Some Good News for a Change

AMX69PHATTY

What a bummer with the axle shaft :shock: Guess it makes pretty good torque huh ? Remeber, the Crank turns twice for one dizzy rotation so a 10 deg adjustment at the crank is a 5 deg adjusment at the dizzy.

1980_Cj7

AMX69PHATTY wrote
What a bummer with the axle shaft :shock:

Yeah, I think the neighbors put a curse on us. Well, at least they are happy.

82Waggy

1980_Cj7 wrote
Oh, and it's plenty spirited off the line. "Somebody" just put the 4:1 t-case in low and jumped on it...and snapped a Dana 60 rear axle shaft in half! Well, it was back on the road for all of a day, now it's sitting again!!!

OK. Thought I read you were dissapointed in the power. Tell us more when you get it running again. Like to know what you think when in high and you get on it.

AMX69PHATTY

Yeah, cause where I now have the same cam, was wondering if I need to retard it to make it work up to 6000 or 6500, but the piston to valve clearance may dictate if I install this cam strait up, advanced or retarded. I guess as long as I have sufficient P to V clearance it'll be ok, otherwise I'll probably have to start from scratch. I remember ready all your good cam tech info 82Waggy. Don't tell me, I'm barking up the wrong tree with this cam ? Sounds like 1980_Cj has just about got it squared away except "someone" was having fun and found the yield point of an axle #-o

82Waggy

AMX69PHATTY wrote
I remember ready all your good cam tech info 82Waggy.
Don't tell me, I'm barking up the wrong tree with this cam?

Well, I don't know that I am any less confused then the rest of you when it comes to choosing a cam - Manufacturers recommendations are all over the map and pretty much less than helpful.

I try to follow some rules of thumb when choosing a cam and then make adjustment until I'm satisfied (adv/rtd adjustments, change cams, etc.).

I can tell you that, in general, if you need to retard a cam past the manufacturers straight up recommendation for intake lobe centerline then you probably have the wrong cam for your application. BUT, don't confuse that with using a timing gear keyway that may be different then the straight up position marked on the timing set in order to achieve the lobe centerline recomendation. Retarding a cam delays intake valve closing point and decreases cylinder pressure, so you start to lose torque at some point faster than the higher rpm can make additional hp - a point of diminshing returns.

I'm looking at this solid tappet cam for my 390 build that will be pushing rpm a bit more than my 401:

Camshaft Engle 5002sld
Intake Rocker Ratio 1.6
Exhaust Rocker Ratio 1.6
ILCL (Crank Degrees) 106
ELCL 110
LSA 108
Int. Duration @ .006 275
Exh. Duration @ .006 275
Int. Duration @ .050 245
Exh. Duration @ .050 245
Intake Lobe Lift 373
Exhaust Lobe Lift 373
Intake Valve Lift 597
Exhaust Valve Lift 597

Tappet Lift .020" .050"
Intake Open, ATDC -32 -17
Intake Close, ABDC 64 49
Exhaust Open, BBDC 68 53
Exhaust Close, BTDC -28 -13
Overlap 59 29
Hydraulic Intensity 30
Recommended RPM's 2000 - 6000

Blown7

1980_Cj7 wrote
It has a Mallory Unilite distributor we got from Blown7 with mechanical advance. Don't know if he had it recurved or anything. I think he was running it in a 360

Nope that came straight out of the box 15 yrs ago went into the 360, stayed in the engine till I removed it and sent it to you.

If all else fails use the tried and true method of a good timing light.
Screw all that vacuum advance gage theory. 111!!!

Jeff

1980_Cj7

Well I found out that my son did check the total advance this morning. He was getting 30* at 3,000 rpms. At least that gives us some indication of what it's doing. I'll have to get with him and check and record where it's at along the way to 3,000 and past there. Got the rear axle torn apart and the pieces all out.

