383 LT1 road race engine water pump gear failure... why?
06-20-2013, 09:06 PM
#1
Registered User
Thread Starter
Join Date: Jun 2013
Posts: 11
Likes: 0
Received 0 Likes
on
0 Posts
383 LT1 road race engine water pump gear failure... why? Hi everybody, new guy here. Quick intro: I do LT1 engine swaps in Porsche 944's, or at least I used to. I moved to a different job a few years ago and no longer produce the kits, but I still keep in touch with some of the owners of the 13 cars I built. Recently I've gotten back involved with one that I built as a NASA road race car about 6 years ago and have purchased a stake in the car to share it. Back when I worked on this car we won 3 consecutive NASA GTS championships with it, but since I left that shop the car has been having constant troubles which is what led the owner to seek me out. I'm a euro car tech and my knowledge of V8's is very limited, so I come here seeking some education.
The guys that were taking care of the car seem to have tried to make up for unreliability by adding horsepower and failed miserably; in the cars last 10 races it finished a total of zero due to engine trouble. I'm trying to sort it out, but don't have tons of dollars to throw at it. I had thought I had gone through enough things and tests to have a crack at a race weekend with it. After 3 sessions a polylock came loose and damaged threads to the stud ended the first day, luckily Summit Racing is only an hour from Road Atlanta. Day 2 made 3 laps before the engine suddenly overheated.
Tear down has revealed that the water pump drive has no teeth left on the gear and the cam sprocket is destroyed as well.
Any ideas why this would happen? I am the kind of person that MUST know why before simply reassembling; I do not want a repeat! The water pump spins freely and the bearing on the water pump drive gear spins freely. I can't run an electric pump due to space. Is there a recommended aftermarket timing set to run? Aftermarket water pump drive?
Engine specs:
-Scat 383 kit w/ forged crank, forged I-beam rods, forged Icon pistons, and 4-bolt mains
-Comp XFI cam, Comp 1.6 roller rockers, chromoly pushrods
-Edelbrock Performer LT1 heads w/ comp 26918-16 springs
-Dry sump feeding through oil filter block off plate
-MSD opti
-Stock cam timing components
-Edelbrock Performer air gap manifold
-Custom headers
-Stock PCM, I tune with tunercat
On the stock bottom end with a Comp cam plus these same heads and intake as I built it originally the car made about 360whp. Since the 383 the best it's done on the dyno is under 350whp, but I haven't dyno'd it since fixing a ton of things after getting the car. That cam I'm sure is choking that engine. I'd like to go bigger to let it breathe and lower the dynamic compression so I can run it on pump gas.
The guys that were taking care of the car seem to have tried to make up for unreliability by adding horsepower and failed miserably; in the cars last 10 races it finished a total of zero due to engine trouble. I'm trying to sort it out, but don't have tons of dollars to throw at it. I had thought I had gone through enough things and tests to have a crack at a race weekend with it. After 3 sessions a polylock came loose and damaged threads to the stud ended the first day, luckily Summit Racing is only an hour from Road Atlanta. Day 2 made 3 laps before the engine suddenly overheated.
Tear down has revealed that the water pump drive has no teeth left on the gear and the cam sprocket is destroyed as well.
Any ideas why this would happen? I am the kind of person that MUST know why before simply reassembling; I do not want a repeat! The water pump spins freely and the bearing on the water pump drive gear spins freely. I can't run an electric pump due to space. Is there a recommended aftermarket timing set to run? Aftermarket water pump drive?
Engine specs:
-Scat 383 kit w/ forged crank, forged I-beam rods, forged Icon pistons, and 4-bolt mains
-Comp XFI cam, Comp 1.6 roller rockers, chromoly pushrods
-Edelbrock Performer LT1 heads w/ comp 26918-16 springs
-Dry sump feeding through oil filter block off plate
-MSD opti
-Stock cam timing components
-Edelbrock Performer air gap manifold
-Custom headers
-Stock PCM, I tune with tunercat
On the stock bottom end with a Comp cam plus these same heads and intake as I built it originally the car made about 360whp. Since the 383 the best it's done on the dyno is under 350whp, but I haven't dyno'd it since fixing a ton of things after getting the car. That cam I'm sure is choking that engine. I'd like to go bigger to let it breathe and lower the dynamic compression so I can run it on pump gas.
06-20-2013, 10:03 PM
#2
TECH Apprentice
iTrader: (6)
Join Date: Aug 2010
Location: Michigan
Posts: 383
Likes: 0
Received 0 Likes
on
0 Posts
Those heads/intake are hurting it too, just sayin.
But seeing that gear all chewed to hell did it not feed bits all through the engine too? Never seen one do that before.
But seeing that gear all chewed to hell did it not feed bits all through the engine too? Never seen one do that before.
06-20-2013, 11:12 PM
#3
Registered User
Thread Starter
Join Date: Jun 2013
Posts: 11
Likes: 0
Received 0 Likes
on
0 Posts
At the moment I really don't care about power, the car already makes too much for the desired class. Only after I've ironed out all of the bugs installed by the previous shop will I worry about either downgrading it to get back to our desired class or moving up a class to be able to upgrade a bit.
