85 firebird/trans am 305 to 406 with t5 world class questions.
10-13-2015, 05:06 PM
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85 firebird/trans am 305 to 406 with t5 world class questions.
So i bought a complete 406 that is mildly built. Got it for 300 bucks but it had spun a bearing and lost oil pressure. I'm in the middle of rebuilding the motor. Having the crank turned and polished now. Putting all new bearings in the motor. My concerns are my machinist wants to recondition my 5.7 rods. But i don't think it needs that done. The motor only has a 1,xxx miles before the oil pressure failure. So if i put it back together with new bearings and a fresh polish on the crank without having the rods reconditioned what problems will i run into? 30 over flat top pistons with 4 valve reliefs stock crank that's going to be 30/30 now. Have 441 heads that have been milled and 2.05's cut on the intake .600 max lift valve springs and roller tip 1.5 rockers. Motor it's going behind stock world class t5 with stock clutch limited slip 9 bolt rear with 3.42 gears on 235/60r tires. Any input is greatly appreciated
Last edited by jon_whit85WS6; 10-13-2015 at 05:10 PM.
10-13-2015, 09:57 PM
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Re: 85 firebird/trans am 305 to 406 with t5 world class questions.
# of miles doesn't matter; if a rod got tore up when the bearing spun, ... you do the math.
Problem you will run into may be, that the rod is trashed, and the bearing doesn't fit tight in it; which in effect is IDENTICAL IN EVERY WAY to the problem of the crank being trashed and the bearing doesn't fit tight to that.
All the crap about the transmission and rear end and clutch and all that floobie dust, even head castings (I SURE AS HELL wouldn't build a motor with those) is irrelevant. Either you build your motor RIGHT, or you take the bus. Not saying "you MUST get your rod(s) reconditioned"; only, measure, measure, believe the measurements, correct the incorrect measurements, do not allow incorrect measurements to exist in your fresh motor, then measure, and measure again, and be ABSOLUTELY CERTAIN that everything is RIGHT. Ergo, if your machinist has MEASURED your stuff and found it out of tolerance, BELIEVE HIM. That's the nice thing about MEASUREMENTS... they're reliable, repeatable, believable, and irrevocable.
Did I forget to mention ... MEASURE? Well just in case the point is not clear, MEASURE EVERYTHING, taking the greatest care to MEASURE it in ways you haven't thought of yet until you pick up the object in question and notice how many possible MEASUREMENTS there are.
Problem you will run into may be, that the rod is trashed, and the bearing doesn't fit tight in it; which in effect is IDENTICAL IN EVERY WAY to the problem of the crank being trashed and the bearing doesn't fit tight to that.
All the crap about the transmission and rear end and clutch and all that floobie dust, even head castings (I SURE AS HELL wouldn't build a motor with those) is irrelevant. Either you build your motor RIGHT, or you take the bus. Not saying "you MUST get your rod(s) reconditioned"; only, measure, measure, believe the measurements, correct the incorrect measurements, do not allow incorrect measurements to exist in your fresh motor, then measure, and measure again, and be ABSOLUTELY CERTAIN that everything is RIGHT. Ergo, if your machinist has MEASURED your stuff and found it out of tolerance, BELIEVE HIM. That's the nice thing about MEASUREMENTS... they're reliable, repeatable, believable, and irrevocable.
Did I forget to mention ... MEASURE? Well just in case the point is not clear, MEASURE EVERYTHING, taking the greatest care to MEASURE it in ways you haven't thought of yet until you pick up the object in question and notice how many possible MEASUREMENTS there are.
10-13-2015, 11:03 PM
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Re: 85 firebird/trans am 305 to 406 with t5 world class questions.
The only thing he measured was the crank. He just assumed. The reason i posted my rear end and tire set up with heads is to get people opinions. Yes i wouldn't have put the money in those heads but the prior owner felt it was worth it i guess. I put every bit of information i have on this motor to see if I'm failing to see an obvious problem. The reason he told me he wanted to recondition the rods was because i was talking about balancing. But that type of set up just isn't in the budget right now and i told him that and he didn't say anything else about reconditioning the rods after that. It just made me wonder. Im by no means new to cars. I have no problem understanding how and why a motor runs. Grew up drag racing every season with my dad. I'm more less trying to figure out if this motor is going to be worth the money if it's more than bearings.
10-13-2015, 11:11 PM
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Car: 1988 Camaro
Engine: 355, 10.34:1, 249/252 @.050", IK200
Transmission: TH-400, 3500 stall 9.5" converter
Axle/Gears: Ford 9", detroit locker, 3.89 gears
Re: 85 firebird/trans am 305 to 406 with t5 world class questions.
