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AQ125A Performance Upgrades

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dr_velocity

Member
"I've read that the AQ125A

"I've read that the AQ125A and AQ140A share the same head and block. The only differences are that the AQ140A runs a different cam, dual carb intake, and an oil cooler.

However, when reading the specs out of the Volvo manuals, I see this:

AQ125A: 107 hp @ 4800 RPM
AQ140A: 123 hp @ 5500 RPM

Why the inceased rev ceiling? Is it due to a hotter cam or does the engine have strengthened innards?

If I were to swap the cams, would it be absolutely necessary to obtain the dual carb intake manifold (with carbs)? Since the Solex 44PAI carb is only adjustable for idle speed and idle air, I can't imagine it'd be able to richen up the fuel delivery for the hotter cam?

Is the oil cooler really necessary? I assume it wouldn't necessarily have to be a Volvo specific oil cooler?

Has anyone done this? Approximately how much did it run you? Is it really worth the theoretical 16 hp increase?"
 
"My guess is that with one car

"My guess is that with one carb the engine would run lean. Also, the AQ125 has an A cam and the AQ140 a V cam. The oil cooler was probably added to dissipate the additional heat generated by the higher HP.

If I was to try to improve performance without getting too complicated, I would try a Weber carb and a higher oil grade. On my AQ140 I was running 15W-40. Here is a link to the Weber marine kits. One of the forum members (Javier Cubero) installed one and reported good results.

http://www.redlineweber.com/html/application_guide/mercury_cruiser_6_4_1_perform anc.htm

http://www.redlineweber.com/html/kits/k861.htm"
 
"Unfortunately, the Webber car

"Unfortunately, the Webber carb is around $700. If I could find the cam, manifold, and carbs from an AQ140A for less, I think it may achieve the same or better results."
 
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