The bits of gear seem to have ended up mostly in the pan, the oil pump (which is destroyed) and the filter. I pulled all of the rod and main caps to check and it's definitely getting new bearings, but none spun and the crank is in good shape. I've found a number of forum topics where the water pump drive gear has broken, but never a good explanation. Even one here: https://ls1tech.com/forums/lt1-lt4-m...need-help.html
The bits of gear seem to have ended up mostly in the pan, the oil pump (which is destroyed) and the filter. I pulled all of the rod and main caps to check and it's definitely getting new bearings, but none spun and the crank is in good shape. I've found a number of forum topics where the water pump drive gear has broken, but never a good explanation. Even one here: https://ls1tech.com/forums/lt1-lt4-m...need-help.html
06-20-2013, 11:18 PM
#4
TECH Apprentice
iTrader: (6)
Join Date: Aug 2010
Location: Michigan
Posts: 383
Likes: 0
Received 0 Likes
on
0 Posts
more so to me is I can't see what could cause it, unless the timing chain were moving around, poor gear mesh on initial instal, or... well god knows what. I have another gear in my toolbox atm that showed a very tiny bit of wear, but nothing I'd be worried about.
I'm interested as to what could/did cause this too.
I'm interested as to what could/did cause this too.
06-20-2013, 11:23 PM
#5
Village Troll 
iTrader: (2)
Pretty unheard of for those gears to fail like that. Wondering how old the timing chain is, and possibly if it already had a cracked gear/chipped tooth that may have exacerbated with the intense acceleration/deceleration loads.
06-21-2013, 06:16 AM
#6
Measure the length on that chain. Why build that combo and not use a double roller or at the least an HD set While racing? That is a stock linked end chain. It's not even a roller. You say this thing has been raced for a while so Id say they got their use out of that chain. You just don't see drive gears fail like that.
06-21-2013, 12:34 PM
#7
Registered User
Thread Starter
Join Date: Jun 2013
Posts: 11
Likes: 0
Received 0 Likes
on
0 Posts
The chain had about an hour of run time on it. About a year ago the driver missed a gear and killed the top end. After that the previous shop replaced the broken top end bits and didn't touch the chain. At the next event the chain broke. The owner let the previous shop replace that broken chain, then put the car in his garage for the better part of a year before handing it to me.
It's possible that the water pump gear was hurt during that and didn't get noticed. I guess at this point I'm going to put a new water pump drive in it and a better chain setup. Is there a recommended chain/gear set?
It's possible that the water pump gear was hurt during that and didn't get noticed. I guess at this point I'm going to put a new water pump drive in it and a better chain setup. Is there a recommended chain/gear set?
Trending Topics
06-21-2013, 01:17 PM
#8
Registered User
Thread Starter
Join Date: Jun 2013
Posts: 11
Likes: 0
Received 0 Likes
on
0 Posts
An EWP is not an option. There is only about 2" between the front of the water pump and the chassis. I seek a timing set recommendation that still drives the water pump.
06-21-2013, 01:32 PM
#9
May want to give these guys a call. Buddy of mine runs one but his version doesn't run the water pump. Perhaps give them a call and see what they have.
http://www.progearweb.com/#
http://www.progearweb.com/#
06-21-2013, 02:58 PM
#11
JC
if I understand the motor was stroked after your involvement with a stock bottom end LT1 350. if so did the new block get assembled with the 2 oil gally plugs just below wp drive gears WITH the holes in them get put in or "solid" ones? It needs the one with the small hole in the center of them.
maybe the timing chain stretched causing some rattle beating the cam gear & wp drive gear
sounds like you have a complete tear down/build so confirm block machineing is right especially in the line bore area.
There is a LT4 "extreme duty" timing set that will work with the WP drive IIRC. You may need to clearance the timing cover on the inside. It has been awhile but a search should cast some light on that. With that said stock Lt1 timing chains have not been an issue with 383 or stock motors before.
also is there a windage tray on this motor since it went 383?
if I understand the motor was stroked after your involvement with a stock bottom end LT1 350. if so did the new block get assembled with the 2 oil gally plugs just below wp drive gears WITH the holes in them get put in or "solid" ones? It needs the one with the small hole in the center of them.
maybe the timing chain stretched causing some rattle beating the cam gear & wp drive gear
sounds like you have a complete tear down/build so confirm block machineing is right especially in the line bore area.
There is a LT4 "extreme duty" timing set that will work with the WP drive IIRC. You may need to clearance the timing cover on the inside. It has been awhile but a search should cast some light on that. With that said stock Lt1 timing chains have not been an issue with 383 or stock motors before.
also is there a windage tray on this motor since it went 383?
06-21-2013, 07:04 PM
#12
JC
if I understand the motor was stroked after your involvement with a stock bottom end LT1 350. if so did the new block get assembled with the 2 oil gally plugs just below wp drive gears WITH the holes in them get put in or "solid" ones? It needs the one with the small hole in the center of them.
maybe the timing chain stretched causing some rattle beating the cam gear & wp drive gear
sounds like you have a complete tear down/build so confirm block machineing is right especially in the line bore area.
