ventura ace wrote: I believe I saw a similar dip in Bernie's torque curve from his Dyno testing a while back
Yeah, I see what you mean. In my case, I think the 38DGS transitions from "medium" to "hi" jet around 3500 RPM. Maybe a different emulsion tube? Like yourself, I'm pleased enough with the results to quit here. I've got a stock-looking engine bay with approximately the same power as an Abarth.
No offence intended but you're utterly wasting your time analysing a power curve from regrinds on the 8v TC, however intriguing it may seem, because the core problem is the cams themselves.
You cannot grind an effective 'new' profile onto those billets that will produce a torque curve even as good as the standard ones. I've been saying this for 20 years but folk are still 'rolling out' regrinds - and in some cases those firms should really know better. I think I'll stop saying it. Hell, maybe I should sell regrinds too and just ignore the 'flak' that follows and just say 'you get what you pay for..'
I hear you, boss. The engine I'm depicting uses new 80/40, 40/80 cams from our US sources.
I'm a slow learner, but now a believer that the cams on the Spider engine are definitely not holding back power. (I just have to prove things to myself sometimes; it's part of being old and cranky ) So for us emissions-exempt guys, it's carb first, then intake, then exhaust improvements?
Bernie, I reckon that may be why your set-up has a little more torque that mine, most other things being similar or equal.
Guy,
Which cams specifically do you recommend, knowing the rest of the particulars for this engine. Keep in mind that I'm not racing the vehicle, just looking for a good combination of reasonably strong performance with smooth streetability in the daily driving range.
It won't be the easiest modification, since I presently have extended valve tips for the small base circle of the regrinds. I may need to pull the head and grind the valve stems down. If I'm lucky, I may get away with 2 thicknesses of cam tower gaskets, I think I have about .015 - .020" to give by going to thinner shims. I believe the base circle radius that I have is about .055" less than the stock camshaft.
I believe you suggested a 'Stage 2' intake and a stock exhaust cam, when we spoke recently. Would you please provide me the profile or other info describing the recommended cam (s). My e-mail is in the signiture line. Thanks for your input. I've been reading more in your manual about the merits of more dwell at the wider valve opening, expressed as lift at TDC, I believe.
One of the experts here in "the colonies", John Logan, highly recommends the stock exhaust cam with an 80/40 intake for this type of application. You could possibly convince me, Ace, to try this. If you're interested, your purchase of my other 80/40 would partially fund re-timing and valve adjustment, which I must farm out. I'll throw in a stock exhaust cam, if you've discarded yours. PM me if interested.
Alvon, I got a copy of your dyno tests today. First thing I noticed was at 3200rpm, where your torque curve dips, your a/f curve goes lean in 4 of the 5 tests. Coincidence? I think not.
IMHO, 40/80 cams are way too agressive for most street-driven Fiats. All you're doing is mitigating the fact you chose the wrong cam by using a stock exhaust cam and don't have an adequate exhaust system. How often do you rev your street engine to 7k?
It sure would be nice if our other vendors would weigh in on the subject of camshaft(s) selection. Specifically IAP Midwest/Bayless and Vick, who between them probably sell more than the ROW combined.
And how about less "it sure feels more powerful" and "designed for street performance applications", and more real numbers
Alvon, I have read through the above threads and some things jump out at me. First, for your engine setup you should start at 135-140 mains with 180-200 air correctors 55 idle jets. My street motor with the 1.8L 10.8 cr big valves 40/80 intake (not regrind) stock exhaust 4/2/1 header 40idfs 32 chokes: runs great with this setup I can pull full throttle in 5th gear from 2500rpm. Secondly your dyno guy should not be looking at AFR at 3000 rpm under "no load", the carbs are still on the idle circuit and not a good indicator of the WOT condition. Thus start at 135 and adjust the AC to bring in the AFR at WOT. Thirdly, Marks comment about the 40/80 not being a good street cam is just that, his opinion and the rest of us who run with it could not be more happier.
Ted
Ted
1978 124 Spider, Complete Restoration
1974 Fiat 124 F Production Race car
it is no different than with american v6's and v8's - when adding a big re-grind cam you have to do other modifications to the engine & car in order to make it run good with the new cam profile. The 40/80 80/40 set that you speak of has an advertised duration of 300 degrees and a lift factor of .433 inches on 110 degree lobe centers that adds up to a hell of an over lap putting the power curve in the upper rpms. So performance carbs, intake, and headers with a performance exhaust is a must in my opinion. Plus with that kind of overlap your compression needs to be higher in order for it to build power properly. I think the gear ratio of the stock rear-end for the five speed probably is fine for that cam set. anyway...just my two bits...
Ted, as I wrote, it is my opinion that the 40/80 cams are the wrong choice for the MAJORITY of street-driven Spiders. Most of the owners I talk to never see 6-7krpm. I'm sure there are owners such as you that are thilled with those cams but unless you're flogging that engine you could make a better choice. It all depends on what you want/expect from your engine and how you plan to use it
One other thought is using adjustable type cam pulleys so that you could either advance the cam timing or retard the cam timing easily. Advancing would lower the usable RPM range a little. The only way to tell the effectiveness of that would be with a dyno. Has anyone noticed an improvement by advancing the cam say 4 degrees? Makes a difference in bigger engines like V6's and V8's but torque is better in those engines... soo...again only my opinion...
I've read that IAP cam data. As I have said in my new book (where I have attempted to explain cam characteristics at some length) duration and lift per-se are meaningless - where a regrind is concerned you must examine the area under the cam curve - the lift x degree function. In every case of a regrind on an 8V TC you will find that a regrind will have significantly less area (and thus flow potential) than a billet of 'equivalent' characteristics.
And if you regrind on these (and all engines are not the same in this regard, it depends on the bcase circle diamter to a great extent) to achieve higher lift your new profile will necessarily also have an increase in lift at TDC (affecting the overlapping phase) commensurate with the increase in peak lift. In order to generate more lift and longer duration you will also radically change the opening and closing ramps potentially setting off bounce and float and spring/seat damage and at the same time reduce the cam area thus reducing the charge momentum during the very induction phase you are trying to augment.
It is my strong advice that you AVOID regrinds on this engine and ALWAYS buy billet.
) So for us emissions-exempt guys, it's carb first, then intake, then exhaust improvements?
