Valve guides

need4speed · Post by **need4speed** » Mon Sep 01, 2008 11:03 am

Seeing as my last thread was well and truly hyjacked....

Will machining 0.1" off the top of the guides affect how the stem oils seals fit?
I take it i need to machine the top of the guides so the valve collets wont hit the top of the guides/stem seal when using high-lift cam??

kiwicar · Post by **kiwicar** » Mon Sep 01, 2008 2:21 pm

Is this suposition or have you measured the clearance at full lift? just if you havent stuck a checker spring in and a dial indicator on the valve I would do so as how much comes off the guides also depends on how far they are set into the head. As for the stem seals it depends on how they are retained in place, but if they use a groove just below the top of the guide then this will have to be re machined.
Mike

CastleMGBV8 · Post by **CastleMGBV8** » Mon Sep 01, 2008 6:24 pm

Need4speed,

Apologies the thread just seemed to evolve into the other aspects of fitting a higher lift cam.

Yes it is to prevent the colletts hitting the guides and doing a lot of damage.

Mikes suggestion will give you a more accurate answer but Real Steel suggest that you need to remove 100thou. and although that probably errs on the safe side it would make very little difference whether you have to take off 80 or a 100 thou to provide the required clearance.

Do I get the impression that you are trying not to remove the heads which is understandably more work, but I dont really think you can do it properly without removing them.

As to the stem seals if your using the old O ring type no additional maching is required, if you are intending using the later style that go over the guide I believe an additional step needs machining to the top of the guide that the seal then slips on to. For the later seals the guides need shortening any way to take into account the additional thickness of the seals so you may need to remove more from the guides, best to double check with Real Steel.

Kevin

need4speed · Post by **need4speed** » Mon Sep 01, 2008 6:43 pm

Thanks guys. Thats ok Kevin, dont worry about it. At least ive got good answers now

My heads are off already, and they are the later 4.6 type so incorporate the neoprene seals.. as you say i'll check again with rs because they dont mention if the 0.1" is for early or late heads..

CastleMGBV8 · Post by **CastleMGBV8** » Mon Sep 01, 2008 6:52 pm

If memory serves me correctly the later heads have guides with a step in them if so you will need to remove 100thou the the top and the step so that the seals will still fit.

Kevin.

Post by **katanaman** » Mon Sep 01, 2008 9:59 pm

CastleMGBV8 wrote:If memory serves me correctly the later heads have guides with a step in them if so you will need to remove 100thou the the top and the step so that the seals will still fit.

Kevin.

I am pretty sure this is the case as well. If you don't then the seals wont fit anymore and even if they stayed on the length would effectively be the same as before with the seals sitting on the top. An easy option might be to drive the guides further into the heads by 0.1" and if flow is a concern then take the end off in the ports.

Tony what did you do with your heads M8 or did they already have shorter guides fitted?

need4speed · Post by **need4speed** » Sat Sep 06, 2008 2:45 pm

Ive deicided just to buy a full set of shortened, bulleted guides and have the machine shop fit them. The guides arent that expensive and tbh because i have the late heads it would prob take more labour to machine all my existing guides than just fit new ones.
Oh and i'll get the added bonus of improved flow...

Post by **katanaman** » Sun Sep 07, 2008 11:28 am

remember and get all your valve seats cut as well. Most often (but not always) the valve doesnt sit on the seat square after new guides are fitted.

Eliot · Post by **Eliot** » Sun Sep 07, 2008 11:30 am

need4speed wrote:Ive deicided just to buy a full set of shortened, bulleted guides and have the machine shop fit them. The guides arent that expensive and tbh because i have the late heads it would prob take more labour to machine all my existing guides than just fit new ones.
Oh and i'll get the added bonus of improved flow...

My late father was a head specialist of 30 years and this is what he would of told you to do - rather titting around maching the existing ones.

Eliot · Post by **Eliot** » Sun Sep 07, 2008 11:35 am

katanaman wrote:remember and get all your valve seats cut as well. Most often (but not always) the valve doesnt sit on the seat square after new guides are fitted.

Yes - but if they are cut back too much, you will need shim the rockers!

need4speed · Post by **need4speed** » Mon Sep 08, 2008 1:59 pm

jeeeeeeez. all this just because i want to fit a stump-puller cam???

CastleMGBV8 · Post by **CastleMGBV8** » Mon Sep 08, 2008 3:22 pm

Sods law, change one thing and you have to change three others.

Personally if the existing guides are within spec, I would just have the guides machined down as recommended and also have the guides machined in the ports, and the valve throats taken out to seat size, this will improve flow and yield approx 30BHP on it own on a 3.5. plus whatever the new cam gives you.

As for oil seals just use the original O ring type on the inlets but make sure that you have the crankcase vent system working properly or you will get oil down the inlet guides.

Kevin.

kiwicar · Post by **kiwicar** » Mon Sep 08, 2008 4:19 pm

If you cut the valve seats deep enough you won't have to buy lash caps to sort out the geomitry, just shorter push rods

It'll breathe like an asthmatic hedgehog on the pull but you'll be sorted on geomitry (probably be sorted for guide clearance aswell!!

.

Sorry what I am trying to say is I would decide how you want to solve this, ie get the new guides, fit them as far into the head as you think will work, cut the seats, mock up the valve seals, checker spring and valves and valve retainers and measure what you actually have , them stick the valve springs into a retaining jig of some sort, compress them to max lift and see what clearance you have. Finally stick the rockers onto a pair of valves with checker springs on and see where the contact point wanders as the valve opens, it doesn't take long and you will know for certain.
there are many variables but also the rover V8 rocker geomitry is not a highly critical.
Mike

topcatcustom · Post by **topcatcustom** » Fri Jan 16, 2009 4:34 pm

Dragging this up to save starting another similar topic- I am going to be using Real Steel's Blower cam, which has .480" max lift (seems a lot!!)

My heads are the later 14 bolt EFI ones, before the neoprene seals came out (and no I would NOT rather have newer heads as the combustion chambers are so much smaller!- Need the low compression for obvious reasons!) I am also using composite head gaskets to further lower the compression ratio.

Am I right in remembering that in Des' book he says that these 'mid' period heads have the most capacity (in std form) for valve lift?

So my question(s):

1st, will I have to mill a little off the top of my valve guides or can anyone tell me how far they should stick out so I can measure them?

2nd, with the composite gaskets being (.5mm?) thicker I guess I should machine down my rocker pedestals or the bases where they sit- but this will undoubtedly upset my geometry- so would it be less hassle to get some adjustable pushrods, and how strong are they? Don't have much faith in tiny threads in thin tube having to massacre double valve springs at 6000+ RPM!!!!

Oh, just to get this off my mind too- 3rd, double valve springs will go straight on won't they? i.e. no machining required?!

Help much appreciated as always guys, TC.

Post by **katanaman** » Fri Jan 16, 2009 5:03 pm

Cant help with the measurements and stuff but the cam sheet will tell you if the guides need machining from standard. No double springs wont fit the standard heads you need to machine the valve seat.

As a side note personally I would rather you started a new thread for your questions other than bumping up an old thread. It makes searching easier in some cases.