more 305 to 350 questions

[BigSteve1967]

i have a few questions...i would like to swap the motor from my 95 taho to my '88 celebrity 210v with the 305 200hp motor 1 piece rear seal and 2 bbl carb thunderbolt ignition in it the motor is basically gone. now what i was wondering is i have heard time and time again about marine cams and cams in trucks are somewhat similar i have a 1995 chevy tahoe 4wd with the 350 engine in it that the truck itself is just dying around a very very solid motor would i be able to take the motor from the truck and put that in the boat? what would i have to swap from the 305 to the 350? i would guess intake manifold and carb but could i leave the distributor in it seeing as they are both hei ignitions? any help would be greatly appreciated i do understand fuel system is marine specific but would i be able to take the components off the dead 305 and put them on the 350? would i be able to swap the distributor from the engines also any help would be great thanks

thanks

Steve

 

[lmannyr]

Re: more 305 to 350 questions

Steve,

There are some parts that must be marine specific (I'm assuming you have a stock mil in the boat). For example:

Starter
Alternator
Carb Flame Arestor
Exhaust Manifolds/risers
Bronze Freeze Plugs
Cooling System Parts
Water/Fuel Separator (if equiped)
Ignition system (unless you flash the pcm from the tahoe for no o2 sensor)
Intake (If the tahoe had fuel injection and your not gonna flash the pcm)
You'll need the wiring harness for the pcm (Or custom wire it) if you keep the tahoe intake/ingnition/FI.

But in short, yes you can swap the long block in. It's not as bad as it sounds.:redface:

Good luck and post back with updates!!

 

[Mjust]

Re: more 305 to 350 questions

Go MSD Marine Ignition Model 6AL for this swap. Also, You want a high rise intake manifold along with a 750CFM Carb. You could go 600CFM but if your looking for more HP you want the 750CFM. I would also go with a better cam than the stock. The stock will work but remember that is a truck engine not a 350 out of a camaro...big difference in cam and heads.

 

[RCSConstruction]

Re: more 305 to 350 questions

Plan on putting on new head gaskets. You will want a stainless steel fire ring type head gasket. It may already have one, but make dang sure.
Be carefull with the cam. I wouldn't go any higher than a edelbrock performer cam (not performer RPM) or equivalent.
The 750 cfm carb is going to big for a 200-220 hp motor (unless you tune the h@ll out it) Stick with a 500-600 cfm 4bbl.

 

[180shabah]

Re: more 305 to 350 questions

Ditto, no need for a 750

 

[Bondo]

Re: more 305 to 350 questions

Basically,........

Strip the Tahoe motor down to the Long Block configuration,+ then install Everythingelse back onto it from the Dead 305.........

If you want to go to a 4bbl. Carb,..... I'd go with the Edelbrock Performer series...........
And,.......
I'd stick with the Merc. T-Bolt ignition..........

 

[drivehard]

Re: more 305 to 350 questions

I just did a similar swap. I forgot to drain my 305 block (crack), but everything on the motor was in great shape. I bought a new 355 block at the local race shop, new pistons, and a new bearing set, and had some fun. I used everything from the 305 on the 350 (rods, crank, heads, starter, distributor, everything) except for an upgrade to Edelbrock performer intake and 4 bbl. Edelbrock marine carb. I do now have to run at least midgrade fuel, as I have about 10:1 compression, and the 305 ignition advance is a bit faster than the 350 advance. Never heard her knock, but I like to play it safe.

Be sure to get marine head gaskets.

 

[MikDee]

Re: more 305 to 350 questions

I just did a similar swap. I forgot to drain my 305 block (crack), but everything on the motor was in great shape. I bought a new 355 block at the local race shop, new pistons, and a new bearing set, and had some fun. I used everything from the 305 on the 350 (rods, crank, heads, starter, distributor, everything) except for an upgrade to Edelbrock performer intake and 4 bbl. Edelbrock marine carb. I do now have to run at least midgrade fuel, as I have about 10:1 compression, and the 305 ignition advance is a bit faster than the 350 advance. Never heard her knock, but I like to play it safe.

Be sure to get marine head gaskets.

Sounds cool drivehard, seems like you did it right, Good Luck to ya!

 

[BigSteve1967]

Re: more 305 to 350 questions

guys thank you very much for the help i was hoping it would be pretty simple as swapping the intake and water pump, as for the distributor would you suggest putting the one from the 305 into the 350 or just leaving the 350 one in? as for the head gaskets yes i did plan on changing them to very good gaskets as it only takes another few minutes to do that after the motor is out plus i have to swap the intake anyways. my other question is why couldnt i just use the 2 bbl carb off the 305? im really not looking for speed boat i basically just want a nice family cruiser, i figure with the 305 in her she got up on plane nicely and cruised at 3300-3500 rpms nicely and at wot 4300rpm she topped at about 36-37 which is exactly what we want(4 kids and 2 of them under 2 we dont need to go that fast lol)i would guess the 350 with the 2bbl should perform similar and not beat up the pocket for gas lol any more ideas would be great thanks

Steve

PS i love this place lol

 

[RCSConstruction]

Re: more 305 to 350 questions

I used my 305 2bbl on my 350. Shouldn't be a problem really. Just watch for any lean conditions.

 

[BigSteve1967]

Re: more 305 to 350 questions

oh just remembered a question, how do you guys feel about those exhaust bellows on the outdrive that are connected to the transom side and have a larger opening at the other end so the outdrive side slips into it when trimmed down? i heard the reason for them is for backpressure issues with bigger motors? the reason i ask is i do know that backpressure is hell on head gaskets (had a few early 90 thunderbird supercoupes where the backpressure from a restricted factory exhaust ate head gaskets we use to quickly open up with larger exhausts and they were great after that) just a thought thanks

Steve

 

[mtnrat]

Re: more 305 to 350 questions

I used the distributor off my 305. You would need a marine distributor anyway, so cannot use the one from the tahoe. There is no spark suppression in the automobile version. Fuel use was the same with 4 bbl, so that is up to you.

 

[180shabah]

Re: more 305 to 350 questions

Steve,

If you are already replacing your drive bellows then go ahead and substitute the exhaust tube. You will not see any big gains in power or major reductions in back pressure. However, you will protect your sanity, the exhaust bellows are a PITA to install, the tube isn't.