AMX69PHATTY

Yeah, I don't use a vacuum gauge to set timing or mixture either. Maybe to look and see what it is and get indications, but not as a go-by. But I do keep one hooked up in the car for indications of carb function. Generally an out of the box Dizzy has "conservative" mechanical advance weights and springs in it, light weights and heavy springs, which means it starts late and slowly adds advance all the way up to maybe 6000 rpms. Guess they do this to avoid detonation. And the Mech Adv travel limiter usually will allow more mech adv than desired. I would be surprised if the Mallory has only 24 deg and it's all in by 3000 rpms. MSD units come with 3 different travel limiter bushings and 3 different strength of springs. They provide advance curve charts for picking desired pieces. Generally, initial should be about 10-12 degrees. mechanical should start coming in right off idle, ~1200-1500 rpm, and be completely in by about 3000, maybe 2500 and total available mech adv should be about 24 degrees, add to that the 10-12 initial, and the total advance @ ~3000 is ~34-36. Mech Adv should come in as fast as it can without causing detonation, but should not start coming in or "bouncing" at idle speed. Vacuum Advance is not included in the 34-36 total, it is in addition to the 34-36 total and is for economy. 82Waggy, not very much overlap on that Mech Cam. hmmmmmm Exhaust seems to close really early and Intake seems to open really early but I'm not used to lookin' at solid lifter profiles.

82Waggy

AMX69PHATTY wrote
82Waggy,

not very much overlap on that Mech Cam. hmmmmmm
Exhaust seems to close really early and
Intake seems to open really early
but I'm not used to lookin' at solid lifter profiles.

Not very much overlap? Compared to the Sumt 8601 the overlap at advertised duration is higher (solids are measured at higher tappet lift to account for lash), and it is 28deg more @ .050. Hydraulic intensity is much better than the 8601.

Timing it on a 106 ILCL may be too much advance.

1980_Cj7

The Clevite is a hydraulic cam, not solid, at least ours is. Can you please explain "Timing it on a 106 ILCL may be too much advance"? What's ILCL? Intake lobe centerline?

82Waggy

1980_Cj7 wrote
The Clevite is a hydraulic cam, not solid, at least ours is.

Can you please explain "Timing it on a 106 ILCL may be too much advance"? What's ILCL? Intake lobe centerline?

I was talking about the solid lifter cam I am looking at for my 390 (I've about spent all the money I need to on my FSJ and am getting started rounding up parts for my 69 Javelin project now).

Yes, ILCL = Intake Lobe Centerline. AMX69PHATTY was suggesting that the valve events are early and I was simply stating that they were shown at an ILCL of 106, which was completely arbitrary on my part. The cam being discussed is also a single pattern design ground on an LSA of 108. When I get closer to making a final decision I may elect to increase exhaust duration and change the LSA. The main point was that the advertised and .050 duration result in a pretty good hydraulic intensity figure - this cam has a relatively high .050 duration but should still be well mannered enough for a "Saturday Night Special" street car due to its' 275 advertised duration. It has fast ramps and .597 lift - should be a good lobe grind when combined with Edelbrock heads and 10.5:1CR. Anyway, this is for a completely different application than a Jeep.

AMX69PHATTY

Ah, ok, didn't catch that specs were at .020 & .050,
was thinking .005 & .050 and overlooked a "-" sign.

Man yesterday and today have been really nice weather here in Cincinnati.

82Waggy

Blown7 wrote
1980_Cj7 wrote
Screw all that vacuum advance gage theory. 111!!!

Jeff

I'm with you on that point Jeff! :razz:

Hey, when are you going to put that blown Jeep back together?

1980_Cj7

Well, found a used stock axle in a local junk yard, and got 'er back on the road again tonite. Already shopping for aftermarket alloy axles though.

AMX69PHATTY

:t: No more 4 wheel low burnouts for now right ? #-o Hope it's runnin' good. Do the 190* T-stat ? Did it help ?

1980_Cj7

We solved the weakest link, the axles, for now by lightening up... the drivers right foot. Gotta luv those full float axles. They are SOOOOO easy to work on. Didn't change the t-stat, but we reset the timing (with the timing light) to 5* advanced, and it seems to be staying between 190 and 200 degrees now. We originally had it at 10* advanced. Might have just been a combination of being brand new and tight and having a little too much initial timing. Didn't seem to be pinging though. Don't have any tune up specs for a 401, but a stock 304 is showing 8 or 10 degrees advanced for automatic tranny applications, depending on the year. We recorded the total advance every 500 rpms from 1,000 thru 3,500. It maxed out just past 3,000 rpms at 31*. I don't have all the numbers in front of me, but will post them later.

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