mk e is right. There are only 4 valve specs that determine the tip's location relative to the valve seat, the back cut location & angle aren't relevant !!! Overall length - head face to tip Head Diameter Margin width - Distance between valve face & beginning of the seat cut. What mke is saying is that the beginning of the back cut simply limits the width of the sealing surface between the valve & the seat. It does not affect the depth of the valve in the seat. The 15' difference in the valve seat angles ensures the valve intersects the seat right at the valve's margin. Lapping will affect this a bit, but only by a few tenths. The head diameter & margin width are the valve parameters that control how far down into the seat a valve sits. The valve seat specs that control valve tip height are the seat height, depth of the seat groove in the head, the outside diameter of the seat cut, and the seat cut angle. Image Unavailable, Please Login
Brilliant explanation. I can't be the only one benefitting from this. Valves should be at ferrea tomorrow. Will report back
Some good news. Ferrea called and had received the valves earlier today. Their intakes are .050 too short and their exhausts are .040 too long. I could hear the 'oops' look when he confirmed their engineering schematics got it wrong. All will be right shortly.
Ferrea's schematic for these valves appears to be wrong. Their schem shows the intakes as 109.25mm long while the stock valves are 109.85 long. I think what they have is a Daytona or boxer valve with their length as I believe both of those are slightly shorter but retain the same head. Can anyone confirm? As for the exhaust valves, their solution is to knock .040 off the stem and send em back.
Great thread, thanks for keeping it updated. Is there any info about which method they use to "knock" off the extra material? I am curious.
no idea really. because they are the manufacturer I have confidence in their modifying their own products
I second the confidence but there are so many ways to remove material I was curious as to the preferred method.
John, Did they verify that the 0.040" excess exh. valve length they're removing is between the keeper groove & the tip? The length between the valve face & the keeper groove is a critical dimension as it affects valve spring closed length. Darryl, As hardened as valve stems are, using metal or even carbide bit type cutting tools is unlikely. I'd expect them to wet grind the excess off, probably with successive coarse & fine wheels. Wet grinding avoids heat buildup that could cause dimensional changes during the process. I'm sure they have a custom designed machine to do this with great precision. BTW, grinding to shorten valve stems is fairly common. Many valve grinding machines have a stem grinding attachment.
I did bring the keep groove to the valve face to their attention to review and validate it is correct to the samples I forwarded, which they indeed are. The .040 will be right off the tip. I left a message for Zeke at Ferrea who is handling my debacle here regarding status and method of removing the material. You have me curious as well. I am betting Ferrea is doing a more thorough search in regards to the intake valve length. I too would be confused if I had a catalog item for 15 years that all of the sudden turned out to be too short. I am wondering if the '76 cars perhaps had a slightly longer intake valve then that of their later 2v counterparts although this would make zero sense. We'll see........
John glad to hear you are getting to the bottom of this . The set of P6's were finally packaged today so should get them on their way next week !
NO. I just checked the 308GT4, '81-'82 GTSi/GTBi, and Mondial8 FPCs. All 3 list the same valve p/ns: 103575 Valvola di aspirazione Intake Valve 106553 Valvola di scarico Exhaust valve I then went to Ricambi's web site to double check the 'used on' lists: 103575 This item is used in the following applications: Vehicle Quantity Table Location Where Used 308 GTB (1976) 8 7 3 TIMING SYSTEM - TAPPETS 308GTB/GTS 8 7 3 TIMING SYSTEM - TAPPETS 308GTBi/GTSi 8 7 3 TIMING SYSTEM - TAPPETS 308QV 1 44 26 PEDAL BOARD - CLUTCH CONTROL (VARIANTS FOR RHD VERSION) Mondial 8 8 7 3 TIMING SYSTEM - TAPPETS The listing for the QV clutch cable fork is a scanning or data entry error, my QV FPC clearly lists that part as 108575. 106553 This item is used in the following applications: Vehicle Quantity Table Location Where Used 246 Dino 12 6 20 TIMING 308 GTB (1976) 8 7 4 TIMING SYSTEM - TAPPETS 308GT4 8 7 4 TIMING SYSTEM - TAPPETS 308GTB/GTS 8 7 4 TIMING SYSTEM - TAPPETS 308GTBi/GTSi 8 7 4 TIMING SYSTEM - TAPPETS 512 BB 12 4 62 CYLINDER HEAD (LEFT) 512 BBi 12 4 62 CYLINDER HEAD (LEFT) Mondial 8 8 7 4 TIMING SYSTEM - TAPPETS It is interesting that the 512BB uses the same exhaust valve as the 308, but a different intake valve: #102662. This supports your hypothesis that they may have sent you Boxer intake valves. Would be interesting to know if the 512BB intake valve is 0.60 mm shorter than the 308 intake valve. FastRado, do you happen to have an old Boxer intake valve that you could measure?
