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Large intake valve small bore ???

Large intake valve small bore ???

Old January 12th, 2019, 11:23 AM
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Large intake valve small bore ???

The 400 G is a small bore engine that used a D or C head from the factory with 2.067 intake.
The Canadian 442 400 G engine some times came with C heads with a 2.00 intake.
Would it be worth my time to try the smaller intake heads with the small bore?
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Old January 12th, 2019, 01:34 PM
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With the goal being what?
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Old January 12th, 2019, 02:19 PM
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Originally Posted by cutlassefi View Post
With the goal being what?
Maybe his Olds is too fast and he needs to slow it down...

I'm curious where it's documented that Canadian-built 442s got small valves. That's news to me.
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Old January 12th, 2019, 03:45 PM
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Originally Posted by joe_padavano View Post
Maybe his Olds is too fast and he needs to slow it down...

I'm curious where it's documented that Canadian-built 442s got small valves. That's news to me.
Bernhard wrote:
Not all 1969 442 400 Canadian C headed cars had smaller intake valves. We just happened to have one, it was years latter that we came across this in print.
I do not have documentation that this was standard practice, my current Canadian 69 442 400 G has the larger intake valve.



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Old January 12th, 2019, 04:04 PM
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Originally Posted by cutlassefi View Post
With the goal being what?
The valve is shrouded so the larger intake may not be an advantage.
It might be a waste of time but we have two members that have lots of flow bench experience so I thought I would ask the question.
I know magazines always focus on max lift flow but what I found interesting is that the stock/super stock racer focus on low lift to max lift flow not just max lift flow.
That's one reason they do so much with so little.

Its just like rear gear ratio some times less gear makes the car quicker.
I talked to a few guys that ran the 400G back in the day and they said the car did not like as much gear as the 400 E.




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Old January 12th, 2019, 04:16 PM
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Originally Posted by Bernhard View Post
I talked to a few guys that ran the 400G back in the day and they said the car did not like as much gear as the 400 E.
Optimum gearing has a multitude of variables. Torque curve of the particular engine, tire diameter and stickiness, trans gearing, etc. It's no surprise that the long stroke G-block would run out of steam and not want to rev. This is not an applicable example to the small valve discussion. In any case, do you know that the small valve 400 you had still had original heads, or even was original to that car? G-blocks in Vistas got small valves.
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Old January 12th, 2019, 05:44 PM
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Originally Posted by joe_padavano View Post
Optimum gearing has a multitude of variables. Torque curve of the particular engine, tire diameter and stickiness, trans gearing, etc. It's no surprise that the long stroke G-block would run out of steam and not want to rev. This is not an applicable example to the small valve discussion. In any case, do you know that the small valve 400 you had still had original heads, or even was original to that car? G-blocks in Vistas got small valves.
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The 69 442 was a numbers matching original 400 G and had no problem revving past 5500 rpm until we spun rod bearings multiple times.

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Old January 13th, 2019, 06:57 AM
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OK, an update. I did more research on this. All 2bbl G-block motors got small valves (including 1968 442s with the L65 Turnpike Cruiser package). All 4bbl G-block motors got big valves.
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Old January 13th, 2019, 07:36 AM
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Im not sure. The best way to test would be to start with a small valve G, test the numbers, machine for the large valve and test again. Or I guess I could test the heads that I have on a small bore fixture and see how much if any that they loose.
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Old January 13th, 2019, 02:15 PM
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Originally Posted by joe_padavano View Post
OK, an update. I did more research on this. All 2bbl G-block motors got small valves (including 1968 442s with the L65 Turnpike Cruiser package). All 4bbl G-block motors got big valves.
Our 69 442 was not a turn pike cruiser it was a factory 4bl 325 hp auto bucket seat console car. We had a factory manual and the build sheet for the car. I still remember checking the carb, distributor, intake, block, heads, alt, trans and diff. When we pulled the heads and measured the valves we were surprised by the smaller 2" intake valves. It was only years later that we read about some Canadian 69 442 coming with 2'' intake valves. We had that car apart and back together and apart so many times.

Last edited by Bernhard; January 13th, 2019 at 02:17 PM.
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Old January 13th, 2019, 02:21 PM
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Originally Posted by ChevyZ06 View Post
Im not sure. The best way to test would be to start with a small valve G, test the numbers, machine for the large valve and test again. Or I guess I could test the heads that I have on a small bore fixture and see how much if any that they loose.
The question is do you think it is possible that the 2" valve could be a advantage with a small bore?
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Old January 13th, 2019, 02:32 PM
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Originally Posted by Bernhard View Post
The question is do you think it is possible that the 2" valve could be a advantage with a small bore?
I would not expect it to make any difference.
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Old January 13th, 2019, 02:36 PM
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Originally Posted by Bernhard View Post
The question is do you think it is possible that the 2" valve could be a advantage with a small bore?
With a larger valve you’ll still have a larger area elsewhere than just against the cyl wall. The wall of the chamber will effect it as well.
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Old January 13th, 2019, 05:28 PM
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One interesting thing the factory did to improve the flow of the factory 400 G block is that they finished the top of the cylinder bores with multiple angles like that of valve seat cuts. They used to angles at the top of the bore.
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Old January 14th, 2019, 04:36 PM
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You need to measure the throat, then select the proper size valve.
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Old January 14th, 2019, 06:12 PM
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head games

IF your heads came from the factory with small valves....
It will not benefit you to buy parts and try to make them BIG VALVE HEADS

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Old January 14th, 2019, 06:37 PM
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Originally Posted by 11971four4two View Post
IF your heads came from the factory with small valves....
It will not benefit you to buy parts and try to make them BIG VALVE HEADS
Why?
I know a few Oldsmobile engine builders that stated that they like to start with the small dia intake valve head then open up the throat with a cutter and cut fresh seats.
This way the valve is not sunken into the head do to previous valve seat cuts.
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Old January 14th, 2019, 06:41 PM
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Originally Posted by VORTECPRO View Post
You need to measure the throat, then select the proper size valve.
So measure the valve throat size to see what valve would work better in the head?
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Old January 15th, 2019, 06:59 AM
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Originally Posted by Bernhard View Post
Why?
I know a few Oldsmobile engine builders that stated that they like to start with the small dia intake valve head then open up the throat with a cutter and cut fresh seats.
This way the valve is not sunken into the head do to previous valve seat cuts.
And that makes sense. I would want to be around 86-87 percent valve to throat diameter on those heads.
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