josh817 Posted January 22, 2010 Share Posted January 22, 2010 There is an other than stock cam in this head and I don't know what to adjust the valves to. Cam lift is .480" and this motor (SU type) is suppose to have a .440" cam. I adjust the valves to .010" on the intake and .012" on the exhaust. Stock is .0079" intake and .0118" exhaust I believe, and thats suppose to be when its hot. My situation is that the head is off the block, I am turning the cam and it is pretty tough to turn. I suspect the valve springs are stiff ones because before I put the cam in (everything was disassembled) I lubed thoroughly and properly torqued the bearing caps. Upon finally getting one of the lobes of the cam to open a valve, as soon as the lobe goes around the rocker, it snaps shut violently, like the spring has so much pressure it slings the cam. Like if you had your finger there, it would bite. I'm having to use a 12" pry bar to turn this thing at its sprocket bolts so thats just how much leverage I need... Thoughts? I'd hate to put this thing back together, start it up and have it get funk-a-fied. I'll try to make a video tomorrow to demonstrate what I mean. Quote Link to comment Share on other sites More sharing options...
MONGO510 Posted January 22, 2010 Share Posted January 22, 2010 It sounds like you have stiff springs. The fact that it willclose the valve by itself says the cam is not bound up. .010-.012 hot sounds ok. You might want to check piston to valve clearance with a piece of clay to make sure of clearance. the U-20 tends to have head gskt leaks at the rt. rr. of the head. Otherwise it is a pretty good engine. By the way, You may be able to get parts for it at a Nissan forklift dealer. The used that engine in some of the older forklifts. Mongo Quote Link to comment Share on other sites More sharing options...
josh817 Posted January 22, 2010 Author Share Posted January 22, 2010 We already have all the parts. Block is coming in on Saturday from the machine shop. We bored it .060" and bought domed pistons. I lightened the rods by 100 grams and polished them etc. I put the head together tonight and checked the lash. It was that valve snapping shut that I thought would be questionable. Now that the cam is in the head I want to check the duration and check the valve lift again since I just used some calipers last time to check the lift. Other than that, the head looks cool! The valves are HUGE and so are the ports compared to our Z's! Should make a nice motor for the little car. Quote Link to comment Share on other sites More sharing options...
MONGO510 Posted January 22, 2010 Share Posted January 22, 2010 We had clearance problems with R-16 domed pistons, pistons hit the valves, had to flycut the pistons. Make sure and check clearance!!! Mongo Quote Link to comment Share on other sites More sharing options...
josh817 Posted January 22, 2010 Author Share Posted January 22, 2010 I'll check, if we have any problems I'll PM you and maybe you have some flycut dimensions we can copy... Thanks! Quote Link to comment Share on other sites More sharing options...
Tony D Posted January 24, 2010 Share Posted January 24, 2010 Valvetrain turning forces soak up far more horsepower than most people think. The advent of roller cams in domestic V8's isn't to allow more radical camshaft profiles, it's literally giving up 30HP to the wheels which is otherwise wasted internally by the very forces you witnessed! Imagine how much smoother that cam would turn if you had rolling friction instead of sliding friction... Quote Link to comment Share on other sites More sharing options...
josh817 Posted January 24, 2010 Author Share Posted January 24, 2010 Valvetrain turning forces soak up far more horsepower than most people think. The advent of roller cams in domestic V8's isn't to allow more radical camshaft profiles, it's literally giving up 30HP to the wheels which is otherwise wasted internally by the very forces you witnessed! Imagine how much smoother that cam would turn if you had rolling friction instead of sliding friction... Oh yes I'm fully aware of that. I'm stuck in a lull right now. Expected the motor to be done at the machine shop today but it wasn't. He was shot peening the rods, inserting the pins into the pistons and rods, putting in new small end bushings, installing jackshaft bearings, boring and vatting the block. I checked the valve lash, everything looks good. I did a mix of the blue bottle STP additive and assembly lube and that made the cam spin a little easier but still pretty tough. I think my problem is that I'm comparing it to a Spitfire head and thats wrong because Spitfire valve springs I can compress with one hand... Oh and I'm glad I clearanced the oil pump before we bought a new one... FOR $500! I knew this motor was fairly new and something went wrong. Upon clearancing, everything was pristine! Quote Link to comment Share on other sites More sharing options...
Daeron Posted January 24, 2010 Share Posted January 24, 2010 Thats the only inline four-cylinder I love A large part of that may be because its the only one I have been around extensively (the rest of the I4s in my life have been, wham, bam, thank you cam, and on their merry way.) Is this a customer engine or are you diversifying your Datsuns? Quote Link to comment Share on other sites More sharing options...
josh817 Posted January 25, 2010 Author Share Posted January 25, 2010 Thats the only inline four-cylinder I love A large part of that may be because its the only one I have been around extensively (the rest of the I4s in my life have been, wham, bam, thank you cam, and on their merry way.) Is this a customer engine or are you diversifying your Datsuns? Customer motor. If it were mine I'd say screw the U20 and put something else in. You're looking at around 3-$4000 and its not terribly special. Just a bigger cam, lightened/balanced +-1g/polished rods, over bore domed pistons. I don't know if I posted it once before but a complete timing chain assembly with the sprockets, guides, tensioners, and chains are getting "hard" to find. The ones I did find as a set were over $1000.... Oil pump $500... Pistons $600... So yah, luckily its not my money but then again its a suck ass situation because the car has been taking up a spot in the shop for a year now while the customer makes payments slowly. I think we quoted him $4000 for a complete build and that was a mistake because I have a feeling my profit margin is going to be very small considering how many hours I'm putting in. Its not too bad though since the shop is 5 minutes from the house and because of the large gap in customer payments, I just work when I have nothing else to do and I love to do all this stuff so its fun. Quote Link to comment Share on other sites More sharing options...
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