RB20DET is a interference type engine

Discuss the RB20, RB25 and RB26 series engines.
PsiloX
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I found out yesterday that the RB20DET engine is an interference type engine. So watch your timing belt. And yes, I know this for sure. On the Skylines Downunder forums some say it is, some say it isn't. And I've heard on these forums that it is non interference. It's for sure a interference type engine. The valves will hit the pistons if the timing belt isn't contolling valve timing.

I was resealing my water pump saturday. I finished with the pump and was putting it all back together I got it all back together and started the engine the engine. I heard the belt slip and imediately shut the car off. I took every thing apart again and when I took the lower timing belt cover off a bent up washer fell out. Somehow I dropped in there without noticing it when I was reassembling. I think I bent my #4 intake valve a little. So it looks like I'll probably be doing a little porting and polishing since I'll have the head off the thing. Anyone know where to get a couple of intake valves?



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Eikon
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That sucks!!! Sorry to hear about it.

I always heard from WDRacing that the RB20 is a non-interferance engine... he says that he has turned it over many times without anything happening.

So you dropped a washer into the timing belt gear or tensioner or something like that and it made the belt slip?

Email this guy.... [email protected]'s from NICO as well. I have been buying a couple parts from him (CAS and a cam retainer). He's a really nice guy... ships pretty fast. He is parting out a head. I think cylander 1 in his blew up and messed up both the block and head. Hopefully his valves for cylander 4 are good?

Do you have a stock head gastket? I can't remember... Would going to a thicker head gasket make more clearance and allow for the engine to not interfere?

Hey... when you are going to start putting it back together... will you give me a call? I would love to watch you rebuild it.... I'm sure I woudn't be much help in the actual work, but I'll help with whatever I can. I would sure learn a lot watching.

PsiloX
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Yes, it wasn't a good day.

I'm kind of waiting to take it apart to see what all is screwed up and needs to be replaced. I've gotta find some free time though. I do have a cheapy head gasket for it but I'm not going to use it and I think it's bent anyhow. I'm going to get a Cosmetic brand metal head gasket and ARP head studs for reassembly.

As far as watching me reassemble it, my schedule is to inconsistent to have someone meet me, but I'm going to try and video tape it and put it on my web site. That should serve as a good reference for others.

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WDRacing
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I don't know what to say man, I've had my timing belt snap and then turn over several times in the process of troubleshooting why I had no spark. I never hit a valve once...

The only thing I can possibly think of at this point was that I was using a 2mm headgasket and that was just enough to get the valves by without any contact.

FliMSiCaL
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actually, from local shop experience, most smaller displacement engines are interference engines, due to manufacturers trying to eek more power without adding cylinders. I think WD either missed due to headgasket issues, or lucked out and the cam stopped in a spot that wouldn't intefere. Regardless, i am always EXTREMELY careful when doing anything involving timing belts and chains.

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Carl H
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FliMSiCaL wrote:actually, from local shop experience, most smaller displacement engines are interference engines, due to manufacturers trying to eek more power without adding cylinders. I think WD either missed due to headgasket issues, or lucked out and the cam stopped in a spot that wouldn't intefere. Regardless, i am always EXTREMELY careful when doing anything involving timing belts and chains.
hrmmm that sounds awfuly familiar..........

FliMSiCaL
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what do u mean by that?

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WDRacing
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We had discussed this in another thread. This is how he contributes...cool huh.

unstable240
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PsiloX wrote:I found out yesterday that the RB20DET engine is an interference type engine. So watch your timing belt. And yes, I know this for sure. On the Skylines Downunder forums some say it is, some say it isn't. And I've heard on these forums that it is non interference. It's for sure a interference type engine. The valves will hit the pistons if the timing belt isn't contolling valve timing.

I was resealing my water pump saturday. I finished with the pump and was putting it all back together I got it all back together and started the engine the engine. I heard the belt slip and imediately shut the car off. I took every thing apart again and when I took the lower timing belt cover off a bent up washer fell out. Somehow I dropped in there without noticing it when I was reassembling. I think I bent my #4 intake valve a little. So it looks like I'll probably be doing a little porting and polishing since I'll have the head off the thing. Anyone know where to get a couple of intake valves?
I have the valve if you need it. If you need one let me know...

PsiloX
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I'll be pulling it apart this weekend, I'll figure out what I'll need and get a hold of you.

PsiloX
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Well, I pulled the head this weekend. ALL the intake valves hit the pistons. But all exhaust cleared. So from what I've seen it does interfer slightly. None of the valves look bent however, leading me to believe that there is only a slight interfernece. So I have to agree that the 2mm head gasket WDracing has, is what saved him and may be a worth while upgrade and insurance for your head and valves for the rest of us.

So it looks like a lot more work for me.

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Eikon
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Forgive my lack of knowledge...

If your valves are not bent, what damage is there, and what do you have to repair. You mentioned that you have a lot of work left. Is it just a lot of work left to reassemble? Or do you have to fix things?

just curious to learn more. Thanks

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skillzilla
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I have a 1.2mm head gasket and none of my valves hit, Ive rotated my cams around with the timing belt off plenty of times, with cylinder #1 at TDC.

is the interference that minimal?

PsiloX
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It really could be that minimal. I don't know. But I do know I have 12 intake valves with marks on them from where they hit the pistons, but none of them look bent. Since they hit there must be some damage done. So now I get to track it down. Unfortunatly I don't have tool to measure straightness in a valve.
Modified by PsiloX at 12:13 PM 6/8/2005

PsiloX
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I finally got time to check the valves to determine if there are bent or not. After lapping them, I found that they were still all straight and actually in very good condition. So while all twelve of the touched the piston the must have barely touched enough to leave slight marks in the carbon on the pistons and the valves.

So I'm thinking the ticking noise must be a colapsed lifter. Hopefully after running it a little more it will go away. Othwise I just pop in a new lifter. I'm about 90% sure they're the same as the z32 300zx lifters. The have the same outer diameter and bore tolerence according to the FSM's for each engine. They look identical too.

unstable240
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The springs, retainers, and lifters are all the same as the Z32...

Sil240
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Heyhow are your valve seats???are they shot? Do you know where to get valve seats & valve guides for the RB20DET?


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