Semi race motor advice

[whitehause]

So I'm planning on a little hill climb and maybe a track day or two.
2L Engine being bored to 84.4, standard valves, Isky springs, electric fuel pump, standard 79 ignition, 4-2-1 exhaust, single holley 5200 carb on single plane 1800 manifold, adjustable cam gears, automatic trans (yes keeping the auto for now ) 3.58 rear, progressive springs.

So the question is 4mm or 8mm domed pistons
80/40 or 82/42 cams

Will do some spirited street cruising as well, but not real worried about it being a smooth daily driver.

[engineerted]

Go big or go home! If this is going to be a track car/hill climb/auto-x and you have access to 100 octane then by all means go with the 8mm domes.
i'm not sure where you live but in the Detroit area you can buy 100 and 110 octane fuel at the pump. You can try the link below to find some thing near you.
https://www.sunocoracefuels.com/fuel-finder


You could also go forged custom piston 13:1 Like mine.

IMG_0468.JPG (1.36 MiB) Viewed 691 times

[whitehause]

The local airport will sell 100LL avgas for about 4.50 a gallon, so not that bad really. We have a local place that sells 95 Real gas, no ethanol. I figure either should work for 10.2 to 1.
Now 13 to 1....that's a different story...lol

[SimcaBertone66]

Agree with Ted and the go big or go home school I drive a "retired" vintage spec 124 on the street all the time a 13.1 cr, TC on 110 is just like, DRUGS at 8k +rpm's … it's only $$ why not spend it on race fuel.....lol

[whitehause]

I think I'm doing the 8mm dome, but might do the 80/40 cam instead of the 82/42. It's not going to be "totally" race, so I'd like the power band to start a little lower in the RPM range. Plus with the automatic trans, I want to keep some of the low end torque.

[SimcaBertone66]

20 + years driving "mild" TC motors with the usual Mondial or Borgo cast HC pistons, full rotating assembly balance, messaged stock rods, lightened steel flywheel, twin 40 with 42/82 cams the whole time mostly street driving ….auto X and full track TT's … the 42/82 is not a "radical cam" ….. just sayin … NY to WV for FFO 2000 as far as long distance driving with that combo...…….

[ST3Racer]

Tim,
Stagger the cams. Go lesser on the exhaust side than the intake side. This will give you the power you want, but widen the power band. You will get less on the top end - slightly, but gain on mid-range torque. If you will want more help on this, post back or PM me. It depends on your budget for cams...

[fp55scca]

20 + years driving "mild" TC motors with the usual Mondial or Borgo cast HC pistons, full rotating assembly balance, messaged stock rods, lightened steel flywheel, twin 40 with 42/82 cams the whole time mostly street driving ….auto X and full track TT's … the 42/82 is not a "radical cam" ….. just sayin … NY to WV for FFO 2000 as far as long distance driving with that combo...…….

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--Ok Tim, I've been biting my tongue for months now, watching you prepare this project. "A semi-race motor" really? That's like being "a little bit pregnant"? Just kidding you know, but like these guys said, go big or go home! Still kidding.

--But, as Joe said, I think what you really need to build is a solid and reliable "high performance street" motor. Tim, I believe you know (and so do all of the others here), whatever you choose, it has to be in balance from intake-to-tailpipe. No sense in more compression than the rest of the system can support. You acknowledged months ago that you were not trying to make this the most competitive hill climb car, but would be using it mostly on the street.

--Using JD's formula then, I think some 9:8 cast pistons with stock 2L rods would do fine. If you want to lighten and rebalance the rods, that would be good too, and even replace the rod bolts with ARP as we discussed. Personally, I think there is a ton of labor involved in lightening and rebalancing rods (did it for years), and therefore I believe it's a process of diminishing returns considering the remainder your engine build. You are mating this engine to an AT, so there is no opportunity for a lightened flywheel. Stock 2L rods will do fine, unless you want to consider an aftermarket set that already come lighter and fitted with ARP bolts.

--Holley 5200 series carb? I think you acquired one of these? If going with a single carb, this would not be my choice. The Holley 5200 is great carb, essentially a progressive, Weber 32/36 progressive. Easy enough to convert to synchronous for more performance, but keep in mind that while the primary and secondary is 32mm and 36mm, the chokes are really only 26mm and 27mm. If going with a single carb on an 1800 ported, single plane manifold, it's hard to beat a 40 DCNF, because like a 40IDF, a DCNF is so completely tunable from chokes, to jets, to emulsion tubes, etc. Ideally, I think most here would recommend dual 40IDF's, unless you want to eliminate your brake booster and move your MC and go with 40 DCOE's.

--The above is all in consideration toward cam choice. I would be in favor of something like to 42/82 cams; or check with Bill McMahan who has a stash of some pretty exotic equivalents. All of this will demand some very extensive head work, that is well outlined in the GC book you retrieved online. There's enough information and guidance in his book to prepare a very competitive head. Or, you could just send the head to Jon Logan at Midwest Bayless and he will do an excellent job for you. "Most of the power is made in the head".....

--Tim, I promise this will be the last time I say this: I just don't see this working in a hill climb with an OEM Fiat 124 Spider automatic transmission? Without total rpm control, it scares me to even think about trying it!

[SimcaBertone66]

GM TH 180 ….. find a shop that builds "race" automatics, could do some mods "shift kit" valve body mods … Converter ???? I enjoyed the AT in my 124 Sedan … shifted hard at 6K with a warmed over 1488 pushrod motor …. I use a 500 CFM Rochester, fabricated adapter … too much trouble, found some Trans Adapt bits that will alloy any 2G Rochester base to make with a bit of tweaking to the 1.8 manifold …. have fun

[SimcaBertone66]

Missed Jim's last bit … yes , have Logan do a head and install some 82/42 and have his shim it spec, plus and play ...... love spending .. others peoples money ...lol