straight up timing set and engine emissions?
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Junior User
Joined: Sep 2009
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straight up timing set and engine emissions?
About to do timing set, water pump and main seals on my 84 F250, 460 4bbl. It will retain the stock cam, and traditional Holly. I'm not after a monster truck, just healthy enough for hunting, towing & mild wheeling. I've read a few posts here recommending
Cloyes Gear 9-1122 - Cloyes Street True Roller Timing Sets - Overview - SummitRacing.com
Also referred to as "Straight up" timing sets. Doing this mod has been suggested to provide increase in horsepower due to taking away valve timing (retarding it). The hp increase comes from making the 'engine as an air pump' work more efficiently, and can be measured by higher intake manifold vacuum and dyno test, etc.
But is there a significant penalty of increase in emissions? I'm inclined to think both hydrocarbons and CO2 would go up a little, but if engine is working more efficiently, those parameters won't rise beyond correctable.. In other words, I think I can temporarily alter the ignition timing and fuel/air ratio to pass emissions without appearing as too much of a hack. eg Not make it a lean miss.. And then go back to a more healthy profile afterwards? Your thoughts?
Cloyes Gear 9-1122 - Cloyes Street True Roller Timing Sets - Overview - SummitRacing.com
Also referred to as "Straight up" timing sets. Doing this mod has been suggested to provide increase in horsepower due to taking away valve timing (retarding it). The hp increase comes from making the 'engine as an air pump' work more efficiently, and can be measured by higher intake manifold vacuum and dyno test, etc.
But is there a significant penalty of increase in emissions? I'm inclined to think both hydrocarbons and CO2 would go up a little, but if engine is working more efficiently, those parameters won't rise beyond correctable.. In other words, I think I can temporarily alter the ignition timing and fuel/air ratio to pass emissions without appearing as too much of a hack. eg Not make it a lean miss.. And then go back to a more healthy profile afterwards? Your thoughts?
pedant
Joined: Jan 2008
Posts: 23,576
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From: EXTREME southwest CT
I've had one of these timing sets in my truck for at least 15 years and have never had an issue passing the emissions test.
I have never needed to adjust fuel mixture or ignition timing to pass.
The Cloyes set has three keyways, you want the one with the dot centered on the tooth.
IIRC the retarded timing was done mostly to reduce NOX, though I can see how opening the exhaust valve later would allow for more complete combustion.
My EGR and AIR pumps are still fully functional because of required testing.
I have never needed to adjust fuel mixture or ignition timing to pass.
The Cloyes set has three keyways, you want the one with the dot centered on the tooth.
IIRC the retarded timing was done mostly to reduce NOX, though I can see how opening the exhaust valve later would allow for more complete combustion.
My EGR and AIR pumps are still fully functional because of required testing.
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Junior User
Joined: Sep 2009
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Thanks for feedback. Dave, your point is well taken, the comment helped me see how I could have asked my question better. I was wrong to assume that to pass emissions, the timing had to be monkeyed with when using the straight up set. Jim, thanks, that was exactly what I needed to know. Thanks, alex
