351W heads on 289
11-15-2014, 11:02 AM
#1
2nd Gear Member
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Join Date: Oct 2012
Location: Puerto Rico
Posts: 204
351W heads on 289
Folks,
This is a purely "academic question", since I no longer have the car/engine. Sold it 30 years ago! However...I have long been curious about one aspect of it. You see...the engine was a stock-bore '66 289 block and lower assembly, with '69 351W heads. Heads were flat-milled .040 AND angle-milled .062. I was running TRW (remember them?!) 12.5:1 forged dome pistons. To this day...I have NO idea what my actual comp. ratio was. It must have been pretty high, but never had any detonation issues, and ran the engine for over 3 yrs on premium pump gas (don't recall what octane levels were in Tennessee in 1980). The long duration cam (.500 lift; 300 degrees advertised duration) probably helped. Also...I did have some valvetrain issues (broken rocker studs) with this setup. Back then, I didn't know to check for proper pushrod length, so was probably running the wrong pushrods, too.
So...just purely for curiosity's sake...what was the likely "true" comp. ratio of this setup, and with all that head milling, how much would that have altered pushrod and rocker arm geometry?
This is a purely "academic question", since I no longer have the car/engine. Sold it 30 years ago! However...I have long been curious about one aspect of it. You see...the engine was a stock-bore '66 289 block and lower assembly, with '69 351W heads. Heads were flat-milled .040 AND angle-milled .062. I was running TRW (remember them?!) 12.5:1 forged dome pistons. To this day...I have NO idea what my actual comp. ratio was. It must have been pretty high, but never had any detonation issues, and ran the engine for over 3 yrs on premium pump gas (don't recall what octane levels were in Tennessee in 1980). The long duration cam (.500 lift; 300 degrees advertised duration) probably helped. Also...I did have some valvetrain issues (broken rocker studs) with this setup. Back then, I didn't know to check for proper pushrod length, so was probably running the wrong pushrods, too.
So...just purely for curiosity's sake...what was the likely "true" comp. ratio of this setup, and with all that head milling, how much would that have altered pushrod and rocker arm geometry?
11-15-2014, 01:06 PM
#2
6th Gear Member
Join Date: Apr 2007
Location: California
Posts: 10,468
A lot less than 12.5:1 most likely, with iron heads it would have probably detonated a lot, even on premium.
And milling heads can effect rocker geometry if you take enough off. It'll be more of an issue with a solid setup, and less issue with hydraulic if it still falls inside the adjustment range of the plunger.
And milling heads can effect rocker geometry if you take enough off. It'll be more of an issue with a solid setup, and less issue with hydraulic if it still falls inside the adjustment range of the plunger.
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