Gentleman (and Ladies): I'm wrapping up my frame/ body repairs on my '74 and turning my attention to my stock 1.8L carburated power plant.
With so many variables to consider, I thought I'd throw it out to you for your thoughts on a good combination.
Starting with a stock 1.8L, the goal is build an engine with a balance of power and efficiency for a daily driver with a kick.
What I have found so far, for consideration is:
1. Increase displacement with a longer stroke: 71mm to 78mm (and corresponding
rods)
2. Larger P/C's from 90.5mm to 94mm (or 96mm)
3. Mild cam (Webcam 86a or 494)
4. Switch to dual carbs vs. the current single.
This combo would provide an increase from 1.827L to 2.165L
The questions that come up are:
1. Will this combo meet the goal?
2. Are 1.8L heads okay on this engine or do I need to find 2.0L heads?
(the 86a cam would require better valve springs I gather)
3. Should I lighten up the flywheel?
One other biggie, since I'm in the Northeast: Where can I have machine work done? Loads of places in CA, do I need to ship my heads and possibly the case out to CA or is there someone closer? There's a lot of wisdom and experience out there, any help would be greatly appreciated and might save me a couple bucks!
Thanks! ScottD
I was told to start with a 1.7 case because of some additional webbing inside the case. Hopefully someone else will chime in that actually knows.
I also think that the 2 liter 3 stud head flows better. This I believe is the largest HP gain. Again, a motor guru will hopefully chime in.
Carburetors and efficiency don't seem to go together to me. Microsquirt, stock stroke (starting with a 2.0L engine) and 96mm pistons with a Raby cam is the plan for my next engine.
Lets start with some of the simple questions.
The 1.8 liter heads are the ones that have been used for hotrodding for many years. They have alot of meat to work with and they are less prone to cracking then the 2.0 liter ones.
Given that, the big difference is the location of the plug. H.A.M states that its worth at least 10HP to move the plug to the 2.0 liter location.
New valves and valve seats are a must. Plan to spend money on the heads. HAM is located in Georgia, use him for the heads.
For the heads and cylinder work..use HAM. He is on the east coast.
For the case, find a local machine shop to blueprint your case, or clean it up and ship it to HAM... I have had good success with local shops for the case work...its not rocket science. Do blueprint the case...ensure you have all your deck registers machined flat to the centerline of the case/crank. Have the shop measure up the crank journals BEFORE you do anything with the case...then decide from there.
These cases are fairly rugged and dont typically have the need for line boring, so dont believe it without VALID measurements to prove it...
Talk to Jake about some decent engine combos and think about buying a kit that is complete and proven.
Rich
Gentleman, Thanks for excellent starting points. I will definitely mic out the case carefully and look for signs of pounding in the mains to see if I need an align bore.
HAM sounds like the place to send the heads and I've heard that the old school sodium filled valves should be replaced with stainless steel. New guides an seats are a must, but the spark plug hole? That's interesting! 10HP! It's probably not that expensive to have done and they are likely cracked anyway.
What are your thoughts on a small flycut to increase compression ratio a bit? I don't what to push up to need a higher grade gas either.
Rich: your reference to "deck registers". Are you referring to the seating surface where the cylinders seat on the case?
I cracked open over a hundred cases over a brief span 30 years ago. Threw in new parts and down the road. This one will be interesting with an engineering background to add to the mix plus a healthy respect for cleanliness, precision and the time to do it right. Should be fun! Thanks for the advice. Now off on my hunt for HAM! ScottD
Here are the websites you need for machining and parts:
http://www.aircooledtechnology.com/store/home.php
http://www.haminc.biz/
Also check out Jakes forums for info on your Type 4 build:
http://forums.aircooledtechnology.com/
Thanks Rich, Lots to consider. Guess the 1st step is a tear down/ clean up to see what I have, should be interesting.
teh 2.0 chamber is different shape also.
Gentlemen, Thanks to all, you've given me a lot to think about. I'd go right for the 3.1 L combo Jake mentioned if my pockets were deep enough, but reason has to enter in at some point.
I was going to keep the engine on its stand in the corner while I finished up my body work, but it sounds like I should take a weekend for engine disassembly to see what I've got.
Once I make a few decisions, I can ship parts off for machine work and use the wait time for body work. I'll post what I find and go from there. Thanks again. ScottD
Very wise.. Tear it down, report back with pics and I'll tell you what you've got..
Jumping right in and spending big bucks on parts that aren't compatible happens all the time..
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