[DeTomaso] Pushrod guideplate adjustment?
Dave Londry
davel at emspace.com
Tue Apr 13 22:03:48 EDT 2010
I have a bottoming tap coming in by usps, but just running a regular tap
down it I got it to 0.75",
so I think I'll be able to get it in untrimmed.
dave
wkooiman at earthlink.net wrote:
> At least you got to the bottom of it. My guess is the shop screwed up when they did the screw-in studs.
>
> My 2nd guess is you're okay as long as you have enough thread engagement and everything is lined up. That's only a guess, though. You want to get advice from someone else (not me) on this one.
>
>
> -----Original Message-----
>
>> From: Dave Londry <davel at emspace.com>
>> Sent: Apr 13, 2010 6:36 PM
>> To: wkooiman at earthlink.net
>> Cc: detomaso Forum <detomaso at realbig.com>
>> Subject: Re: [DeTomaso] Pushrod guideplate adjustment?
>>
>> This is more interesting still, Will.
>> - the shop who did it was somewhere around Portland - before my time.
>> - of course I have the heads on now with $100 of gaskets under them
>> - the spacing of the top of the studs is hard to measure repeatably.
>> I ended up running nuts on 2 turns and measuring inside to inside of
>> the nuts
>> 5 - 2.457 1 - 2.456
>> 6 - 2.453 2 - 2.425
>> 7 - 2.416 3 - 2.401
>> 8 - 2.422 4 - 2.417
>> So # 8 doesn't stand out - but the new rockers are far from centering
>> on the valvestems.
>> - I went to change out the all the rockerstuds to CompCams Magnums
>> and found that some greasehole had nicely cut the head-side of the
>> stud to 0.615 from 0.800.
>> This is because the tapped hole is only about 0.650.
>> This leaves 0.540 engaged in the head - or 1.24 diameters, down from
>> 1.66.
>> - So I could only change the exhaust rockerstud.
>> - I found that both #8 studs had wear patches down the shank.
>> Small on intake & big on exhaust.
>> Here's where it gets ******weird******
>> - I decided to see if the misalignment tracked the pushrod guideplate so
>> I swapped the guideplates for #7 & #8
>> - Now #8 lines up fine AND #7 DOES TOO.
>> #7 alignment wasn't good before - but #8 was very bad
>>
>> So I think I can get some more depth in the hole for #8I by using a
>> blind tap,
>> trim my new rockerstud to about 0.700 and put it in with a hi-test
>> threadlocker.
>> Then if I can get a decent witness print on the stems, get on with it.
>>
>> What do all y'all think?
>> dave
>>
>>
>> wkooiman at earthlink.net wrote:
>>
>>> Measuring the distance from the studs sounds like a good idea.
>>>
>>> You might also consider taking the heads to a different machine shop. i.e. not the one that converted the heads to screw-in studs.
>>>
>>> Someone mentioned that the rocker studs might have been tapped off center (or crooked).
>>>
>>> Regardless, a decent machine shop should be able to tell if the studs are where they're supposed to be.
>>>
>>> The bottom line is if the studs are bent or crooked, the rocker will be crooked too, and even if you cut/reweld the guide plates, you're still going to have a rocker related failure.
>>>
>>>
>>> -----Original Message-----
>>>
>>>
>>>> From: Dave Londry <davel at emspace.com>
>>>> Sent: Apr 6, 2010 12:17 AM
>>>> To: wkooiman at earthlink.net
>>>> Cc: detomaso Forum <detomaso at realbig.com>
>>>> Subject: Re: [DeTomaso] Pushrod guideplate adjustment?? [Re-trying to get this post.]
>>>>
>>>> No pain Will;
>>>> that's a bonus question Will - and I haven't.
>>>> You can tell I'm used to rockershafts or direct acting.
>>>> I guess I should be able to measure the centre to centre distance of the
>>>> studs on #8 and compare them to 2 or3 other cylinders.
