I have a 455 that I had the short block built buy a engine shop. I just got the exhaust on and started it up and, KNOCK!. I heard what sound like a bottom end knock. The engine is new, the car is still being built so it has 0 miles on it. It has been run maybe 20 minutes total. Where do I start chasing this down. I am hoping that it is not what it sounds like. I put the rest of the engine together myself but the short block was all together. Any ideas?
Also this is my first Pontiac so learning lots on this one. I also noticed once the exhaust was on that the intake has a opening where the choke goes and it appears to be open to the exhaust. I did not cover it because I thought it was a warm air channel only for the choke. Is it suppose to be a direct opening to exhaust. If it is can I just block it off until I figure out what out what is suppose to be there? What is suppose to be there? Thanks for your help. EB
How did you start your newly rebuilt engine,??.. From what I understand your suppose to let it run for at least twenty minutes @ 2000 rpm's to break it in, or you could round off the cam lobes.. if not that might be the knocking noise your hearing..
The block was cleaned, crank turned, bored to clean up the cyl. and new flat top pistons, 480 comp cam,lifters,bearings through out. Heads rebuilt but left stock,headers. I covered the cam and lifters with break in grease/fluid and used break in oil. I manually pumped up the oil pressure and started it up. I ran for about 15 to 20 minutes before I shut it down. It has set since, (several months) and I started it today to hear my new handy work, (the exhaust). Don't know what else to add. I shut it down right after hearing the knock so I did not chase it with a probe but it sounded low and drivers side. EB
That I don't know. I hate to say this but I ASSUMED they did what was needed to be done when they turned the crank. I will find my invoice and see if that was done. EB
That I don't know. I hate to say this but I ASSUMED they did what was needed to be done when they turned the crank. I will find my invoice and see if that was done. EB
It's also a good idea to get engine balance with your harmonic balancer. Plasti-gauge the bearings as well.
So.......I am guessing the only way to know is take it back out $#@$$ %$##$ and tear it down!!!! %%#$@* Did it do much extra damage before you found out. I checked the oil and it looks totally clean. EB
No damage to my engine. Just torn engine down again, got the rods turned and then rebuilt it. But there is no guarantee that is the problem. You need to get the guys from the machine shop or an expert to have a look at it and hear it before you tear it down again. Do not start it up again until an expert is on site. I fixed mine after it was on the road for 1000 miles. Rings seated fine.
Get a engine rebuilding book and the Jim Hand book before you reassemble. When the shop only does the short block how much time do you think they spend on checking clearances etc.?
Hey Gus,, Really Nice Looking Ride.. Coolie water Sandwich..
Thanks but what does "Coolie water Sandwich.." mean?
...................... Not to be cornfused with the Aussie Version of " Vegimite sandwhich".. Were talkin Blues Brothers,, Coolie Water Sandwhich....""The other day, I had me a coolie water sandwich and a sunday-go-to-meetin' bun. That is to say, I had me a slice of watermelon and took a little ole lady to church, What do you want for nuthin,?.. a Rubber bisquite?????? Elwood
Guess who's just about ready to install a Pontiac rebuilt 400 engine this coming week?????????.. I also, have had everything done to this engine , BUTT,, I did not have the Rods Turned.!!!!!!!!....ESP.!!... What are the odds?
David, I went out to look at the intake and I don't see how I could put it on wrong unless there is a left and right that is different. The bolt holes are different and would not allow me to put it on backwards but I am still listening. Is there something else that could make it possible to put them on wrong. Gus68, I was planning on asking someone from the rebuild shop to come over and listen so I am not trying to explain what the sound was. TA69vert, I am running the lower octane from the local station, nothing special but it is not drivable yet just started it up for break in a few months ago. The exhaust leak that I am trying to figure out coming from the choke area on the intake is loud, like open headers, and I am going to block that off so I can hear the sound better. As for the Chebby engine, If I had it to do over again that is what would be in there, cheaper to build all around and I know how to work on those. EB
Sounds like you have a mis matched intake and heads. The later intakes have a different sized port for the heat crossover. If you don't have years that match up you will have that problem. It is a direct opening to the exhaust ports and yes it will be loud. I say fix that and see if your noise goes away.
I wonder if you have too low of octane, could that cause a knocking sound also??, or maybe at lower rpm's with no load maybe it won't matter,, I don't know,, just wondering.. Timing maybe??..
That I don't know. I hate to say this but I ASSUMED they did what was needed to be done when they turned the crank. I will find my invoice and see if that was done. EB
It's also a good idea to get engine balance with your harmonic balancer. Plasti-gauge the bearings as well.
All this I learned the hard way!
... Question... I was told that my motor did'nt need balanced with the flywheel, because the manual flywheel I bought was already balanced and I did'nt need to balance it with the engine, is this true???.. EB,, is yours a auto or manual???.
