v4 "bubbleback? noob question what is it?

[pcrussell50]

in the v4 crossflow world for a year now, with a 1975 135hp version. but mine has been so trouble free, i have only just now started to read about them. i keep hearing the word bubbleback. is that the dome shaped thing in between the vee of the cylinder banks?

if so, what is special about it? is it something that the 115's don't have or something? IOW, is it specific to the 135-140'?

also, what are "intake stuffers"? someone on another forum listed them as one of the things OMC did to turn turn the 115hp into the 135/140.

thanks. sorry for the noob question. but i'm slowly learning.

-peter

[Paul Vaillancourt]

http://i36.photobucket.com/albums/e18/LittleSnakey/IMG_0995.jpg
Here is one. It is the exhaust tuner some of the v4's have a flat tuner.
This one I am polishing up. The intake stuffers you should have.


in the v4 crossflow world for a year now, with a 1975 135hp version. but mine has been so trouble free, i have only just now started to read about them. i keep hearing the word bubbleback. is that the dome shaped thing in between the vee of the cylinder banks?

if so, what is special about it? is it something that the 115's don't have or something? IOW, is it specific to the 135-140'?

also, what are "intake stuffers"? someone on another forum listed them as one of the things OMC did to turn turn the 115hp into the 135/140.

thanks. sorry for the noob question. but i'm slowly learning.

-peter

[EMDSAPMGR]

The bubbleback does refer to the exhaust cover at the back of the engine. OMC designed this to improve the exhaust breating of the Crossflows, first found on the V4 engines at 135 hp in 1973. The performance engine the year prior (72) was a flatback 125-then the bubble back appeared in 73 rated at 135. Best guess is that the exhaust bubble assembly provided a 10 hp improvement. In 1977 the bubbleback version went to 140 hp. The extra 5 hp was attributed to a machining change to the bottom end in the exhaust web of the block in that timeframe and the intake filler blocks (322684). By the mid to late 80's the engines changed from Crankshaft ratings to Propshaft ratings, the high compression heads were dropped, and the bubble back became a 115. A prop-rated bubble back 115 will still perform well, but it did not have the high compression heads and by that time the intake filler blocks were discontinued.

[pcrussell50]

very complete synopsis, thanks.

-Peter