There is a LT4 "extreme duty" timing set that will work with the WP drive IIRC. You may need to clearance the timing cover on the inside. It has been awhile but a search should cast some light on that. With that said stock Lt1 timing chains have not been an issue with 383 or stock motors before.
also is there a windage tray on this motor since it went 383?
if I understand the motor was stroked after your involvement with a stock bottom end LT1 350. if so did the new block get assembled with the 2 oil gally plugs just below wp drive gears WITH the holes in them get put in or "solid" ones? It needs the one with the small hole in the center of them.
maybe the timing chain stretched causing some rattle beating the cam gear & wp drive gear
sounds like you have a complete tear down/build so confirm block machineing is right especially in the line bore area.
There is a LT4 "extreme duty" timing set that will work with the WP drive IIRC. You may need to clearance the timing cover on the inside. It has been awhile but a search should cast some light on that. With that said stock Lt1 timing chains have not been an issue with 383 or stock motors before.
also is there a windage tray on this motor since it went 383?
Those 2 plugs have little holes to spray oil on the chain/gear.
06-21-2013, 07:22 PM
#13
****** read he said drysump.
far as the failure, IMO it was most likely unfound damage from the past issues, or just a fluke.
That said this whole build is so bad you should scrap the whole thing and start over, maybe an aluminum 5.3l with heads and cam.
The fact the 383 made less power suggests some very bad shortblock specs or bad machining.
far as the failure, IMO it was most likely unfound damage from the past issues, or just a fluke.
That said this whole build is so bad you should scrap the whole thing and start over, maybe an aluminum 5.3l with heads and cam.
The fact the 383 made less power suggests some very bad shortblock specs or bad machining.
06-22-2013, 12:36 AM
#14
No need to scrap just because of parts used but current condition warrants a full tear down and inspection of major components and full on rebuild. Certainly a good set of heads could wake this car the hell up but it can be a double edged sword. The build is still ok at best but yes unseen damage or unseen floating debris could have easily caused this. It is what it isn't and a full on build is not always a requirement especially when transplanted and traction is an issue in road racing and a car that is technically different in balance then the 3 cars this engine came in. Less Hp and Tq can definitely make quicker lap times when it's about cornering speed and momentum. N/A V8 power is a huge improvement over Built or unbuilt 4 banger turbo unpredictability (or Inconsistency) or N/A 4 banger on a road coarse with that car. Rebuild it. Check the chain any way and make sure, it is a stock style chain and a very uncommon failure for these engines. You asking why it failed...Find out don't speculate and no one over a PC or Mac is going to answer it definitively for you. Question the obvious but question everything and come to a common sense conclusion... or pay someone for an answer that wont be the correct answer or maybe it will. As far as I see there are about 5 people on the planet that could actually say for 100% sure what caused this very rare failure and is it really worth an answer... What happen to the top end before is a wild card since it was not fully torn down. Very easy to miss something. It needs to be rebuilt. Too much metal **** has made it's way into every orifice that engine, It's oiling system and components have. Hope the block and major parts come out ok for you to rebuild. I would guess trash in the drive gear roller bearings but it is just a guess. It could have been a big piece that trashed it in less then a lap. Clean that pig out there may be a smoking gun.
06-22-2013, 08:04 AM
#15
if he picked the Edelcrap stuff what are the chances he picked a machinist that was any good. A good machinist would likely laugh at him for the rest of the parts of the engine.
I mean who bothers to machine for 4-bolt when the Edelbrock complete kit is rated for less flywheel HP than most of us expect from ported GM heads UNPORTED intake at the friggin tire.
When you look at the whole picture so much of it is so bad you have to assume what you can't see is complete junk as well.
I mean who bothers to machine for 4-bolt when the Edelbrock complete kit is rated for less flywheel HP than most of us expect from ported GM heads UNPORTED intake at the friggin tire.
When you look at the whole picture so much of it is so bad you have to assume what you can't see is complete junk as well.
06-22-2013, 11:07 AM
#16
06-22-2013, 01:02 PM
#18
The car is raced so "parts" can break. given the damage caused by the broken parts scattered throughout the engine a complete rebuild is in order.
with the various hands the motor has been in the answer to 'why" it happened may be elusive.
06-22-2013, 02:16 PM
#19
yes I was asking the "?" about a windage tray. I don't know if OP initially installed the dry sump or that was done during his absence from the car when it went 383 and wanted to know if the tray was still in.
The car is raced so "parts" can break. given the damage caused by the broken parts scattered throughout the engine a complete rebuild is in order.
with the various hands the motor has been in the answer to 'why" it happened may be elusive.
The car is raced so "parts" can break. given the damage caused by the broken parts scattered throughout the engine a complete rebuild is in order.
with the various hands the motor has been in the answer to 'why" it happened may be elusive.
Just my $0.02 worth.....I have yet to see an LT1 timing chain that is fairly taut, so I'm suspicious the timing chain is "whipping" while the RPMs are varying significantly, and the cam sprocket is transferring the harmonics to the water pump drive.
