RB 30 interference or freewheeling

[harry3]

I did a google search and all there say its not freewheeling but is interference

in other words if your cambelt breaks, some piston tops will collide with some open valves

comments please

[jdl6666]

My guess is that may depend on whether the engine has stock components like the camshaft, cylinder head and pistons. Guessing these would all play a vital part as to whether you get valves hitting the pistons or not if you busted a timing belt. I don't think it'd be a problem if stock, that's for sure, but a high lift cam and flat-top pistons along with a shaved head could possibly do it.

My guess, just by looking at the 2 motors i've got here at home which have been stripped down, is that with a standard configuration, there should be no dramas! One way to tell might be to get a cylinder head with its cam on there and associated rocker gear and rotate it and see if the valves move past clear of the cylinder head face.

Cheers!
Jim.

[Not_An_Abba_Fan]

The RB30 is an "interference" engine, so regardless of the components, the valves will hit the pistons if the timing belt breaks.

[jdl6666]

Thought I'd go for a walk to the shed and check it out! Looks like the valves will travel around 4mm past the cylinder head face. I guess with an average head gasket being around 2mm, it'll probably just clear, but if you was to deck the block for zero clearance and maybe plane down the head you'd possibly be in some trouble and that's with a standard cam. Would likely be in some valve trouble with a gts1 or 2 cam in there that's for sure!

Cheers!
Jim.

[detox_nath83]

its a free-spinner if cam belt breaks it doesn't hit ur valves

[Not_An_Abba_Fan]

No it's not. It's interference.

[Munz]

its a free-spinner if cam belt breaks it doesn't hit ur valves

+1

I asked my mechanic mate about this and he reckons it won't be bending valves when it snaps...he better be right cause i'm waitin till she goes..

[harry3]

I wouldnt wait as damage can be severe, I remember a friend in a ford who waited and it was expensive

[vn_v6]

No it's not. It's interference.

you sir are a goose, its a non interference engine, and i know this because ive snapped my cam belt last week, i had the first piston TDC, and turned the cam wheel a full turn and it didnt hit anything. trololol stick to your exhausts mr guru

[Not_An_Abba_Fan]

I've replaced a timing belt on a VL that snapped, had to do 4 valves as well because they hit the pistons and bent.

Sometimes you can be lucky when it goes the cam is in just the right spot where the valves just have clearance, but generally, they will hit. Everywhere I have looked to confirm it before I posted says the same thing the majority of the time.

[detox_nath83]

I wouldnt wait as damage can be severe, I remember a friend in a ford who waited and it was expensive

1 Word "FORD"

[vn_v6]

it is a NON INTERFERENCE ENGINE, you must be looking at engines with shaved heads and cams with bigger lift
"Depends on the car aswell.

I've seen a few vl's with the rb30 6 cyl motor go 300 000km on the same timing belt, 23yrs old. Doesn't matter too much if it breaks because its a non interferance engine."

[jdl6666]

By the looks of things the valves may just clear if you do break a belt on a totally stock engine by looking at the cut-outs in the tops of the pistons to sort-of accomodate valve clearance. I've done some rough measurements, and the clearance should be a good 2mm+ if everything's stock! But then again, if you snapped a belt at a real high rev it's possible for them to just touch but I've never seen one personally do this and it hasn't happened to me yet. Thank god!/Touch wood! lol.

It'd be a dead set certain that you'd bend them with a high lift cam, and a good chunk of face taken off the cylinder head!

Cheers!
Jim.

[Jxw]

no they don't clear, they're an interference motor, i've seen 2 stock na rb30's with bent valves due to belt failure