Rb25det wiseco piston valve clearance question

[gdubsmsp]

I finished by engine build which consists of wiseco 8.5:1 pistions (+.020) and a cometic head gasket and when i got it together it was running smooth but literally sounds like a diesel when running. At first i thought was just the hydraulic lifters not pumped up yet, but after it was running for almost a half hour and the noise was still there, I knew it was internal. I knew the bottom end was tight cause i double checked everything, so I took the head off to look at the valve train and found that the valves are just "kissing" the top of the pistons. Neither the head, nor the block were decked, and i verified that timing was correct before pulling the head off.

My question is has anyone else run into this valve clearance issue running the 8.5:1 wisecos, and a 1.2mm cometic head gasket? Or has anyone done this combination and had no problems?

Modified by gdubsmsp at 5:21 AM 4/9/2009

Modified by gdubsmsp at 8:30 AM 4/9/2009
Modified by gdubsmsp at 3:36 PM 4/15/2009

[Darius]

This doesn't sound normal. Are you sure the timing belt was set properly and teeth were not skipped. I doubt that even if the head was decked that the clearance between the pistons and valves is so close that a headgasket thickness change of < 0.5mm would cause them to collide.

[Shocker]

Are you running rb26 pistons? They are slightly taller than Rb25 pistons...

Or like Matt said could be a timing belt related issue.

Measure your deck height at TDC, the quench well on the piston should be basically flush or slightly below the deck on the block.

[Darius]

I think you have that backwards. The wrist pin location in the RB26 pistons is higher so the piston stays lower in the bore with equal rod length. And the RB26 also have shorter rises on the piston decks themselves.

Yes, definitely check the piston vs deck height and double check timing. Maybe you should switch to a slightly thicker head gasket while you're at it.

What is the lift on the cams BTW? Are they stockers?

[Shocker]

I think you have that backwards. The wrist pin location in the RB26 pistons is higher so the piston stays lower in the bore with equal rod length. And the RB26 also have shorter rises on the piston decks themselves.

Correct, I'm thinking wrong with a 26 crank that would case such an event with rb25 pistons attached. Thanks for the clarification Matt.

[gdubsmsp]

I agree completely with both you guys that this sounds off for sure. I am a technician by trade so setting up a timing belt is no new thing to me and i can say that my timing was definately correct when it was on the engine stand. However, after running for about an hour, the timing jumped and i ended up bending valves, which is why the head is off now. The crazy thing is it did run perfectly smooth until it jumped other than the noise. The only thing i can think is that somehow between engine stand and start up something happened with the timing. I am waiting on valves now, so i will have another shot at all this, i just wanted to make sure noone has heard of anyone having this clearance problem with this combination.

And it is rb25det pistons wisecos-not rb26, and stock cams.

[Shocker]

How did the timing jump? Was the belt not tensioned properly? Did something interfere with the belt and cam gear?

[gdubsmsp]

I dont know how it jumps-obviously something was not right. Thats why i was wondering if it was a valve clearance issue that was causing the noise and at one point hit hard enough to make the timing jump (cause with hydraulic lifters they give alittle). I know the tensioner was tight, but i am not sure if something fell down onto the crank pully cause the upper cover was off. If something fell in a got in the teeth is would cause it to jump. Just found out today that the valves are on backorder for 3 weeks so i am desperately looking for alternatives that don't include spending $1000 plus on ferreas, so if anyone knows of a head for sale, let me know!

[Darius]

Were you running the engine without the timing cover on? I never trust myself enough to do that no matter how cool it looks to see the belt go round and round. haha

Is there any evidence that the tensioner spring broke or the bolt that it pre-tensions against?

If neither of those two, I would have to say that the belt was not tensioned enough during initial installation.

Look on SAU, there are several guys selling complete RB25 heads for $500AUD which is ridiculously cheap right now in USD. I think it is like $360USD?

Now that I mention this, if anybody is interested in a 6boost manifold, now is the time to buy. The exchange rate is at $0.72 so they are only $720. Steal!

[gdubsmsp]

I would look into aus but i am rediculously short on time right now. I have to be from miami to minneapolis, mn by april 23 (granted the car is being trailered it would be nice to be able to drive it on the trailer). I found a shop here in miami that has a full set of ferrea valves for $560 but ferrea is closed today for good friday so i wont know if they can get them drop shipped by next week until monday. I had the timing cover off cause i was checked to make sure cam timing was on to try and diagnose the knocking noise i was hearing. I thought if the cam timing was off, then light valve on piston contact (not enough to do damage but enough to make noise) would cause that noise. I know the tensioner was good and the spring and that it was tight, but i am beginning to definately think something fell down in the timing area and got stuck in the belt (a washer or nut or anything).

