Finishing a hot 1800 build

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Nut124
Posts: 748
Joined: Wed Oct 25, 2017 6:39 pm
Your car is a: 1978 124 Spider 1800

Finishing a hot 1800 build

Post by Nut124 »

I would like to share some info regarding my recent project.

I haver been working on a total engine rebuild on my -78 1800 since about April or so. Getting close to being done. The engine/trans is back in the car. Working on carb tuning and ignition timing.

Some build details:
- 1800 block, crank
- 2L head, ported
- MLS head gasket
- 8mm dome cast pistons. Total Seal steel top ring.
- 10.5:1 static CR
- 1mm larger valves
- 5 angle seat job by me using manual cutters from Neway. Seats cut as wide as the insert allows.
- Dual Weber 44 IDFs
- My old "Alquati" 40/80 cams - Will look for more cam this winter. Want more lift and "fatter" lobes.
- Abarth Rallye style 4-2-1 header. 2" exhaust.
- AASCO aluminum flywheel
- Adjustable cam pulleys. 108/108 cam centers.
- Undersize alum crank pulley
- Russian LSD 4.30 steel billet rear end (kept breaking the OEM cast ones)

I did all the work except for the block bore/hone, crank polish and head resurface.

The engine pulls very strong. With 40 DCNFs and less CR, the previous build ran 16.1s 1/4mi at a track. This one feels stronger. Hits 6800 in 5th pretty easily.

A few pictures below:

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18Fiatsandcounting
Posts: 3791
Joined: Fri Mar 15, 2019 11:23 pm
Your car is a: 1969 and 1971 124 spiders
Location: San Francisco Bay Area

Re: Finishing a hot 1800 build

Post by 18Fiatsandcounting »

Nice! If I recall, 6800 rpm in 5th works out to 120 mph. Also very nice! I'm too old and timid for this stuff anymore, but I did run my '69 spider between Phoenix and Los Angeles in about four and a half hours, back in the late 80s. In traffic. The engine seemed to love it!

-Bryan
jon8christine
Patron 2018
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Posts: 130
Joined: Sat Mar 12, 2011 10:05 pm
Your car is a: 1976 Fiat 124 Spider
Location: Wyoming

Re: Finishing a hot 1800 build

Post by jon8christine »

Looks great. I'll be starting something similar this winter. Anything you would do differently? That dual carb setup looks expensive, where did you get it? How much do you think the dual carb setup contributed to the power increase vs HC pistons, cams and head work? Looking for the best "recipe" for a hot street / autocross setup to get mid range power.
Nut124
Posts: 748
Joined: Wed Oct 25, 2017 6:39 pm
Your car is a: 1978 124 Spider 1800

Re: Finishing a hot 1800 build

Post by Nut124 »

jon8christine wrote:Looks great. I'll be starting something similar this winter. Anything you would do differently? That dual carb setup looks expensive, where did you get it? How much do you think the dual carb setup contributed to the power increase vs HC pistons, cams and head work? Looking for the best "recipe" for a hot street / autocross setup to get mid range power.
I think I built this just about the way I wanted to, other than wanting more cam. I had bought and ran a rad cam that was very powerful but very noisy, no decel ramps. Wanted to finish the build so put the old 40/80-80/40 cams back in. I did not have the rod big ends checked out by a machine shop, probably should have had.

As to what makes power - that's hard. I would recommend the Guy Croft Fiat Twincam book if you can find it on the used book market.

This what I'm thinking based on having tried quite a few things, just my opinions:
- CR alone does not do much at all but will allow other mods to yield better results. Need to be in the 9's and not higher than 10.5.
- A good header is a must if you plan on a bigger cam. I would recommend a 4-2-1 style header with long primaries. Or at least a stock manifold with two long secondaries. I cannot remember what these came with from the factory. A single downpipe results in inlet flow reversal with any kind of a performance cam.
- I would consider 2" exhaust all the way.
- The 40/80 cams run nice. Not too rad.
- Factory heads have the seats cut too small, even for Factory valve size. Open up seat to max allowed by insert and match valve diam to seat. In general the heads (ports) are very good as is until ultimate street or race spec.
- The twin webers are cool and the sound is awesome, but are not easy to set up. I'm not aware of a ready to bolt-on IDF kit. I bough the manifold, had to massively port it to enlarge for 44mm IDFs. Was made for 40s. Had to do some serious engineering, testing to fabricate the carb linkage, levers. IDFs can be had for about $350 ea.
- I hear that single carb engines can be pretty powerful if the rest of the stuff is done right.
- Modern HP and period (-70s) reported HP do not seem to be the same. Modern HP seems to be at least 10% more powerful. I'm thinking my car has 135-140 period HP but only about 120 modern HP.
- Head porting is likely the last mod and not worth it unless seeking ultimate HP.
- Cam and ignition timing is important and should be carefully checked, adjusted. Need an electronic ign, no gaps.
- Modifications generally do not increase peak torque but instead allow the engine to produce the torque at a higher RPM thus increasing HP. What follows is that unless you spin the engine faster, there is no gain. 4.30 rear makes this easier than the 3.90 while making highway cruising less enjoyable. My engine turns at 4000+ rpm at highway speeds.
- Good machine shops are hard to find anymore. Or they are too busy with your one off project.
18Fiatsandcounting
Posts: 3791
Joined: Fri Mar 15, 2019 11:23 pm
Your car is a: 1969 and 1971 124 spiders
Location: San Francisco Bay Area