Sorry to HiJack the thread... but----> Perhaps FastRadio or Newman can chime in on this... Does this mean the 512 uses a different valve on the "right" side cylinder head?? Rick
Too often we are flying along fine, then KABOOM!. Sorry your getting whacked, strange its coming from someone so well known. But it should straighten itself out. Hope you havnt let it stop you elsewhere though. You know you dont need the heads installed to slap the block down onto the gearbox. Not trying to rush ya, lol, Lord knows ive gotten sidetracked. But you were moving forward so rapidly you had everyone here holding their breath. We just knew it couldnt continue without something sabatoging your progress. IOW, were looking for more pics, LOL.
No, If you look at one of the online FPCs you will see that it just means that TAV 4 which shows the LEFT side head lists the valve P/Ns for all 12 cylinders.
The boxer uses the same exhaust valves as the 308 but different intakes, same left and right of course. The problem here is two-fold. The wrong valves were sent and the machine shop over-looked the error. This should have been caught by the machinist so they are on the hook as far as im concerned for any additional cost after ferrea sends the correct parts.
What's most strange is Ferrea keeps feeding me the line that hey have been making these valves as a catalog item for better part of 15 years, and their schematic has not changed and of course hundreds of these valves have been sold. My solution given to me by Ferrea was to have them make new custom valves. The exhaust valves should be done by Tuesday and the charge to have those cut and re-hardened is very small. Here's what I am going to do and I am surprised I did not think of this before. Switch to a shim under bucket system. This will easily correct this and I will have no worries about where my extra .040 will come from, and should I switch to a more extreme cam later I will have no worries about shim flipping. Nope, not going to put the engine on the transaxle just yet. It is my desire to keep it on the stand while dialing in the cams. Thanks for all the research everyone has been doing. I spoke with a couple people who have told me they think this is a boxer intake valve as well, because off the top of their head they recall the boxer intake valve also being 42mm, but the length slightly shorter.
Exactly... Simple problem, simple soultion. There's no need for custom valves, shims under buckets or any other novel solutions. With the correct valves installed, there are no issues to contend with...
The problem is according to Ferrea, the correct valves were sent. The larger issue is the machinist did not check new vs old because he is an idiot. Now Ferrea will not accept returned valves nor admit their valves are wrong due to the number which have been sold in the past. Not worried, just frustrated and ready for this fire to be put out
I have some Ferrea exhaust valves in stock I can check ... I never had a problem with overall length. If the valves are .04" short the protrusion of the tip of the valve above the retainer/keeper will only be .02" or less ... meaning if the bucket tips it might hit the reatiner if it's that close. This would be obvious to a person familiar with this valve train. Shim under you have to change retainers to capture the shim. I have valve train CAD layouts for all these scenarios that I'll post if I get some time. cheers
I guess the fact I have correct valves from Ferrea is irrelevant at this point. Here's a valve train layout ... a bit more clearance there than I remembered (edit: the dim is .08" ... the PDF isn't showing up for some reason on my screen) Good luck. Image Unavailable, Please Login
Fabulous rendering. Thank you ! As a side note, I was measuring valve guide clearance. Getting about .0017-.0023. I have always preferred to have them as close to .001 as possible but in this case since this is how they were out of the box from Si I can't really do anything about it. Should be fine.
Heads are back together! These valves and guides are *tight*. As in, they do not budge/wiggle at all. Ferrea cut .040 off the ex valve stems and re-hardened. Intake valves are new and now correct. I lapped all the valves and cc'd a combustion chamber. I am getting 37.5cc. Thankfully, upon installing, all the installed spring heights are where they need to be so no worries there. I just ordered a few shims. Once those are in I will bolt these heads to the block............finally. Cam bolts are loose and the degree wheel is fitted to the crank.
John 37,5cc chamber volume , don't I remember 42cc being std ( unskimmed ) Am I correct in saying a fair bit of material has been removed ? Now that's going to help your CR ! Have you worked out what it is ?