Cam going flat?
Thread Starter
Le Mans Master
Joined: Nov 2009
Posts: 6,882
Likes: 234
From: Bangkok, Thailand
Cam going flat?
I'd like everyones opinion on my old stock cam. I did my Renegade install this weekend and now feel like I should have just stopped when I saw the cam lobes that I could see through the oil return holes in the valley. The lobes were all polished VERY shiny, no Parkerization left with some ugly looking ridges/grooves.
In the picture below you can see that some of the lifters are going down flush with the tops of the lifter bores. It's also pretty obvious when cranking the engine around to adjust the valves that some of the valves are getting significantly less lift than others. I'm pretty convinced that the cam is flat but I can't get back to tearing into the eninge till this weekend. In the mean time, I'd like opnions from those with extensive cam experience regarding the hieght of the lifters in the bores. Note the #6 exhaust lifter and the #8 intake lifter especially.
Sorry for the huge picture but I wanted to give as much detail as possible.
In the picture below you can see that some of the lifters are going down flush with the tops of the lifter bores. It's also pretty obvious when cranking the engine around to adjust the valves that some of the valves are getting significantly less lift than others. I'm pretty convinced that the cam is flat but I can't get back to tearing into the eninge till this weekend. In the mean time, I'd like opnions from those with extensive cam experience regarding the hieght of the lifters in the bores. Note the #6 exhaust lifter and the #8 intake lifter especially.
Sorry for the huge picture but I wanted to give as much detail as possible.
Racer
Joined: Dec 2007
Posts: 298
Likes: 1
From: Escondido CA
From what I have seen my Small block chevy past, (MANY ENGINES) everything appears to look OK here..
It is not uncommon at all for the lifters to sit a little lower in one bank of cylinders, then the opposite side... If you cam was actually flat, none of the lifters would be up that high!
On the other hand, looks like your already about 1/2 way there if you wanted to swap out the cam!
It is not uncommon at all for the lifters to sit a little lower in one bank of cylinders, then the opposite side... If you cam was actually flat, none of the lifters would be up that high!
On the other hand, looks like your already about 1/2 way there if you wanted to swap out the cam!
Last edited by neverendingprojects; Oct 12, 2010 at 12:56 AM.
Le Mans Master
Joined: Dec 2006
Posts: 5,139
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From: H-Town Texas
I'm not positive, but I really don't think one can get a real good look at the cam lobes through the oil return holes. I know that when I had a lifter noise and we replaced lifters, the best visual came from looking through the lifter hole directly down on the lobe. Using a flashlight you should be able to see if the lobe is being worn down. It is possible, especially if those are tappet lifters. Of course, the only real way to be positively sure is to use a dial indicator and measure the precise lift of each lobe.
If I'm not mistaken, you have flat tappet lifters. These are also prone to wearing down. Did you pull the lifters to inspect while you had the valley exposed?
If I'm not mistaken, you have flat tappet lifters. These are also prone to wearing down. Did you pull the lifters to inspect while you had the valley exposed?
Race Director
Joined: Oct 2005
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From: Rolla Missouri
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The reason you see some of the lifters high in the bore and others low, is because you have cam lobes.
The lifters that are low in the bore are sitting on the base circle of the cam, allowing the valve to close.
The lifters that are high in the bore are up on the cam lobe, in order to open the valve.
The lifters that are low in the bore are sitting on the base circle of the cam, allowing the valve to close.
The lifters that are high in the bore are up on the cam lobe, in order to open the valve.
Thread Starter
Le Mans Master
Joined: Nov 2009
Posts: 6,882
Likes: 234
From: Bangkok, Thailand
I have a dial indicator and will use that this weekend.
I think the point you guys are missing so far is that some of the lifters are on the heel of the lobe and riding much lower in the bores than other lifterw that are also on the heel. Obviously, as the cam rotates and the lifter moves up the ramp and onto the nose of the cam lobe the lifter is going to rise. But my concern is the heel side being worn away (as well as the rest of the lobe) and the lifter not getting all the motion it should.
I think the point you guys are missing so far is that some of the lifters are on the heel of the lobe and riding much lower in the bores than other lifterw that are also on the heel. Obviously, as the cam rotates and the lifter moves up the ramp and onto the nose of the cam lobe the lifter is going to rise. But my concern is the heel side being worn away (as well as the rest of the lobe) and the lifter not getting all the motion it should.
Burning Brakes
Joined: Jun 2000
Posts: 913
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From: Chatsworth, Ga.
cam
I have a dial indicator and will use that this weekend.
I think the point you guys are missing so far is that some of the lifters are on the heel of the lobe and riding much lower in the bores than other lifterw that are also on the heel. Obviously, as the cam rotates and the lifter moves up the ramp and onto the nose of the cam lobe the lifter is going to rise. But my concern is the heel side being worn away (as well as the rest of the lobe) and the lifter not getting all the motion it should.
I think the point you guys are missing so far is that some of the lifters are on the heel of the lobe and riding much lower in the bores than other lifterw that are also on the heel. Obviously, as the cam rotates and the lifter moves up the ramp and onto the nose of the cam lobe the lifter is going to rise. But my concern is the heel side being worn away (as well as the rest of the lobe) and the lifter not getting all the motion it should.
