Chevy & GMC Vans

he did that in the mock up and its been crued and let me tell ya vance did a hell of a job we started breaking in the motor about 6 today had a crack in the radator so got that fixed finished break in we made sure the fuel cut off didnt work(he had it removed)videos coming we got her up to about 110mph and then i pi55ed off his neighbor!!!!!!! i did a beautiful burnout one urban will even be happy with. (videos coming soon also) and its now 11:00 and i need sleep so talk to you all later!
Danny

T prop wrote:Hello, new guy here.

I was at work today and I had nothing to do so I was surfing the net and ran across this site. This thread interested me because several years ago I did this swap on a friends Astro van. It was similar to what's happening in this thread, I rebuilt a small block for him and installed it. It ran great for years and was a fun to drive project.

What prompted me to register and post was this picture from page 1:





I noticed that the pistons are installed upside down, the eyebrows on the pistons should be towards the intake side of the engine. Was this corrected before the engine was finally assembled?






...

Please tell me that the engine is NOT running like that.

read previous post!
it was in mock up, makeing sure the rods would clear the block when he was putting it together since it was stroked.
Danny

Thanks for the buffing info....

you are welcome darren, did you see what rebel said also, some good tips there.
Danny

Ok, sorry for not getting on here for so long. It has been a busy few weeks. Anyways.

I have seen the ruckus about my pistons supposidly being in backwards. Someone please let me know why the valve reliefs need to be on the opposite side of the cylinders from the valves. The picture shows the pistons in the way that they are currently in. There is no problem with the build and quite frankly, I dont know who that guy was who said this, but I am not too sure that he is right. I am 21 and I dont claim to know everything, so if someone knows something I dont, please someone speak up. here are to pictures that show that the valve reliefs are directly under the valves.




so please people, please inform me if I am missing something. It doesnt hit the valves so I guess it doesnt matter one way or the other.

-Vance

It was I who brought this up, I'm sorry if I have created turmoil but I thought bringing it to your attention might save you some engine problems.

If you look at this cutaway picture, you can see the valve angle in relation to the piston. If you have a low lift cam you may be clearing now but at high rpms, it's hard to say what will happen.

With a "stroker" engine the rod ratio is so bad that the piston doesn't spend much time at TDC so he may get away with them backwards.

well, ill tell you what. I have put approx. 200 miles on this motor and I have gotten on it a few times, there has been no problem. I tried to do the CKP learn processes and i hit the fuel cut off. this was at 5500 rpm. If it can do this in park, do I have to worry about it hitting anyother time? Can I check with a borascope at tdc of exhaust/intake stroke to see how close it comes to hitting?

-Vance

Well, having never owned a V8 before, I'm not too familiar with the piston orientation, although a quick search through google images leads me to believe they are in backwards.
Now, you may be able to run it without valve to piston interference, but installing them backwards can lead to so many other problems. For instance, out of balance issues, which can lead to accelerated wear on other components. Most piston are not "symmetrical", one side, the thrust side, will carry more mass than the other. Not all piston pin bosses are centered either. Another is volumetric effeciency, or, how well the cylinder can fill with air/ fuel mixture.
Like I said, I'm not familiar with small blocks, so these may not pertain here, but there are so many other concerns other than just piston to valve interference.

phatmaxx87 wrote:well, ill tell you what. I have put approx. 200 miles on this motor and I have gotten on it a few times, there has been no problem. I tried to do the CKP learn processes and i hit the fuel cut off. this was at 5500 rpm. If it can do this in park, do I have to worry about it hitting anyother time? Can I check with a borascope at tdc of exhaust/intake stroke to see how close it comes to hitting?

-Vance

The bore scope sounds like a plan. If the cam timing is advanced, the inlet valve will be closest to hitting the piston and if it's retarded the exhaust valve will be in the most danger. The longer the con rod in relationship to the stroke, the more time the piston stays in the danger zone. With your stroker the piston doesn't stay there as long and may be why you're getting away with this. If the bore scope works, it will either allay your fears or scare you to death. Good Luck !!!

Check with the piston manufacture to verify the piston pin offset. If there is offset then those pistons need to be installed correctly.

T prop wrote:It was I who brought this up, I'm sorry if I have created turmoil but I thought bringing it to your attention might save you some engine problems.

If you look at this cutaway picture, you can see the valve angle in relation to the piston. If you have a low lift cam you may be clearing now but at high rpms, it's hard to say what will happen.

Vance given the amount of time and money you have put into this,I would think you wouldn't be happy just getting away with something that is wrong.I am in no way trying to add to a fire about this and I want to be very clear about that.

I don't believe balance issues come into play here.

I do think the way the eye browes face "could" effect the way a cyclinder flows because of shourding(sp) of the intake valve.

Cold checks don't rep running temps or RPM clearances.I mean you got to know what those clerances really are by measuring them.

To back up what I have said-I did without tell them who or where,called two tech lines and both said you need to teardown and change the pistons to the correct side.Told then you have 200 miles on the engine without hitting and both still said it needs to be changed.Most of the stuff I have done in the past has been high dome/high lift cam stuff which would have hit already.

Vance,all I can do is suggest and I feel very badly it happened to you.If it where me,I would be very ticked off because of a mistake,but in the long run,I would feel much better knowing it was right every time I turned the key.

Gary

The guys are correct. It looks like you should be tearing that engine down ASAP! The pistons are installed wrong. I can send you pics of some engines I have built if you need some more info. The only reason you have not had a problem is that you are running a very low lift camshaft. I would bet that you are running VERY close tolerences and the first time you rev the engine too much it will cause a castestrophic failure.

What the heck.... I'll through my two cents in as I can see you are in a tough spot. The more info you that the more confidence you will have in your decision. Not to say that my opinion is even worth 2 cents…

I am doing a 383 for my project and have had thoughts of clearances and such. Without going back through the 8 pages, did you use the scat low end kit or the old fashioned 400 crank? If you got the balanced kit and you are running 87-93 octane chances are that your CR is lower than 9.7:1? You most likely use 5.7" rods (or 6") and installs dished pistons. Was it a factory cam or non aggressive? Is the valve lift over 1.5? You are not running a high rpm machine (over 8000) so you most likely won't hit at any point in your use.

But... (They always give you a but...) If the pistons are in the wrong way, it will lead to premature engine failure and increased cylinder bore wear. How fast this happens is anyone’s guess but it will wear sooner. Maybe if the normal life is 150,000 miles on your build it could go to 75,000 miles before having performance issues? I don't think anyone can actually tell you how long this will last as it is. I don't think that it will be next week either.

And the longer you wait to swap them may result in having to rebore the walls. At this point you should be able to just hone them.

I can dig an older book out on how to rebuild SB Chevy’s. In it I believe Visard or who ever wrote it, spoke specifically about this issue and what would happen as a result. I'll see if I can find that reference and post back..
Good luck...