imported_fiercecivic

k heres my problem, i am currently rebuilding a d16y8 that had a blown rodbearing, so i replaced the crankshaft and pistons that are from an d16A6, the only real diffrence between the two is that the y8 pistons have a deeper dish and deeper intake slot in the piston. when i put the head on and torqued it to specs when i got to turn the crankpulley the valves on the intake side are hitting the top of the piston. i have two questions about it, first- when the timing is set correctly do the intake valves open when the piston is at the top of the cylinder, or at the bottom? Second, if i do end up grinding the piston so that the valves will fit into the groove on the piston, does the groove have to be exactly the same size as the valve? or is there margin for imperfectness?
thnx

zeeman

iTrader: (1)

the intake valves open with the piston at the top of the cylinder at the beginning of the intake stroke and will close and stay closed until the end of the exhaust stroke.
I would take the piston to a machine shop to have them cut larger valve reliefs...as i am sure there is probably a very slim margin for error.
....waiting for steve leitner to chime in with his expertise....

imported_fiercecivic

yeh i cranked the head over a couple of times with the pistons at deck height and i can see where they have been hitting just on the outside of the reliefs. are the valve relifes a critical part to your compression?

punkindrublic

i've heard of people cutting larger reliefs on b20 with dohc vtec heads... using a dremel so it doable... i guess as long as they are all the same cut and all smooth it'd be ok... but a machine shop is the best bet obviously

bbarbulo

iTrader: (2)

Oh man, actually doing it with a dremel would kinda worry me, I'd definitely wanna have a machine shop do it. doing it yourself may end up causing a lean spot in the cylinder and increase your chance of detonation.

"when the timing is set correctly do the intake valves open when the piston is at the top of the cylinder, or at the bottom"

ok well logically speaking, the intake valves should begin to open after TDC following the exhaust stroke. so that means:

a. piston at TDC going down (sucking in air - intake valves open)
b. piston on the compression stroke, spark ignites (all valves closed)
c. piston on its way down after ignition (making power)
d. piston on it's way up to vent exhaust (exh valves open)
... and then it goes back to a.

imported_fiercecivic

so if i set the timing correctly it shoulndt hurt, but uf my timing belt breaks im screwed. the toher thing im worried about is when vtec kicks in the vlaves stay open longer and they might hit then...

scott newman

If you dont know how to get this running, maybe you shouldnt building it. Just a thought

LEITNER

how much has that head or block been cut? at least .060 for the valve to be clipping the back side of the valve relief. just a stupid question: did you use a head gasket? the intake valves open at the end of the exhaust stroke not the begining of the intake stroke. on that engine if it was stock you should not hit the pistons so i would say the you have the timing retarded by a tooth or 2. i agree with scotts comment.

imported_fiercecivic

the block hasnt been shaved, i got it set up i had the timing off by a tooth. wtf, did i say "i dont know how to get it running", i was asking a simple question. that dosnt mean i know dick all bout engines

scott newman

I wasnt making that comment to be mean to you or anything, but if that was the simple solution, and you know everything about engines, then that question really shouldnt have been asked, granted you did figure it out and all I was just making a comment, when I was going through school to learn how to build engines, the first thing they taught was suck sqeeze bang blow. I just thought that if you knew alot about the basics, you would know that info. sorry if i offended.

imported_starboy869

I was thinking the same thing with this line from his first post.

fiercecivic says:

"i have two questions about it, first- when the timing is set correctly do the intake valves open when the piston is at the top of the cylinder, or at the bottom?"

I myself thought "OK rebuilding a engine without knowing how it works"

I'm with Scott on this one. My automotive classes started out with the basics (2 and 4 stroke), points (old) systems, etc.,

I still have to give you a for rebuilding an engine. I'm in the process of rebuilding an old VW OHC carb. 4 cylinder for work.

ELGUY

wow, guys give this guy a break. He's got ***** for doing what he's doing and is looking for help. be nice

PSI_Envy

I have to commend this person. He's got the ***** to let it all hang out there and give this mod a try. Yes, he might not know exactly everything about a motor but, chances are, we tech boys didn't know much about engine before until we made mistakes and learned from them and continued on. Knowledge is built on experience. Hell, I started by taking apart my first car and putting it back together and I had no previous experience with it. I just learned as I went along...finding out what this part did, what that part did. And now look at me. You can't crucify him because he may not know how to do it. I'm positive there was a time when we didn't know jack either. As long as he's willing to learn, that is the most important thing here even if the motor does blow up. (not that it would...it's just an example) It's the experience that is gained that's worth the risk.

My hats off to you buddy. Good luck with the build.

imported_fiercecivic

thnx at least there are some people that understand

LEITNER

look its just better if you do research on something before you start so you dont look foolish asking a basic level question. this is an engine not a modle airplane. i have learned everything i know by trial and error but i had the basic foundation of how engines work to start. i give you props for trying but first you should start here...
how engines work

its very informative and has a table of contents at the bottom.
this is a must know thing for you if your serious. good luck with your engine. pm me if yu have any other questions, but please read the link i gave you cause it can only help.

imported_fiercecivic

first of all, know how engines work, the only reason i was asking that question was to make sure of myself. I took four year of automotive class and have torn and rebuilt a few engines. every single mod on my car, whether interior, exterior or mechanical has been done by me. You cant judge a person on this forum by one simple question that they have asked, for all you know the person that asked the question could know more about sh*t than the person judging him/her. lay off

LEITNER

nice attitude...alot of good 4 years did you if you werent sure of such a BASIC concept that they teach in atuo101. the person asking the question doesnt know more than the guy answering THATS FOR DAMN SURE.laying off now.

crvtecEG

you might just be burning a bridge you WILL want to use later....trust me.
Steve really, really knows his stuff.....first hand experience owns.

imported_fiercecivic

im just saying you cant judge a person ny one question they ask, plain and simple