Camshaft Mystery SOLVED!, Elgin 6408 - what can you tell me about it? Options

[bbrock]

After 2 years of trying to find the specs on my camshaft, they were under my nose the whole time. I was putting in an oil pump on my engine and decided to peek at the camshaft to see if there were any stamps that would help solve the mystery. Sure enough, there it was! It reads 'ELGIN 6408'.



So what does it mean? (IMG:style_emoticons/default/confused24.gif) I had my cam reground in the late 80s through Automotion. They sold this grind as their "Mild Street Grind" and recommended it for carbs. Google turned up two hits on this cam. Below are the specs from Elgin Cams web site. The description is a little vague to me but it seems to say this grind can work for either carbs or FI but will run rough on the FI (I assume that would be the idle). I know what lift and duration are but know nothing about how they affect carb/FI performance. Is this a decent cam for carbs on a street car?

[anderssj]

I've been running an Elgin 7008-4 in my modified 2L since 1982. Engine has ~ stock displacement with Mahle euro PC set and dual DRLA 40s. IIRC, the cam is 280* duration (net intake lift = .420 @ cold .006 lash, net exhaust lift = .403 @ cold .008 lash). It's been great! I think Bayside in Redmond WA built at least one similar motor using the same cam in the mid- to late 1980s.

"lonewolfe" (member here on this site) was running the same cam in his 2258 motor with carbs. I think he liked it too.

All that said, I'm not sure if Elgin is still using the same naming/numbering system he was back in the 1980s. Last time I talked to them they had no record of the 7008...

[Mark Henry]

The lift numbers seem small, are they without the rocker ratio? (IMG:style_emoticons/default/confused24.gif)

FI compatible #73 Webcam has .426 lift, my cam has .507 lift.

A scat C-25 has .425 lift, mild carb cam, it runs carbs better, but IMHO w/40 webers no more power than Stock 2.0 FI.

Any more lift than .425 and you have to use HD springs and valvetrain.

[bbrock]

The lift numbers seem small, are they without the rocker ratio? (IMG:style_emoticons/default/confused24.gif)

FI compatible #73 Webcam has .426 lift, my cam has .507 lift.

A scat C-25 has .425 lift, mild carb cam, it runs carbs better, but IMHO w/40 webers no more power than Stock 2.0 FI.

Any more lift than .425 and you have to use HD springs and valvetrain.

I thought the same thing. I assume since they say "cam lift" whereas Web Cams lists "valve lift" that Elgin is posting just the lobe lift. Is it correct that you would multiply the "cam lift" by 1.3 to get valve lift? If so, that makes .385 which is still less than all the Web Cam grinds. I'm too stupid to know if that is good or bad. I'm just looking for something with stock performance or maybe a little better with 40IDF carbs.

[Mark Henry]

Web 86 if you're keeping stock valvetrain.

Web # 86a or 494, but needs manton PR's, 1.7 mod rockers, shaft spacers, 8mm rocker studs, 911 adjusters and HD single springs.

Cams at around .500 lift, like I have in my '67 2.6L t4 bug, need dual springs and higher CR pistons

[bbrock]

Thanks Mark. Right now I'm mostly interested in what characteristics I might expect from this cam that is already installed. I know Elgin has been around a long time and seem to have a great reputation and this was the cam recommended when I bought my carb kit.

I think my question might be more about what makes a "carb cam" and why is it needed? All I know now is you need different cams for carbs and FI but know nothing about what or why.

It's a little confusing because how cam specs are published isn't standardized, but from what I can tell, this Elgin cam I have is roughly stock lift (a little higher intake and a little lower exhaust) with longer duration. I don't know if they are correct and I'm not sure if the duration figures are apples to apples with the Elgin, but I found these specs for the stock cam on The Samba:

.302 @ the cam on the intake ( 7.67 mm)
.283 @ the cam on the exhaust ( 7.19 mm)

Duration @ .050 intake is 210°
Duration @ .050 intake is 206°

[Mark Henry]

Hot cams have more duration and valve overlap, when both valves are actually open for a few degrees.

FI needs a good vacuum signal, duration/overlap kills vacuum.
Carbs can run lots of duration/overlap.

My big cam is meant for carbs, I have a crap vacuum signal for my EFI MAP sensor, so I have to run TPS only. Same thing as running in alpha-N for MS users.