I got my block back from the machine shop two days ago and began to piece everything together, and i finished last night. I put 30 miles on the motor and it sounds slightly like a diesel engine, not that loud but louder than stock. i know that forged pistons usually rattle a little during warmup but even after its warm it does the same thing, again not rediculously loud just noticeable, wat u guys think?
btw i got a 94 GSR with CP 9:1 pistons and Eagle H-beam rods, NO boost yet, just na for a about 2 months...thanx in advance

 

i got a feeling this is bad news

 

Did you sleeve the block? I have heard that forged pistons do not work in the stock FRM sleeves. I am by no means an expert but that's what I have heard.

 

Check your valve clearance! Sounds like you need an adjustment!

 

i know it aint the valves, i had a slight valve click before, this is more like a diesel motor sound, or a rod knock

 

any other thoughts?

 

I'd suspect the clearances being too loose. Does it smoke any?

I'll post up a vid and some pictures of an improperly clearanced block with 2618 alloys.

 

Mostly likely it's piston slap. My engine does the same thing and I have put about 4500 miles on it with no problems it, even NOSed it a couple of times. What kind of machine shop did the work on the block, do they do high performance stuff or just regular rebuilds? If they do regular stuff(which is the kind I used!), then more than likely they machined the bore too big.

 

I'm running a JG Engine Dynamics Pro Series D16Z6 with Arias pistons.
It has alot of piston slap noise. Its been this way since it was new. It has about 8000 miles on it and know problems. Did a leak down and compression test on it this fall and everything looks great.

 

thanx for the replies guys...yea i got a bad feeling its slap too, i talked to the guy today and he said that even tho the pistons are oversized for a 81.5mm bore, the sheet that came with them claimed a 3.209 bore, which is larger than 81.5, at least thats wat he said, so he claims he went to 3.206 with the bore then 3 thousands more off with the honing. he said to check oil press. ect and let him know, im doing a valve adjustment tomorrow also...any other thoughts would be great
p.s wat kind of compression #s should i be pulling with 9:1 os and a fresh bore?

 

close to 180 psi after 7-8 strokes.i wonder once you get the turbo on,the engine may quit down a little,those pistons were made for turbo,so you may not have enough heat to have them expand to the size they are supposed to be.

 

When my maching was done I gave them the pistons with the block to make sure they got it right. Make sure you do the compression test by the book.

 

I think he rebuilt the motor with those pistons back in NY two years prior to when I got to know him and before he was my roommate. The build had like 10k-11k miles on it by the time we took it apart.

Nov 2002 - Compression test on the motor was 260psi all the way across.

March 31st, 2003 - Dyno Day
7.1MB AVI - My roommate's car at idle.
http://portfolio.iu.edu/bchang...I.AVI

1.9MB AVI - Getting rolling on the dyno
http://portfolio.iu.edu/bchang...I.AVI

Dyno plog:


Oct 2003 - What started as replacing a head gasket, turned into rebuilding the motor. Up to the end, the motor never smoked. Ring sealing was just fine.





Forged pistons, esp 2618 alloy slugs, are supposed to wear the bore, but I don't think this level of wear is normal unless the installation was faulty.

From the looks of things, the pistons were probably in there too tight.






Other info: The pistons were never clearanced in according to him. I'm not even sure that the bores were even honed if that gives you an idea of the level of carelessness the motor was put together with.

I'm pretty sure the JUN pistons are 2618 alloy, but I wouldn't quote me on that.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Zimmlude &raquo;</TD></TR><TR><TD CLASS="quote">Did you sleeve the block? I have heard that forged pistons do not work in the stock FRM sleeves. I am by no means an expert but that's what I have heard.</TD></TR></TABLE>

If he had the coating on his cylinder walls that would be true but that isn't a prelude.

 

yea im kinda wondering the same thing. i had a guy around here who works on hondas and stuff take a look at it and he said that it seems normal to him and im paranoid and that it even sounds a little like detonation? anyway the car runs good and like i said i talked to the machine guy and he said to drive it and he will look at it, so i will drive it and if it takes a ****, then he will pay for the rebuild...thanx for the info and thoughts guys, keep em coming

 

wow, i just listened to that video and that is definetly a whole lot louder than mine, in fact unless the motor is right at 750rpms, its hard to hear outside the car, but inside u can pick it up even thru light acceleration up to 3k or so....

 

Forged pistons require more piston to cyl wall clearance than OEm pistons. Forged pistons expand when they get hot thats why the cpiston to cly wall is sert higher. If you don't have the piston to cyl wall clearances correct then you take a chance a seizing the pistons like the pics above show. You can also seize a piston if you spin forged pistons up high before they swell to operating temp. Its hard to say what the problem is but if you can find out what the piston to cyl wall clearance was it would help determine if that could be a problem. Hopefully you gave the machinest the spcs before he installed them.

 

all i know is that he recieved the block and new pistons/rods/bearings ect. before doin any machining...the spec sheet that came with the pistons called for the final bore to be 3.209 and he bored to 3.206 and honed an additional 3thousands out to get the final bore, he also said u need at least 5 thousands overbore to achieve a pistons slap, who knows...im hoping thats not it, we will see

 

Did you give the machineshop the pistons and block? That way they can bore it correctly with whatever piston-cylinder wall clearance you want. I had put .0035" (WISECO) and I think I should have went lower because the diesel sound sucks.

 

oh u got the diesel sound too? when does it happen? at idle? when its warm is it there too? how long have u had that?

 

the weird part is when i start the car and the revs are at about 1500 or so i cant hear the diesel sound hardly at all, it isnt until the motor warms up and the idle drops down and then i can hear it, again, mostly just from in the car

 

What kind of bearings did you use, and what were the clearances?

 

could be your fuel injectors,some aftermarket injectors are alittle noisy like RCs rotary type.

 

stock fuel injectors and i used ACL rod bearings and ACL thrust washers, i used Federal Mogul main bearings, he said all the clearances were in spec on those so who knows

 

sorry im on my buddies name and cant get it to log out, this is ChillOutWayne