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Author Topic:   Blown motor...
dode
Member
posted July 08, 2002 10:07 AM
Well, it looks like our race motor isn't in too good of shape. I haven't totally disassembled it yet, but it pretty much looks like we lost #7 and #8 cylinders due to problems with the cam. It looks like the cam is in two pieces, and the pushrods from 7 and 8 are nowhere to be seen, other than the one sticking through the bottom of the oil pan. Sheesh...

Anyway, my first question is what would cause a cam to bust in half. I would like to try and pinpoint the cause of this. I know it could have just been a "soft" cam, but it could be other things too I guess. It appears that there a bunch of lifter parts in the lifter valley. Maybe one of them came apart and locked things up? I wasn't there at the time, but evidently he started losing power, and then the engine just died on him. Where should I start looking? Also, I am sure the cam and bearings are totally shot? What other things should I look for? I have never actually put a cam in. Can anyone give me any tips? I can do this with the short block assembled can't I, and change the cam bearings? We have a second engine that was running when it was removed about a year ago, but I have never seen it run, and I was told it smoked a decent amount, but it had a broken rocker arm, so I would say that is probably the cause of that. What should I check out with that one, should we decide to go with that one? Also, as far as I know it has a stock cam in it too, though I can't be for certain. I have a couple of decent cams laying around I could put in, but as I said, I don't have much experience doing this. It doesn't seem like the easiest thing to do, but both engines are in short block form right now.

I would really appreciate any advice. Again, I am running into new territory, but I am learning a lot, so that's a good thing. Oh, by the way, we weren't spinning it too fast (maybe 5300-5400 is about the most it has ever turned). Thanks guys. You guys are always a big help.

John

BayouGent
Member
posted July 08, 2002 11:11 AM
John, first you need to pull that engine out of the car. There are a few things that could have caused what you are seeing. I've broken a cam in half before, but it broke because the broken connecting rod basically found a way to slap it into 2 pieces. I'm not wishing a broken rod on you, but you need to pull the pan and look to see if one broke. Another thing I've seen happen is a lifter break in half. We were fortunate that the bottom half of the lifter found it's way to the oil pan and the top half of the lifter rode the cam like a shorter lifter. The cam was badly grooved when this happened but the pushrod didn't fall out. You may have had a lifter break and your pushrod went onward to the bottom of the engine. Somehow it may have jammed the camshaft and snapped it on it's way South. It's hard to say because when things start coming apart anything can happen inside an engine.
Now, to fix whatever problems you may have, regardless of what you need to replace (camshaft, lifters, connecting rod or 2, etc.), I strongly suggest that you tear that engine completely down and bring the engine block to get tanked and have fresh cam bearings installed. Then any and all other parts that you are reusing need to be thoroughly cleaned. When those parts came apart, zillions of metal shavings and slivers went all thoughout the bottom end of that motor, including through the oil pump which sent the shavings straight to all the engine bearings. Install new crank and rod bearings because you'll probably see scarring on your existing bearings where metal was introduced to them. The pistons should be fine as long as nothing hit them. I'd recommend replacing the rings while your that far into the motor, especially since they too could have also sustained a little damage from metal shavings. Either replace the oil pump or have someone that knows what to look for pull the pump apart to clean it out and inspect it for damage. And finally you'll need a new camshaft and lifters, because even if your cam didn't break in half, the lobe that the lifter went to pieces on is probably badly damaged. I would also suggest trying to find a friend at the track that has some experience building engines to give you some help with this project, because I'm going to assume that if you haven't changed a cam before, you've never overhauled an engine before either. The only bright side of this is that you'll get a chance to learn how it's done. Now, if you don't want to go through all of this, you can use your other shortblock, BUT, there are a few unknowns about it from what you are writing. It would be a shame to assemble that engine for your car only to find out that the rings are shot and your car will smoke and bring the black flag out on you. However, if the blown engine does have bad rods, crank, or pistons, you can always put some fresh rings, bearings, cam, and lifters into that spare short block you have there and then you'll KNOW what you've got. Just a few cents worth to help put you in the right direction. I do not I repeat do not recommend you just replacing the cam, lifters, and oilpan on the engine that just went kaput and go racing, because you'll be tearing it apart again about this time next week. Good luck!!


