Hi all.

This is my first post. Ive been read the forums and theres alot of good knowledge here. So here's my plan I have a 1989 rochester q-jet carbed gm 305 HO. The motor is actually in a boat. I plan on ditching the stock iron heads and wimpy cam. The motor is hydraulic flat tappet. I'd like to go hydraulic roller. the cam I've selected is comp cams hydraulic roller XM270HR which is available in a retrofit kit. For heads I'm thinking a set of assembled trick flow super 23 175's. Would there be any interference with this setup? How do I figure out what length of pushrods to get? Also with the roller cam is there a good timing chain cover that you guys would recommend with a cam button to adjust cam play.

 

You might want to do a search on how to retro fit a non-roller block to accept a roller cam. You can't just put it in there, there are modifications needed in the lifter valley and oil passage modifications.

 

A quick question here , Captain Baretta ,

I have run into a situation before where a car engine cam couldn't go into a boat engine cause the crankshaft's rotation was opposite of the car engine , and it is the grind of the cam that determines Marine or Automotive proper rotation .

Does your Boat's crankshaft rotate in the same direction as a car engine's does ? If so , your golden . If not , best to find out now BEFORE ya buy a cam that you may not be able to use .

 

I built a 305 with these heads ... Thread is "LO3 rebuild hp estimates" still trying to get it tuned .. Wish I woulda went one step bigger in the cams duration tho

 

Yeah it's a single engined boat n rotates the same as a car engine. The cam is a marine grind so it should be ok. Biggest thing in a boat is not going too far in duration with stock exhaust to prevent water reversion back into the engine since the boat spits out the cooling water through the exhaust with a raw water cooled engine. I'm looking to make ~300 hp at the flywheel. 1991sleeper did you find out what your new motor puts out? How were the trick flow heads?

 

Just say no.

You can build or buy a better performing 350 for the same or less money.

 

When it comes down to it u will spend more money on a 350hp 305 than u will spend on a 350-400hp 350 ..... N yes I'm very pleased with my motor but it coulda been better for cheaper I believe ... .... The heads are awesome tho and can be used on a 350 also .. I hope to have track times in March when tracks open back up no dyno time here .....

 

If memory serves, that Merc 305 had right at 200 HP brand-new.

I doubt you'll be able to get it ANYWHERE NEAR 300, while keeping the RPM range the same. You'd have to increase the torque by 50% at the same RPM, meaning, burn 50% more fuel, or extract 50% more energy from the same fuel, or some combination of the above. Ain't happenin. 15%, maybe, if you're willing to buy better fuel than the usual, so you can run higher compression; 50%, no way.

You'll find in fact that the exhaust is the main limit to the power output. Might want to look at some better manifolds than the stock ones. I'd suggest GLM. http://www.glmmarine.com/ Might give you a couple hundred more RPM at the top and more torque as well.

 

I was hoping to keep what I have to use as a platform instead of going out n buying a whole new motor. I was also going buy this article: http://www.superchevy.com/technical/...d/viewall.html . My stock motor was a Volvo penta aq231a which is rated at 229 hp so it's similar to the build these guys did? I'm also looking into a set of marine power aluminum performance manifolds n risers

 

For the price of retro-fitting a roller cam into a non-roller block, it definetly isn't worth it, especially on a 305