Engine question on my 98 Glastron gs205

[38special]

I'm not sure if this is the right forum to ask but here i go. I bought my 98 gs205 with out an engine and am currently looking for one. Would a 400 small block work in place of the 305 vortec that was in the boat or is the flywheel differance going to kill that idea? My drive unit is an sx cobra.

 

[etracer68]

Re: Engine question on my 98 Glastron gs205

The 305 is an internaly balanced crank, and I think some, or maybe all 400s were externaly balanced. You cant just swich flywheels, unless there balanced with the crank. We used alot of 400s in racing, and had them all internaly balanced.

 

[38special]

Re: Engine question on my 98 Glastron gs205

I am figuring on the cost of a balance job. The boat came with the flywheel from the 305 but the flywheels used on the vortec are different than say the flywheels used on the 400 cid engine aren't they? I guess that is my question, is there a flywheel for the 400 that will let me use the 400 to replace the 305 vortec and can i use the same drive coupler from the 305 to connect the 400 to the sx cobra?

 

[etracer68]

Re: Engine question on my 98 Glastron gs205

I would say that if you get the 400 internaly balanced, you should be able to use any balanced flywheel, and damper. The crank will have to come out, to be balanced, then new rod and main bearings. We, on race motors, would also have the rods balanced, and the pistons. But of course we didnt used stock parts, only forged steel H beam rods, forged pistons, and forged steel cranks.

 

[etracer68]

Re: Engine question on my 98 Glastron gs205

You should be able to use the 305 flywheel as long as its balanced. I dont know if there is a differance in marine flywheels. The bolt pattern should be the same on all small block cranks.

 

[superpop]

Re: Engine question on my 98 Glastron gs205

Why not just drop in a fresh 350. The SX drive is only designed to handle around 300HP BTW, so if you are building up a HP monster out of the 400 you will probably break something if the HP goes much over 300. Marine parts are also much easier and cheaper to find for the 350. Not sure on the manifolds and risers as I am not that familiar with a 400 block. And nothing against a Glastron but that model of boat is not designed to go 60-70 MPH if that is what you are hoping to get out of it, I would worry about structural integrity and handling.

 

[gbeltran]

Re: Engine question on my 98 Glastron gs205

The bolt pattern on the crank between those two engines will be different. The 305 has a 1 piece rear main seal and the flange is smaller than the 400 crank which would have come with a 2 piece rear seal. I don't know if you can get a coupler for the older flange. If you want more cubes a late model 350 is a no brainer swap, or build a stroker engine, you can get the stroker cranks forthe one piece seal engines.

(the change from the 2 piece to the 1 piece rear main took place in the mid 80's)

 

[Don S]

Re: Engine question on my 98 Glastron gs205

Going to a 350 long block will allow you to use all the marine accessories bolted on to your 305, very easy swap. Then if you want faster planing time, faster top end, and more control, install a DP lower unit to your upper drive.
The, you will have a wicked 20 ft boat.

 

[38special]

Re: Engine question on my 98 Glastron gs205

Thanks for the reply's. I've seen a lot of 400 engines lately for sale and found out you can use the vortec heads on them also. I was just hoping there was an affordable flywheel drive coupler combo. A lot of troque to be found in that engine minus a lot of high dollar parts.

 

[Don S]

Re: Engine question on my 98 Glastron gs205

I was just hoping there was an affordable flywheel drive coupler combo

The 400 was never uses in a marine application. It just didn't work very well. But have at it, you may be able to reinvent the wheel.
There are no marine parts for a 400.

 

[38special]

Re: Engine question on my 98 Glastron gs205

The 400 was never uses in a marine application. It just didn't work very well. But have at it, you may be able to reinvent the wheel.
There are no marine parts for a 400.

I'll pass on the idea. A 350 will be Ok. I do like your DP idea but the only way i'll ever be able to afford that is if someone has one for sale that does not know new or used price's on one. Lol