Need input from big cam users.

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Morning spinman.
I did a little searching around this morning about the MP/purple solid cams. I know yours is unknown at this time, but they used to sell a .508 solid that had some pretty radical numbers for the street, like [email protected] and 76* overlap. Something like that could give a pretty low vac reading. Just thinking outloud for now. I'll be interested to see how the adjustments work out.
 
Rick,

Thx for the effort. Not sure if this cam is that one of course. Seems odd that the guy that originally did the car would put such a radical cam and leave a stock converter in it. Makes no sense. The guy that sold me the car is not any help. He will make no effort to find out anything. I laid into him pretty hard after I specifically told hym the engine pinged before I bought it and he said it had been checked out by his so called great mechanic. Oh well I will do what I can and if push comes to shove I will have the engine pulled and rebuilt with a more suitable cam.
 
Angry Jones,

Can you elaborate a bit. The air bleeds. We are not talking idle adjustment correct? And the secondaries. Let me see if I understand. You want me to crack the secondaries just a bit to allow intake to flow there so I can reduce the amount the primaries are open at idle. And the reason is because there is a point where the primaries make a transition one does not want to pass during idle. What effect does having the primaries too open at idle have on how the carb provides fuel? Oh and on the air bleeds. These are like jets? So I buy smaller air bleeds or is not that easy?

I did some research.

http://www.carcraft.com/techarticles/ccrp_0807_holley_carburetors_basics_guide/viewall.html

So I have a better understanding. Looks like drillng holes is the first step according to the article, but I suspect your secondary crack is a easy way to confirm how much it will improve the stumble. As far as the air bleeds. I think I understand that they are for mixture. I am fairly sure this thing is running pretty fat. Plugs are not black, but the insulator is not white either. More like a dull gray. Engine will die if I crank idle jets all the way in, but it will still ru at about 3/4 turn out. Not sure is that helps. One question you may be able to answer. With the low vacuum I have, is it possible for the power valve to open slightly and allow fuel to be added at idle? I am guessing that is a no, but I figured I should ask.
 
what port on the carb are you using for the vacuum gauge?? one port on a holley is vacuum,,,and one port is timed for the vacuum advance,,,, also you said the motor pinged ??? that to much advance and thats why your timing at idel is so high

i have a 528 lift 284 dur solid cam,,,timing at idel is 18 degrees,,
 
Back the total timing off to get rid of the detonation (pinging)...I would try 32° total.

If you are wanting a milder motor, you can replace the cam relatively inexpensively (~230 bucks for cam/lifters/gaskets)....and you don't have to pull the motor to do the cam swap.
 
Why not lock out the distributor advance and go all in at idle?? That's what a lot of guys with big cams do. Install a switch so you can crank the engine over without the ignition, then kick it on while the motor is spinning.
 
Fish,

The pinging was occuring at load. I have recurved he diss to deal with that. Now I think I am dealing with one of two issues.

As to your question. Of course I have the guage hooked to manifold vacuum. There is no port vacuum at idle. All my tuning is being done with out any vacuum advance at this point. Current timing is 22 initial and 34 total. 6 degrees diss 12 crank.

The issues are. Low and highly fluctuating vacuum at idle and even fluctuating vacuum at higher non load RPM. I can understand the bounce at idle, but at 3000 RPM? I would think it would settle down.

The second it idle in gear. In neutral I am at 1000 RPB and it drops to near 700 in gear. Stock converter is not helping.

This weekend I will check the lash on all the valves and do a compression and leak down test to see if I have any leaking valves. That could explaing the vacuum issues.

All in all the engine runs well in the higher range. Like 3000 RPM and up. Of course the trans shifts at 4000 RPM so unless I do a manual shift it never gets into the real power band. One other possibility is the cam is retarded and or the chain is stretched. When timing I do see a jump from 22 initial to around 30 initial at times. Like a blip and I hear a stumble when it does that. Almost as thought the cam is suddenly advancing. My guess would be chain. Diss is new.
 
Drilling the throttle blades should be an absolute last resort. I've got/had bigger cams with more overlap than what you have, not a single throttle blade was drilled.

Take the carb off and see what the size of the transfer slot is. If it's more than a square in size, open the secondaries and close the primary side down.

Google "holley transfer slot" and look at the images.
 
crackedback said:
Drilling the throttle blades should be an absolute last resort. I've got/had bigger cams with more overlap than what you have, not a single throttle blade was drilled.

Take the carb off and see what the size of the transfer slot is. If it's more than a square in size, open the secondaries and close the primary side down.

Google "holley transfer slot" and look at the images.
Click to expand...


Crackedback,

Just got off the phone with the mechanic that the owner used. First the owner did not have him check the ping issue. The mechanic said he has not touched the engine other than oil change in over two years. He did offer that by memory he recalls the cam was an ISKY cam. He thought the lift was around 540. But I think it is more likey this cam. 280 Mega. 485 lift 280 duration. Lash is 000 hot. This should be fun. I think I will try checking all the valves and look for the one with the biggest gap and check the rest against that. Like a baseline cold and then run it hot and see if any are tight.

As far as the primaries. Hard to tell from the top, so I will have to take the carb off. They actually don't look that open though. But I did check and I have a full turn on the butterfly adjustment screw. Not sure if that tells you much.
 
Rick,

oops your right. So I am going to go with the 505. Lash hot 28. Play it safe. Can you explain how lash can be so much different on cams. Could be the Z35 as well. Heck it could be anyone of these. There must be a way to find out. If lash is 28 hot, what would it be cold?

