Engine Build

[ChrisSRT]

I am looking to rebuild the engine in my 78 Spider. I am looking to get around 125 relieable hp. From what I seen searching the forum it should be doable, but I need some help from the experts on the combination (pistons, cams, valves, machine work, etc) to get there. The car will be used for rally cross primarly, but possibly hill climbs, vintage rally, etc. so it will remain street driveable.
Thanks,
Chris

[mdrburchette]

Are you looking for 125hp at the wheels or crank? You could go with higher comp pistons, have the rods and flywheel lightened, deck the block a little, slap on a port matched and polished 1592 head, have Miller's Mule make you some light pullies, including adjustable cam pullies, install some big cams and bigger carburation and I think you'll be well on your way.

[ChrisSRT]

would love to have it at the rear wheels, but realisticly crank. Will the 1592 head work with the 1800 block? I was planning on doing IDFs.

[baltobernie]

Some of sanctioning bodies of the events you mention have restrictions on engine mods, so maybe you'd want to check with them first.

You're looking at $3-5k to build a motor to the level you and Denise describe. The rest of the drivetrain can easily handle that much power, but any weaknesses in the transmission, etc. will become apparent in semi-competition driving. Rollbar, belts, kill switch and other required safety equipment. Is your suspension already modified, or do you need to add springs, shocks, anti-roll bars, wheels & tires in there, too?

I guess what I'm getting at is asking you to take a look at the overall condition of the car, and see if you can justify the money it would take to make an entry-level car. Vintage racing and rallying has become a huge sport in the USA, and most of these guys are serious. I did a back-of-the-envelope estimate of prepping a 124 coupe for this type of activity, and passed the $10k mark in under a minute I'll bet if you attended one of these events, you'd be hard pressed to find entrants who've driven their cars to the event.

My 1800 engine makes 104 RWHP, about 125 SAE. I'll e-mail you the particulars if you're interested. It's a great street car, but I'd need to spend a lot more money (and change its character) to participate in the activities you describe.

[ChrisSRT]

I've already rebuild the suspension and brakes, planning on a full cage build to spec for SCCA/NASA use. Primary use will be Rally Cross where only factory hardtop is needed though. Just want the extra safety of cage, and being able to run a vintage rally for fun would be a bonus. I know a guy in AL that is building an Opel Kadet to vintage rally specs and is a wealth of knowedge for the cage. I'd be interested in the specs on your build. Thanks

[mdrburchette]

What work can you do on your own? If you can build the engine, the price is more reasonable, but it can be expensive. My 1608 is around 125 hp at the crank but I've got a lot of custom internals. It can be done less expensively than what I did, but we wanted to make sure the car could be taken passed the 8k rpm range without coming apart. There are several pics showing my rebuild. You may have to wade through a few other Fiat pics to see them though:
http://gallery.italiancarclub.com/124og/SPIDER-LADY-72/

[BEEK]

Are you looking for 125hp at the wheels or crank? You could go with higher comp pistons, have the rods and flywheel lightened, deck the block a little, slap on a port matched and polished 1592 head, have Miller's Mule make you some light pullies, including adjustable cam pullies, install some big cams and bigger carburation and I think you'll be well on your way.

150hp + if the right combination of parts mentiond above are used, but i would not recomend lightening the crank or rods. just my opinion.

[manoa matt]

Sorry to jump off topic but:

Maria, whats the advantage of the 1592 head over the 1800 head aside from the lack of air injection ports, which if plugged the heads are virtually the same with minor differences. I have both heads and the differences I found are:

Larger coolant galleys on the 1800 head = better coolant circulation/distribution, more even, and lower temps across the head.

Larger oil galleys on the 1800 head = More drain down from the cam boxes, and more oil fed up from the pump.

One advantage of the 1592 head comes from the smaller coolant galleys. Since the coolant galleys are smaller there is more material thickness between the intake/exhaust port walls and the coolant passages. Therefore, the 1592 head intake and exhaust ports can be opened up more to provide more flow.

[BEEK]

ALSO THE 1592 HEAD HAS SMALLER COMBUSTION CHAMBERS = MORE COMPRESSION

[manoa matt]

I've been told that the 1592 and 1800 heads have the same combustion chambers at 49cc (they certainly look the same) while the 2L head has 52cc

[mdrburchette]

Interesting, Matt. I'll have to look into that, especially since I was discussing this with a Fiat racer and was under the impression the 1592 would give more compression, just like swapping the 1995 with the 1756 head. Maybe I'm wrong since I have only dealt with 1608s.

[ChrisSRT]

I can do most of the wrenching myself, but will probably leave to assembly to the machine shop to insure that all goes well.

I was wondering the same thing about the 1592 head.

I would love to have more power, but want it to remain reliable. If I feel the need to faster I can always drive one of my other cars. I went to watch a Rally Cross and the event organizer let me race his prep'd 81 RX7 w/header (maybe 115hp) and rally tires and I had a blast. Ended up being about 1.5-2 secs off his pace and ended up beating one of the WRX's. I was already planning to do an Abarth tribute, so now it will be prep'd to Rally Cross, but needs to remain street driveable.

[Newell33]

Great photos Denise

I do have a quick question for you. I see you have what looks to be a Holley carburetor on your performance engine. Are you using the 350cfm model? The only reason I ask is that I have a couple of these laying around from my IMCA stock car days. I'm guessing, though, that it would takes mods similar to yours to make that carb work. The carbs I have were designed to run on fairly stout 355's, 383's and 406's. Do you have any idea what kind of cfm would be best for a stock 1800 engine? Doing a rough calculation I'm showing anywhere from 150 to 175 cfm.

Thanks!
Josh

[mdrburchette]

Good eye. It is a 350 Holley. My husband loves his Holleys because they are less complicated than a Weber and he's always used them in his racing....so, the Fiat got this race ready Holley. The problem with it was it ran extremely rich at idle and leaned out at higher rpms so I built a set of Weber IDFs and learned how to balance and tune them. I don't know what cfm's would be best for an 1800, but I had read somewhere where the cfms for the Weber dual idfs were around 100 cfms per throat so that equates to more than the Holley. I wish I understood why a little ole 350 is sufficient for a big 350 but a little ole 1608 can handle a carb per runner. The Holley setup is now sitting on my 1608 engine in my Lemons racecar because of the awesome torque.

[Zmatt]

not to derail the thread, but regarding the holley carb, what advantages do they have over the weber, and how hard are they to use wit a stock engine? Holley's seem a lot cheaper than webers, but I haven't seen anyone use them on spiders, are they worth it?



Also just to throw an idea out there. I haven't seen a spider owner do this, but I know it can be done, and it has been, but why not a carb'ed turbo build? With the carb the turbo loop requires far less hardware, you can salvage a small turbo from something like an old volvo and if you can weld a header can be made pretty easily. I have been reading a very good turbo book lately called maximum boost and it has a chapter dedicated to carb builds. The Fiat twin cam is low compression and should take a turbo well, the only downside is with a carb you get all your umph at one spot, which is more or less true with turbos anyways so you would have an engine with all of its power in one spot. still could be a cheap (relative to building the engine) and awesome way to make a lot of power.