It's a 400 block with 5.7" rods... That means eaither it is new aftermarket rods, or some other used chevy sbc rods as the 400 used short rods.
So, if it's an old set of GM rods they may have needed to be resized before the 1st build and the PO didn't have it done.
Which bearing spun? Main or rod?
If it was a rod bearing that spun... No question about it, have rods resized... Or replace them
So, if it's an old set of GM rods they may have needed to be resized before the 1st build and the PO didn't have it done.
Which bearing spun? Main or rod?
If it was a rod bearing that spun... No question about it, have rods resized... Or replace them
10-14-2015, 12:11 AM
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Re: 85 firebird/trans am 305 to 406 with t5 world class questions.
It was the second main bearing back from the front that spun. I haven't ran any numbers on the rods to see if they are aftermarket or not. I do know they have arp bolts and have been clearanced for flat tappet cam. I'm pretty sure they didn't oil the pump or anything for that matter on assembly because the oil pump is bad. Has a bunch of slop in it and when you spin it, makes a grinding noise doesn't spin smoothly. I think that's why it spun the bearing after it lost oil pressure. Everything looks good clean and smooth. Except bearings.
10-14-2015, 07:08 AM
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Re: 85 firebird/trans am 305 to 406 with t5 world class questions.
If a bearing actually "spun", then it gouged out the inside of the rod. A new bearing will not fit tight in there, won't "crush" into the bore like it's supposed to. Has no chance whatsoever of survival like that: it'll just spin again. That little tang on the bearing isn't meant to be the thing holding it in place; it's really just an assembly aid.
Oil pumps hardly ever "go bad". It's highly unlikely that the pump was the cause of the meltdown. More likely, it was ruined AFTER the motor blew up, from getting metal debris in it; the chips from whatever failed, destroyed it. You don't have to "oil" it anyway, because when you pour the oil into the motor before starting it up, the pump is a couple of inches deep in it. Submerged.
In this day and time, there's no point in re-sizing stock rods, like we all used to religiously do back in the day. Aftermarket ones are just so much cheeeeeeeeper now than they were, that by the time you replace the bolts in a set of stockers and re-size them afterwards like must be done, you'll end up with more money in them than just replacing them. If yours weren't re-sized after changing out the bolts, that's a possible cause of the failure.
When a motor blows up in a block, it sheds metal shavings, which then proceed to get circulated throughout the entire oil system. The vat doesn't dissolve those; only reliable way of cleaning up that mess, is to run rifle brushes through EVERY oil passage in the block. There are several between the rear main cap and the oil filter, a vertical one up the rear face, 3 front-to-rear ones around the cam, the grooves behind the cam bearings (which is where chips hide the worst), and the 4 passages that feed the front 4 cam bearings and main journals. I usually prefer to tear the block down and remove all the plugs and the cam bearings myself, have it vatted with the cam brgs already removed (which is why I remove them myself: there can be no question that they were out before the tank), pick the block back up from the machine shop, take it to the quarter car wash along with acoupla cans of engine degreaser (the store brand is fine... anything that's just diesel fuel in a spray can, works great) and a set of rifle brushes and a small toothbrush shaped wire brush. I run the rifle brushes through all the passages (.22 through the small vertical passages, .410 through most of the rest) and scrub the cam brg grooves with the toothbrush, using liberal helpings of solvent; then blast every passage with the car wash to remove any and all metal chips that are dislodged. I do this in the morning on a nice warm sunny day when possible; leave the block out in the sun to dry, turning it frequently to warm up all the surfaces; paint it; put grease, oil, or transmission fluid on all the important surfaces to prevent rust; then install all the plugs and the cam bearings myself.
Unless this is done, there's a good chance that shavings will remain in those passages, and THE VERY FIRST THING that will happen to your new crank and bearings is, they will get flushed right directly into those nice shiny pristine new bearings, and ruin everything. Failure to do the above clean-up steps is the usual reason for serial blow-ups.
Here's the layout of the passages between the rear main cap and the filter. Note the ½" plug installed about an inch above the register surface of the main cap: it's not impossible that a contributing factor to your blow-up was that it wasn't put in at all. People often overlook it.
Here's a horrible drawing showing most of the passages through the block. It's more of a "schematic" than an actual "drawing", but it at least shows kinda how the oil gets from the pump to the bearings.
If you take a freshly blown-up motor and build a new motor in the block without cleaning the metal chips out of it, you will almost certainly be right back where you are now again, within a few hundred miles. It's not impossible in fact, that that's why you're facing the situation you're facing now: somebody had already done what you are proposing to do, and the motor stood no chance of survival whatsoever from the get-go.
