Release Valves?

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Feb 7, 2021 | 05:02 PM

Tony Tharp

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5th Gear

Joined: Jun 2018

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From: Leander, TX

Release Valves?

Taking TC-88 to 98 ci. 585 cams, 10.5:1 compression. Will I need pressure release valves? (Not using Easy Start cams).

Feb 7, 2021 | 06:27 PM

djl

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From: san antonio

Quote:

Originally Posted by Tony Tharp

Taking TC-88 to 98 ci. 585 cams, 10.5:1 compression. Will I need pressure release valves? (Not using Easy Start cams).

How do you know compression is 10.5? Pistons must be domed; guessing 6cc with a .030" head gasket and .005" deck on both cylinders with 85cc chambers puts static at 10.3, corrected at 9.24 and CCP at 193. If the configuration is close to that, you are on the cusp. IAW, maybe releases not NEEDED but if it were mine, I would add them. Upside is extended starter and battery life; no downside except a few $$ more which considering what has already been spent is nothing.

Feb 7, 2021 | 07:20 PM

Tony Tharp

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5th Gear

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From: Leander, TX

Thanks for the good response. Your on the same page as the tech doing the work. I was looking for a second opinion so I feel better about it.

Feb 7, 2021 | 09:01 PM

Clammy

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Joined: Nov 2004

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From: Ottawa, CANADA

Similar to my 98ci build. Go with the compression releases. Your starter and battery will thank you.

Cheers!

Feb 7, 2021 | 09:20 PM

Arseclown

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Joined: Jun 2014

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From: Batcave

Quote:

Originally Posted by Tony Tharp

Taking TC-88 to 98 ci. 585 cams, 10.5:1 compression. Will I need pressure release valves? (Not using Easy Start cams).

Why not use the easy start version of the 585 cam? Work great and a no brainer for me.

Feb 7, 2021 | 11:09 PM

Tony Tharp

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5th Gear

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From: Leander, TX

The tech doing the work doesn't trust 'em. He has used 'em with no problems reported back, but he said he has heard of them failing.

Feb 8, 2021 | 05:37 AM

eighteight

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Joined: Oct 2019

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From: OH

Similar build here, added MCR`s 'just in case" as mentioned above
Glad that I did

Can`t recall reading about any EZ start "failures" here.
But this and the anecdotal report from your tech are simply that.

Enjoy your build

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Feb 8, 2021 | 05:54 AM

Hillsidecycle.com

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Releases will be needed.
Scott

Feb 8, 2021 | 07:41 AM

#10

98hotrodfatboy

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Joined: Mar 2010

Posts: 21,115

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From: Poolville

I recently upped my compression on my 103" and the comp is right around 10.2 with ccp of 200 psi. The heads I put on are older style that were not machined for ACR's but the porter did install MCR's. If I try to start the bike without using them it will start very hard and did kick back.. With them, it fires right up no issues.. All of this is not good for the starting system.. Do the MCR's..