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9 port red six heads - modified open and closed chamber

Started by _Hot_179_ , Jul 09 2019 01:17 PM

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7 replies to this topic

#1 _Hot_179_

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Posted 09 July 2019 - 01:17 PM

Hi,

I currently have a modified open chamber head on 202. Still on car and specs that I know are as follows (see pictures from when I last had it off - no port shots sorry)

- had a fair bit milled off it flush with finger prints down to 47.5
- fair bit of port work in that the ports are larger than a standard gasket.
- looks like some chamber work?
- it had been flowed but I can’t recall any detail.
- screw in studs
- large valves think In was 1.7ish from memory

I have another YT small chamber which I’m looking at getting cleaned up and CCd. I want to lose about 5 CC on my current set up so want about 43 CC new head chamber if possible.

I think this spare head I have will create better squish, more compression etc. I only run 226@50 hydraulic and 457 lift. Might change to solid 231@50 458-480 lift. Triple 1 3/4 SU with basic extractors and 2.5 inch collector.

Valves on spare head are 1.685 and 1.438. Not much port work looks like basic YT. Was going to get screw in studs and some milking and tidying up.

Am I on the right track swapping to the spare head? In hindsight maybe the current head was intended for some type of forced induction given port work and larger chamber volume?

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#2 _Hot_179_

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Posted 09 July 2019 - 01:19 PM

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#3 _Hot_179_

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Posted 09 July 2019 - 01:33 PM

Just to be clear - it’s just a street car/engine. Needs to be versatile and good torque down low etc. Most driving is 2000-4000rpm and I really only use ~6000ish when having a bit of fun. Manual trans. 3.36/13 inch wheels.

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#4 _Drag lc_

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Posted 09 July 2019 - 05:25 PM

have you worked out the actual comp ratio?

if it were me id run the closed chamber one.

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#5 _Hot_179_

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Posted 09 July 2019 - 06:53 PM

Yes I’ve looked at CR and want to lose 5cc, so that will be a major benefit of head change.

Other than CR though how do they compare?

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#6 I'm a Red Motor fiend

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Name:Adam
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Posted 10 July 2019 - 06:30 AM

Are you 100% on your comp ratio? What did your calculations yield?
If your slugs are at zero deck and you put a head with 43cc chambers on with a mild cam like yours, you will be in all sorts.

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#7 _Hot_179_

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Posted 10 July 2019 - 08:16 AM

Thank you. Good question on comp ratio. My calcs are estimated as followed and to be confirmed after current head removal:

Slugs ~6cc dish
Deck 0.040 down
Standard composite gasket about .040 - 0.060
0.040 oversize bore

That puts my comp way down near 9.0 on the calcs even with a 47.5cc head (part of the reason I cannot understand how Holden ever got 9.4 with a 54cc head).

I want to get close to 10.0:1 to suit the street cam and get advance to a suitable level. Shane about deck and piston type but I’m on a budget!

Do I need to be worried about the basic level of porting? I’ll get photos of my old head ports to compare when I remove it - it’s prob way over the top for the application.