Sewing Machine...
07-15-2010, 06:07 PM
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Sewing Machine... Well, I was going down the highway today and meant to downshift to 4th but accidentally shifted to 2nd at 75-80mph. Jerked like hell and the low traction light came on, but I put it back in 6th and it drove fine the rest of the way home and shifted through all the gears just fine. But when I revved it from about 2k on up, I got a sewing machine/machine gun type sound. Did I bend a pushrod or something? I did a search for sewing machine on here and it seems like that's probably what I did. How bad is this? I'm doing a turbo install this winter and was planning on upgrading the pushrods anyway. I will probably only be putting another 200 or so miles until then. Is it imperative that it is done right away or can it wait? Sounds like most guys who do H/C swaps end up with that sound afterwards and most don't worry about it.
07-15-2010, 06:43 PM
#2
People run with bent ones sometimes without knowing it not that its good. It probably wont blow the motor to hell but you should definetly replace it if you did indeed bend one which it sounds like you did. If you were going to upgrade them anyway why not just do it now? Just remove the valve covers and rockers then replace the PR's takes maybe an hr.
07-15-2010, 07:33 PM
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K maybe I'll just go ahead and do the pushrods now. When I upgrade to 6.0 heads will they still use the same length pushrods or will I have to get different ones? Stockers are 7.400" correct?
07-15-2010, 08:05 PM
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Hope you find out what the problem is. I had a similar experience with the shifting when I first got my car-except I went from 2nd back to 1st. I noticed the sewing machine sound shortly thereafter and would like to know if replacing the pushrods solves your problem.
07-16-2010, 12:13 PM
#6
The ls2 heads are the same as ls6 (243 castings) which still use the 7.4 pushrods so yes. If either of you want to check before pull the pushrods out and roll them on a glass table you should be able to see if they are warped. Downshifting and over revving is the most common way to bend one. A pushrod should tick slower at lower rpms then escalate with the rpms.
07-16-2010, 01:04 PM
#7
You need to pull the pushrods and check them. What you did was mechanically over rev the engine, which the rev limiter can't save you from. It's very possible to bend pushrods, valves, or both when doing this.
Pull the pushrods and check them. If any are bent, then I'd have a leakdown test done to make sure you didn't bend any valves. If pushrods are bent but valves are good, throw some new pushrods in there and you're good to go. If valves are bent, the heads have to come off.
Either way, I definitely wouldn't go about your business and "not worry about it". Mechanically over revving the engine is something that needs to be addressed.
Pull the pushrods and check them. If any are bent, then I'd have a leakdown test done to make sure you didn't bend any valves. If pushrods are bent but valves are good, throw some new pushrods in there and you're good to go. If valves are bent, the heads have to come off.
Either way, I definitely wouldn't go about your business and "not worry about it". Mechanically over revving the engine is something that needs to be addressed.
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07-16-2010, 09:32 PM
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Thanks redbird and Damian; I will definitely take a look at the pushrods sooner than I would have before. I'm sure the OP will too. I know it's probably not that hard to get to the pushrods once everything is out of the way. What preliminary stuff has to be removed to make it fairly easy to get the valve covers off?
07-16-2010, 10:57 PM
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Guess I'll be pulling some pushrods this weekend. Thanks guys, I'll post the results once I figure things out. If I bent a valve I might just switch my FI plans to H/C plans haha.
07-17-2010, 06:29 PM
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I wonder if it's best to go ahead and upgrade to harder pushrods even if you're gonna leave it stock (like I would)? I've heard some say that the pushrods are kinda like the "weakest link" in the valvetrain, and that's a good thing if it's true, but I have no evidence to back this up.
07-17-2010, 11:51 PM
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If it ain't one thing it's another...
A while back I blew the 50 amp ignition fuse. Replaced it and all is well. Well, it happened again yesterday at the post office and this time it blew 3 more new fuses so I'm grounding a wire somewhere in the system. Had to have it towed and have to have someone else look at the damn thing. I'm a bit pissed with this car right now... First time in 2 years it's given me any problems and they just seem to keep coming.
A while back I blew the 50 amp ignition fuse. Replaced it and all is well. Well, it happened again yesterday at the post office and this time it blew 3 more new fuses so I'm grounding a wire somewhere in the system. Had to have it towed and have to have someone else look at the damn thing. I'm a bit pissed with this car right now... First time in 2 years it's given me any problems and they just seem to keep coming.
