summarize the v4 crossflow carb bore sizes for me?

[pcrussell50]

could somebody, [jeff maybe], give me a quick rundown on the which years and which bore sizes of carbs were used on the most powerful bubbleback v4's? IOW, the 135/140/and the later, bubbleback 115's.

i don't know where to find that info in one place.

thanks

-peter

[dynobo]

the basic carb of choice for the "bubble back" flows was the 1 5/16. The early flatback 115's also had the 1 5/16 I believe.

[JWTjr.]

1-5/16" = all 140 from 1980 on, 115 from 1985 on

1-3/8" = 1977-79 140

The 1-3/8" versions provide a very slight top end advantage on a lightweight, well set up boat

Tiger

[flabum1017]

The 1 3/8" carbs came on some bubbleback V-4's They provide more flow, weren't too good on the flatbacks. you get better acceleration with the smaller carbs, especially on heavier boats.

[EMDSAPMGR]

JWT has some good information. That carb sizing info is just not readily available anywhere. The 1 3/8" carbs worked well on those early 140's because of the high compression heads and the rubber intake filler blocks. Most later 115 bubble backs did away with the rubber filler blocks and went to low compression bathtub heads. On those later 115 bubble backs, stick with the 1 5/16" carbs.

[pcrussell50]

by the way, i always thought the bubbleback 115's were the equivalent of the 140 power-wise, but got redesignated because of the change from crank rating to prop rating. is that true?

BUT if that is true, AND they got rid of the filler blocks and high compression heads, how did they not lose horsepower in the process, (assuming the later 115's have more or less the same power as the old 140)?

IOW, even though they lowered compression and took out the filler blocks, did they do something else to keep the resulting horsepower for the new 115's more or less the same as the old 140?

-peter

[JWTjr.]

the 1985-up 115 was not the same as the 140 and therefore did not produce the same power. As you noted, the 115 used "softer" heads and did not employ the intake stuffer blocks.

I raced a stock 1984 140 in the 1980s and had it dynoed @ SEI, on their propshaft dyno. It produced 127 hp. Without the good heads and intake filler blocks, the later 115s likely produced between 115 and 120 propshaft horsepower.

John