[DeTomaso] Pushrod guideplate adjustment?
Dave Londry
davel at emspace.com
Tue Apr 13 19:36:05 EDT 2010
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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