902 heads, big valves

Kolie

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Guys,

I am working on my 902 heads.  I want to put in 2.19 / 1.88 valves.  I understand that in order to do this the head itself is physically cut, not installing new larger seats.[ My nailhead has valve seats cut into the head casting].

For the 2.19 /1.88 valves, anybody have any idea of the "drill diameter" needed?  How deep into the head casting do you go?  Looks like a problem if you go too deep.  [water jacket?]

Second question, I understand that larger valves w/o port relieving is of no benefit.  Any idea of where the porting should be done?  Anybody have some good pictures? [Thank you Dave and Ted!]

I'd like to know what's involved so I can do most of the head work myself before I take it to the machine shop.

Later,
Kolie


"My goal in Life is to be the man my Dog thinks I am"
 

MOCRUZN

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If you haven't searched with the words  'head porting'  give this a try and it should give you a days reading.  Much has been posted and discussed here on this subject, including pictures ..
 

JW

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  Kolie

  Where I get to be the "bad guy"

If you have never ported a set of cylinder heads much less a set of cadillacs I would suggest that you find a single head and get lots of practice before undertaking this because it is much easier to make them worse than better.
 
  I would also suggest that you find a set of smaller valves than the 2.19/1.88 especially the 1.88 diameter exhaust.
  No factory cadillac head needs a exhaust valve that big and it will actually inhibit airflow as opposed to improving it.

Opening up the intake to 2.19 from 2 inch will require you to do more work in the port to see as much benefit as using smaller valves and less work with better results and less chance to do something to go very wrong and waste alot of time making a good general port design into a trainwreck.

  I would suggest using

  Pontiac RAIV valves that are 2.11+1.77 diameter and are 5.23 approx long but make sure you get the ones with the 45Deg seat.
 
  I have a set of customer first time ported heads here for a driver street engine for a 81 SDV and he did a really good minimalistic port job that i spent maybe 2 hours tweaking on and here ill even post some flow numbers.
 
  this is on a JKM bench that is usually about 5-7% lower than any other flow bench that ive ever encountered but its consistent and they dont charge me anything to use it.
  This is on a 4.25 bore that I cheated the head over and the numbers are rounded by the computer soft ware.
  Again superflow 600/1010 numbers would be 5-7% higher

  Lift        INT        EX

.100        62          57

.200          133      100

.300          174        136

.400          208        155

.500          237        176

.600          251        195

  These might not be earth shattering numbers but for a street engine with an edelbrock intake ,9:2-1 compression ,a little cam that is about the same as a MTS #10 cam this engine will make plenty of "grunt"

  DAVEM from this board has heads that were built with these valves and had better airflow numbers then again they were professionally ported and the numbers should be higher.

    Just a suggestion

  JW
 

dave brode

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TORQUE INC said:
  Kolie

  Where I get to be the "bad guy"\

TI,

Nicely put, for a bad guy.  :devil: Seriously, Kolie, I can't agree more. It ain't fun, and it's really easy to spend 10s of hours. Bad enough if you are pretty sure to improve the heads.

TI,

At what point do you use bigger than 2.11"? With more cam, compression, or what?

TIA
Dave
 

JW

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  Dave

  Its all in feedback from the customer as to the intended use of the engine.

  TI
 
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