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 Post Posted: Sat Jan 29, 2011 3:55 pm 
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Although my engine isn't due to freshen up I have it out and heads off. I warmed it up and leaked it down beforehand and had 1 cylinder leaking 24%. The cylinder that is leaking now had a problem last year and I had an exhaust seat put in it because it was leaking between the seat and the head. The same valve is leaking now. I was told by a local guy that does a lot of performance machine work/engine building that sometimes a new seat will move around some and will need "touched up" some after it has been run. This isn't the guy that did the seat so I don't think he's blowing smoke. I really need to replace these heads but it's just not in the budget right now so I think I will have the valves touched up and add some seals. I have never ran valve seals before but Barry pointed out in a different thread that the oil getting in the combustion chamber may be causing some performance issues and I think he has a good point. So I'm not sure if I should run seals on both the intake and exhaust or intake only. What type of seals does everyone else use? If it makes any difference the valves are titanium.

I had a pan gasket end seal that was partially out because I had the pan off earlier last year and apparently it slipped on the install. It had leaked some but I thought the rear main seal that I had never been able to completely seal up had just gotten worse. Never leaked on the track but would leave a little spot on the trailer floor. So now I'm thinking my vacuum pump may not have been helping as much as it could have because of the pan leak. I will have a vacuum sensor for the data logger on this when it goes back together.

Like I said, the heads really need replaced and because they're so old and odd-ball I will have to change the pistons when I do. This thing should have another season of racing left on it but I will have to patch it up a little to get it. I am considering gas porting the pistons but I don't know if it will be worthwhile. It's been honed and re-ringed a couple of times and I think the pistons might be a little loose in the bore. So what's a safe piston to cylinder wall clearance? I shift at 8,200 which is about my trap RPM at the end of the 1/4. So how much should I expect gas-porting to help or is it even a good idea to do it on this engine? I run a single .043 compression ring. The rings have about 150 runs on them and I didn't plan to replace them. Would they have to be replaced and would I use a different end gap?

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 Post Posted: Sat Jan 29, 2011 5:34 pm 
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Hi Chuck,

NO SEALS AT ALL!!!!! O:) O:) Wow, anyway, my cyl head guy uses the white teflon/plastic ones without the metal bands on them, and your guides may need to be machined a tad to fit them, they usually do to use them, but I have them on both the intake & exh. and it works well for me.

I know when you set up a new engine, the bore to piston should be in the .005 range for cleanance and that is on the JE piston jobber sheet I have too, but different shops use different numbers and I guess it also takes into account if it is a drag or oval type engine. As far as how much is too much!, good question, but I can find out for you on Monday if needed, just let me know.

I use one of them Moroso one piece rubberized pan gasket and it is nice, use a little silicone and slap it on and forget about it, just some food for thought. ;-)

John

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 Post Posted: Sat Jan 29, 2011 7:32 pm 
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I would think a new seat could move to some extent. I am running valve seals and gas ported pistons with .043 rings. I don't know how much the gas porting would help , but I don't think it would hurt anything.

Chuck I would like to recommend this machine shop. Bob does excellent work. http://www.jetboatbob.com/


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 Post Posted: Sun Jan 30, 2011 12:03 am 
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Why not grind only the valve/seat that leaks? Less $$ and less chance of the VJ flowing poorly in an effort to seal it. Sending back to the guy who ported them to get the correct VJ is likely expensive and a local guy could touch up that one seat w/o much performance risk. Have you tryed lapping it to see where/why it is leaking?

Valve seals - I have run with no seals myself, but now run them only on the intake for the reason Barry mentioned and I run Teflon seals.

Gas-porting - I think it is a plus, especially with thinner rings (.043"). I am working on a friends engine and am planning on making a fixture to gas port (vertical) his pistons by hand.

Piston clearance - I've seen some up to .010" measured about a 1/2" -1" up from the skirt end. They get a little noisy when cold but are not much concern at least to there. How loose are they?

Rick


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 Post Posted: Sun Jan 30, 2011 8:28 am 
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You guys that do this may already know but the shop that did my machine work showed me something really cool..(I thought so anyway =; ) Now this is a one man shop...Lay the head flat with the chambers facing up and turn the lights off and shine a flashlight around the edge of the valve and look in the port...Some times you will see that the valve is not sitting on the seat in one area. Now this is with no spring on it...Just though that was interesting to see and wanted to share it....

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 Post Posted: Sun Jan 30, 2011 10:43 am 
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Newly installed valve seats do move a bit, (usually referred to as seasoning), and could use a touch up after a few heat cycles. New heads pretty much do it every time.

I prefer to run the seals on both intakes and exhaust myself.