08-04-2010, 04:27 PM
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Ordered new pushrods, LS6 springs, and a timing chain from TSP yesterday. Will be tearing the valvetrain apart in a couple of weeks. I'll let you all know what I find. God I hope the valves are alright.
Might be a good excuse to bump up to 6.0 heads for the turbo in the living room though
Might be a good excuse to bump up to 6.0 heads for the turbo in the living room though
I hope everything works out for you.
08-08-2010, 12:11 AM
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Ha thanks man.
Well, like an idiot I drove the car a couple of miles the other day and ended up having to get it towed home. Made some funny metal clanking noises on the way and when I tried to fire it up again, it died a few seconds later. I could feel the clanking through the shifter. Gonna take off the valve covers and pull the pushrods on Tuesday.
I honestly think I'm just going to take off the heads and replace them with some cheap low mileage 853s. Gotta put in new springs anyway and I have a bad feeling there is a bad valve or two in there. I'll probably end up upgrading to LS7 lifters as well for the FI build anyway.
Can you reuse the stock head gaskets if they are in good shape? All I really think I'll need to replace is the timing cover gasket (gonna throw on the LS2 chain and Melling oil pump), head bolts, and crank balancer bolt.
I honestly don't see any reason to not pull the heads. With the way the car is acting I'm sure there is a damaged valve or lifter and it will give me the opportunity to check out the pistons while I'm in there. Will also make the spring swap a breeze.
Well, like an idiot I drove the car a couple of miles the other day and ended up having to get it towed home. Made some funny metal clanking noises on the way and when I tried to fire it up again, it died a few seconds later. I could feel the clanking through the shifter. Gonna take off the valve covers and pull the pushrods on Tuesday.
I honestly think I'm just going to take off the heads and replace them with some cheap low mileage 853s. Gotta put in new springs anyway and I have a bad feeling there is a bad valve or two in there. I'll probably end up upgrading to LS7 lifters as well for the FI build anyway.
Can you reuse the stock head gaskets if they are in good shape? All I really think I'll need to replace is the timing cover gasket (gonna throw on the LS2 chain and Melling oil pump), head bolts, and crank balancer bolt.
I honestly don't see any reason to not pull the heads. With the way the car is acting I'm sure there is a damaged valve or lifter and it will give me the opportunity to check out the pistons while I'm in there. Will also make the spring swap a breeze.
08-17-2010, 08:20 AM
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Ha thanks man.
Well, like an idiot I drove the car a couple of miles the other day and ended up having to get it towed home. Made some funny metal clanking noises on the way and when I tried to fire it up again, it died a few seconds later. I could feel the clanking through the shifter. Gonna take off the valve covers and pull the pushrods on Tuesday.
I honestly think I'm just going to take off the heads and replace them with some cheap low mileage 853s. Gotta put in new springs anyway and I have a bad feeling there is a bad valve or two in there. I'll probably end up upgrading to LS7 lifters as well for the FI build anyway.
Can you reuse the stock head gaskets if they are in good shape? All I really think I'll need to replace is the timing cover gasket (gonna throw on the LS2 chain and Melling oil pump), head bolts, and crank balancer bolt.
I honestly don't see any reason to not pull the heads. With the way the car is acting I'm sure there is a damaged valve or lifter and it will give me the opportunity to check out the pistons while I'm in there. Will also make the spring swap a breeze.
Well, like an idiot I drove the car a couple of miles the other day and ended up having to get it towed home. Made some funny metal clanking noises on the way and when I tried to fire it up again, it died a few seconds later. I could feel the clanking through the shifter. Gonna take off the valve covers and pull the pushrods on Tuesday.
I honestly think I'm just going to take off the heads and replace them with some cheap low mileage 853s. Gotta put in new springs anyway and I have a bad feeling there is a bad valve or two in there. I'll probably end up upgrading to LS7 lifters as well for the FI build anyway.
Can you reuse the stock head gaskets if they are in good shape? All I really think I'll need to replace is the timing cover gasket (gonna throw on the LS2 chain and Melling oil pump), head bolts, and crank balancer bolt.
I honestly don't see any reason to not pull the heads. With the way the car is acting I'm sure there is a damaged valve or lifter and it will give me the opportunity to check out the pistons while I'm in there. Will also make the spring swap a breeze.
if you are going to take the heads off i would replace all the gaskets just for peace of mind. dont forget new head bolts if you go that route.
08-17-2010, 11:25 PM
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Yeah after reading up on it, I will definitely be replacing the head gaskets. Got the passenger side head off today. No problems to speak of. Bent pushrod was on the other side and will be getting to that tomorrow.
