Bronze guides=oversized valves?

[silicosys4]

I have tried searching and haven't found any answers, so I decided to post and ask.
I'm in the middle of having a head pretty much fully built except for monster porting and o-rings. New cams, springs, retainers, keepers, bronze intake /copper exhaust valve guides, seats, seals, SS valves, etc.
I am looking for a reputable place to have everything assembled, and possibly some porting work done. I am talking with one well known dsm-oriented machine/tuning shop, and here is a direct quote:

"We charge $&% to remove and install a set of high performance bronze valve
guides. Please be aware that if the guides are replaced you have to go to an
oversized valve.

That bums me out, because I already have my standard size SS valves, and thought I had researched bronze/copper valve guides pretty thoroughly, and nothing I found suggested that I'd have to automatically oversize my valves because of my guide material. I did read that if the valve guide is cast into the head that reaming it out makes it necessary to go to a thicker stem size to accommodate the missing material, but thats a cast-iron v8 head. I asked other machine shops about bronze/copper guides before this one, and nothing was said about oversizing the valves because of the guides.

Are they just trying to sell me their proprietary nitride coated oversize valves?

 

[kthackst]

They have to knock out the old valve guides and push new ones in. The new valve guides are no longer true or inline with the valve seat. Therefore the valve seat must be recut and going to a bigger valve/seat cut will insure a new good sealing surface. They use the new valve guide to grind the seat to make sure they are true to each other.

I dont know that you HAVE to go to a bigger valve but I can see why they would want to. I have had quotes before from machine shops to knock out valve guides and put new ones in that use a stock size valve but I just found it to be cheaper to get another used head with good guides.

 

[silicosys4]

I have seen too many heads with bronze valve guides and standard size valves to believe that I "have" to have oversized valves put into my head with my guides. To me that's just a machine shop trying to gouge me $200+ for their oversized valves and whatever it takes to machine the head for oversized valves, at least $100. The guides that are in the head are brand new, but they are cast iron and I don't want my SS valves galling on the iron.

 

[Zefal151]

When i rebuilt my head, i used the eBay (reputable seller though) valves, bronze guides, and 3g lifters. When i got it back, it was about as perfect as perfect could get with a used head, and didn't have to go over sized

 

[silicosys4]

Here is the reasoning:

Question: Why do I need to go oversized valves when replacing guides?

"Because when the guides are replaced the do not locate the valve in the same place. When the seat is cut, more material has to be removed and when you try to install a stadard size valve it will actually “sink” which causes problems with valvetrain geometry and spring pressure problems. It also inhibits air flow."

To me it sounds like they are saying "Either Ferrea didn't make em right or we can't put em in straight".

I also don't want to have to buy valves again. Why even make standard size SS valves if you can't use them with cast iron guides because of galling, and you can't use them with bronze guides because of this issue?

 

[laserspeeddemon]

They have to knock out the old valve guides and push new ones in. The new valve guides are no longer true or inline with the valve seat. Therefore the valve seat must be recut and going to a bigger valve/seat cut will insure a new good sealing surface. They use the new valve guide to grind the seat to make sure they are true to each other.

I dont know that you HAVE to go to a bigger valve but I can see why they would want to. I have had quotes before from machine shops to knock out valve guides and put new ones in that use a stock size valve but I just found it to be cheaper to get another used head with good guides.

That is flat out wrong.

Putting in new valve guides does not, in anyway, justify larger valves.

Ask me how I know?

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[BogusSVO]

Here is the reasoning:

Question: Why do I need to go oversized valves when replacing guides?

"Because when the guides are replaced the do not locate the valve in the same place. When the seat is cut, more material has to be removed and when you try to install a stadard size valve it will actually “sink” which causes problems with valvetrain geometry and spring pressure problems. It also inhibits air flow."

To me it sounds like they are saying "Either Ferrea didn't make em right or we can't put em in straight".

I also don't want to have to buy valves again. Why even make standard size SS valves if you can't use them with cast iron guides because of galling, and you can't use them with bronze guides because of this issue?

No you do not NEED to go to OS valves.

http://www.dsmtuners.com/forums/newbie-forum/341218-how-change-valve-guides-4g63t-head.html

what they said is true about valvetrain geometry, and the valve sinking and the spring installed height.

they are not going to go in stright and on the same index as the old guides

by going with the OS valves it elimiates the above issues.

there is another way to solve the above issues, have new seats installed.
http://www.dsmtuners.com/forums/newbie-forum/341297-how-replace-seats-aluminum-head.html

you have a four options at this time.

1) leave the factory installed guides alone
2) use the parts you have with the stock seats, and have sunk valves
3) buy new os valves
4) have all new seats installed

I know it is fustrating to find out this kind of info after you have bought and paid for parts.

 

[silicosys4]

Ok, so they have a point, bums me out that in all the threads, websites, and articles I read, nothing was mentioned about this problem. Which makes me wonder how big a problem it actually is. I reeeeeally don't want to go with oversized valves, I've heard its not worth the money, and can rob you power if its not done correctly. However, Its pretty obvious from peoples experiences that its not necessary to go oversize when changing guides....how much of an issue is it really, how much power would I be losing, how much reliability, etc...if I don't go oversize valves? At this point I'm $1500 into the head in parts alone so if I have to have the oversize valves...whatever...it will get done....but I hate it when I'm told it "has" to be done just for the sake of selling a few hundred dollars more parts and services when its really unnecessary.

 

[BogusSVO]

well machinist do not tend to share info redily.
how big of an issue is it to cut the seats for the stock valves? depends on what equipment they use.
there are tons of heads out there that have stock valves and replacement guides, for the most part, stock engines.

you should not have a decrese in performance when going to an OS valve, for the most part if not done corectly, you will flow the same as a stock valve.
unless there is issues with the valve shrouding.

Like I told you above, you have the 4 choices.. you need to pick the one you can live with the best.

Have you talked to the company you bought your valves from? they may swap you out to OS ones.

 

[kthackst]

That is flat out wrong.

Putting in new valve guides does not, in anyway, justify larger valves.

Ask me how I know?

First, my post was not flat out wrong it is more of an explaination of why they would want to go oversized.

Second becareful with your word choice you come off as an arrrogant know it all who provided no information in his post.

Third I knew OS valves were used to salavge seats but thanks Bogus and silosys for explaining about the valves sinking after a seat recut with standard size valves. A rep for each of you!!!