lunchindabox Posted April 3, 2011 Share Posted April 3, 2011 Hey guys, I got a busted Tbelt on my 2003 3.3L Frontier. Is this a interference engine? Can I expect bent valves? Can I expect piston damage? Is it safer to just toss in a new motor? -Thanks in advance. Link to comment Share on other sites More sharing options...
adamzan Posted April 3, 2011 Share Posted April 3, 2011 Yeah it's interference. I think it would be cheaper to check the pistons for damage and if they're good (theres a chance they are) you can put some new heads on it or rebuild your current ones. Link to comment Share on other sites More sharing options...
lunchindabox Posted April 4, 2011 Author Share Posted April 4, 2011 thanks for the info...I don't think I have the patience. Might just go for an engine even though this baby only has 130k... -HH Link to comment Share on other sites More sharing options...
JamesRich Posted April 4, 2011 Share Posted April 4, 2011 From what I've heard the 3.3 are not interference motors. Not unless you put a larger cam. I would put a belt on it first before condemning it. James Link to comment Share on other sites More sharing options...
Simon Posted April 4, 2011 Share Posted April 4, 2011 VG33's are interference motors. Essentially the same design as the VG30 in a WD21. Link to comment Share on other sites More sharing options...
JamesRich Posted April 5, 2011 Share Posted April 5, 2011 I have found info stating both interference and non interference. I know the design is the same but the VG33 cams have less lift than the VG30. Lunchindabox, how about just put a new belt on it so we can see? James Link to comment Share on other sites More sharing options...
adamzan Posted April 5, 2011 Share Posted April 5, 2011 The quest one I think was made to be non interference. Maybe so when the family gets stranded on the side of the road they don't need a new engine too. Link to comment Share on other sites More sharing options...
sewebster Posted April 5, 2011 Share Posted April 5, 2011 Why didn't they just put slightly bigger cutouts in the pistons to get rid of this problem? Interference engines frustrate me, but probably I just don't understand the rationale... From my measurements the VG30 is barely interference... only the intake valves would hit, and then not by much. Link to comment Share on other sites More sharing options...
Kingman Posted April 5, 2011 Share Posted April 5, 2011 Why didn't they just put slightly bigger cutouts in the pistons to get rid of this problem? Interference engines frustrate me, but probably I just don't understand the rationale... From my measurements the VG30 is barely interference... only the intake valves would hit, and then not by much. They hit under the force of the engine running, but not spinning crank and cams by hand. If I remember right, there's roughly 1/32" clearance between the piston and valve on a 9:1 VG engine. Link to comment Share on other sites More sharing options...
JamesRich Posted April 6, 2011 Share Posted April 6, 2011 The quest one I think was made to be non interference. Maybe so when the family gets stranded on the side of the road they don't need a new engine too. I can tell you the quest is non interference because I was a lazy ass and didn't change the belt on my wife's 01 quest until it broke at 118K, no bent valves. James Link to comment Share on other sites More sharing options...
lunchindabox Posted April 6, 2011 Author Share Posted April 6, 2011 Here is what I got... I am trying to figure out if this is an interference motor or not in this Nissan...conflicting info on the pathfinder and frontier forums...and everywhere else for that matter as seen above. I think officially it is interference...but a good portion of people who just slap a belt on end up okay. Does that even make sense? This might might be worth a shot if I can slap a belt on. Or I can pay the shop ~$500 and gamble since I generally don't get my hands dirty...and if it fails...I can always just pay the shop to do the heads I guess... And a pic of the beast being pulled by the other beast. Link to comment Share on other sites More sharing options...
sewebster Posted April 6, 2011 Share Posted April 6, 2011 They hit under the force of the engine running, but not spinning crank and cams by hand. If I remember right, there's roughly 1/32" clearance between the piston and valve on a 9:1 VG engine. Interesting... how does it happen... do the valves move further with the "fast" push of the rocker or something? Even if thats the case though, wouldn't you expect them just to "bounce off" the pistons without causing a problem? I thought the problem with interference was that there was no way for the engine to revolve without stuff getting bent, but if you can turn it by hand... Link to comment Share on other sites More sharing options...
