found the problem with my race built 383
03-29-2003, 12:03 PM
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Car: 1992 Firebird Coupe
Engine: 357ci Carb
Transmission: 700r4
Axle/Gears: 3.73 posi, stock rear
found the problem with my race built 383
For those of you that remember, I had ordered a race built 383 stroker from furios racing engines. It's a solid roller motor, around 243 duration and 565 lift...
Upon starting the engine for the first time, I bent a pushrod on the #3 exhaust.. The engine only ran about 30 seconds and I turned it off.
Today i removed the intake manifold, and I found the cause. The damn roller lifter for #5 exhaust was resting on the circular cam journal, not the lobe of the cam!!! I dont know how this happened. Its like the cam needs to move 1/8" towards the front of the motor and all would be well. I looked at the other cyclinders and didnt see this problem.
I removed the roller lifter in question and it looks fine, i dont see any damage. The pushrod surely bent because the journal kept the valve from closing and the piston must of nailed it. It doesnt keep it open all the way, but a little bit. I'm hoping the piston and valve in question are fine. I am gonig to run a compression check on that cylinder later.
What would you do in this situation? Should i remove all the lifters and pushrods and check the torque spec on the cam? Would you take the motor apart or remove the cam and inspect it? Maybe its wishfull thinking but i dont think there is going to be much or any damage .. I'm thinking about replacing the cam for safety's sake.
Give me some direction please. I can ship the engine back to the builder, but i really dont wanna pull it. I'd rather change the cam with it in the car or something like that.
Thanks,
Shane
:-(
Upon starting the engine for the first time, I bent a pushrod on the #3 exhaust.. The engine only ran about 30 seconds and I turned it off.
Today i removed the intake manifold, and I found the cause. The damn roller lifter for #5 exhaust was resting on the circular cam journal, not the lobe of the cam!!! I dont know how this happened. Its like the cam needs to move 1/8" towards the front of the motor and all would be well. I looked at the other cyclinders and didnt see this problem.
I removed the roller lifter in question and it looks fine, i dont see any damage. The pushrod surely bent because the journal kept the valve from closing and the piston must of nailed it. It doesnt keep it open all the way, but a little bit. I'm hoping the piston and valve in question are fine. I am gonig to run a compression check on that cylinder later.
What would you do in this situation? Should i remove all the lifters and pushrods and check the torque spec on the cam? Would you take the motor apart or remove the cam and inspect it? Maybe its wishfull thinking but i dont think there is going to be much or any damage .. I'm thinking about replacing the cam for safety's sake.
Give me some direction please. I can ship the engine back to the builder, but i really dont wanna pull it. I'd rather change the cam with it in the car or something like that.
Thanks,
Shane
:-(
03-29-2003, 01:21 PM
#2
Shane,
Personally, I wouldn't do any more to the engine until speaking with the builder. If you can, get photos of what you described and email them to the supplier.
Are you sure it is the journal and not the bearing shell? If that's the case, the cam may have slid back in the case, but the timing chain should have limited the travel. Usually, a cam tends to "walk" forward, not backward in the case. The retainer plate of a stock roller cammed engine is there to prevent that. The distributor and oil pump load will tend to pull the cam backward into the case, but the rear face of the cam timing sprocket will prevent that motion unless you have gears, a trashed needle thrust bearing, or some other oddity in your buildup.
Personally, I wouldn't do any more to the engine until speaking with the builder. If you can, get photos of what you described and email them to the supplier.
Are you sure it is the journal and not the bearing shell? If that's the case, the cam may have slid back in the case, but the timing chain should have limited the travel. Usually, a cam tends to "walk" forward, not backward in the case. The retainer plate of a stock roller cammed engine is there to prevent that. The distributor and oil pump load will tend to pull the cam backward into the case, but the rear face of the cam timing sprocket will prevent that motion unless you have gears, a trashed needle thrust bearing, or some other oddity in your buildup.
03-29-2003, 01:52 PM
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Car: 1992 Firebird Coupe
Engine: 357ci Carb
Transmission: 700r4
Axle/Gears: 3.73 posi, stock rear
Originally posted by Vader
Shane,
Personally, I wouldn't do any more to the engine until speaking with the builder. If you can, get photos of what you described and email them to the supplier.
Are you sure it is the journal and not the bearing shell? If that's the case, the cam may have slid back in the case, but the timing chain should have limited the travel. Usually, a cam tends to "walk" forward, not backward in the case. The retainer plate of a stock roller cammed engine is there to prevent that. The distributor and oil pump load will tend to pull the cam backward into the case, but the rear face of the cam timing sprocket will prevent that motion unless you have gears, a trashed needle thrust bearing, or some other oddity in your buildup.
Shane,
Personally, I wouldn't do any more to the engine until speaking with the builder. If you can, get photos of what you described and email them to the supplier.