Re: Finishing a hot 1800 build

Post by 18Fiatsandcounting »

Nut124 wrote:- Good machine shops are hard to find anymore. Or they are too busy with your one off project.
My machinist gave me three tidbits just yesterday:

1) Many suppliers of parts for American race V8s have shut down due to COVID-19, so he's got plenty of engines stacked up but can't get parts (gaskets, lifters, pistons, etc). A six month wait time in some cases. May not apply to Fiats as a lot of parts come from Italy.

2) Racers are still racing, but with no crowds, their income is down. So, they aren't doing preventative maintenance on race engines, and the result is: when they blow, they really blow, and my machinist is spending time fixing some serious engine issues.

3) Plenty of weekend racers now have extra time due to COVID, and so they're bringing work to his shop.

Bottom Line: more work than he can handle. My suggestion: Treat your machinist well and hope for the best.

-Bryan
jon8christine
Patron 2018
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Posts: 130
Joined: Sat Mar 12, 2011 10:05 pm
Your car is a: 1976 Fiat 124 Spider
Location: Wyoming

Re: Finishing a hot 1800 build

Post by jon8christine »

Yeah I'm planning on headers with a full exhaust, Allison's reports better gains with his, but it costs twice as much as Vick or AR 4-2-1. There is one small engine machinist here that milled the heads on my kids V6 when he blew the gasket. He seemed good and only had a week backlog.

I'm leaning toward the 40-80 cams, seem just right for what I want. Planning on the bigger valves everyone sells. Do they need the bronze valve guides and performance springs or just if the originals are worn and sloppy?

What electronic ignition do you like?

Right now I'm running a 32 36 carb but am having vapor lock? issues when it's hot half way through an autocross day. I see Pierce manifolds sells a dual 40 setup with manifold for $1300...I think I'll stick with the single for now and try to get it running right.
Nut124
Posts: 748
Joined: Wed Oct 25, 2017 6:39 pm
Your car is a: 1978 124 Spider 1800

Re: Finishing a hot 1800 build

Post by Nut124 »

Yes, I would replace the valve springs and use bronze guides. I have ran the Isky springs hard for 20 years and they held up well. I put in a new set again. The guides I bought had too much interference fit - I had to turn them down a bit. Removal and installation can be a pain. I had the guides in the freezer and the head in the oven. They must be ID reamed or honed to spec after installation. If you try to do guide work, you will need to get a guide driver that drives on the shoulder, not on the tip. Plus the reamers.

Bigger valves will do nothing unless the seat ID is opened up to match valve. Like I stated, the seat inserts are too small. Some shops may refuse to cut the seat to the bigger valve size due to inadequate seat insert "margin". I cut mine to the very edge. If the valve is not centered in the seat, this will not be possible or will be no good.
Nut124
Posts: 748
Joined: Wed Oct 25, 2017 6:39 pm
Your car is a: 1978 124 Spider 1800

Re: Finishing a hot 1800 build

Post by Nut124 »

Regarding electronic ignition - I'm running the Fiat factory dizzy. The later models are gapless, electronic distributors.

A programmable unit would be ideal. I had to fab, replace the advance springs in mine. It is very important that the advance is no more than about 38deg at full throttle, above 4000rpm. Less than 32-34 may result in reduced power. It can be difficult to get the advance correct. Lack of advance at low speeds will cause missing, spitting. Too much under power can cause detonation damage.
Nut124
Posts: 748
Joined: Wed Oct 25, 2017 6:39 pm
Your car is a: 1978 124 Spider 1800

Re: Finishing a hot 1800 build

Post by Nut124 »

Ran two 1/4mi passes today at a very busy track.

15.80s @85.0mph
15.76s @85.34mph

Had hard time hooking up in 1st with street tires. Shifted at about 7500-7600rpm.

Overall, I'm starting to be pretty pleased with how this project is running. The car is a pleasure to drive and sounds awesome. Want more cam though.

