Performance head questions

[Scrymerr]

I took my head to the machine shop and the machinist talked to me about having to install new valve seats to accomadate the 1mm OS valves. Is this usually the case, or are the stock seats large enough to machine to accept the larger valves.

He also said he does not recommend bronze valve guides as they are not as durable as cast. Opinions?

He also said something about extra work if the valves are not exactly the same length as stock due to incorrect clearances when contacting the rocker arms and the lifters. I am using SI valves, anyone shed some light on this?

I am also using supertech (FP) springs, retainers and seats. The machinist said it will take extra work to machine the head to achieve the correct seat pressures specified on the data card. any idea how much work needs to be done if any?

Dan

 

[Scrymerr]

I need to get back to the machinist this week to have him begin the work on the head and still undecided about the bronze valve guides and such. Can anyone point me in the right direction?

 

[FORMONTOYA]

I took my head to the machine shop and the machinist talked to me about having to install new valve seats to accomadate the 1mm OS valves. Is this usually the case, or are the stock seats large enough to machine to accept the larger valves.

He also said he does not recommend bronze valve guides as they are not as durable as cast. Opinions?

He also said something about extra work if the valves are not exactly the same length as stock due to incorrect clearances when contacting the rocker arms and the lifters. I am using SI valves, anyone shed some light on this?

I am also using supertech (FP) springs, retainers and seats. The machinist said it will take extra work to machine the head to achieve the correct seat pressures specified on the data card. any idea how much work needs to be done if any?

Dan

1. Yes, he will have to machine the new valve seats as now they will have to be enlarged to accomidate the 1mm larger valves.

2. Bronze is not as durable, but bronze is not as abraisive as cast on the stems, your call.

3. After he machines the new seats, he might have to adjust the stem hight to correct for the proper "lift".

4. No, ask him about the "worst case" and to give you an estimate on this for a ballpark price.

Jim

 

[Scrymerr]

1. Yes, he will have to machine the new valve seats as now they will have to be enlarged to accomidate the 1mm larger valves.

2. Bronze is not as durable, but bronze is not as abraisive as cast on the stems, your call.

3. After he machines the new seats, he might have to adjust the stem hight to correct for the proper "lift".

4. No, ask him about the "worst case" and to give you an estimate on this for a ballpark price.

Jim

Thanks for the reply, however I didn't quite understand #1. Do the stock seats have enough "meat" on them to where they can just be machined .004" over, or does the seat need to be replaced with a larger one?

And on number 2, what is your personal experience or knowledge when using bronze guides? Do they wear out significantly faster, or is this negligable? I am trying to gather real world info to make the decision on which guides I will run.

Thanks,

Dan

 

[FORMONTOYA]

Thanks for the reply, however I didn't quite understand #1. Do the stock seats have enough "meat" on them to where they can just be machined .004" over, or does the seat need to be replaced with a larger one?

And on number 2, what is your personal experience or knowledge when using bronze guides? Do they wear out significantly faster, or is this negligable? I am trying to gather real world info to make the decision on which guides I will run.

Thanks,

Dan

1. The "seat" is just the spot/pocket where the valve rest/seals inside the head. It is not a seperate item, but just a portion of the head casting. It is just a machined surface that he will machine a little more for the 1mm OS valves. There is plenty of clearance for this operation. On a side note: http://www.ffwdconnection.com/ has a head with 2mm OS valves without any problems.

2. It is really a personal preference. I have always used broze guides when available on past cars because they are less likely to scar the stems and therefore don't wear out the valve stem seals as quick. They last roughly the same and the cast will break just about as easy as the bronze if the timing belt breaks.


Jim

 

[dsm-onster]

I took my head to the machine shop and the machinist talked to me about having to install new valve seats to accomadate the 1mm OS valves. Is this usually the case, or are the stock seats large enough to machine to accept the larger valves.

He can cut the seats to match 1mm oversize. If he can't then he can't cut much else on your head and is worthless as a machinist.

He also said he does not recommend bronze valve guides as they are not as durable as cast. Opinions?

FWIW, I've been running cracked stock cast guides for 10,000+ miles and to 8500 rpms very often... with no problems yet. I even jumped timing between then and just threw new stock valves in 1500 miles ago and still no problem. I jumped timing because i was foolish and didn't tighten my cam gear bolts tight enough.

He also said something about extra work if the valves are not exactly the same length as stock due to incorrect clearances when contacting the rocker arms and the lifters. I am using SI valves, anyone shed some light on this?

Correct me if i'm wrong but because we have hydrolic lifters they are "self adjusting". meaning that any clearance variations will be overcome by the oil pumping the lifters higher and forcing the rockers to the right stance/clearance. When replacing my valve with new stock valves and adding new FP2X cams in the mix, there was no need for adjustment. There was less noise than when stock.

 

[BrokenTsi]

Find a new machinist. Stock seats can easily be cut 1mm o/s. Bronze guides are very durable and wear better than cast.

 

[Scrymerr]

Well, I just talked to the machinist today, and he said the stock seats are fine. He said it was running a tad close on the intake side, but no problems whatsoever. And are you sure about the seats, FORMONTOYA? I thought the seat was in fact a seperate item made out of steel or something a lot harder than aluminum? And thanks, dsm-onster, I am fairly confident the stock guides will work as well, however I wanted to get some feedback from people. Broken-Tsi, can you give any more information regarding bronze guides?

Thanks all, keep the info coming!

Dan

 

[pneumo]

DSM valve seats are steel inserts pressed into the head.

 

[FORMONTOYA]

And are you sure about the seats, FORMONTOYA? I thought the seat was in fact a seperate item made out of steel or something a lot harder than aluminum?
Dan

pneumo is correct. The valve seats are a seperate item. Sorry, had to much going on at work. However, the shop should have no problem with it.

Jim

 

[blue1]

Bronze guides have better lubricating properties than cast and will last longer than cast, Stainless valve stems tend to pick up with cast guides due to metal dissimilarities and is very common practice to fit K-line guides (bronze) when using stainless valves.
Cracked valve guides long as you are sure that a piece of the guide is not going to break off and go through you engine or turbo you can use them but that is your choice, me personally i would change them, because when they are cracked the clearence will be greater at that part guide, so you can really say they are worn.