Gas porting does help I've seen the before and after several times. Goodson has a tool to do the lateral, (horizontal), gas ported with a hand drill. With the single ring piston like you are running I would think gas porting would be a must. Make sure you look into a good light tension ring to promote the gas ports. Gas ports will help stabilize the rings up around your shift point. (Everywhere else to actually) Gas porting loves vacuum pumps to.

Here is the link to it as posted in Kens thread.
http://www.goodson.com/technical_suppor ... %20078.pdf

I have seen up to .014" piston to wall run with no problems at all. Worst engine I've seen was a guy who had me to put together a bunch of parts he had laying around. It had about .016"-.018" piston to wall clearance. Pretty much did it under protest, but he wanted it. Thing rand for a good 5-6 years before he did something different.

Don

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 Post Posted: Sun Jan 30, 2011 12:28 pm 
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I notice that you didn't mention that the leakage was actually blowing out the exhaust port. Could you hear it blowing out the header, or just assumed it was because of the previous problem with the valve seat? Not picking, just asking.


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 Post Posted: Sun Jan 30, 2011 2:55 pm 
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Thanks for the input guys.
John, I have never used valve seals on this engine but I think the guides will accommodate seals without any machining. I don't think Moroso makes a pan gasket like that for a SBF and I have a Milodon pan that eliminates about 2/3 of the pan bolts on one side so I feel better using a gasket that I can glue to the block. I normally use the felpro hp gasket.

Randy, I appreciate the recommendation on the machine shop but it looks like he's a 2 hour drive from here. There are a couple of machine shops close to me and I didn't intend to sound like I have a problem with the guy that did the valve seat. He had a heart attack not long ago and isn't quite back on his feet yet. I just didn't want to bother him while he was recovering.

Rick, I actually had planned on just working on the valves that were leaking. The shop that did the work last time has a vacuum tester that they check the valves with and the before and after test indicated the valve was sealed up then. I need to check the springs and install seals anyway so I might just give lapping them a try. Is there an advantage to vertical gas porting? I haven't had a chance to get the pistons and cylinders measured but I should be able to next week. I think it's around .008".

Don, how much difference do you normally see with the before and after gas porting and is this on the dyno or ET? I checked out the gas porting instructions in the link but I can't find the tool on the website that you have in your sig. Can you provide a link?

Javier, I could hear it leaking in the header both times. I would never take a comment like that as picking.

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 Post Posted: Sun Jan 30, 2011 3:26 pm 
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This is the link to ordering the tool.

http://www.goodson.com/store/template/d ... 457f8b1fe1

Go to www.goodson.com and to to ordering. Type in gpt-062 or gpt-043 and you'll find it on the site. Goodson has changed their site around a bit since I've set up the link at the bottom I guess. Call Goodson and ask for the tool and thaty can help you.

The results I have seen are at the track. I have seen as much as a tenth. Done this on circle track and drag engines.

Don

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 Post Posted: Wed Feb 02, 2011 1:33 pm 
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I got the pistons & cylinders measured today. Looks like I'm right at .012. I know that's a little on the loose side but I Think I'm just going to touch up the valves, gas port the pistons and throw it back together. It needs some new heads and it will have to have different pistons when I do that so maybe if I can scrape together some better stuff I can build it better next winter. I always heat soak it before I put any RPMs on it and I think that should help. The guy at my machine shop said he has a gas porting fixture and said I was welcome to use it. He said he would even show me how and it will do both lateral and vertical ports. I think I'll go with the lateral because it looks easier to do and I only plan on putting about 100 or so runs on it.

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 Post Posted: Wed Feb 02, 2011 1:59 pm 
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Chuck you can also Knurl the pistons to tighten them up some...

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 Post Posted: Wed Feb 02, 2011 5:13 pm 
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Actually I was thinking about having the graphite coating done but I had a guy tell me the difference that makes up is insignificant, something like .0002". I'm not afraid to run it at .012 although I think a little tighter would be better.

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 Post Posted: Wed Feb 02, 2011 5:42 pm 
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Chuck I did the knurl think on a set in the vega to get one more season out of it and it did work very well and it went the fastest it ever went...It was cheep to do it also...

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 Post Posted: Wed Feb 02, 2011 11:56 pm 
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gearhead1011 wrote:
Actually I was thinking about having the graphite coating done but I had a guy tell me the difference that makes up is insignificant, something like .0002". I'm not afraid to run it at .012 although I think a little tighter would be better.

I think the coatings can be as much as 0.0008, but yes it's still not much.


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 Post Posted: Fri Mar 25, 2011 5:39 pm 
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oops...

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