Need our engine experts to help me out.

[Itoldyouso]

I'll try to make this a brief as possible. I have put together a lot of engines over the years, but I am by no stretch of the imagination an "engine builder/expert." We have guys on here like Pat, Dave, and others who REALLY know how to put one together, checking every little spec and clearance as it goes together. Me, I might use some plastigage, and that is about it. But for the most part mine have worked ok.

But the 331 stroker I put together has me puzzled. I mentioned that the galley plug blew out after 5 minutes of running and oil pressure went to zero. We shut it down IMMEDIATELY, and after I put in the new (screw in) galley plug I prelubed it and fired it up. All was good. Oil pressure is 60 psi at idle and the engine sounds strong, takes gas well. However, after putting the exhaust system on (I had been running it with loud open headers) I could hear a noise coming from the engine. It is a rhythmic knock that sounds like a rod bearing.

First I pulled the valve covers as I thought one of the roller rockers had come loose or something, no, they are all moving as they should. The noise seems to be coming from deep in the engine. So, I pulled the engine tonight and turned it upside down on a stand. I fully expected to find some scored bearing(s), but they are all nice. A few have slight scratching on them, but nothing that wasn't caused by a little dust in the engine block. I saw no signs of the stroker crank hitting anything because of clearance issues either.

The only thing that I noticed was you can move a pair of connecting rods slightly sideways on the crank journal. It makes a slight "knock" as you move it sideways. I put a feeler gauge in there and an .008 feeler gauge will slide down into the gap between a connecting rod and the crank journal. Is that normal? I have also never done an engine with full floating pins before, so maybe these move more side to side?

Here is what I have:

90 Mustang 302 block. Align bored, bored 30 over, decked, finish honed with deckplate.

Scat 331 stroker kit, balanced, Probe flattop pistons. All 28 oz imbalance.

Ford Racing X303 roller cam, Comp Cam timing chain, Harlan Sharp roller rockers, Ford Racing pushrods.

Edelbrock Performer RPM aluminum heads, set up for roller rockers.

Melling standard oil pump with ARP hardened driveshaft.

Any thoughts on what I should do next? Thanks in advance guys.

Don

[pat mccarthy]

make sure your not hitting the bottom side of the piston to crank counter weigths .oilpan screen or wind tray.oil pan hitting crank counter weigths check that the crank counter s are not rubbing on block casting .check bottoms of pistons bores that rods are not hitting . rods side at 008 is abit thin .built them with much more .i would say thats not it or floaters .less one of the pistons pin s is working its way in to the piston bore . you have the rigth firing order ? for your cam

[Itoldyouso]

Yep Pat, firing order is now 351 order because of the cam. I also looked to see if anything like rod bolts or connecting rod is coming close to anything, couldn't see any problems or scuffed areas where something had rubbed. Counterweights are not near piston or bore. I examined pan and dipstick too to see if they were getting in the way, no marks or anything.

I am seeing some metal particles in the bottom of the pan. Looks more like machining left overs than bearing material. Not a lot of it, and I just wiped out the pan when I did the galley plug replacement. Not sure where that black dirtlike stuff is coming from. I've changed the oil twice already, running Rotella T 15-40 with Comp Cam break in lube too.

What do you mean .008 is "thin?" Is that tight or loose?

Thanks for the help Pat.

Don

[pat mccarthy]

Yep Pat, firing order is now 351 order because of the cam. .

What do you mean .008 is "thin?" Is that tight or loose?

Thanks for the help Pat.

Don

i did not think the bottom of bores would be hitting but you never know as for black mud or past could be molly lube . or your making iron past were some thing is cutting in to the block, what is your cam ? roller or flat lifter . the cam could be moving ??? front cam plate on the block ? i seen were a guy used the wrong fire order on a 351w made a low thunking sounds he was going nuts .i moved his plug wires a round 008 is tight like to see abit more

[Itoldyouso]

It's a roller cam with new Ford Racing roller lifters. That's the thing that has me puzzled, the ONLY used part on the entire engine is the block and it has been totally remachined. Every other part is brand new and matched. I've built engines with lots of used parts and haven't had this sort of problem.

The cam has it's front plate installed, so I don't think it is walking. The one thing I did notice is that my new Comp Cam timing chain now has some slight slop in it, where it was tight when I installed it. I know they stretch out a little, but this seems too soon.

Don

[pat mccarthy]

piston to valve was good ? did you check for coil bind or valve seals hitting the retaners . rocker arms hitting on studs poly nuts ECT ? push rods rubbing the block .roller lifters hitting block /hold downs?you can check your oil pump and drive some are to long and work on the oil pump bottom pump plate making the pump gears wear in take cover off the oil pump some thing may of went thru it

[Itoldyouso]

All great ideas Pat, thanks. I wish something would have jumped out at me when I pulled the pan, but nothing looked odd. Guess I am going to have to tear it all the way down and see if all of those items you suggested are within specs. The spring bind should not be a problem as the heads are rated for a higher lift cam than I have. But I want to pull the heads anyway to make sure a valve didn't kiss a piston top.

