305-350 swap

[mtnrat]

I have a 1981 18 foot campion with a 305 volvo penta AQ200D and 280B leg. The engine is tired and I want to swap in a new longblock 350. I am looking at the similar 1967-1985 version. Will all of the parts and tin swap over? Also the AQ200D is a 2bbl carb and I would still like to use for the time being the 2bbl manifold and carb that the 305 came with. Will the 350 run fine with the 2bbl or will I need to install a 4bbl right away.
Thanks for your help,

 

[Silvertip]

Re: 305-350 swap

The 305 and 350 of that vintage are dimensionally identical externally so they can be interchanged. Heads on the 305 have smaller valves and combustion chambers. All the other electrics and accessories will bolt on. The two barrel manifold will bolt to the 350. The 2bbl carb will leave some top end performance at the dock, it will work.

 

[mtnrat]

Re: 305-350 swap

Thanks Silvertip.
I just went out and carefull performed a dry and wet compression test.
I warmed up engine for 15 min to full operating temp.
Put throttle at WOT.
Disconnected dist cap lead.
CYL# Dry Wet
1 112 130
3 105 118
5 110 130
7 119 138

2 126 150
4 126 137
6 125 140
8 120 130

The specs are 142-156psi
What do you folks think.
Thankyou.

 

[Bondo]

Re: 305-350 swap

I'd say she's Pretty Tired...........Looks like there's hardly a Ring left in it.......

 

[mtnrat]

Re: 305-350 swap

"The 305 and 350 of that vintage are dimensionally identical externally so they can be interchanged. Heads on the 305 have smaller valves and combustion chambers. All the other electrics and accessories will bolt on. The two barrel manifold will bolt to the 350. The 2bbl carb will leave some top end performance at the dock, it will work." Quote from Silvertip.

I know it will not perform as well as a 4bbl but should I expect a reasonable performance gain going from the 305 to the 350.
Thanks

 

[Bondo]

Re: 305-350 swap

Ayuh.......

 

[mtnrat]

Re: 305-350 swap

Ayuh.......

Yep kind of a dumb question that I already knew the answer to.
Thanks.:$

 

[Bondo]

Re: 305-350 swap

Ayuh.......

d
d

 

[Silvertip]

Re: 305-350 swap

A 15% increase in displacement amounts to roughly 15% increase in torque so one could say with little doubt you'll see a fair increase in performance. Especially hole shot.

 

[rodbolt]

Re: 305-350 swap

actually your number spread does not look bad, do a good decarb then a leakdown test, you may find its not as bad as you think.
I place no faith in the wet test. I have seen it screwd up to many times.

 

[mtnrat]

Re: 305-350 swap

I took the numbers into a good friend of mine who is an exellent independant mechanic and shop owner. Very smart fellow. He also owns and modifies boats. He figures the numbers are not all that bad and wants to check for timing and distributor issues first. Will know on wednesday, and will report back.
Sean