Engine Build Suggestions

[kmac33]

I am about to pull the motor on my 74 Spider as part of the body restoration/repaint process and figured I should take this opportunity to add some performance to the current engine which is bone stock except for having had all emissions "junk" removed a number of years ago. I am trying to gather as much information as possible to decide exactly what to do. I would appreciate any input all of you experts can provide in guidance, to help me accomplish this task successfully. (A big thank you to Alvon for spending the time on the phone running through his powerplant journey for me!). Here are my goals: Keep the cost reasonable - If I was rich I'd just order an insane motor from John Logan or Mark! I will mostly just have to worry about parts cost. build will be done by myself and a friend(builds motors for a living, just not Fiats).
I want an agressive street motor, 135-140 horsepower or so seems to be a realistic target from what I've been reading. Needs to be realiable, not a daily driver but I don't want to have to spend hours and hours wrenching to keep her running right.
Plan so far is: Slight overbore, possible domed pistons for increased compression. Cams - getting all kinds of differing info here, but sounds like fairly agressive intake cam and mild or stock exhaust cam will work well. Valves - undecided, had planned at a minimum racing springs. Carb - Since I have "the best stock carb" is the performance gain from a dual set up worth the cost of the intake and the carbs, or would a rebuild(with venturi overbore) and rejetting be close enough to the dual set up? Ignition - goodbye points. Crane 700 unit or other - suggestions? Flywheel will be lightened. Exhaust - performance header and exhaust.
I know the different combinations and options for engine builds are almost endless, but please fire away with any and all suggestions!
I would also appreciate any suggestions for sourcing the necessary parts.
Thanks to all

Kevin

[mdrburchette]

Hey Kevin! I know you'll get a lot of ideas to make your car go faster. Are you doing this in time for the Carolina FLU's regional event at the end of June? We're working on a catchy name so we can start posting specifics.

I think you've already got one of the best setups stock wise. I would consider more agressive cams, say 40/80s, up the comp to right around 10:1, lighten the rotational mass with a lightened flywheel and nice aluminum pulleys and slap a bigger carb or dual IDFs on it. Make sure you have everything balanced to the block so you'll have a smooth purring engine that will last a long time. If you're planning on dogging it, I'd also consider using racing valve springs and I'd definitely work on opening up the head.

[kmac33]

Denise,
Thanks for the reply and input! I'm not sure if I will be up and running by the end of June, but I sure hope so. Nothing is seeming to stay on the schedule I had planned . I was hoping to have the paint work completed already, but the prep work keeps expanding - my friend that will actually spray the car is a bit of a perfectionist, so at least all of the extra work will pay off in the way the car looks when finished. He actually talked me into pulling the motor so we could spray the engine bay - I want to be back driving so bad I was going to let the engine bay "slide" and do the motor in a year or two. I know I'll be glad I went ahead and did it all now though! Once I have decided exactly what to do motor wise and get all of the parts, my friend has said it will take 2 weeks or less to do the build, so as long as the body and paint work don't hit a major snag, I should be up and running in June. Do you have any suggestions for sourcing parts?

[baltobernie]

Do you have the 1756 motor and a single-plane intake manifold?

[mdrburchette]

Kevin, I just ordered a set of 3 coil valve springs from Guy Croft.
Miller's Mule http://www.millersmule.com/ makes pulleys and adjustable cam wheels for our Fiats at a reasonable price.
If you want just an aggressive intake cam, list your desire in the parts wanted section of the forums. There are several people that have used just one cam in their setup and the exhaust cam can be used on the intake side with some modification. I got my 42/82 cams from IAP and don't think their too aggressive.

[ga.spyder]

Hey Kevin,
get busy on that thing! We expect you at the event(Cars and Cornbread,Dixie FiatFest,Southern Fried Fiats...)in June.Sounds like things are coming along just fine.My suggestion is to find a 82 and put that F.I. motor in there.Problem solved.I will email you with the details on the june ''event(we need a name!),hope you can make it .
I just looked at the pix of your resto.The interior looks fantastic.I may take you up on your offer to help me with upholstery when the time comes.
Craig
ps..snow in Atl. on Sun??

