Engine 1: 2.0 Bus engine, seller said it has around 5-6k miles on the last rebuild. Has been sitting for around 5 years, but turned by hand regularly and spins freely. I originally wanted to just slap this into the Fastback as-is, but decided to go for a bit more power...
Engine 2: advertised as a 1.7 914 engine, but turned out to be a 1.8 with the 371S heads with stock valve size, but flycut to approximately 53.5cc per chamber. Was sitting outside for a long time, seized up, but I got it for cheap. Had almost all of the engine tin, so between what came with engine 1 and this one, I've got a complete set of tins.
Pulled it apart, and found why it was junked! Someone dropped a nut down the intake, which made its way into the chamber. THEN they tried to get it out with a magnet, which also fell in! Must've made a nice "clang" when it squished!
Witness mark on the head, after vapor blasting:
I still have a lot of questions on how to get the most bang for my buck out of this build, and would appreciate any feedback. Here is my rough plan:
Rotating Assembly/Short Block:
• Reuse stock 2.0 case - this will work best for my Type 3 swap, rather than the 914 case
• Reuse stock 2.0 crank, assuming in good condition
• Reuse stock 2.0 rods *OR* get some H-beams
• 96mm Keith Black flat tops
Heads:
• Option 1: rebuild 371S heads with stock valve size (41x34); they definitely need new guides, and will need to be cut for dual springs for the cam I plan to use.
• Option 2: rebuild 371S heads with 42x36 or 44x36 valves, plus guides/dual springs.
• Option 3: AA 2.0 castings with 42x36 valves, dual springs, cut to ~53cc.
Valvetrain:
• Scat C45 w/ matching Scat solid lifters
• Solid rocker spacers
• Machined rockers for elephant foot adjusters
• Thorsten Piper adjusters
• HD rocker studs
• Dual valve springs
• Chromoly retainers
• Cut to length pushrods
Fuel:
• IDF 44's with 36mm vents
• Shortened CB T4/IDF manifolds
Exhaust:
• Vintage speed equal length primaries
• Vintage speed log muffler
With the C45, I've read that I should target between 9.0-9.5 static CR, which with a 53-54cc chamber will be easily accomplished with an 0.040 to 0.060 deck height and shims. I'm hoping to spin this up to around 6000RPM, maybe 6500RPM if possible, and put down around 120WHP. With 514cc displacement per piston, the 36mm vents should make peak power right around 5700ish RPM and pair well with a 41-42mm intake valve and the power band of the C45. Planning to run 93 OCT which is readily available here in Austin, TX.
Questions:
1. Rods - I've read that stock rod bolts can be a concern at my target rev limit. Also that the stock rods are HEFTY and ought to be discarded when building for higher rev's. This isn't a race car, but I drive my cars hard and don't want to window the block. Are H-beams required?
2. Pistons - how does the 24mm pin height compare to a stock 2.0 bus piston? Would I be better off to get a different length H-beam rod to use with these KB 96mm's to make life easier when setting deck height?
3. Exhaust - when removing the heater boxes, how do folks seal the lower tin for proper use of the thermostat? I'm leaning towards leaving it open and running without the thermostat, but still leaving the flap in place so that fan air is still distributed to the oil cooler and heads, and blocking off the lower ducts on the fan shroud.
4. Heads - from the photo above, and also the photos below, you can see that these heads aren't in perfect shape. I've got the witness marks from that squished bolt, plus some corrosion in the combustion chamber. They also have some corrosion along the inlet runners and intake manifold mating surfaces. Most of the valve seats look pretty good, although one has enough corrosion that replacement or re-grinding is in order. Valve guides are toast, as are the valves/springs/keepers/retainers. But after getting them blasted, there are no cracks around the exhaust ports or anywhere else.
I figure that I can pull the studs on the IM mating surfaces, put down some JB Weld or similar, and bastard file it flat. Not sure if this would be a good idea inside the inlet runners, or if a light cleanup with a carbide bit would be better.
From a cost perspective:
Option 1 (stock rebuild, cut for dual valve springs): ballpark quote of around $650
Option 2 (big valve rebuild, dual valve springs): ballpark quote of around $850-950
Option 3 (new AMC 2.0 heads, 42x36, cut to 53-54cc): ~$1200 direct from AA
What are your thoughts? Are the 371S heads that I have toast? I'm debating between Option 1 and 3 the most - for the cost to do a big valve rebuild on the old heads, just a few bucks more gets me a new set with the better spark plug location. If the old heads are still worth rebuilding, will I really miss that last mil of intake and 2 mil of exh? Will I regret going with so much cam, in terms of frequency of valve adjustments or overall valvetrain life?
Thanks in advance,
Sam