[Cjmartz2k]

I've got a set of stock valves sitting around in good shape if you want. $100? I just noticed this today. I could ship them monday, but I'm in Japan, and it's taking on average 7-10 days for stuff to get to the states priority. My email addy is in my profile since we don't have PM's on this board

I know that's probably going to be too late for you, but let me know if you want.

[gdubsmsp]

Thanks for the offer, but i actually just bought a set of ferrea valves (in and ex for 560). Plus the 7-10 days wouldnt have worked. If anyone is interested in the ferrea deal i got, call TD Autowerkes in Miami-hands down best deal on ferrea valves anywhere.

P.S. i checked out the link to your car-that is very nice. Kudos on that build for sure!

[Darius]

Make sure they are for a S1/S2 motor. Back when I bought mine, they only had valves for the NEO RB25.

[gdubsmsp]

Yeah i verified that they were for the r33 and not the neo-on that topic, do you know what the difference is between the neo and the r33 heads?

[eh?]

Was the block decked to wiseco specs? Wiseco has some funky specs for their pistons, I would have purchased them recently but the 8.0-8.4:1 CR makes me wonder if they have the right specs.

[gdubsmsp]

The block was not decked and either was the head, i am planning on running some high boost so i wanted the lowest compression i could get with that set up. I know the cometic head gasket is thinner than stock, but not enough to cause valve clearance issues i didn't think. The problem with hydraulic lifters is that they are not pumped up with the motor assembled and spun over on the stand by hand, so I cannot be sure that when they pump up i am not getting some light contact. I need to call wiseco today and talk to a tech guy.

[eh?]

So you're really running around 8.0:1 compression, stock HG thickness is 1mm. You're suppose to deck the block to get 8.4. If you indeed have clearance problems you need to double check which pistons you have.

[Darius]

Sounds like they're just cross-referencing the RB26 forgies for the RB25 motor because that's what the SCR would come out to be with standard RB26 pistons in an RB25...very low. Especially if they're "specifying" that the block be decked. Sounds shady to me. And honestly, that low of a SCR would be a total dog out of boost.

The difference in the S1/S2 vs. NEO heads is significant. The valve train went from hydraulic to solid so the NEO valves are a cm or two longer. If I remember correctly, the other valve dimensions were identical.

[Bluefire]

Did the valves hit on every cylinder or just a number of them?

[eh?]

Sounds like they're just cross-referencing the RB26 forgies for the RB25 motor because that's what the SCR would come out to be with standard RB26 pistons in an RB25...very low. Especially if they're "specifying" that the block be decked. Sounds shady to me. And honestly, that low of a SCR would be a total dog out of boost.

They list the RB26 CR as 7.9-8.25 and RB30/rb25 head as 7.0 Seems like nothing has changed in 5 years.

[Darius]

hahaaa They probably had some custom drag RB25/30 guy wanting super low compression and they turned around and sold those as their standard forged pistons for that swap. I'd personally sell them off if you haven't decked the block yet. Hell, at least the CP's are 8.5:1. LOL @ 7.0:1!!

[otightitzjim]

I finished by engine build which consists of wiseco 8.5:1 pistions (+.10) and a cometic head gasket and when i got it together it was running smooth but literally sounds like a diesel when running. At first i thought was just the hydraulic lifters not pumped up yet, but after it was running for almost a half hour and the noise was still there, I knew it was internal. I knew the bottom end was tight cause i double checked everything, so I took the head off to look at the valve train and found that the valves are just "kissing" the top of the pistons. Neither the head, nor the block were decked, and i verified that timing was correct before pulling the head off.

My question is has anyone else run into this valve clearance issue running the 8.5:1 wisecos, and a 1.2mm cometic head gasket? Or has anyone done this combination and had no problems?

Modified by gdubsmsp at 5:21 AM 4/9/2009

Modified by gdubsmsp at 8:30 AM 4/9/2009

i had simular problem with my build also. i was running tomei 1.2mm HG, cp piststons 86.5 bore 8.5:1 compression. supertech over sized valves, decked block and head, the valve was kissing the piston on cylinder number 6. it was a big pain figuring out wat was going on with it

[Chaos the Xile]

What is the lift on the cams BTW? Are they stockers?

I think its 248/248 for the S1 and S2 RB@% not sure about the NEO

[gdubsmsp]

Ok figured it out! The block was supposed to be bored over .020, and it was only bored .010 (86.25mm instead of 86.5 mm). The noise was not valve clearance, it was piston rattle against the wall. This may have had something to do with the timing belt jump also, but not sure. Unfortunately I cannot go further with this at this time as I am moving across country next thurs. I am going to box it all up and finish in a couple weeks when i get to Minneapolis. Good side of all this is that i am now going to have the chance to deck the block and head a bit after the points made in this topic. Thanks everyone for your input.
Modified by gdubsmsp at 5:52 AM 4/17/2009