Andy

We have heard of theis before as it seems comon with the Hyper pistons as in most cases the cylinder are over clearanced and have not been tourque plate honed and one other thing not using a 6 inch rod seems to make it worse as well do to the rod angle of the shorter rods.

 

Sounds like piston skirt slap.
Poor machining/hone job probably as mentioned previously.

 

Andy,

Which pistons, how big is the cam, and how big are the valves ? The reason I ask is that one of my customers had the same problem a few years back and it turned out that the valve reliefs in the pistons were not quite large enough diameter for the intake valves he was using. The intake valves were just barely touching the od of the valve relief and it sounded just like a Diesel truck. MIght not be your problem, but if you can't find anything else, you may have to go there.
The engine should definitely not sound like that especially with Hypereutectic pistons which are generally run fairly tight.

 

Man This Sucks I Posted About My 327 Doing The Same Thing 3 Weeks Agaon And No One Responder And U Guys Jump Right To His But Its No Big Deal..................THIS WAS MY POST i got my 327 runnin good but when it is at a idle it sounds like a disel runnin i got the timein set with a light and ever thing but u can give it a little gas and it runs smooth no ticking or anything can drive it and no vales rattel or nothing but stop at a red light and it sounds like a disel runnin could it be the 100, raceing gas makein it do it or??? i can idle it up and it stop can drive it stop at red lights and it makes no disel sound it only does it when i idle it down to where its suppose to be any help will be great full...thanks

 

Kenny,
Not everyone is watching this forum every hour of the day. Sometimes a post just gets put on at the wrong time and never gets seen by someone that might have an answer. It ends up going down the list. Personally, I only spend about an hour online every evening, if something is not there at that time, I dont see it.

 

keep in mind piston slap can lead to the skirt breaking and major damage

 

sorry bill i know some posts get sliped bye im really sorry .

 

keep in mind piston slap can lead to the skirt breaking and major damage

Unless it's one of the newer 5.3 or 6.0 Chevy engines-- in which case you get a little piece of paper with the truck saying the noise is "normal." :sad:

I'm with everyone else, sounds like the piston/bore clearance is too large. Someone goofed when doing the machine work, and unfortunately your brand new engine needs to come back out and torn down.

 

thanks for the input guys. My 383 has a comp cams mag. 270H w/ rhoads lifters and 2.02 1.60 valves in GM heads worked over from Wheeler motorsports. Not sure what brand of hyper pistons they are, came w/ stroker kit from speed-o-motive.

 

Andy,
Just wanted to mention that all of us here are speculating as we can not actually hear the engine run. If you assembled the engine, see if your machine shop, or another local engine builder will listen to it BEFORE you take it apart to find the problem. If you had the engine built by someone, he will want to listen ot it. I have seen guys take an engine apart for no reason whatsoever because they did not realize that the noise they were hearing was either normal, or something external to the engine. It makes it a lot easier to look for a problem if you can hear it first.

 

. My 383 has a comp cams mag. 270H w/ rhoads lifters

=
Me thinks you just answered the question to your problem
Why do you have Rhoads lifters on that cam?
There is a very good chance the noise will go away if you put the lifters in that belong on the cam

Could be wrong but I'd bet this is your problem,,,

 

Boy, I missed the Rhoads lifters comment .... they are noisy as heck. See ... thats why I recommended somebody actually listening to it. Good catch Mike !

 

I'll 3rd the Rhodes, don't need em with a cam that small.

 

I built the motor and when i was picking the pieces, i didnt fully understand the rhoads concept (i now do). I can stand the noise if it is them and they aren't hurting anything. BUT, im not sure it is them. I here what i think is them before the motor is warmed and by the time it is warmed up good, it sounds like a diesel. The noise isn't concentrated and doesn't sound like it has anything to do with the lifters. I dunno........just gonna have to have some knowledgeable folks listen to 'er. thanks for all the help, yall are awesome.

 

Just my 2 cents. If it is piston slap, wouldn't it be louder when its cold? I got the same damn noise in my 88 GMC pickup. Has 80,000 miles on it. I don't think it was rebuilt. I just got the truck 2 years ago. This diesel sound only occurs when the engine is at operating temp at idle. NO noise when cold. Been driving it like that for awhile now, so I don't think its really bad. Nothing happened yet.


Jay

 

I'll kinda knix the Rhoades lifter thing. I'm running them in my 383, and it just sounds like an old solid tappet cam at idle - tick, tick, tick, and kind of varies around the engine.

Skirt slap would be a "deeper/heavier" sound, and louder when cold.

 

I'll kinda knix the Rhoades lifter thing. I'm running them in my 383, and it just sounds like an old solid tappet cam at idle - tick, tick, tick, and kind of varies around the engine.

Skirt slap would be a "deeper/heavier" sound, and louder when cold.

=
You may have Rhodes & they may just go tick-tick in your engine but trust me, they can & will sound like crap in some applications depending on cam lobes, oil temperature, oil viscosity, what valve covers you are running & how you adjust them.
I have had a bit of experience in more than just one engine in restricted circle track deals with a vacuum rule & they do not react the same under all conditions.
BTW, they normally get louder with temperature.

 

so, if i replace my rhoads and my cam is already broken in, will it be bad for it if i put in some comp cams hydraulic lifters? also, are there any functional downsides to the rhoads if i have a CC 270H cam?