Author Topic: #6 350 heads, dowel pin location?  (Read 325 times)

mikekop

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#6 350 heads, dowel pin location?
« on: January 12, 2019, 06:45:30 AM »
Hi guys!
I have a set of 1970 #6 Olds 350 heads that I am getting ready to put in my 1978 T/A 403.
It is commonly mentioned that you need to drill for an extra dowel pin that doesn't exist in a 350 head, but can anyone point out the location of this dowel pin? I have checked the head and compared to the new head gasket for 403 that I have, but I am unable to find the dowel pin spot? Thanks in advance!

olds403

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Re: #6 350 heads, dowel pin location?
« Reply #1 on: January 12, 2019, 10:25:28 PM »
It’s the size.  Measure them. 
What are you doing to the heads?

mikekop

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Re: #6 350 heads, dowel pin location?
« Reply #2 on: January 13, 2019, 01:15:23 AM »
Drilling for 1/2" head bolts, New valve sleeves and 2" intake valves, maybe 1,65" exhaust valves. Only shaving off for flatness if needed. So the dowel pins are in the head bolt holes? What size are the dowel pins?

mikekop

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Re: #6 350 heads, dowel pin location?
« Reply #3 on: January 13, 2019, 01:22:26 AM »
The reason I'm asking is that I don't want to tear apart my engine before the 350 heads are ready to install, so I can't just compare with the 403 heads. So the location can be found on the head gasket, by just measuring the size of the hole in the gasket?

mikekop

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Re: #6 350 heads, dowel pin location?
« Reply #4 on: January 13, 2019, 01:34:36 AM »
Also, I would like to get some advice on my current cam, I have a Comp Cams XE262 in there now, will it be enough with the increased compression? I have 3.23 gearing, Thornton JR manifolds, and R.A.R.Es true dual x-pipe exhaust. Prepped TH350 and higher stall converter.
I would also appreciate an explanation of where the so called egr hump is found, I was gonna ask the machine shop to grind it off.
Sorry for all the rookie questions, I have never worked with heads before, although I have done all the mods on my car myself, except for buying a finished transmission.

Re: #6 350 heads, dowel pin location?
« Reply #4 on: January 13, 2019, 01:34:36 AM »

olds403

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Re: #6 350 heads, dowel pin location?
« Reply #5 on: January 13, 2019, 12:19:50 PM »
Hello, the cam should be fine.  Its not that big of a cam, but run what you have.  The head swap will wake it up.  Several things you should think about.  Once you swap heads the valve train should be converted to adjustable.  You should use a shop that knows Olds.  The last three sets of heads we had done were by champion racing and shipped them to them.  If interested, PM me.  All was coordinated with Cutlassefi on classicoldsmobile. 

Below are some pics of a 403 block and you can see the guide dowel pins on the block and the dowel holes on the heads.  Those need to be opened up for the 350 heads on the 403.  The egr bumps are at the roof of the exhaust port. You can see the roofs of the ported vs stock.   I’ve done mild to full port work on 350 heads and two sets last year.  Now, I have been screwed before where a shop used longer valves and then took an angle grinder to get them to the right installed height - junk ! Use a good shop.  That was a $500 plus mistake and send them to champion. 

What intake are you using? 













mikekop

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Re: #6 350 heads, dowel pin location?
« Reply #6 on: January 13, 2019, 05:09:54 PM »
Thanks for the reply and pictures!
So, valve train, "should" or "must" be adjustable? I was hoping to be able to use stock valve train... Thanks for the tip on a good machine shop, unfortunately I'm in Sweden, Scandinavia, so I'm not shipping the heads to the US ????
It looks like the dowel pins are right next to the guide holes for the push rods, on each outer end?
I intend to get a Edelbrock Performer 2711, and putting on a FiTech too.

mikekop

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Re: #6 350 heads, dowel pin location?
« Reply #7 on: January 13, 2019, 05:18:56 PM »
The 4 ? was supposed to be a  :-D
On the picture of the block, there are 2 dowel pins, but on the picture of the head, there are 3 holes?

olds403

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Re: #6 350 heads, dowel pin location?
« Reply #8 on: January 13, 2019, 05:52:39 PM »
350 heads have three dowel holes.  403 block has two.
With that cam and stock head gasket - felpro you can probably get away with it. 

mikekop

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Re: #6 350 heads, dowel pin location?
« Reply #9 on: January 13, 2019, 06:07:34 PM »
Now I'm confused. So I need to put an extra dowel pin in the 403 block, not drill an extra hole in the 350 heads? Is it really necessary then?
Do you mean I can get away with using stock valve train? It works great as is now, although I have replaced the stock aluminum pedestals with the steel rocker "half-moons" and pedestal supports.

olds403

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Re: #6 350 heads, dowel pin location?
« Reply #10 on: January 13, 2019, 06:54:37 PM »
The 403 block will accept 350 heads.  3 dowels does not matter.
Ideallly, you should measure with push rod checker.  Chances are you will be fine

mikekop

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Re: #6 350 heads, dowel pin location?
« Reply #11 on: January 13, 2019, 07:07:13 PM »
Thanks, this was helpful!

Re: #6 350 heads, dowel pin location?
« Reply #11 on: January 13, 2019, 07:07:13 PM »
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