Oil pumps hardly ever "go bad". It's highly unlikely that the pump was the cause of the meltdown. More likely, it was ruined AFTER the motor blew up, from getting metal debris in it; the chips from whatever failed, destroyed it. You don't have to "oil" it anyway, because when you pour the oil into the motor before starting it up, the pump is a couple of inches deep in it. Submerged.
In this day and time, there's no point in re-sizing stock rods, like we all used to religiously do back in the day. Aftermarket ones are just so much cheeeeeeeeper now than they were, that by the time you replace the bolts in a set of stockers and re-size them afterwards like must be done, you'll end up with more money in them than just replacing them. If yours weren't re-sized after changing out the bolts, that's a possible cause of the failure.
When a motor blows up in a block, it sheds metal shavings, which then proceed to get circulated throughout the entire oil system. The vat doesn't dissolve those; only reliable way of cleaning up that mess, is to run rifle brushes through EVERY oil passage in the block. There are several between the rear main cap and the oil filter, a vertical one up the rear face, 3 front-to-rear ones around the cam, the grooves behind the cam bearings (which is where chips hide the worst), and the 4 passages that feed the front 4 cam bearings and main journals. I usually prefer to tear the block down and remove all the plugs and the cam bearings myself, have it vatted with the cam brgs already removed (which is why I remove them myself: there can be no question that they were out before the tank), pick the block back up from the machine shop, take it to the quarter car wash along with acoupla cans of engine degreaser (the store brand is fine... anything that's just diesel fuel in a spray can, works great) and a set of rifle brushes and a small toothbrush shaped wire brush. I run the rifle brushes through all the passages (.22 through the small vertical passages, .410 through most of the rest) and scrub the cam brg grooves with the toothbrush, using liberal helpings of solvent; then blast every passage with the car wash to remove any and all metal chips that are dislodged. I do this in the morning on a nice warm sunny day when possible; leave the block out in the sun to dry, turning it frequently to warm up all the surfaces; paint it; put grease, oil, or transmission fluid on all the important surfaces to prevent rust; then install all the plugs and the cam bearings myself.
Unless this is done, there's a good chance that shavings will remain in those passages, and THE VERY FIRST THING that will happen to your new crank and bearings is, they will get flushed right directly into those nice shiny pristine new bearings, and ruin everything. Failure to do the above clean-up steps is the usual reason for serial blow-ups.
Here's the layout of the passages between the rear main cap and the filter. Note the ½" plug installed about an inch above the register surface of the main cap: it's not impossible that a contributing factor to your blow-up was that it wasn't put in at all. People often overlook it.
Here's a horrible drawing showing most of the passages through the block. It's more of a "schematic" than an actual "drawing", but it at least shows kinda how the oil gets from the pump to the bearings.
If you take a freshly blown-up motor and build a new motor in the block without cleaning the metal chips out of it, you will almost certainly be right back where you are now again, within a few hundred miles. It's not impossible in fact, that that's why you're facing the situation you're facing now: somebody had already done what you are proposing to do, and the motor stood no chance of survival whatsoever from the get-go.
10-14-2015, 07:23 PM
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Re: 85 firebird/trans am 305 to 406 with t5 world class questions.
If a bearing actually "spun", then it gouged out the inside of the rod. A new bearing will not fit tight in there, won't "crush" into the bore like it's supposed to. Has no chance whatsoever of survival like that: it'll just spin again. That little tang on the bearing isn't meant to be the thing holding it in place; it's really just an assembly aid.
Oil pumps hardly ever "go bad". It's highly unlikely that the pump was the cause of the meltdown. More likely, it was ruined AFTER the motor blew up, from getting metal debris in it; the chips from whatever failed, destroyed it. You don't have to "oil" it anyway, because when you pour the oil into the motor before starting it up, the pump is a couple of inches deep in it. Submerged.
In this day and time, there's no point in re-sizing stock rods, like we all used to religiously do back in the day. Aftermarket ones are just so much cheeeeeeeeper now than they were, that by the time you replace the bolts in a set of stockers and re-size them afterwards like must be done, you'll end up with more money in them than just replacing them. If yours weren't re-sized after changing out the bolts, that's a possible cause of the failure.
When a motor blows up in a block, it sheds metal shavings, which then proceed to get circulated throughout the entire oil system. The vat doesn't dissolve those; only reliable way of cleaning up that mess, is to run rifle brushes through EVERY oil passage in the block. There are several between the rear main cap and the oil filter, a vertical one up the rear face, 3 front-to-rear ones around the cam, the grooves behind the cam bearings (which is where chips hide the worst), and the 4 passages that feed the front 4 cam bearings and main journals. I usually prefer to tear the block down and remove all the plugs and the cam bearings myself, have it vatted with the cam brgs already removed (which is why I remove them myself: there can be no question that they were out before the tank), pick the block back up from the machine shop, take it to the quarter car wash along with acoupla cans of engine degreaser (the store brand is fine... anything that's just diesel fuel in a spray can, works great) and a set of rifle brushes and a small toothbrush shaped wire brush. I run the rifle brushes through all the passages (.22 through the small vertical passages, .410 through most of the rest) and scrub the cam brg grooves with the toothbrush, using liberal helpings of solvent; then blast every passage with the car wash to remove any and all metal chips that are dislodged. I do this in the morning on a nice warm sunny day when possible; leave the block out in the sun to dry, turning it frequently to warm up all the surfaces; paint it; put grease, oil, or transmission fluid on all the important surfaces to prevent rust; then install all the plugs and the cam bearings myself.
