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Old 11-03-2006, 07:39 PM
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sbc cylinder heads #492

Anyone have any information on these heads as to flow or low end power? Also any info. as to chamber volume?

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Old 11-03-2006, 07:47 PM
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"492" – 3991492. Good performance head. They were found on 1970 LT-1 engines. They had 2.02/1.60" valves, 64CC combustion chambers, DO have accessory holes, intake port volume should be 161CC's, exhaust port volume should be 62CC's. These heads have double hump casting marks. This particular casting head was also available as an "over the counter" head from GM in straight or angle plug configurations
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Old 11-03-2006, 07:52 PM
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Is it critical to work the ports on these heads?
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Old 11-03-2006, 07:59 PM
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Huh?

I suspect there are thousands of these heads "as cast" working hard right now.

I further suspect that there are several hundreds of sets in landfills because someone "did a little porting work" on them.
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Old 11-03-2006, 08:01 PM
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Understand that! Thanks for the info.
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Old 11-04-2006, 06:54 AM
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You power rewards would be far better off from aftermarket heads then a 30 year old design. Not to say in there day they were not a good head. Unless you are restoring a car that use that head.
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Old 11-04-2006, 06:59 AM
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There are so many out there-which for the money would be the best? i looked at Sportsman II heads but I don't know which is considered the better ones.
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Old 11-04-2006, 07:03 AM
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Choices in cast iron World Sportsman II Dart, RHS and EQ Lighting.
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Old 11-04-2006, 07:18 AM
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Thanks--I've been looking around to see who had the best deal on the Sportsman heads. Probably 64 cc with flat top pistons a good combination??
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Old 11-04-2006, 12:23 PM
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You never have mentioned your engine size, but assuming you have a 350, 64 cc heads with flat-tops (7 cc's of valve relief) will result in a static compression ratio of about 10.2:1, too high for iron heads on pump gas. Let me re-phrase that.....REALISTICALLY too high. Yes, you can run 10.2 on pump gas with iron heads if you build in a very tight squish of maybe 0.035", but octane at the pump is probably not going to improve. I've heard rumors that 87 will be the limit in California in a few years and the rest of the country will probably follow. The other thing is, you'll have to run a longer cam with the 10.2 than you would with a more realistic 9.0 motor. Now, I don't know what you're looking for in a motor, but if you want to run a stock converter and have good vacuum for brakes, etc., then stay around 9.0:1. If you want to operate with a looser converter and make power higher in the rpm range, then go for the higher compression. You see, here's the thing. You choose a cam based on your static compression ratio. The intake closing point on the cam has to match the c.r. in order for the motor to operate properly. So, make a decision and we'll try to help you further. By the way, with 64 cc heads, you'll need a dished piston such as the Keith Black KB142 (18 cc dish) to get you to 9.1:1. I like the KB pistons because they provide a perfectly flat plateau on the crown that matches up nicely with the flat underside of the head to provide a really nice squish pad.
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Old 11-04-2006, 12:50 PM
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The block is a stock 350 and probably will be bored to .030 over, have not gotten it apart yet. Cam I want to run is the 327/350 hdry. 222/222-adv dur 290/290--lift 447/447--degree lobe cntr.110/118. The cam is suppose to be a match to the old 350ci/350 hp that was used around 69/70. I want the most efficient head for the combination I can. I really appreciate the help.
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Old 11-04-2006, 01:24 PM
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Vortecs flow more out of the box at 170cc than the World flows with 170cc. Same velocity, more flow, half the price. CHP magazine tested several heads and this is what they had to say about the World iron SR torquer:
Quote:
This head is very similar to the 882 head tested earlier. The valves are larger and the flow numbers at 0.400-inch lift are almost identical
The 882 head is a 151 cc intake runner, so basically they are comparing a World products head to a small port smog head from the 70s. I'm not a big fan of World heads. They are beefy for porting, but they flow almost identically below .500" as a 151cc smog head. Not wise in my opinion.

Even the Dart Iron Eagle needs 174cc and 2.02 valves just to produce 89% of the flow that Vortecs make at 170cc with 1.96 valves.

You're talking about low RPM performance... Vortecs are the only choice as far as I'm concerned. You want intake velocity, which means smaller intake ports like 170-180. Since you can get plenty of great mid-lift and peak flow out of a 170cc intake runner, why would you go bigger and sacrifice flow when you have a production head that makes more sense?

Compare the heads at this site http://www.chevyhiperformance.com/te...se/index4.html

Jegs sells assembled Vortecs for $269 each.
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Old 11-04-2006, 02:13 PM
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Posted by dmx6:
"I want the most efficient head for the combination I can."

It all comes down to money. How much do you want to spend. I agree with curtis73 about the Vortecs, they are fantastic heads, but $269 each is not the end of the story. You have to use a Vortec-specific intake manifold and also have to make some provision for aligning the rocker over the valve stem, either with rail rockers or guide plates. The good news is that they are compatable with the cam lift you have chosen.

Speaking of cam, you will want to build the motor at somewhere between 9.5 and 10.75 to match up with that 327/350 cam you want to use. If I were doing it, I'd use Keith Black KB106 pistons. With a 64 cc chamber, they result in a c.r. of 10.2:1. Then I'd figure in a squish of 0.035" to 0.040". For instance, if you zero deck the pistons, you would want to use a Fel-Pro 1010 head gasket with a compressed thickness of 0.039". You can juggle the head gasket thickness and the deck height to arrive at the proper squish. In other words, if the deck height was 0.025", you could use a steel shim gasket of 0.015" thickness to arrive at the proper squish.
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Old 11-04-2006, 03:07 PM
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yes, the problem is I want to stay with stock intake and stock non-centered valve covers. So I've got to use stock style heads either true factory or aftermarket stock like. I don't fully understand the .035-.040 clearance you mentioned--will the block have to be cut? Thanks-
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Old 11-04-2006, 03:51 PM
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0.035" to 0.040" is the recommended squish. It's the clearance between the crown of the piston and the underside of the cylinder head at the top dead center position of the piston. This is done to maximize the efficiency of the motor and make it octane tolerant and much less prone to detonation. What happens is that as the piston nears top dead center, it squeezes out the mixture which is between the piston crown and the underside of the head and "blasts" it towards the spark plug, thus minimizing "dead space" and homogenizing the mixture for a more efficient burning. It would not surprise me if you found you could run without detonation (ping) on 87 octane fuel at 10.2:1 static c.r. with a tight squish and the cam you want to use.

I'm not sure of the validity of this story, but this is the way it was told to me:
Ford Motor Co. had a go-around with squish (or lack thereof) in the early 70's with the 400M. The motor was designed as an open chamber motor (no squish) and they had to reduce the static compression ratio down to 7.8:1 before they got detonation under control. There was no high octane fuel available at the pumps during that period of time due to the Arab Oil Embargo.

Whether you will need to deck the block or not is dependent on the deck height (measurement from the piston crown to the block surface at top dead center). You may have to mock the short block up (less rings) and measure it on four corners (I do this on every motor I build) to see where you are.

Here is the explanation again:
For instance, if you zero deck the pistons, you would want to use a Fel-Pro 1010 head gasket with a compressed thickness of 0.039". You can juggle the head gasket thickness and the deck height to arrive at the proper squish. In other words, if the deck height was 0.025", you could use a steel shim gasket of 0.015" thickness to arrive at the proper squish.

Last edited by techinspector1; 11-04-2006 at 03:57 PM.
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