High compression head ????

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Modeltmike
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High compression head ????

Post by Modeltmike » Tue Nov 05, 2019 10:36 pm

I’m helping a guy get a car running after 15 years. It starts and runs smooth. It has this after market head. I am assuming it is a higher compression. I think it is a “Giant” brand. When doing a compression test what PSI reading should I get? Thanks
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Scott_Conger
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Re: High compression head ????

Post by Scott_Conger » Tue Nov 05, 2019 10:56 pm

Assuming it is a 5.5:1 head, somewhere under 5.5 x 14.7... so something in the range of 72-75PSI would be quite good

another source puts it at only 4.3:1, which would be something under 4.3 x 14.7, or around 58PSI

hopefully someone who has cc'd one will chime in
Scott Conger

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ewdysar
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Re: High compression head ????

Post by ewdysar » Tue Nov 05, 2019 11:09 pm

According to the Tulsa Club technical page on head design, the Haibe, Giant Power, and Simmons Super Power heads are similar in combustion chamber design and volume. Measured at 255 cc, the resulting compression ratio on an un-milled example would be 4.3:1. http://mtfctulsa.com/Tech/head_design.htm

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Mark Gregush
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Re: High compression head ????

Post by Mark Gregush » Wed Nov 06, 2019 12:44 pm

Not all era replacement head were higher compression, some were just better designs that allowed better firing and combustion.
I know the voices aren't real but damn they have some good ideas! :shock:

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lesvonnordheim
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Re: High compression head ????

Post by lesvonnordheim » Wed Nov 06, 2019 11:39 pm

I have been running a Giant power head on my 13 touring and have been happy on performance. Do not consider it a High compression head.....just a head with better design. The head is cast iron, larger coolant capacity and does not eat out like aluminum heads. Better squish design compared to stock high or low head. The Z and Puris aluminum head have smaller combustion chambers, improved design and provide more compression =better performance. JMHO

Les


Topic author
Modeltmike
Posts: 164
Joined: Sat Mar 09, 2019 5:12 am
First Name: Mike
Last Name: Sleep
* REQUIRED* Type and Year of Model Ts owned: I have 26 & 24 coupe, 25 pickup, and 26 Fordson.
Location: Kansas
MTFCA Number: 31639
MTFCI Number: 31639

Re: High compression head ????

Post by Modeltmike » Thu Nov 07, 2019 5:57 pm

THANKS for all the info. Going to try to give the old car a test drive this weekend. Been sitting for a few decades.


Chris Barker
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Re: High compression head ????

Post by Chris Barker » Sat Nov 09, 2019 11:11 am

I have a Giant Power Head. Before fitting it I measured it and calculated 5.1:1 compression ratio.
It does have the 'squish' areas above the pistons.
It makes a significant improvement to performance.
On most of those hills where in High with the stock '26 head you gradually slow down from 30 to about 22, it holds 30 or close.

Before the Giant, I tried an aluminium head with a higher CR (above 6:1 I think). Not a 'Z' or a Prus, but well made with steel washers counterbored into the top for the bolts. No identifying marks. This also performed well, but I felt it was a bit too much and that something would break sooner or later.
Giant = Goldilocks for me.

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