Unless this is done, there's a good chance that shavings will remain in those passages, and THE VERY FIRST THING that will happen to your new crank and bearings is, they will get flushed right directly into those nice shiny pristine new bearings, and ruin everything. Failure to do the above clean-up steps is the usual reason for serial blow-ups.
Here's the layout of the passages between the rear main cap and the filter. Note the ½" plug installed about an inch above the register surface of the main cap: it's not impossible that a contributing factor to your blow-up was that it wasn't put in at all. People often overlook it.
Here's a horrible drawing showing most of the passages through the block. It's more of a "schematic" than an actual "drawing", but it at least shows kinda how the oil gets from the pump to the bearings.
If you take a freshly blown-up motor and build a new motor in the block without cleaning the metal chips out of it, you will almost certainly be right back where you are now again, within a few hundred miles. It's not impossible in fact, that that's why you're facing the situation you're facing now: somebody had already done what you are proposing to do, and the motor stood no chance of survival whatsoever from the get-go.
Oil pumps hardly ever "go bad". It's highly unlikely that the pump was the cause of the meltdown. More likely, it was ruined AFTER the motor blew up, from getting metal debris in it; the chips from whatever failed, destroyed it. You don't have to "oil" it anyway, because when you pour the oil into the motor before starting it up, the pump is a couple of inches deep in it. Submerged.
In this day and time, there's no point in re-sizing stock rods, like we all used to religiously do back in the day. Aftermarket ones are just so much cheeeeeeeeper now than they were, that by the time you replace the bolts in a set of stockers and re-size them afterwards like must be done, you'll end up with more money in them than just replacing them. If yours weren't re-sized after changing out the bolts, that's a possible cause of the failure.
When a motor blows up in a block, it sheds metal shavings, which then proceed to get circulated throughout the entire oil system. The vat doesn't dissolve those; only reliable way of cleaning up that mess, is to run rifle brushes through EVERY oil passage in the block. There are several between the rear main cap and the oil filter, a vertical one up the rear face, 3 front-to-rear ones around the cam, the grooves behind the cam bearings (which is where chips hide the worst), and the 4 passages that feed the front 4 cam bearings and main journals. I usually prefer to tear the block down and remove all the plugs and the cam bearings myself, have it vatted with the cam brgs already removed (which is why I remove them myself: there can be no question that they were out before the tank), pick the block back up from the machine shop, take it to the quarter car wash along with acoupla cans of engine degreaser (the store brand is fine... anything that's just diesel fuel in a spray can, works great) and a set of rifle brushes and a small toothbrush shaped wire brush. I run the rifle brushes through all the passages (.22 through the small vertical passages, .410 through most of the rest) and scrub the cam brg grooves with the toothbrush, using liberal helpings of solvent; then blast every passage with the car wash to remove any and all metal chips that are dislodged. I do this in the morning on a nice warm sunny day when possible; leave the block out in the sun to dry, turning it frequently to warm up all the surfaces; paint it; put grease, oil, or transmission fluid on all the important surfaces to prevent rust; then install all the plugs and the cam bearings myself.
Unless this is done, there's a good chance that shavings will remain in those passages, and THE VERY FIRST THING that will happen to your new crank and bearings is, they will get flushed right directly into those nice shiny pristine new bearings, and ruin everything. Failure to do the above clean-up steps is the usual reason for serial blow-ups.
Here's the layout of the passages between the rear main cap and the filter. Note the ½" plug installed about an inch above the register surface of the main cap: it's not impossible that a contributing factor to your blow-up was that it wasn't put in at all. People often overlook it.
Here's a horrible drawing showing most of the passages through the block. It's more of a "schematic" than an actual "drawing", but it at least shows kinda how the oil gets from the pump to the bearings.
If you take a freshly blown-up motor and build a new motor in the block without cleaning the metal chips out of it, you will almost certainly be right back where you are now again, within a few hundred miles. It's not impossible in fact, that that's why you're facing the situation you're facing now: somebody had already done what you are proposing to do, and the motor stood no chance of survival whatsoever from the get-go.
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