[mdrburchette]

ps..snow in Atl. on Sun??

Yeah yeah yeah. They've teased us with snow every Sunday for a month. Now if we could get a good dumping in March like we did in 1993, that would be awsome!

[kmac33]

Denise, Thanks again for the suggestions and input.
Bernie, Yes to both questions.
Craig, Don't give me any ideas on putting an 82 FI motor in, I happen to know where I can get a nice one to "borrow", just a little drive north of me . I think I could probably get an "all new" front end from the same source .
The project is progressing - I need to take some new body pics. I pretty much have the entire body block sanded - I just need to do the door jambs and the interior portion of the doors and the body prep will be done except for pulling the motor and prepping the engine bay. . The hood, hood cowl, trunk lid and lower side valance panels have all been painted and look great. Don't know what the weather has been like for you today, but I've gotten about 4 inches of snow so far and its still coming down.

[baltobernie]

Kevin,

I'm building an engine similar to yours right now. (Well, not right now because we have 8" of snow, and it's still coming down. And I have Robert Cray tickets for this evening in Virginia ) Anyway, I hope to have it finished in another couple of weeks, and will post results then. I will be tuning on a chassis dyno, so we'll have real numbers to work from. 0.8mm over, 10:1 Vick pistons, 40/80/80/40 cams from IAP, etc. I'm using a single 38 DGS carb, which is widely used as an upgrade to 2-litre BMW and other performance street engines.

I dunno about 135+ hp from 109 cubic inches without a considerable loss of low- to medium-RPM performance. MIght not be possible without dual carbs or FI in any case.

[kmac33]

Bernie,
Can't wait to hear how your build turns out. I'll be interested to see what the Dyno shows. The friend that is doing the majority of my build has a chassis dyno too, so I'll have concrete before and after rear wheel horsepower numbers as well after mine actually happens.
Good luck getting to the concert tonight, the roads down here are pretty much clear now. All of the snow on the ground is supposed to be melted and gone by tomorrow.

[So Cal Mark]

peak hp and torque figures aren't quite as important as WHERE in the rpm range it occurs. Losing midrange makes a street car pretty useless and not much fun to drive. Unless you live in an area where you can flog it constantly (and like to drive that way), building a street engine with low and midrange power is the only logical path. Realize that the engine has a much shorter life if it's run at the limit constantly

[mdrburchette]

I dynoed my engine before and after the rebuild and gained 24hp and 10 lbs of torque. What surprised me is with the 42/82 cams I used, I thought the hp and torque curves would have been more different. A lean fuel problem and irratic ignition problem did show up on my new dyno run so I'll be running it again with my IDFs and the ignition problem fixed.
Here's my "before" run:


And here's my "after" run:

[pope]

what do the 2 lines on the upper parts of each graph represent? One line says 30.9 and the other says 62?
Am I reading it right where I think that there is not much power increase left after 5500rpms?

[mdrburchette]

I don't know what those numbers mean. I'm sure they explained it to me at one time, but this was done a few years ago. As for peak power being around 5500 rpm, that's what it's saying but I don't know if I lost something with the ignition going haywire and the carb leaning out. That's one of the reasons I wanted to have this test done again.

[baltobernie]

Pope, the "62" line is the torque curve; use the scale on the left. The "30.9" line is horsepower, corresponding to the scale on the right. The two numbers themselves are probably where the cursor was when the document was captured. The max torque and hp are listed in the header. This looks typical of a street engine, where the horsepower flattens a little below the redline and increases slightly until the engine runs out of breath.

Denise, it does appear that you've experienced a fuel or ignition malfunction, as you say. Those 42/82 grind cams are pretty wild, with a torque peak at 4,000 RPM. Is the "before" picture using stock cams? 'Cause that's the torque curve I'd like to see on my new motor (only flat to the redline).