View Full Version : 18' Engine Build

01-30-2015, 03:19 PM
Ok here is what i have:
350 sbc 5.7 95-00 Gen1 GM block #10243880 came out of a 25' cruiser with mercury "duo prop setup"
We believe it has the roller cam in it?
The heads are #10239906 "L31" Vortec with 64cc chamber, 170cc intake port, 1.94"/1.5" valves.
Looking for a little more HP gain from either upgrading the heads, intake and cam. I really love the rough idle sound and I believe it is MRFixxu2 on You tube having a Comp cam 270h in his 18'.
So gentleman start your engines and give me feed back on possible recommendations. I would love to turn it into a 383 stroker but not sure if I want to go through all the machining but its not off the table.

This will be going into my 1968 18' Donzi.

Thank you in advance!!

01-30-2015, 11:05 PM
You may want to consider stripping off your accy's and selling the long block then buy a 383 long block if that's the route you choose.
Personally I would just install what you have and enjoy. The Vortecs are a roller cam motor. With a decent intake it should be making in the 300 horsepower range.

joseph m. hahnl
01-31-2015, 09:41 AM
An HR270 is a lot of duration for stock compression. You might have to advance the cam to keep cylinder pressure and compression up. Vortec valve springs are good for up to about .500 lift .528 if they are Z28 springs . They are also the best flowing head GM makes not to mention they out flow many aftermarket heads.. You need to decide now if your going to stroke it, because compression ratio is the key driver in cam selection and head material selection. If you go with the 350 I think you'd be better off having the stock heads ported . Also the stock heads most likely have pressed in rocker studs. So those would need to be pulled and the bosses machined and threaded for screw in studs. Those heads worked for full flow would probably cost the same as a set of as cast heads. AFR heads are CNC ported but I think they are not a very robust casting. This link will help identify what you have :biggrin.:http://www.gmpartsdirect.com/performance_parts/store/catalog/Category.jhtmlCATID=624.html

Here's the info from the link. the valve seats can be machined too:kingme:http://www.gmpartsdirect.com/performance_parts/store/catalog/Product.jhtmlPRODID=673&CATID=671.html