funny rattle after rebuild

[mopargoob]

I just finished installing a 2.5 in a 88 Daytona. The short block assembly was put together by an extremely competant engine builder using Ross forged pistons, and FM bearings. did all the important stuff, like prelubing and all the attention to detail type stuff ( I work as a tech in a Mopar shop for the last 20 years) and under load the engine rattles like the rods are wanting to come out.
put it in drive, and it barely taps, increase throttle and it rattles quite well up to about 2500 rpm and quiets down completely. I have around 50 psi at 1100 rpm and above, and 20 psi at hot idle. I really don't think its the rod bearings, but why does the rattle go away in the higher rpms??? I never seen an engine do this before now. any help is much appreciated.

[russ jerome]

No chance the flexplate bolts are loose is there? Regardless if it
is an auto remove the 4 flexbolts and fire it up and listen. Cracked
flexplates are common on these cars as most domestic low quality
pieces of iron built from old Toyotas.

[overboostperformance]

+1 ^

i have also had the wrist pins clips come out and make a rattle under load but under cruise nada . sounds like rocks in a coffee can was very hard to diag.

Norm

[4 L-bodies]

Quote:

Originally Posted by russ jerome No chance the flexplate bolts are loose is there? Regardless if it is an auto remove the 4 flexbolts and fire it up and listen. Cracked flexplates are common on these cars as most domestic low quality pieces of iron built from old Toyotas.

If it is a manual tranny, The same thing applies. I have a very good friend that had this happen to with a 85 GLHT while under warranty. He also is in the auto industry, and thought, crap the bottom end is letting loose. The mechanics agreed. The motor was torn down like three times trying to find out why the rods where making so much noise. The car had like 2000 miles on it. A newbie mechanic at the dealership saw all the veterans scratching their heads and talking about it over lunch/ breaks etc. The newbie said immediately, that sounds like the flywheel bolts are loose. We see that occasionally at the service station garage where I used to work. Of course they laughed and rolled their eyes at the newbie. Well after tearing it apart for the third time, out of desparation, one of the mechanics pulled the tranny and found the flywheel bolts had started to oblong the flywheel bolt holes. In the meantime, a NEW shortblock had been ordered from Chrysler. Well, the veterans learned something new that day, and the newbie gained some acceptance at the dealership. Most of all, the my friend finally got to enjoy his GLHT. Lesson learned!

[mopargoob]

well, I've run across that lots of times also, but this engine only has 10 miles on it and when I put the flywheel on and assembled it to the trans, I used new crank bolts, new flexplate bolts, and plenty of blue locktite and torqued them all to spec. I was talking to a local hot rodder/racer, and he claims he has a 440 with Ross pistons that rattles like a bastard because of the way the pistons are clearanced and such, but nothing is wrong with it after a couple of inspections. I guess a call to my engine builder is in order. Thanks for all the replys and such so far.

[mopar2ya]

If the Ross is anything like a Venolia piston, you get a Holy Crap look on your face when you first start it. It does sound like a rod knock but should gradually get quiet after the engine warms. If it doesnt the pistons are way to loose or something else is wrong.

[4 L-bodies]

Quote:

Originally Posted by mopar2ya If the Ross is anything like a Venolia piston, you get a Holy Crap look on your face when you first start it. It does sound like a rod knock but should gradually get quiet after the engine warms. If it doesnt the pistons are way to loose or something else is wrong.

I have used Ross pistons in close to a dozen 2.2 applications and they are never noisy at start up. I agree with Wallace, that you may have way too much piston to wall. Since Ross doesn't have a stocked piston for our application, they are all custom made, your engine builder must have given Ross some specs for the application. Ask your builder what piston to wall clearance they used. Should have been .004-.0045 for a turbo application. Ross pistons don't need the clearance that Venolia pistons do. If they did run like .008-.010 clearance (top of skirt) that Venolia suggests, yeah they're going to be pretty noisy. The instructions that Ross sends with the pistons are quite clear on this and what ring gaps they recommend. Ross is in the camp that wants to see larger second ring gap than the top ring.
I stopped using Ross only because they take WAY too long for turn around time. The last set I ordered I gave up after a 3.5 month wait. Diamond pistons had my custom pistons in hand in 2.5 weeks. Been using them ever since.

[Endo]

Dont get to comfortable thinking its only the forged pistons heating up. When i finished putting my rebuild together this summer, I had some tapping that i figured was only my Wisecos heating up. Turns out all the cam caps were finger tight or less! Dad saved my bacon on that one.

[TurboDeano]

Doesnt sound like a funny rattle to me.....

Pull the head off and check it out.

[black86glhs]

What about the intermediate shaft bearings? Could they cause such a noise?

[turbogod]

Quote:

Originally Posted by TurboDeano Doesnt sound like a funny rattle to me..... Pull the head off and check it out.

I have run across
loose cam gear bolt, a stock cam in an oversized cam journel that dodge did from the factory, I did my first motor with .010 clearence and it rattled when cold, and the the lose converter bolts sounds real loud! Oh and if oversized wrist pins you will find problems, or at least 2 sets my buddy installed in his car..