Kingman Posted April 6, 2011 Share Posted April 6, 2011 Interesting... how does it happen... do the valves move further with the "fast" push of the rocker or something? Even if thats the case though, wouldn't you expect them just to "bounce off" the pistons without causing a problem? I thought the problem with interference was that there was no way for the engine to revolve without stuff getting bent, but if you can turn it by hand... Correct, the inertia of the engine allows the valve and piston to connect. They barely hit, but the force of the engine bends the valve stem when the tip of the valve connects. OP: you can try a new timing belt, and then do a compression check. That'll tell you right off hand if there are any bent valves. If there are, all you'd need to do is have the valves replaced and you're good to go. Link to comment Share on other sites More sharing options...
thehuntersam Posted April 7, 2011 Share Posted April 7, 2011 Try the new belt, you never know. The bolt to my belt tensioner broke causing the timing belt to jump. The pathy would still start after the valves got bent up and would still run, but it sounded horrible. Which led me to the VG33 swap. The VG33 is an interference motor for sure. Link to comment Share on other sites More sharing options...
Tungsten Posted April 7, 2011 Share Posted April 7, 2011 old trick jam a screwdriver into the valves and straighten those things back out 1 Link to comment Share on other sites More sharing options...
thehuntersam Posted April 7, 2011 Share Posted April 7, 2011 old trick jam a screwdriver into the valves and straighten those things back out I've seen it done and it worked like new. Link to comment Share on other sites More sharing options...
madhornet Posted April 7, 2011 Share Posted April 7, 2011 (edited) i had this happen one valve was bent too bad so i ordered one and another was slight i did not notice until i lapped the valves i put it in a vice and hammered it strait i only did this because it was almost 2 weeks for delivery for a valve the other valve i seen at first disassembly. i ran that for years after the quest engines are 100% identical no difference AT ALL u got lucky hope u went and bout a lottery ticket LOL Edited April 7, 2011 by madhornet Link to comment Share on other sites More sharing options...
Kingman Posted April 7, 2011 Share Posted April 7, 2011 i had this happen one valve was bent too bad so i ordered one and another was slight i did not notice until i lapped the valves i put it in a vice and hammered it strait i only did this because it was almost 2 weeks for delivery for a valve the other valve i seen at first disassembly. i ran that for years after the quest engines are 100% identical no difference AT ALL u got lucky hope u went and bout a lottery ticket LOL No, when the original deal was made between Nissan and Ford for the vans, Ford required that the engines being put in to the Mercury Villagers were non-interference. The guy I work for has a VG30 Villager, his timing belt let go getting on the highway about a month ago. No bent valves... do that with any standard VG and it will bend valves. Link to comment Share on other sites More sharing options...
beastpath Posted April 7, 2011 Share Posted April 7, 2011 its because the quest/mercury pistons have deeper grooves cut into them. look at Nissannuts webpage about his vg33 swap and he has a side by side shot of the quest vg33, regular vg33 and vg30 pistons. Link to comment Share on other sites More sharing options...
sewebster Posted April 7, 2011 Share Posted April 7, 2011 its because the quest/mercury pistons have deeper grooves cut into them. look at Nissannuts webpage about his vg33 swap and he has a side by side shot of the quest vg33, regular vg33 and vg30 pistons. Ugh, but if this is the case why did I just put new pistons in with small cutouts. Seems like it would be great to just get bigger cutouts and solve this interference problem with minimal to no downside? Link to comment Share on other sites More sharing options...
beastpath Posted April 8, 2011 Share Posted April 8, 2011 Ugh, but if this is the case why did I just put new pistons in with small cutouts. Seems like it would be great to just get bigger cutouts and solve this interference problem with minimal to no downside? i know right? youll get slightly less compression with the deeper cutouts, which i assume would mean slightly less power. IDK if it would be significant though. Link to comment Share on other sites More sharing options...
lunchindabox Posted April 8, 2011 Author Share Posted April 8, 2011 I am surprised that you all have not hashed out this interferance/non-interference issue already...I was waiting for someone to tell me "search" or point me to a link where it was thouroughly discussed.... In anycase, I sold the truck as-is and it is a non-issue for me. Good luck! Link to comment Share on other sites More sharing options...
lunchindabox Posted April 14, 2011 Author Share Posted April 14, 2011 As an update, the dude I sold it to just slapped a belt on and it runs great. Apparently, in this case the engine was not interfered with. Link to comment Share on other sites More sharing options...
JamesRich Posted April 14, 2011 Share Posted April 14, 2011 Link to comment Share on other sites More sharing options...
madhornet Posted April 18, 2011 Share Posted April 18, 2011 the downside is the ford engines would have less horsepower with the bigger cutaway it would drop the compression ratio but not by much lol Link to comment Share on other sites More sharing options...
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