>>>> (unless the pedestals were bored skewed)
>>>> I'm guessing that they're compcams magnum, everything else is,
>>>> so for $53 for a set plus another $35 to get them here, I can just try
>>>> a new pair.
>>>> And I'll need some hi-temp threadlock I guess.
>>>>
>>>> You're right.
>>>> I'd really like to get rid of the problem without extra clanging noises.
>>>> dave
>>>>
>>>> wkooiman at earthlink.net wrote:
>>>>
>>>>
>>>>> What about the rocker stud? Have you verified it isn't bent?
>>>>>
>>>>> Sorry to be a pain. I'd just hate for you to spend lots of time getting it back together only to bend something else.
>>>>>
>>>>>
>>>>> -----Original Message-----
>>>>>
>>>>>
>>>>>
>>>>>> From: Dave Londry <davel at emspace.com>
>>>>>> Sent: Apr 5, 2010 7:11 PM
>>>>>> To: detomaso Forum <detomaso at realbig.com>
>>>>>> Subject: Re: [DeTomaso] Pushrod guideplate adjustment?? [Re-trying to get this post.]
>>>>>>
>>>>>>
>>>>>> OK I get it. Thanks guys.
>>>>>> Sounds like a "measure lots - tack once" job.
>>>>>>
>>>>>> Will & Jack
>>>>>> - both #8 rockers, all the valves and all the valve springs have been
>>>>>> replaced.
>>>>>> The pushrods are as straight as my granite flat and I still need to move
>>>>>> them about 0.110 closer together.
>>>>>> (but that's quite a bit less than when the bent rocker was still there)
>>>>>>
>>>>>> dave
>>>>>>
>>>>>> -------------------------------------------------------------------
>>>>>> Dave,
>>>>>>
>>>>>> I think most people actually cut the guideplates in two and retack them back together once they have the correct alignment.
>>>>>> Julian (Kift)
>>>>>>
>>>>>> ----------------------------------------------------------------------
>>>>>> Actually from that picture it looks like something is bent. It shouldn't be off by that much.
>>>>>> (Will Kooiman)
>>>>>>
>>>>>> --------------------------------------------------------------------
>>>>>>
>>>>>> hemipanter at hemipanter.se wrote:
>>>>>>
>>>>>> Cut the guidelate in the middle and weld a washer over the connection.
>>>>>> I did this 100:eds of times.
>>>>>> Goran
>>>>>>
>>>>>> JDeRyke at aol.com wrote:
>>>>>>
>>>>>>
>>>>>>
>>>>>>> rockers, guide plates and pushrods- are hardened steel and cannot be
>>>>>>> straightened if even slightly bent. Matter of fact, if anything IS bent, throw it
>>>>>>> away before it breaks in two and takes out the top end or worse. It may only
>>>>>>> be a matter of visual perspective, but better to spend a couple of hours
>>>>>>> checking than find out the hard expensive way. good luck- J DeRyke
>>>>>>> _______________________________________________
>>>>>>>
>>>>>>> Check everything. All the parts involved- the valve stems, pivot
>>>>>>> studs, the
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>> -------------------------------------------------------------------------------------------------------------
>>>>>>
>>>>>>
>>>>>>
>>>>>>> I'm re-assembling #6143's valvetrain now and I don't see how to do
>>>>>>> guideplate adjustment.
>>>>>>>
>>>>>>> http://www.poca.com/index.php/gallery/?g2_itemId=15138
>>>>>>> The is a pre-teardown pic but it shows my question nicely.
>>>>>>>
>>>>>>> The roller-end of both intake and exhaust need to be moved outward
>>>>>>> (from the bore centre).
>>>>>>> That means the pushrods need to be closer together.
>>>>>>> Do I put more bend in the guideplate to do that?
>>>>>>>
>>>>>>> thanks in advance
>>>>>>> dave
>>>>>>> (never did pedestals before)
>>>>>>>
>>>>>>> --
>>>>>>> Dave Londry
>>>>>>> davel at emspace.com
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
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>>>>>
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