Are you sure it is the journal and not the bearing shell? If that's the case, the cam may have slid back in the case, but the timing chain should have limited the travel. Usually, a cam tends to "walk" forward, not backward in the case. The retainer plate of a stock roller cammed engine is there to prevent that. The distributor and oil pump load will tend to pull the cam backward into the case, but the rear face of the cam timing sprocket will prevent that motion unless you have gears, a trashed needle thrust bearing, or some other oddity in your buildup.
I am not an engine builder, which is why i ordered the engine complete from intake to oilpan. :-(
I guess i will pull the damn thing out and ship it back.
Thanks !
Shane
03-29-2003, 02:05 PM
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Car: 4
Engine: 6
Transmission: 5
Sounds like a mismatch of a factory roller cam timing set and non-roller-cam block; or a missing retainer plate; or something like that. The timing gear is the thing that's supposed to locate the cam at the correct front-to-rear place.
If it was me, I would contact the motor builder first; and then pop the timing cover off and look at the timing set, and make sure it has the right one on it.
If it was me, I would contact the motor builder first; and then pop the timing cover off and look at the timing set, and make sure it has the right one on it.
04-02-2003, 01:20 PM
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In speaking with an engine builder where I work this very topic came up. He said any time you get a block machined the builder needs to look down the lifter holes to make sure the cam lobes are centered in the holes. He said many times he has had to tap the cam one way or the other to get everything to line up. I guess sometimes the cam journals are too shallow or too deep. He also said this problem has wiped out many cams.
We were discussing this because I'm using a solid roller in my next SBC. He said to check the cam, and of course use a cam button (old style block).
HTH,
Chris
We were discussing this because I'm using a solid roller in my next SBC. He said to check the cam, and of course use a cam button (old style block).
HTH,
Chris
04-02-2003, 02:20 PM
#7
Originally posted by C h r i s
In speaking with an engine builder where I work this very topic came up. He said any time you get a block machined the builder needs to look down the lifter holes to make sure the cam lobes are centered in the holes. He said many times he has had to tap the cam one way or the other to get everything to line up. I guess sometimes the cam journals are too shallow or too deep. He also said this problem has wiped out many cams.
We were discussing this because I'm using a solid roller in my next SBC. He said to check the cam, and of course use a cam button (old style block).
HTH,
Chris
In speaking with an engine builder where I work this very topic came up. He said any time you get a block machined the builder needs to look down the lifter holes to make sure the cam lobes are centered in the holes. He said many times he has had to tap the cam one way or the other to get everything to line up. I guess sometimes the cam journals are too shallow or too deep. He also said this problem has wiped out many cams.
We were discussing this because I'm using a solid roller in my next SBC. He said to check the cam, and of course use a cam button (old style block).
HTH,
Chris
I believe they call that indexing the lifter holes a lot of times the holes are not exactly where they should be for proper alignment for lifter rotation so they are bored out and bushed for this.
I really like a hyd. flat tappet cams for the street. I've had solid Rollers and they tend to break stuff to often when driven often. Solid flat tappets tend to go flat with prolonged idle situations with the big springs. Hyd. Rollers are good but expensive and have more of a tendacy to valve float. But I guess its all depends on what your building.
BTW addressing the post I'd just ship it back because you go digging through it might void the warranty and like you say you really don't know what your looking for Piston valve contact could very well bend the valve head leaving the motor to run decent on 7 1/2 cylinders for a while and then causing BIG trouble later.
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04-02-2003, 03:24 PM
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I plan to use the spring Comp calls for, which has a 155lb. rate. Others have mentioned the same problems, but as you said it is with the stiffer race springs.
I think indexing the lifter bores is a machining process, what I'm talking about is just getting the cam deep enough (or a bit less deep) into the block. The builder I spoke to clarified it for me: he said it is the cam plug (looks like a big freeze plug) in the back of the block that needs to be moved, either a little forward or a little rearward. He said it just depends on how deep the machine shop tapped this in.
I agree - talk to the builder first.
Chris
I think indexing the lifter bores is a machining process, what I'm talking about is just getting the cam deep enough (or a bit less deep) into the block. The builder I spoke to clarified it for me: he said it is the cam plug (looks like a big freeze plug) in the back of the block that needs to be moved, either a little forward or a little rearward. He said it just depends on how deep the machine shop tapped this in.
I agree - talk to the builder first.
Chris
04-02-2003, 04:12 PM
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The plug in the back of the cam bore is NOT supposed to act as the cam retainer. Also, "tapping the cam" is entirely ineffective; it goes wherever it wants to, front to rear, so it doesn't matter where you leave it when you build the motor (within reason), it will find its "happy" place. Whoever told you that, you need to find a new engine builder, IMMEDIATELY, or at least before the next motor you need built. That guy doesn't know what he's doing, and is dangerous.
A flat tappet cam is not "flat", but rather, the lobes are tapered a few thousandths, from the edge of the lobe nearer the front of the engine, to the rear edge; and the lifters are slightly convex. The rear of the timing gear locates itself against the front face of the block; when it does this, the front edge of the lobes is about 1/8" behind the front edge of the lifter bore. Because of this design, the tall edge of the cam lobe is the only part of it in contact with the lifter, and the only part of the lifter in contact with the cam is out near the edge; this forces the lifter to rotate. If it doesn't rotate, it will die, VERY rapidly.