Obviously, this is not a drag racer, but 1/4mi time, speed is a good way to assess engine HP.

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18Fiatsandcounting
Posts: 3791
Joined: Fri Mar 15, 2019 11:23 pm
Your car is a: 1969 and 1971 124 spiders
Location: San Francisco Bay Area

Re: Finishing a hot 1800 build

Post by 18Fiatsandcounting »

That's really cool, Nut! Any idea what your HP is?

-Bryan
jon8christine
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Posts: 130
Joined: Sat Mar 12, 2011 10:05 pm
Your car is a: 1976 Fiat 124 Spider
Location: Wyoming

Re: Finishing a hot 1800 build

Post by jon8christine »

That's awesome. So did you bore your block to 85mm and upsize the piston diameter?
Nut124
Posts: 748
Joined: Wed Oct 25, 2017 6:39 pm
Your car is a: 1978 124 Spider 1800

Re: Finishing a hot 1800 build

Post by Nut124 »

Thanks for the nice comments! I appreciate it very much after having spent countless hours on this project with many worries and redos.

I did not bore the block for extra displacement. I bored it to what was required to true the bore. It was bored to 84.4 last time years ago and was still true and good. We did a good hone job and it cleaned up nice. So 84.4.

As to HP. There are a number of HP vs 1/4mi calculators there online. They suggest anywhere from 125 to 145HP. The best case for comparison is the Miata. Motor trend tested a -99 Miata: 2300lbs car, 1.8L/140HP, 15.9s @86mph. This is pretty much identical to what I have.

I do think that modern HP is stronger than 1970's HP. Most Fiats back then ran 1/4mi in 18-21sec, some with over 100 advertised HP. The Abarth Rallye 1800 was listed at 128HP and 17.1s at 1/4 mile. Could be that the instruments back then were not as good.

The car runs great but I feel like I want more cam. I have mixed feelings about whether I want to push it for a few more HP and risk reliability. I kind of want to drive the car now, not work on it, for a while.

I do think that a fat lobe cam and 38 chokes might be good for 10 more HP at 7000+ and maybe low 15's at the 1/4mi. Availability of such cam is also spotty at the moment in my experience. I will not buy another cam without having the complete specs at hand for review; Need LATDC, lobe centerline, duration at at least two different lift values, total lift and recommended valve clearance. European cam makers provide all this.

If anyone has experience with this, I would like to hear about it.
Nut124
Posts: 748
Joined: Wed Oct 25, 2017 6:39 pm
Your car is a: 1978 124 Spider 1800

Re: Finishing a hot 1800 build

Post by Nut124 »

I ordered and received some bigger cams for my Fiat project.

I did degree them to map the profile but have not started to install yet. These cams are a lot like the Alquati 42/82 but a bit more low and medium lift it seems, fatter lobe.

My engine has all the other parts needed to make power. I believe it is cam limited as is at the moment.

I would expect HP to peak at around 7200-7300 with these vs at ~6300 with the old 40/80 cams. The question is how much will around town drivability be hurt vs my current cams. My current cams run awesome, have great low/mid torque and make about 140HP and 15.75s 1/4mile.

I would expect with these cams to do 150-155HP and low 15 second 1/4mile, we'll see. Perhaps I'm too optimistic.
justrhines
Posts: 42
Joined: Sun Jan 05, 2020 6:43 pm
Your car is a: 1975 Fiat Spider

Re: Finishing a hot 1800 build

Post by justrhines »

Awesome build. I've got the dual carbs and headers working great. Now for cams and pistons.

Jon- if you're concerned about price but want to try for a dual carb setup, you may want to try the knockoff EMPI HPMX carbs (which are themselves Weber 44 IDF knockoffs) and the Pierce manifold. You can get these pretty cheap and they seem to be running great. Only required adjusting the throttle plates as they are not seated properly from the factory.
Nut124
Posts: 748
Joined: Wed Oct 25, 2017 6:39 pm
Your car is a: 1978 124 Spider 1800

Re: Finishing a hot 1800 build

Post by Nut124 »

justrhines wrote:Awesome build. I've got the dual carbs and headers working great. Now for cams and pistons.

Jon- if you're concerned about price but want to try for a dual carb setup, you may want to try the knockoff EMPI HPMX carbs (which are themselves Weber 44 IDF knockoffs) and the Pierce manifold. You can get these pretty cheap and they seem to be running great. Only required adjusting the throttle plates as they are not seated properly from the factory.
What intake manifold and throttle linkage are you using? Most dual IDF manifolds I saw were for 40mm carbs. I had to modify my Pierce manifold extesively and fab my own linkage. A lot of work.
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