I'll get those off tomorrow and let you know what I see. I did have it 180 out of time when I tried to restart it and it backfired through the carbs and headers, so maybe I did some damage there.

Pat, thanks for all the suggestions and help, I'll get back tomorrow.

Don

[John Palmer]

Don, you listed that you have "flat top" pistons. Is it possible that one piston is reversed, with the "pin offset" going the wrong direction? They will knock just like a rod knock sound. Just a thought.

Good luck chasing it down.

[pat mccarthy]

if wire locks for the pin s you have to watch that they seat. as for the spring s they say there good and they may be fine i still would check every thing for size and fit

[pat mccarthy]

were is the piston to wall at ?

[Itoldyouso]

If you mean are the pins moved up into the piston for the longer stroke, yes, the pin is pretty high and the pistons are very short, compared to the stock sbf pistons I'm used to.

John, sorry, I just noticed your post in there. I think the pistons are in right because they had a notch that goes to the front on each one and I installed it that way.

Pat, I didn't check piston to wall.....I know I should have but I'm not that sophisticated in these things. I just trusted that the block is 30 over and that is what kit I got.

The more I think about it the more I think my backfire bent something. It really backfired and even blew the rubber plugs off of the vacuum ports on both carbs. I got it somehow 180 out of phase for the restart after the galley plug incident, and when we cranked it the thing backfired out the carbs and flames out the headers. I bet I bent something.

I'm going to tear it down and I bet I find some damage caused by my dumbness. The noise in the engine was not there the first time we ran the motor for 5 minutes, it was only there after the galley plug/backfire thing. I could slightly hear the knock even with open headers after I put the motor back together, so I think whatever happened happened the second time around.

Don

[jerry clayton]

two items come to mind that haven't been mentioned---Bolts that hold cam plate on may have heads that are too thick to clear the gear--- some aftermarket cam gears are wider and hit block area above the oil galley area, plug you put into galley may not be deep enough causing back of chain/gear to hit it,and also some strokers have interfernce at where the oil pump mount area is on block(counter weight hits.

also ---fuel pump eccentric????

ok maybe more than 2 but I'll only charge for two!!!!!

[stovens]

Don I had a 302 crank years ago on a 289 block(stamped 302) where the valves were hitting the piston. I am sure by reading what you have said this isn't the case for you since you didn't hear anything the first go round. I'm also wondering about the screw in plugs, since that's the only difference between before and after, unless something got bent? This will be a good diagnostic thread to follow! Hope it's simple and inexpensive.

[Mike P]

Don over the years I've had some engines with noises that really had me pulling my hair out.

An enginge knock that turned out to be the oil baffel in the valve cover coming loose and being hammered by the rockers.

A noise deep in the engine that turned out to be a crank counterweight hitting in one spot on the custom pan.

A noise that sounded like loose lifters that turned out to be the mechanical fuel pump coming apart.

A couple of cracked flex plates that sure sounded like rod bearings when you first listened to it.

I guess what I'm getting at it that you don't want to overlook the simple stuff while you're tracking down the problem.

[Itoldyouso]

Thanks all for the suggestions, they are all good ones. I just came home from tearing down the engine.......it is now a bare block again. I was expecting to find something very obvious when I pulled the heads or pistons, but everything looks really fine. A couple of the rod and main bearings have VERY minor scratches on them, obviously some piece of trash got under them, but nothing that would cause a knock.

Jerry, you mention the fuel pump eccentric. I had the same thought because I always have run an electric pump before, but this time decided to run a Carter mechanical pump. The outer ring of the eccentric seems sloppy and a little out of round, like it has been deformed by something. Not really badly, just a tad. But I could wiggle the outer ring on the inside one and it makes a little noise.

The biggest thing I noticed is that my cylinder walls have vertical lines going up and down them from top to bottom, but only in the very top of them and at the bottom. I envision that the stroker crank is pushing the pistons in those two planes as it rotates. The rest of all of the cylinders have the normal cross hatch pattern , but every cylinder has these scratches that cover an area about a half inch wide going from top to bottom (see my little drawing) It looks like the piston is scuffing the walls in that area. This seems extremely premature as the motor probably has 15 minutes on it tops.

Finally, I noticed that the very bottom of each cylinder is a little jagged, like there is a lip that needs smoothed there. You can run your finger around the very bottom edge of the bore and it is sharp. The skirts on the pistons go below this line, so they are passing over this sharp edge.

I am going to take my camera back to the shop now and take some pictures, hope they show the things I mention. In the mean time, thanks again guys for the help.

Here is my little drawing showing where the scuffing seems to be on each cylinder.

Don