exhaust valve stuck 3 times now. help?

Posted By: rxod

exhaust valve stuck 3 times now. help? - 03/21/11 03:55 AM

I just rebuilt a 318 for my 73 dart swinger. I did the port work on the stock heads and sent them out to a machine shop for new steel guides and smaller 11/32 stem valves (increased valves size to 1.905/1.6). They also put in pc valve seals, comp cams springs and retainers. After about 50 miles, the #4 exhaust valve stuck open and bent the push rod. Took the head off and back to the machine shop. They said the stem had galled itself to the guide, probably from oil starvation. So, they put a new valve in as well as a bronze guide to fix it. When I reassembled the motor, I used an old valve cover with the top cut off so I could observe the oil flow. Oil was flowing abundantly through the stock rocker shafts and running out to the tip of the valves. Seemed good to me. Drove it for 5 miles and "bink", it siezed again, this time #2 exhaust.
Called the machine shop and they were baffled, so they said they would try to open up the stem to guide clearance from 1 thou to 1.4 thou. They installed another new valve and bronze guide. I thought my stock rockers may not be pushing enough oil to the stem tips so I replaced all of the rockers with new stock ones, observed the oil again, all seemed good. Drove it for 5 miles, and "bink", #2 stuck again.

My question is do you think that the positive type valve seals are starving the valve stems? should I go back to umbrella seals? This is very frustrating. Please help.

Posted By: 1_WILD_RT

Re: exhaust valve stuck 3 times now. help? - 03/21/11 04:02 AM

I would go back to umbrellas but seizing in five miles seems like theres something else going on.....

Posted By: rxod

Re: exhaust valve stuck 3 times now. help? - 03/21/11 04:06 AM

The machine shop also said they could not detect any oil on the bad valve stems when they disassembled them, yet oil is flowing and pooling up in the head. Just seems like the seals are preventing proper lubrication.

Posted By: ahy

Re: exhaust valve stuck 3 times now. help? - 03/21/11 04:10 AM

Steel guides are a stock rebuild fix (that along with knurled valves, I've used myself at one time). I'd use the stock umbrella seals... or rebuild to "high po" specs with all bronze guides... and look for a different machine shop for the next project. Since you have checked the oiling, sounds like the PC seal + steel guide setup doesn't work so well.

Posted By: dennismopar73

Re: exhaust valve stuck 3 times now. help? - 03/21/11 04:14 AM

sounds as if the guides to 'tight ' exs, the exhaust side
j m o

Posted By: rxod

Re: exhaust valve stuck 3 times now. help? - 03/21/11 04:27 AM

Did I mention that this machine shop specializes in Fords??
The strange thing is that the third time they failed was with the bronze insert. These were Ferrera SS valves. They tell me that they put these seals on every head they do. Has any one used these pc seals on early heads with stock rockers? Maybe early heads weren't designed for this type of oiling, rather relied on splashing oil on the stems like with umbrellas?

Posted By: SSAAHemiFan

Re: exhaust valve stuck 3 times now. help? - 03/21/11 04:28 AM

with todays erratic fuels and possible mixture problems I like to set EXHAUST stem clearance at LEAST 2 thou.

bronze guides CAN go 1/2 a thou tighter than a steel guide provided they are finished correctly. (straight) but we didn't think it was worth it and just went.002+ on all exhaust regardless of guide material

the shop owner ALWAYS insisted we error on the loose side on exhausts.

Posted By: rxod

Re: exhaust valve stuck 3 times now. help? - 03/21/11 04:31 AM

Is there positive or negative pressure at the stem on exhaust?
I've read both. Negative from outflowing gases, positive from the exhaust pressure.

