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View Full Version : CRAIG LIST BUILD UP 350 vortec Hi performance boat motor in a 98 Z71



TexusTim
11-23-2011, 04:45 AM
Hi, first have to say this site has some very well informed members, I am no expert but have been fiddling around with different versions of the GM 350 since the last carburated version truck to my 98.this is my first time going all the way thru an all vortec motor and may ask some stupid questions and I searched this morning before comming up with this list of qustions..and it may be complicated (at least to me) cuz with this build up I am forced to do it on the cheap as I have been laid off for somtime. so here goes.
1- Vehicle 98 Z71 Silverado short bed push button 4X4 350 vortec original stock truck only upgrade airaid fresh air filter kit.stock wheels and tire size. 254.000 m.
2- Donor rolling assymbly 1999 Tige ski boat 20hr. on boat. block cracked on the outside while sitting this past winter and ran fine but blew water out the side. this block looks brand new the pistons have no carbon at all and no ridge on the cylinders, hyperutectic pistons, and nodular crank PM rods.I dont know what the engine assymbly would be for this boat but is is still together as a short block but the block is not salvagable. cost 100.00 this man replaced it with a gm roller crate motor. I will get back to that later.
3- Donor 350 vortec bare block..came out of a one ton van either 1999 or 2000 4 - bolt main standard the owner has had it for some time were he works. it's so standard and fresh that a vat and block hone is all it needs.. found him on craigs list and he is a builder at a local machine shop and is starting his own on the side, got a clean little shop and very helplfull..as any start up he is trying to build a good reputation and is the top builder were he works.. so lucky timming to come across this guy and the block at the same time.
4- heads...ok here is were I need your help I came across another boat motor out of a newer bayliner the motors like new but crakced block again but it's a 305 vortec and the heads(059) look brand new no need for even a valve job or resurface and the rolling assymbly is like new as well.........so should I just use the "new 305 heads" or get a rebuilt 350 set ? the engine builder has a set of 906 that came off the same van and as a secondary stupid question if I use the 305 heads I know I could go with a thicker head gasget to reduce the compression but what happens when the 350 gasget overlaps the combustion chamber ?
So as this goes on I know I will have more questions and am keeping a running cost on this craigs list build...it's amazing whats out there if you search long enough and due to budget restraints,,,,Im getting the block vated, honed,freeze plugs, and lower assy. installed by my new engine builder for another 50 so right now here is my cost so far and all off craigs list and with the two boat short blocks each owner threw in all kinds of new stuff left over from there engine replacment and all the 305 stuff was free just to haul off his cracked block.
1- 100.00- vortec 350 boat short block (cracked),with new timming set and gm roller cam and rocker assy and complet new rolling assy.
2- 150.00-vortec 880 4-bolt bare block standard bore.
3- 50.00 block service and short block assy.
4- 00000 new 305 heads and rolling assy incl. new cam,timming set lifters,push rods and new GM oil pump.
5- 00000 dead 305 vortec out of a driveway,cracked block,cracked heads,destroyed crank and rods. but was complete and had all the tin and ass.including balancerand new flexplate. also new felpro valve cover gasgets,oil pan, intake set and the guy bought but never used...a lot of dirty work here but all the stuff paid off for that.
6- 300.00 TOTAL- so far and I need a head gasget set and decide on the heads but Im thinking I can trade what I have left or sell for what I need.
thanks in advance for any advice here or even if you think any part of what I'm doing is not correct.

Koots
11-23-2011, 06:07 AM
I'd stick with the 350 heads, I'm not sure abut the vortec motors, but the 305 heads tend to be quite smothering in comparison.

Find whatever block is in the best condition, find the best rotating assembly and have the block machined for the whole setup. If there is a competent engine/machine shop around, having the block machined isn't too costly depending on what you want done. It's gonna cost some bucks but then you know the bores are straight and true and that everything will match up at a level that can only be dreamed of in a backyard.

I'm saying this because it's all out and you've got to pull em all apart anyway. I blew the 700r4 in my K5, got a perfectly good TH350 to swap in and ended up pulling it all apart and spending nearly $1200 on parts because I like to be very thorough when I have things taken apart.

winfred
11-24-2011, 04:38 PM
not only are the chambers on 305s smaller 58cc instead of 64cc but the valves are smaller too, intakes are 1.84 instead of 1.92 if i remember correctly but i can't remember the exhaust sizes, i can get a set of free to me 305 vortecs but they are not really a upgrade for my tbi 350 and just recently looked at the differences

Fast305
11-24-2011, 07:12 PM
not only are the chambers on 305s smaller 58cc instead of 64cc but the valves are smaller too, intakes are 1.84 instead of 1.92 if i remember correctly but i can't remember the exhaust sizes, i can get a set of free to me 305 vortecs but they are not really a upgrade for my tbi 350 and just recently looked at the differences

If the 305 vortec heads are 059 castings, grab them up and run them. Would make a world of difference in flow and compression over a 305 or 350 TBI head. Stock for stock, even with the smaller chamber and smaller 1.84" intake valve, they flow within 8 cfm of the L31 head at .500" and actually flow slightly better in the lower lift area.

winfred
11-24-2011, 07:39 PM
i don't really want that much compression, going from the 76cc tbi heads to 64cc 350vt heads i think gets it from 8.3-1 to 9.3-1 which i think is about all i want for this heavy 3/4 ton 4x4 suburban, i don't want to need to screw with the bottom end as it only has 130k miles, and if i do its getting a LS of some kind