BK19
Member
posted July 08, 2002 12:06 PM
i had the exact same thing happen to me this past sat night the # 7 rod broke slammed into the cam broke it in three pieces hit the valve probably bending them busted 2 pistons put a huge pit in the crank took out a chunk of the bottom of #7 and 8 cyl so yeah you better take the motor apart and have the block and heads checked out it ***** cause i am done for the year now went through 3 motors and 1 car already


racer17j
Member
posted July 08, 2002 02:30 PM
more than likeley that motor you blew is junk now like the others said you will more than likely find that a broken rod took the cam out i would just get that one pulled out and and tare the other one down and see what it needs if you are lucky you might just be able to get a rering kit and hone the cylenders as for puting it back together it's not rocket sceince just get a book. your not running anything fancy so just a basic chiltons manual will take you step by step thats all i have ever done. and there are other books that will tell you how to install the cam and properly degree it myself i just run mine just like a stock one just line the dots up and go


BayouGent
Member
posted July 09, 2002 04:15 AM
Hey John I wanted to pass along some of the lowest priced complete engine rebuild kits and basic rering kits that I've used have come from Northern Auto Parts warehouse. Their website is northernautoparts.com. I'm not sure if they are the cheapest out there, but they are the cheapest I have found. Chevy 350 master kits which include everything for a complete overhaul run around $159 and you can upgrade different aspects of their kits (brass freeze plugs, higher performance cam, fel-pro gaskets instead of Victor, hypereutectic or forged pistons instead of cast, and Clevite bearings. I believe the re-ring kits are around the $59 area and include rings and gaskets. Not all that hard of a hit on the pocketbook to have a fresh engine and possibly make a little more horsepower. Hope this helps!!


dode
Member
posted July 09, 2002 08:33 AM
Well, I disassembled the engine the rest of the way last night, and it is pretty much FUBAR. The #8 connecting rod broke right at the rod bearing, and now the cam is in pieces, like 4 lifters and just totally smashed, there is a chip out of our nice 4 bolt block at the bottom of the #8 cylinder. The crank appears to be pretty much toast, and the cam is in a few pieces. Also, something very odd...The oil pump was sitting in the bottom of the oil pan. This isn't normal isn't it? What holds the oil pump in? There was a large bolt that I couldn't identify in the bottom of the oil pan too, is this what holds it in? It appears that this is undamaged. Now I am worried that the oil pump just fell off. Is this possible?

Ok...well on to the other motor. I got some more info on it. It is a fairly fresh rebuild, with only having a couple thousand miles on it before the rest of the vehicle was junked. What types of things would I need to look for to use it? Is there anything that I would have to do other than putting a new cam in? I am talking about clearancing anything or chamfering oil holes, or whatever, or should we just put a cam in and go? Also, when changing the cam, do we need to put in new lifters too? These lifters are basically brand new as I said. Do you have to put in new cam bearings when replacing the cam, or just use what we have? Any other tips? I have done top ends a lot, but not much on the lower end. Thanks.

JOhn



BK19
Member
posted July 09, 2002 07:51 PM
yeah that big bolt holds the oil pump on the rear main cap it sure is ironic that mine and your motor came apart the same way except my oil pump was still on i wish i had another motor though


racer17j
Member
posted July 09, 2002 11:26 PM
that could have been your problem if the bolt is not broken at all it could have fell out if it was not put in to spec. as for your other motor if it was a good running motor when it was pulled i would go ahead and just change the cam put a good oil pump in it and a good timing chain but you said it was smoking and it had a broken rocker ? a borken rock arm will not cause it to burn oil bad rings or a scratched cylender will however. your best bet will be to take it apart and take it into your local machine shop. you can get it cleaned,cam bearings installed and new freeze plugs for around $100. when you change the cam you should put new lifters.


BayouGent
Member
posted July 10, 2002 01:01 AM
I recommend taking that other motor apart and freshening it up. Get it cleaned, fresh cam bearings, and install some fresh bearings and rings for sure. If your budget won't allow it you can clean it and might get lucky running it just like it is, but if you possibly can take the safer route. Just my opinion.


DirtFreak08
Member
posted July 10, 2002 03:42 PM
Hey dode, I feel your pain. My engine went boom on my first night out this year. Sounds exactly like yours, lost power in one lap and clicked. Took it apart the following night and the oil pan had 4 holes in it. Right where no. 2,4,6,and 8 are but only one rod came off. Everything in the top half was okay. I had two lifters shattered, and my cam was in 7 pieces. None of the pistons were damaged and only the one rod was demolished at the rod cap. I had a handful of metal shavings in the oil pump, and at the bottom of all the cylinder walls there were gashes like maybe the rods were hitting for awhile but only had trouble in one lap. Ran better than ever then boom. I'm pretty new to the mechanical side of racing, but my dad has been doing this for 30 years and he says what he thinks happened is rare but it can happen. Before the race it looked as if there was an oil leak, but we couldn't find it. Nothing was leaking!! He thinks the leak we were looking for was coming from the fuel pump. It went out and the engine was not getting the proper amount of fuel. The cylinder walls went dry and locked up. Lesson learned here. Got the new motor now and getting ready to fire it up tonite. I'm just hoping this motor lasts a while.

Good luck to ya!

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