Posted By: MLR426

Re: exhaust valve stuck 3 times now. help? - 03/21/11 01:43 PM

Guide to stem clearance were set up too tight from the start. extra needed on exhaust, thats the side that takes all the heat and expansion.

logan426

Posted By: JohnRR

Re: exhaust valve stuck 3 times now. help? - 03/21/11 02:23 PM

Quote:

I just rebuilt a 318 for my 73 dart swinger. I did the port work on the stock heads and sent them out to a machine shop for new steel guides and smaller 11/32 stem valves (increased valves size to 1.905/1.6). They also put in pc valve seals, comp cams springs and retainers. After about 50 miles, the #4 exhaust valve stuck open and bent the push rod. Took the head off and back to the machine shop. They said the stem had galled itself to the guide, probably from oil starvation. So, they put a new valve in as well as a bronze guide to fix it. When I reassembled the motor, I used an old valve cover with the top cut off so I could observe the oil flow. Oil was flowing abundantly through the stock rocker shafts and running out to the tip of the valves. Seemed good to me. Drove it for 5 miles and "bink", it siezed again, this time #2 exhaust.
Called the machine shop and they were baffled, so they said they would try to open up the stem to guide clearance from 1 thou to 1.4 thou. They installed another new valve and bronze guide. I thought my stock rockers may not be pushing enough oil to the stem tips so I replaced all of the rockers with new stock ones, observed the oil again, all seemed good. Drove it for 5 miles, and "bink", #2 stuck again.

My question is do you think that the positive type valve seals are starving the valve stems? should I go back to umbrella seals? This is very frustrating. Please help.

Are the PC valve seals the white Teflon seals ?
If so there is a big part of your problem. You need to pull both heads , take them back to the machine shop , probably expect to replace all the exh valves and switch to a viton seal or an umbrella seal.

Posted By: rxod

Re: exhaust valve stuck 3 times now. help? - 03/22/11 01:16 AM

Quote:

Are the PC valve seals the white Teflon seals ?
If so there is a big part of your problem. You need to pull both heads , take them back to the machine shop , probably expect to replace all the exh valves and switch to a viton seal or an umbrella seal.

not sure if teflon or not, but I will find out. whats the problem with teflon? thanks

Posted By: 340SHORTY

Re: exhaust valve stuck 3 times now. help? - 03/22/11 01:31 AM

Quote:

Guide to stem clearance were set up too tight from the start. extra needed on exhaust, thats the side that takes all the heat and expansion.

logan426

I had the same problem on a set of BB heads I had done.. The above statement is the truth.

Posted By: rxod

Re: exhaust valve stuck 3 times now. help? - 03/22/11 01:49 AM

So, should I open the exhaust clearance upto 2 thou and keep the pc seals if they are viton, or go with umbrellas?

Posted By: Performance Only

Re: exhaust valve stuck 3 times now. help? - 03/22/11 04:43 AM

i'm wondering why they went with steel guides in the first place.
i agree with the others, the clearances were too tight for an exhaust valve.
just curious, where in Fl. are you? just wondering if your anywhere near my shop in Delray beach.

Posted By: RapidRobert

Re: exhaust valve stuck 3 times now. help? - 03/22/11 05:01 AM

Quote:

So, should I open the exhaust clearance upto 2 thou and keep the pc seals if they are viton, or go with umbrellas?

umbrellas

Posted By: rxod

Re: exhaust valve stuck 3 times now. help? - 03/28/11 05:10 AM

Performance Only- I'm in Orlando.

I am having umbrellas put on the exhaust, clearance to 2 thou and leaving the pc seals on the intakes @ 1.5 thou. Hope it works, cause I'm over taking these heads off.

Posted By: 268RTs4ME

Re: exhaust valve stuck 3 times now. help? - 03/28/11 05:33 AM

Sounds to me like machine shop did not do guides right,or valve sets cut to deep. Running hydralics right.

Posted By: rxod

Re: exhaust valve stuck 3 times now. help? - 03/28/11 06:39 AM

yes. hydraulics

Posted By: JohnRR

Re: exhaust valve stuck 3 times now. help? - 03/28/11 02:30 PM

Quote:

Quote:

Are the PC valve seals the white Teflon seals ?
If so there is a big part of your problem. You need to pull both heads , take them back to the machine shop , probably expect to replace all the exh valves and switch to a viton seal or an umbrella seal.

not sure if teflon or not, but I will find out. whats the problem with teflon? thanks

They are harsh on the valve stems , not good for a street engine , so I have read ?

I'd change them out while the heads are off and apart .