Drifting
Joined: May 2006
Posts: 1,428
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From: Chewelah Wa
It seems to me that any wear or "flattening" would occur on the lobes themselves. If you had enough wear to affect the base of the cam, I would expect some kind of driveability issues. A dial indicator will tell you for sure, but I would expect some wear to occur and some differences between each lobe. I would try to measure at the top of the lifter. It does concern me that you can eyeball some of this. Anyways, good excuse for a new cam to go with your new manifold. A Lunati Voodoo 101 would be sweet with that combo.
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Le Mans Master
Joined: Oct 2008
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From: Houston Texas
Drifting
Joined: Jan 2006
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From: Ramona CA
You can put other induction on a ZZ4. Doesn't have to be a carburetor. Besides the 650 on the crate engine isn't pulling what EFI could.
Top Flight Corvette in San Diego replaces L98 engines all the time with ZZ4s. A tuned right ZZ4 will produce nearly 400 hp at the fly wheel. I've talked to him about a ZZ4 in my '92. Jerk out the LT1 with opti, insert a ZZ4 with '91 ECM. He says he's done it before. Get more HP, TQ and no opti problems. The HEI distributor will fit under the hood because it does on a '91 (same hood).
Top Flight Corvette in San Diego replaces L98 engines all the time with ZZ4s. A tuned right ZZ4 will produce nearly 400 hp at the fly wheel. I've talked to him about a ZZ4 in my '92. Jerk out the LT1 with opti, insert a ZZ4 with '91 ECM. He says he's done it before. Get more HP, TQ and no opti problems. The HEI distributor will fit under the hood because it does on a '91 (same hood).
Le Mans Master
Joined: Oct 2008
Posts: 9,758
Likes: 49
From: Houston Texas
You can put other induction on a ZZ4. Doesn't have to be a carburetor. Besides the 650 on the crate engine isn't pulling what EFI could.
Top Flight Corvette in San Diego replaces L98 engines all the time with ZZ4s. A tuned right ZZ4 will produce nearly 400 hp at the fly wheel. I've talked to him about a ZZ4 in my '92. Jerk out the LT1 with opti, insert a ZZ4 with '91 ECM. He says he's done it before. Get more HP, TQ and no opti problems. The HEI distributor will fit under the hood because it does on a '91 (same hood).
Top Flight Corvette in San Diego replaces L98 engines all the time with ZZ4s. A tuned right ZZ4 will produce nearly 400 hp at the fly wheel. I've talked to him about a ZZ4 in my '92. Jerk out the LT1 with opti, insert a ZZ4 with '91 ECM. He says he's done it before. Get more HP, TQ and no opti problems. The HEI distributor will fit under the hood because it does on a '91 (same hood).
With a CC502 a bigger cam then the ZZ4 113 heads and a HSR intake my car only made 268 Hp. I think it would have made more. But I dough I could have got another 70hp/400CHP .
Last edited by ch@0s; Oct 12, 2010 at 03:05 PM.
Safety Car
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From: Arizona - If you don’t know CFI, STOP proliferating the myths around it...
Run a 383 with a CF and still beat the C5s. LOL Ask me how I know that.
Ben73 is living proof that a CF 383 will kill even a mildly modded C5 coupe up to model year 2004 and give a 2005 a good run in stock config.
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Le Mans Master
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From: Bangkok, Thailand
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Wow, you have made a ton of progress on your car in a short time. Its going to be like new. Have you figured how much you have in it so far? Are you going to do anything to that Sears and Robebuck house paint job on your vette?
Mike
Wow, you have made a ton of progress on your car in a short time. Its going to be like new. Have you figured how much you have in it so far? Are you going to do anything to that Sears and Robebuck house paint job on your vette?
Mike
Le Mans Master
Joined: Jun 2006
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From: One day you're a Comet...the next day you're dust... Arkansas
No way Jose' that 355 is at crank with a carb. No way it will touch a Z06, even an early one. Why do you keep posting crap like this.
Thread Starter
Le Mans Master
Joined: Nov 2009
Posts: 6,882
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From: Bangkok, Thailand
I'm already scared to add up what I've spent. Between tires, all the J55 brake parts, the intake, the Z-51 rack, Edlebrock rear shocks (still need to get the fronts), assorted small parts from the local Corvette Clinic, roller rockers, Hella headlights, mufflers, well, you get the idea.
Hasn't been cheap, but I love the way the car drives and so far everything has been a good improvement from what it was.
Now if I can just sort out this little problem, things should be good.
Race Director
Joined: Feb 2004
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Multiplying by 1.5 will tell you the valve lift, and this can be compared to the stock specs in your manual.
Based on all the posts I see above, the corvette world seems to think you need a new motor, or upgraded.
Cams have been going flat for years, and in the right situation cam replacement can be a feasibly repair option. I sell engines, and don't think you should let popular opinion sway you that way, until diagnostics prove otherwise. Always entertaining to watch people make recommendations to spend someone else money.