I think I may just bite the bullet and pull the sucker and put a decent hydraulic in. This is crazy.
[FONT=Verdana,Arial]SOLID Cams [/FONT]E-4 Tremendous torque & good mid-range power. 9-10.5:1 compr. , good idle stock converter. 3.23-3.70 axle ratio. Up to 625 Carb. RPM-Range (2000-5500) Valve Lift (.425 .425) Valve Lash hot (.015 .015) ADV Duration (260 250) .050 Duration (216 216) LC 108 390144$132390044$895B-777 Strong mid-range perf. Lopey idle. 2500 RPM stall. 3.70-4.11 axle ratio. 650-750 CFM Carb. 10.5:1 compr. RPM-Range (3000-7000) Valve Lift (.480 .480) Valve Lash hot (.018 .018) ADV Duration (280 280) .050 Duration (240 240) LC 108 390177$132390077$809505-A Bracket racing. Rough idle. 3000 stall. 4.11-4.56 axle ratio. Up o 850 CFM Carb. 10.5:1 compr. RPM-Range (3500-7000) Valve Lift (.507 .507) Valve Lash hot (.028 .028) ADV Duration (300 300) .050 Duration (254 254) LC 108 390157$149390057$919Z-35 High perf. Street/strip. Lopey idle. 2800 stall. 4.11-4.88 axle ratio. Up to 750 CFM Carb. 10.5:1 compr. RPM-Range (3000-7000) Valve Lift (.525 .525) Valve Lash hot (.016 .016) ADV Duration (288 288) .050 Duration (254 254) LC 108 390135$149390035$919555 High perf. Street/strip. Lopey idle. 3200 stall. 4.56-4.88 axle ratio. Up to 800 CFM Carb. 10.5-11:1 compr. RPM-Range (3200-7200) Valve Lift (.555 .555) Valve Lash hot (.014 .016) ADV Duration (296 296) .050 Duration (263 263) LC 108 390155$149390055$9191012-C All out drags. 5000 stal. 4.88-5.13 axle ratio. 850+CFM Carb. 12:1 compr .RPM-Range (4500-8000) Valve Lift (.580 .580) Valve Lash hot (.028 .028) ADV Duration (312 312) .050 Duration (274 274) LC 104 390110$149390010$919
 
Didn't you mention that you got 340 lift on the pushrod side when measuring. If so, that's closer to the .507 lift cam.

That is REALLY hard to read through. :(

254 at .050 is a BIG camshaft.

Any changes to timing when you drop it in gear?
 
As far as different lash settings, expansion would be the same on any of them so i'm speculating that it has more to do with lobe design on the initial ramp as to not punish the lobe or lifter on a specific design.

Back to your issue......all these larger solids require a dual spring which you do not have for some reason. Was it overlooked or is your cam not as big as we might think?????

I would do as we talked yesterday and set the valves cold somewhere in the .020's and do a compression test and see what the numbers are. Then get another vac reading. Detective work to identify as many unknowns as possible is where you need to start. I have lots of ideas, but that will just muck up the situation for now.
 
I doubt the problem has anything to do with the torque converter stall speed. It would have to be one hell of a tight converter to keep it from idling. The converter only knows RPM vs Load, so 750 RPM in a stock engine seems the same to it as 750 RPM in a cammed up engine.
I think you need to verify the valves are sealing correctly & that it's not misfiring 1st. If you have mechanical trouble (like valves) you'll never get the mixture right no matter what you do. If you can, do a leakdown test rather than just a compression test on it because it is way more accurate & you can identify if it's an intake or exhaust valve that's leaking, or rings too. Compression gauges just read peak pressures & won't really show a bleed off in cylinder pressure. An easy way to do it is to remove the rocker assembly from the head(thus closing all the valves on that head) & then blow the air in & check it. That way you can move from one cylinder to the next on that side without having to put each cyl on TDC since you are checking the valves more than the rings. OR you can leave everything in tact & check them as you check your valve clearances cylinder by cylinder. Listen closely for air hissing out the intake or exhaust.
To answer your other question about why valve lash differs so much between cams, it's because of the lobe ramp designs on solids. Hydraulics go with zero lash because you are pre-loading the hydraulic lifter some so there wouldn't be any lash.
Good luck! I hope you find the gremlin soon.
 
Lonewolf,

That is a very good idea? Makes perfect sense. Just pull the rockers. I have a torque wrench so I can reinstall correctly. I think the manual I bought shows the correct torgue. Then reinstall and go through the lash adjustment. But at least I will know if I have some burnt or bent valves. If I get no evidence of a leak then I can and adjust the lash. My guess is that more lash just means a noisier valvetrain and some loss of lift, overlap and duration. I think I will take some measurements on the existing lash before I pull the rockers. Maybe do leakdown test on # 1. If no leak then use the settings on that cylinder for a baseline.
 
Fish,

Runs OK. Cruise is good. It will break the tires loose off the line. 3.23 posi. Ships at 4000 RPM at WOT.
 
1 what is the cranking compression? A purple [email protected] will be about 160 on a used engine,

2 Google vacuum; fast movement starts at a leak, or carb internal-listen to Cracked. Power valves can drive you insane..

3 Make sure mech advance not fluttering around.

If you have a steady rev, and vac gauge bouncing- look at the valves. Engine is seeing a wrong signal to the intake. Hard to put it in words, something else is making vac erractic (at steady revs).
 
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