This also forces the cam rearward in the block. So the cam should end up as far back as it can go (about 1/8" or a little more, usually) from the rear plug, leaving a space for oil to get into and drip back through a little drain hole into the crankcase (if that wasn't there, then oil pressure would pop that plug right out the back of the motor). The timing gear is the rearward retainer for the cam, and the lifter ramp geometry is the forward retainer. That's why engines that have been in wrecks often need new timing covers.
A roller cam doesn't have ramp-shaped lobes, so it requires a cam button in the case of the original sensible roller design, or the retainer plate in the system where the factory re-invented the wheel in a triangle. That retainer plate bolts to the (modified) front of the block, and goes between the (modified) cam nose and the (modified) cam gear, which is thinner by the thickness of the retainer plate than a flat tappet cam gear is. So if you use a factory roller timing set on a "retrofit" roller cam or a flat-tappet cam, it will locate the cam about .100" rearward of where it's supposed to be.... which is of course, precisely the problem in the original post. So I expect that's probably what he's got.
"The simplest explanation that fits all the facts is usually the right one."
— Occam, ancient Greek philosopher, from a time even before they invented hydraulic lifters or roller cams
Incidentally, one of the most common problems that exists in the quality-control-challenged 70s blocks, almost as common as The Problem where the starter bolt holes are in the wrong place, is one or more lifter bores that don't point at the cam correctly. A very tiny error in this alignment will cause immediate, inevitable, unstoppable, total annihilation of that cam lobe and lifter (and it ruins them too). It is not visible to the naked eye (it only takes a degree or 2 of error) unless it has happened in that block so many times that the lifter bore is chewed up from the debris. If you ever see a 4-bolt 350 block like an 010 casting or something, that is going for what seems to be too cheap after the owner had a motor built with it, that's probably why.... after the 3rd cam or so, most people give up on a block, they assume its cursed or something.
A flat tappet cam is not "flat", but rather, the lobes are tapered a few thousandths, from the edge of the lobe nearer the front of the engine, to the rear edge; and the lifters are slightly convex. The rear of the timing gear locates itself against the front face of the block; when it does this, the front edge of the lobes is about 1/8" behind the front edge of the lifter bore. Because of this design, the tall edge of the cam lobe is the only part of it in contact with the lifter, and the only part of the lifter in contact with the cam is out near the edge; this forces the lifter to rotate. If it doesn't rotate, it will die, VERY rapidly.
This also forces the cam rearward in the block. So the cam should end up as far back as it can go (about 1/8" or a little more, usually) from the rear plug, leaving a space for oil to get into and drip back through a little drain hole into the crankcase (if that wasn't there, then oil pressure would pop that plug right out the back of the motor). The timing gear is the rearward retainer for the cam, and the lifter ramp geometry is the forward retainer. That's why engines that have been in wrecks often need new timing covers.
A roller cam doesn't have ramp-shaped lobes, so it requires a cam button in the case of the original sensible roller design, or the retainer plate in the system where the factory re-invented the wheel in a triangle. That retainer plate bolts to the (modified) front of the block, and goes between the (modified) cam nose and the (modified) cam gear, which is thinner by the thickness of the retainer plate than a flat tappet cam gear is. So if you use a factory roller timing set on a "retrofit" roller cam or a flat-tappet cam, it will locate the cam about .100" rearward of where it's supposed to be.... which is of course, precisely the problem in the original post. So I expect that's probably what he's got.
"The simplest explanation that fits all the facts is usually the right one."
— Occam, ancient Greek philosopher, from a time even before they invented hydraulic lifters or roller cams
Incidentally, one of the most common problems that exists in the quality-control-challenged 70s blocks, almost as common as The Problem where the starter bolt holes are in the wrong place, is one or more lifter bores that don't point at the cam correctly. A very tiny error in this alignment will cause immediate, inevitable, unstoppable, total annihilation of that cam lobe and lifter (and it ruins them too). It is not visible to the naked eye (it only takes a degree or 2 of error) unless it has happened in that block so many times that the lifter bore is chewed up from the debris. If you ever see a 4-bolt 350 block like an 010 casting or something, that is going for what seems to be too cheap after the owner had a motor built with it, that's probably why.... after the 3rd cam or so, most people give up on a block, they assume its cursed or something.
Last edited by RB83L69; 04-02-2003 at 04:26 PM.
04-03-2003, 07:23 AM
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Okee Dokee. Thanks for the info. Consider me edu-ma-cated.
To clarify, the builder I spoke of has built engines for himself and others, he is not a professional. I plan to build my engine, so I can make my own grievous errors.
Chris
To clarify, the builder I spoke of has built engines for himself and others, he is not a professional. I plan to build my engine, so I can make my own grievous errors.
Chris
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