Upgrade advice needed

[mosu]

Just a repost from my original Mira posting, I just want to get as many opinions as possible. If you saw it there, feel free to ignore it here

Hi all,

Driving season has come to an abrupt end here in Toronto and upgrade season has
begun! I've budgeted some money for repairs and upgrades, and I'd lack to give
the engine some b@llz to match the looks. The problem is that after reading the
forums I'm a bit confused as to what the best way is to maximize the upgrade
money. There seem to be as many opinions as there are approaches to performance
and I'd like to get some for my particular situation from you guys.

My budget is $2000-2500, which includes parts and any shop labour. My target is
140 hp.

What I have:
- 1608 motor supposedly rebuilt by PO 10K miles ago, but leaking oil like a
shower head; what doesn't leak, it burns
- brand new DFEV carb (I definitely plan on reusing it)
- 4-2-1 exhaust manifold (looks like a rusty stock item)
- 1800 intake manifold
- points distributor in good condition

I poked around the various vendors and saw that HC pistons are sold for 1800+
motors only. This leads me to several questions:
- can I hit my power/budget targets with the current motor as a base?
- if so, what kind of work should I do to it to maximize the cost/benefit ratio?

Any advice would be greatly appreciated!! I can't wait to start working on my
puppy if I can't drive it.

Cheers,

Alex

[racydave]

If you are convinced that the engine consumes oil internally, then your budget might not cover what it needs. Would you consider a good used 1800? You might have spare bucks for mods. Installing a 2L would be alot more difficult.

[mosu]

I would consider it, and I actually thought I came across one locally, but it was priced out of my range. The oil is mostly leaked from what I can see, although 1 qt can disappear in about 600 km or so...the rear crank seal and the underbelly from it backwards are drenched.

Anyhow, the parts for a bottom end rebuild appear quite cheap, but they prob add up quickly. I will try to do as much of the assembly work myself to learn something from the whole exercise. A shop would come in where machine work is required. After all, I have a forum of people with experience to help me along the way

[So Cal Mark]

using the parts you have, I doubt you could get 140hp within your budget

[mbouse]

i may end up with a f.i. real soon that turns over but doesn't fire. how would we get that across the border?

[mdrburchette]

It's going to be hard to get 140 hp out of a streetable 1608 to begin with. You might want to lower your expectations to an achievable number. My 1608 has around 125 hp and is plenty peppy enough for spirited driving.

[MNspiderman]

40/44 IDF Carbs, Cams, Header, Then pistons, if ya got anymore cash. balancing. Bigger Valves help too. You don't even have to change the seats. Thats the General way you have to go to make horsepower.

[mosu]

Thanks, first poster that gives some ideas

Ok, maybe 140 hp is a little optimistic and 120ish sounds good for a sub-tonne car.

I gathered some opinions on Mira and the general consensus seems to be: head porting, bigger valve, keep the DFEV, hotter intake cam, exhaust headers, electronic ignition. All this on a properly machined and built stock bottom end. It sounds achievable in my budget with some shopping around.

BTW, what the stock CR of the 1608? On some sites I see 9.8, on some 8.5...which one is it?

[baltobernie]

Might help if you have some baseline numbers. When I was researching my 1756 project, I came across an article in the August, 1972 issue of "Motor Trend", and it contains the only chassis dyno numbers of any of the dozens and dozens of reviews I've seen on the Spider, from any year.

Your 1608, admittedly with the 29/39 DCF and 8.5:1 compression, produced 52 RWHP out of the box. With bigger jets and a recurved dizzy, they got it up to a whopping 64 RWHP @ 6300 RPM. About 80 SAE horsepower vs. FIAT spec of 104 HP. This was the 1970's remember, and inflation was everywhere, particularly in advertised horsepower

The euro-spec version had 8.9:1 and twin DCOE 40's, and claimed 125 HP. You're working with 98 cu. in. here, so anything above 98 is a healthy engine.

Unless you plan on spending a great deal of time above 5,000 RPM, why not put that nice carburetor and manifold on a known-good 2-litre block, and go have fun driving it? You'll be somewhere in the 110-115 HP range, and you'd have to spend thousand$ on that little motor to get those numbers. The 2-litre would still be quicker with more grunt down low. OK, you'll need to fabricate a custom down pipe to get around the old crossmember, but that's all.

[mdrburchette]

Your 1608, admittedly with the 29/39 DCF and 8.5:1 compression, produced 52 RWHP out of the box. With bigger jets and a recurved dizzy, they got it up to a whopping 64 RWHP @ 6300 RPM. About 80 SAE horsepower vs. FIAT spec of 104 HP. This was the 1970's remember, and inflation was everywhere, particularly in advertised horsepower

That's interesting, Bernie. I dynoed my original 1608 with 116k miles on it before we pulled it out and rebuilt it. I got 72 hp and 74.4 lbs of torque from the rear wheels. After spending untold amounts of money, we ended up with 100 rwhp. 28 hp wasn't bad at all and that was with the 2bbl Holley.

[mosu]

Aha, with these numbers in mind I see why 140 hp is unrealistic. I thought I was starting from the 110 hp figure, so 30 wouldn't be THAT much

I'm probably putting down what Denise was before her rebuild with my 1800 manifold and DGEV carb. Wow, for 70ish whp, the car's surprisingly peppy!

Even when talking 120 hp target, that'll be more like 100ish whp, right?

[narfire]

When the engine is out,shave a few pounds off the flywheel and balance all that rotating stuff. Weight match the pistons as well.

[mdrburchette]

What work can you do yourself? If you're only subbing the machine work, you've got a little more money to work with. Port matching and polishing the head, bigger valves, lightening and balancing rotating mass (pullies,flywheel, pistons, rods) decking the block, adjustable cam wheels, bigger carbs....did I miss anything?

[baltobernie]

I'm probably putting down what Denise was before her rebuild with my 1800 manifold and DGEV carb.!

Probably not, if you're burning a lot of oil, CR is likely way down

Even when talking 120 hp target, that'll be more like 100ish whp, right?

Depends on the dyno; my Miata tuner figures his dyno, when testing cars in the 100 HP range, has a 25% loss. So you'd aim for 95 or so to translate to 110 SAE