Engine Build Suggestions

[pope]

Bernie, Thanks
by reading the first run, it looks like the torque it there from around 2200 and starts to fall off around 4500.
Where as the 42/82 has less torque in the low end but more in the mid to higher end.

That fall off in torque around 4500 in the first run, is that from lack of air or fuel or both.

[mdrburchette]

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).

The first run was with my stock, unmolested engine with over 100k miles. The second run was the rebuilt engine with 42/82 cams, electronic ignition and 350 2bbl Holley. My next run will be with the ignition issue fixed and 40 IDFs. I'm wondering how much the ignition problem and lean fuel problem had to do with the torque and hp readings.

[baltobernie]

What is the year of manufacture of the "stock, unmolested" engine? I don't suppose you saved those camshafts, did you? It's my understanding that there were at least two different "grinds" over the carb'd Spiders lifetime. The pre-emission ones had a performance profile vs. the mid- and late-70's engines. One way to visually identify them is the width of the lobes; the early engines had narrower lobes than later ones. It would be difficult to find NOS or even good used ones that have not suffered excessive wear due to neglect or lubrication issues. I'm suprised that no one has attempted to duplicate that early profile.

[mdrburchette]

The engine was the one you saw in the pics being pulled out of my car and is the original 72 1608. I pulled an engine from another 72 and built that so all we had to do was swap it out so I still have the cams from it and from yet a third 1608 in my shop.

[racydave]

How do you guys feel about re-ground cams? Any profile can be reproduced. Im a little scared of them???

[So Cal Mark]

reground is all I use, no problems ever with any of them.

[baltobernie]

I'm more concerned with the reputation of the seller than the manufacturing process, no matter what product I buy.

Denise, if the 40/80 set I bought from IAP is too hot, I may contact you about one or two camshafts from an early engine.

[pope]

Bernie, I have heard that if it is too hot, just use the 40/80 intake cam and use the original exhaust cam. Anyone else heard of this?

[baltobernie]

Yeah, we talked about this in another posting. But since then, I've heard that the "smog" cams, like the ones I removed, are very weak. Something like 20/40 timing? I think I'd need something more agressive on the exhaust side to more closely match the 40/80 intake.

Perhaps I should have considered other sources. I found 7 or so for the Fiat TC, but most of them were European, with pricing upwards of $500, which is ridiculous. I'm still keeping faith in our local Charlottesville vendor, who's been a supporter of our club. One thing's for certain; I'll be giving the IAP cams every opportunity to work, with a fresh pro rebuild, new carb, recurved dizzy, etc. We'll just have to wait for "the tale of the tape".

[mdrburchette]

Bernie, do you have the 1608 or 1592 engine? I've heard conflicting stories on what the cams specs are. Some say they're all the same, regardless of year model and some say the earlier engines had a more agressive cam. I can measure the lift of 1608 cam if it'll help you.

[baltobernie]

I have a 1756 motor, s/n 671297, probably 1976 vintage. The cams in this engine have a lobe width of approximately 1". I've seen older cams in photos, but haven't measured any; they appear to be about 5/8" wide.

I don't know if measuring the lift of the early cam would be definitive; it's the timing and duration that really differentiates street cam grinds.

[So Cal Mark]

I believe the stories of different oem grinds are myths. I've found the cam sprockets indexed differently, but no difference in cam specs. The parts books don't list different part numbers for cams either.