Thread: How important is a kero tight seal on V8 valves

Valve guides like new are they ? Pity they they dont line up with the valve seats !! (unless the valves are all bent !)
People way understimate the importance of the valve, its seat and bowl ! theres upto 25% more power in getting it right .
Send the heads out to get a proper el cheapo 3 angle job , or if you want a good job find someone with a NEWEN NC valve seat cutter , Its easy to take that 137 FWKW from a std 3,9 and with a good head job produce 170KW from a 3.9.

Lift a valve off it's seat, with the stem still in the valve guide and let it drop back onto it's seat, if it bounces the seat needs doing, the valve should not bounce in a correctly cut and lapped seat, Regards Frank.

Originally Posted by 400HPONGAS

Valve guides like new are they ? Pity they they dont line up with the valve seats !! (unless the valves are all bent !)
People way understimate the importance of the valve, its seat and bowl ! theres upto 25% more power in getting it right .
Send the heads out to get a proper el cheapo 3 angle job , or if you want a good job find someone with a NEWEN NC valve seat cutter , Its easy to take that 137 FWKW from a std 3,9 and with a good head job produce 170KW from a 3.9.

Yep, 3 cut definitely. Lapping even a slightly used surface is never a sure fire way to get a seal if the seats aren't flat. The valve face will cop more wear than the seat in 99% of cases and lapping a worn valve will more often than not damage the seat than correct the valve.
And if your guides are even a little sloppy, it will put everything out of whack.
Valves are relatively cheap these days too so a new set with the modified short guides is the best bet.

Cheers

Andrew.

PS, search my file uploads Phil, I have posted the late head early block LR Bulletin in there plus I think the valve guide mod too... I think...
Sent from my backyard TeePee using smoke signals.

Originally Posted by PhilipA

I am currently preparing a set of almost new 4.6 heads to fit to my 3.9 RRC.
I bought the 4.6 heads about 6-7 years ago from TRS , put them on for 15KK then replaced them with the original 3.9 heads which I had spent a lot of time hand finishing.

I have port matched them and tidied up the inlet and exhaust bowls.

I then gave the valves a light lapping with the old suction cup and stick with paste I have had for about 30 years.

The thing is that after lapping I tested their seal by tipping some kero down the ports. They don't have springs in yet but just holding with my finger several drool a bit of kero out , particularly the exhaust valves.

Now I reckon that the damn things must have leaked from the start and probably leaked a hell of a lot more before I lapped them. If they leaked at 15KK use, there seems little point in being too fussy and spending $400 to have the heads serviced seeing the guides are like new and there is no warp etc etc.
Regards Philip A

G`day Philip ,

i`ve just got myself a vacuum pump to check the seal , theory is if you can suck to 20inches you have a pretty good seal , if it doesn`t drop past 10 inches in 10 seconds you have a good seal .

I also had the idea that the seal of the valves could be checked while the heads were still on , if the need arose .

I pressume you know that not only is the seal important but the thickness of the seal and the position of area of contact on the valve face as well .

From what i`ve seen you`ll see more wear on the valve face than the seat .

At 15k i wouldn`t expect you`d see much wear and the stems are easily measured as are the guides , i have some 3.5 heads that the valve faces and stems show wear but the guide clearence is within factory tolerance .

Your heads should already have the 3 cuts that a couple have mentioned .

You may have to try a different grade of paste , at least 2 grades , i think works best and it should be apparent which ones will seal if you look closely at both face and seat ( i got new readers for this ) and because the angle on the seat and valve are slightly different it will be apparent if they need to have other tools used on them . Engineers blue can also be useful .

I`ve got 4 of these heads on the bench at the moment , i`ll tidy the inlet ports because they have moved in the mould or something 2 need more work and the first 1 i started on has a bent exhaust valve but its the only 1 . I may even use a set of early exhaust valves as they dont have a recess in the top like the 4.6 ones but more thought on that .

Peter

Yeah, I guess I knew the answer to this before I asked, But I reckon the heads leaked from new.

I am pretty sure that the heads TRS were selling back then were production rejects ( as the first one they sent me had a big gouge across the fire ring area. However they did send me another) , and now I wonder less about the care taken in assembly in UK.ie there was none.

One of the heads has 2x air injection /EGR ports while the other doesn't!!!! so one is from the US market while the other is UK.

I must say that the actual casting is much better on these later heads without the core shift in the ports as in my 3.9 heads, but they have a deeply recessed indentations where the mould halves meet.

Ah well time to ask around my mates to find a good head servicer nearer than the one I know at Brookvale.

Regards Philip A

I dismantled and port matched and bowl smoothed the second head today.
Before I started I filled the ports with kero to find all tight except one inlet drool. So I think that carbon build up must seal the valves anyway.
THE INTERESTING BIT
is that I went to lap the valves in the second head and saw on the first (inlet)valve that there was no seat witness on one side. Funny I thought.
Then I turned the valve and it had visible runout.

So I set up the old dial indicator( I knew it would come in handy one day) and found that inlet valve has 0.5MM !! runout and the exhaust valve from the same cylinder has 0.1MM runout. All the other valves were spot on.

All I can speculate is that the head came of a new engine that immediately blew up or then maybe it was an old head well cleaned. So much for paying $1200 to TRS for new heads. Who dismantles a new head to check the valves are not bent ??? They seem to have some dodgy sources for this stuff.

I am sure that I have never ever overrevved the engine in mine , and certainly there were no witness marks on any piston when I changed the heads after 15KK.

So now I am up for 2 new valves as well as the rest.

Ah well, at least I did not have a head place tell me , as I would have had trouble believing it.
Regards Philip A

Originally Posted by PhilipA

I dismantled and port matched and bowl smoothed the second head today.
Before I started I filled the ports with kero to find all tight except one inlet drool. So I think that carbon build up must seal the valves anyway.
THE INTERESTING BIT
is that I went to lap the valves in the second head and saw on the first (inlet)valve that there was no seat witness on one side. Funny I thought.
Then I turned the valve and it had visible runout.

So I set up the old dial indicator( I knew it would come in handy one day) and found that inlet valve has 0.5MM !! runout and the exhaust valve from the same cylinder has 0.1MM runout. All the other valves were spot on.

All I can speculate is that the head came of a new engine that immediately blew up or then maybe it was an old head well cleaned. So much for paying $1200 to TRS for new heads. Who dismantles a new head to check the valves are not bent ??? They seem to have some dodgy sources for this stuff.

I am sure that I have never ever overrevved the engine in mine , and certainly there were no witness marks on any piston when I changed the heads after 15KK.

So now I am up for 2 new valves as well as the rest.

Ah well, at least I did not have a head place tell me , as I would have had trouble believing it.
Regards Philip A

G`day Philip ,

you may get a fright when you price the valves ,
if you do .... rv8engine-parts-shop .

Ebay UK .................... Landrover OEM , 16 valves , full set , wasted ,

ERR 1780 and ERR 7338 .

$111.77 plus $31.54 AU last week .

You may know of cheaper but as they say they are landrover , my EPC stopped working , say`s some error and to contact a help desk , have to fine another , so i can`t check the part numbers .


After i read this post i thought i`d better remind you to be careful , i seem to remember last time you had the heads off you had trouble with your pump and i mean your pump .

Cheers