IAP performance cams

[baltobernie]

And then, after you've done all the measuring, calculating and hand-wringing, you realize that static CR is only the beginning. It's the CR while the engine is running at various RPMs ("dynamic CR") that really matters.

[131lover]

Hi !
I dont want to start any fights, i saw at http://www.131mirafiori.com project forum,motor-upgrade for my Racing, there was a guy that used 8mm domed pistons in 2l with a130Tc head, worked well and at the dyno it gave 136hk, i dont know what the comp was, if to some calculations it should be around 12,0:1 , that seems very high to be true.

It did not blow the headgasket or having problem what i heard of, i know that static comp and dynamic comp is very different, the dynamic comp depends on camtiming/lift, but is the the difference in comp because we talk about both static and dynamic comp and mixing them?

Alf

[maytag]

Hi !
I dont want to start any fights, i saw at http://www.131mirafiori.com project forum,motor-upgrade for my Racing, there was a guy that used 8mm domed pistons in 2l with a130Tc head, worked well and at the dyno it gave 136hk, i dont know what the comp was, if to some calculations it should be around 12,0:1 , that seems very high to be true.

It did not blow the headgasket or having problem what i heard of, i know that static comp and dynamic comp is very different, the dynamic comp depends on camtiming/lift, but is the the difference in comp because we talk about both static and dynamic comp and mixing them?

Alf

No fights Alf!
I don't think very many people talk in "dynamic compression" numbers. We talk about it, and we understand it, but the nature of dynamic compression makes it hard to measure.

As to the 8mm dome pistons working: as someone else has pointed-out (maybe it was me? ): the dome size is only part of the story. what we REALLY need to know is the compression height.

the static CR cannot be calculated without the following information:

stroke
rod length (measurred from center of large bore to center of small bore)
cylinder height (measured from centerline of crank to top of block)
Bore diameter
compression height of piston (measured from center of pin-bore to top of "quench area, around the outside of the piston)
volume of piston dome / dish
volume of flycuts
combustion chamber volume
head gasket compressed thickness and bore diameter.

ANY of those things changing will impact your compression ratio. And the only ones of those that you can really rely on being consistent from motor to motor (unless you've known the motor since birth) is the first three. (within their displacement family, I mean). The first three are not commonly changed in these motors, but it doesn't hurt to measure, since I know plenty of folks who've decked a block and replaced rods.

[leeputmanjr]

Go with advice provided by an experienced Fiat engine builder.

When I did my engine, I implicitly followed Jon Logan's advice. I wanted a lot of extra power, but I also wanted a car with nice 'cruising-manners' that would behave well in traffic and around the neighborhood. I didn't want a fire-breathing race car, but I certainly wanted more than the stock, sedate cruiser the car was previously. I wanted a nice, in-between compromise.

So, Jon gave me the exact spec's of an engine build he's done & tested many times over & over. In his series of builds & tests, he found these build spec's to very consistently result in ~ 165 HP / 155 Torque at the flywheel:

2L block, fully balanced, keyholed crank
10:1 pistons, w/ 4.5mm dome & total seal rings
Aluminum main crank, lightened flywheel
2L fuel injected head (better cross flow), ported & polished
40/80 cams, w/ adjustable cam pullies
Oversize stainless valves with Isky springs
40 IDF's w/ chokes bumped to 34mm, and mains bumped up to 140's
Recurved electronic dizzy w/ centrifugal advance 24-26, w/ base timing at 10 deg BTDC
MSD Blaster-2 w/ Magnacore wires
4-2 cast iron manifold (pre-'73 style), 2-1 downpipe (off an '74 1800)

Jon Logan didn't do my machine work, as he was backed up with lots of his own work, so I used a local shop here in Chicago, Apex Engineering. They have been doing twin-cam work since the early 70's, and Bill Truesdale (who runs the place) knew more about what I wanted than I did! They did the very basic assembly - the head was "done", with the 40/80 cams installed, indexed, and shimmed properly. The block had the pistons & crank assembled. Pistons, bearings, and other assorted bits came from Csaba. The lightened flywheel, adjustable cam pullies, and aluminum main crank were all from Miller's Mule, the cams came from IAP. The hard part is finding a machine shop that know what they are doing, with fair pricing.

I added a full Stebro stainless steel exhaust, and Magnesium CD-3's for even less rotational mass. I've added a few other 'non-performance' touches like a remote oil filter, a stock belly pan & oil pan guard, and a chin spoiler to scoop up as much air as possible for the stock '74 radiator I'm running.

I have put about 6,000 miles on this motor since it got dropped into my car on Labor Day weekend of 2011, with the kind help of many Fiat-friends. I still need to fiddle with my carb jets/chokes/balancing a bit, my cam pullies are still zero indexed, and I still need to install my MSD coil & Magnacore wires. Some sources have criticized my exhaust manifold setup - but honestly, I don't care. This engine runs THAT GOOD, just the way it is! I am overwhelmingly pleased with it!

I can be cruising on the highway in 5th, doing 75MPH, and if I hit the gas - she GOES! The throttle response is wonderful. The exhaust note (while a touch loud) is wonderfully "Italian" (nobody will EVER mistake it for a Brit car, or anything 'Far Eastern'), and it has that perfect Italian deceleration popcorn burbling sound that I love so much.

My understanding is that you can do essentially my same build, but substitute a fuel injection system, with a custom injection map & get even more performance, and even better street manners. However, I wanted a strictly 'old school' build, so I stuck with carbs.

Again, I thank Jon Logan, as the build-spec's & advice were all his. He's done this build many times, and that gave me a ton of faith - I didn't have to re-invent the wheel.

-Lee

[baltobernie]

Sounds like the perfect setup, Lee. Have you taken your car to the dyno? We'd be interested in your numbers, and it would aid you in jetting, at least above 2k.

[131lover]

Thank you all for your replies!
Alot to take in and think about!

Best regards
Alf Andersson

[So Cal Mark]

the most important thing to consider about these mods is WHERE these hp numbers are being created. While 165hp sounds attractive and sexy, ya gotta realize it's not 165hp throughout the rpm range. That number is hit around 7000rpm. Look at the hp and torque curves, if you're not making good numbers at 3500-4000, the car won't be much fun on the street unless you're flogging it. While flat-footing the throttle at 75mph (4440rpm) provides good acceleration I'm more interested in what happens at 25-35mph coming out of a corner. Unless you live in a very rural environment, traveling at 100mph is pretty rare but coming out of a corner hard is a common occurance. Just my experience and opinion