Last edited by TA69vert; 10/02/1104:11 PM. Reason: because
Mine is a 4 speed. Update, I blocked off the leak on the intake and now I can track down the sound better. It does not sound like it is bottom end. It sounds like it is a combination of transmission noise, O Boy another problem and now I suspect cam. I have never had a cam round off during break in so I don't know want that sounds like but this sounds like a lighter knock than a rod. It idles perfect but the sound sounds like a jack hammer and can be heard best by probing on the side of the bell housing. This is a loud sound not a light sound you have to listen for! At first I thought it was just the tranny but I pushed in the clutch and half the noise went away. and the other half kept on knocking. Is there a way to check the cam with out taking it out? Also for the possibility that the intake and heads don't match, I got this engine complete and together, so I think unless someone mixed them up at the machine shop i think they match. EB
Last edited by ebd; 10/02/1104:30 PM. Reason: add text
Pull one wire at a time to see if noise go's away.
Unbolt torque convertor to see if its trans.
Make sure no leak at head pipes. Exhuast leak sounds faintly simular.
FWIW Use snap gauges and mic to check concentricy of rods-n-bearings Sometimes just need to massage back of bearing halves to get correct tolerance. Just make sure no scotch brite particles left during assembly. They eat metal.
Region Warrior, It is a 4 speed, I took the trans completely out and still had the noise. It is getting louder! The exhaust is tight. This is a LOUD noise, not like a little ticking noise like lifters or rocker arm noise. It sounds like a bucket of bolts but still sits and idles like a new car!! Now that I have gone this far there is not much left to take it out and tear it down. I am still wanting to get a pro to listen to it before I unhook everything. The more I worked on it the more it sounds like a rod noise. But like I said I have never flatten out a cam so I don't know that noise, could be that, don't know. If a cam is flatten will it idle so smooth? If it is rod bearings, would that not be the fault of the machine shop? It is one thing to beat one and then have this problem, it is another to have this problem by just breaking it in and not even driving it. If they don't back up their work I will find someone else and probably go back in with a CHEVY SB! Any help on this is appreciated! Thanks Eldon
4 spd...Dulp! Push'n clutch in should determine trans.
A wiped lobe or collased lifter will make it run ruff. Wide vacuum readings. Can still do the cylinder check pull'n 1 wire at a time. If me, i'd pull and tear down(assemble my own). Take no chance of major damage. If shop assembled, let them do it. If they built and assembled, you didnt mess with internals, everything fine on break in, i say thier fault.
I think the best at this point is like you said, don't run it anymore and pull it. The shop assembled the short. I built it from heads up. Cam was in pan was on. I noticed that the sound was getting worse as the day went on. Time to pull and get on with it. Thanks EB
An update: I talked to the machine shop today and they were very nice about the problem and seemed genuine in their concern about it. He told me, after I explained the noise that it sounds more like a contact noise. He said maybe the windage tray in the oil pan. He said pull it, check a couple of things and if nothing is found bring him the short block and they will tear it down and if they find something there they will fix it. So far so good, well good for a bad situation! EB
Mine is a 4 speed. Update, I blocked off the leak on the intake and now I can track down the sound better. It does not sound like it is bottom end. It sounds like it is a combination of transmission noise, O Boy another problem and now I suspect cam. I have never had a cam round off during break in so I don't know want that sounds like but this sounds like a lighter knock than a rod. It idles perfect but the sound sounds like a jack hammer and can be heard best by probing on the side of the bell housing. This is a loud sound not a light sound you have to listen for! At first I thought it was just the tranny but I pushed in the clutch and half the noise went away. and the other half kept on knocking. Is there a way to check the cam with out taking it out? Also for the possibility that the intake and heads don't match, I got this engine complete and together, so I think unless someone mixed them up at the machine shop i think they match. EB
I made the same mistake when I put my intake in and had the loud exhaust noise, can't recall but thought if I flipped the gasket one way it blanked off the crossover and the other way it left a passage. I do recall pulling it and reinstalling and that fixed the exhaust noise...been awhile and I try and forget silly mistakes!
Yup, measure each valve lift. they will be all about the same except 1.5 times stated lift of cam. Or just do "visual" if it ate it enough to make noise you would see the rocker not moving much. If you ate a lobe i dont think it would make much noise as its just not lifting any more. THe only time i heard a cam make noise or "rumble" was in a 66 thunderbird. whomever did the timing chain didnt read the instructions That the cam "shim" is not needed as its built into the cam gear. cam walk was about an 1/8 inch! it moved so much the lifters hit the bearing surface and took huge chunks out of it.Not to mention that the lifters had chunks taken out of them.funny part it really ran ok. i had a rumble like bad main bearings , but too high up.
