks cracked! And what is this? A hole in the case?
Looks like you're off to a good start and getting good advice above. Pistons and Cylinders are usually just replaced with new ones when rebuilt. Some brands are better, some are even forged but the 88's mentioned above will do for a nice displacement increase. Most of the cheap but of maybe acceptable quality vw aircooled parts are imported from China by AAPerformance. ACN is a good parts house for shopping vw parts, they have a lot of info and they discontinue any parts that don't work out for rebuilds very well. Also CB Performance is a good parts supplier for better quality aftermarket VW Racing parts.
The 88mm ThickWall piston&cylinders mentioned above are here:. They require the heads to be machined, opened up to the next size of P&C's which are referred to by the inside bore ie.(88 thick, 90.5, 92mm) I think the actual fly cut is something like 98mm. The heads must not be cracked or the spark plug threads inserted or messed up to be rebuildable. Broken studs are ok, as a machine shop can change those. Good Idea to do anyhow. I went with stainless steel exhaust studs on the last heads I had done. (Not sure how it will be though)
Some of the nice things you may want to consider are A Counterweighted 8 Dowel Crankshaft and Flywheel. A good VW shop can drill the extra dowel holes in the old flywheel and surface it. The original VW flywheels are the best quality. Avoid Cast stuff. (Always check flywheel runout, there are a few bad ones out there ruining cases!) H Beam Rods are really nice to put in an engine but if you're not stroking it with a 74, 76, 78, 80 or 82mm or other stroker crank the original rods can be sized and balanced for $50 to $100 instead of like $289 for the H Beams. The Stock Crank is 69mm and it's not counterweighted meaning that if the engine was revved a lot the case will be messed up. Typically a Case needs and Align bore and the thrust cut. New case thrust on the flywheel main bearing is 22mm and Main Bearings are available in Stock 22mm, 1st=21mm and 2nd=20mm so if the case is already cut and worn below 20mm it shouldn't be used. Same is true with the OD of the main bearings there are 1st and 2nd and 3rd and 4th over for the mains. And the Id for the crank too. It cost about $100 to have a VW crank turned so I usually go with a new CW 69mm crank for $230 or even a 74mm as it will fit a stock block with ARP bolt rods like the H-Beam rods have. A lot of people make the mistake of going to big valve heads on small displacement ie (1585cc-1800cc) VW engine builds loose a lot of bottom end torque and end up with an engine that must rev a lot to have any power. However the Panchito 40X35.5 heads are good on 90.5 -94mm bore engines and even bigger valve heads that get expensive are available for large displacement engines like 2110 and larger displacement engines.
P.S. I always add a Oil filter full flow oiling system when I rebuild a Type 1 VW aircooled engine also Solid rocker shafts and swivel feet type tappet adjusters.
My Spare Bus Engine 74mmX88 video.