Upgrading a 260hp 350
#1
Registered
Thread Starter
Join Date: May 2014
Location: Buffalo, NY
Posts: 1,053
Likes: 0
Received 0 Likes
on
0 Posts
Upgrading a 260hp 350
I know it's been beaten to death, but here's something I stumbled upon. I can pick up a set a 14096217 cylinder heads locally for cheap. They came off a running 270hp 350 Mag. I know these heads are the predecessor to the Vortec head. They are easily capable of making 285 to 300 horsepower, as they were on the 300 hp GM crate motors of the era. I know I need a new intake manifold with 27* center bolts and am wondering which intake to buy. Mind you, this is a budget build....because while the engine is out I will have to replace my wet transom.
Any recommendations on cam and intake would be great.
Thanks!!
Any recommendations on cam and intake would be great.
Thanks!!
#2
Registered
Thread Starter
Join Date: May 2014
Location: Buffalo, NY
Posts: 1,053
Likes: 0
Received 0 Likes
on
0 Posts
Here's a cam I'm looking at.....
http://www.summitracing.com/parts/cc...make/chevrolet
I have to do more digging on the cam specs of that GM crate engine.
http://www.summitracing.com/parts/cc...make/chevrolet
I have to do more digging on the cam specs of that GM crate engine.
#3
Registered
Thread Starter
Join Date: May 2014
Location: Buffalo, NY
Posts: 1,053
Likes: 0
Received 0 Likes
on
0 Posts
The 285hp engine had a cam lift of 447/447 with a 8.8-1 comp ratio
The 300hp engine had a cam lift of 435/460 with a 9.1-1 comp ratio
I really have no idea what pistons are in my engine and really won't know until I pull the heads. I'd be happy with 8.8-1, but of course the 9.1-1 would be best.
The 300hp engine had a cam lift of 435/460 with a 9.1-1 comp ratio
I really have no idea what pistons are in my engine and really won't know until I pull the heads. I'd be happy with 8.8-1, but of course the 9.1-1 would be best.
#4
Banned
Buy that AFR composite intake manifold for the SB Chevy. It has been dynode by David Vizard and he swears by it. It made better HP and Torque # s right out of the box than any other intake manifold including the worked over intake manifolds. Plus you never ever have to worry about that intake manifold producing corrosion problems or dissimilar metals joining together.(dissimilar metals together produce corrosion over time especially in marine apps)
I would also look into bore & stroking the 350 into a 383.
I would also look into bore & stroking the 350 into a 383.
Last edited by BUP; 10-23-2014 at 10:26 AM.
#5
Registered
The GM cast Iron Bowtie highrise intake was discontinued a few years ago. No stock left anywhere. I had sold 100's. GM's 86-95 part# is #14097494
So, a real good 86-95 application high rise Aluminum intake is Weiand's Speed Warrior:
http://www.summitracing.com/parts/wn...et?prefilter=1
So, a real good 86-95 application high rise Aluminum intake is Weiand's Speed Warrior:
http://www.summitracing.com/parts/wn...et?prefilter=1
#6
the pre '86 260hp 350 heads are the same as the 270 horse 350mag post '86 except for the angle of the middle 2 intake bolt holes. You won't see any difference just switching those heads. They are the predecessor to the vortecs in that they came before them, but that is where the similarities end.
#7
Registered
Thread Starter
Join Date: May 2014
Location: Buffalo, NY
Posts: 1,053
Likes: 0
Received 0 Likes
on
0 Posts
I think my heads are 76cc heads, not 64cc heads like the ones I'm looking at. I will pull a valve cover to be sure, but I'm 85% sure I have 76cc chambers on my engine.
#8
Okay, the carbed '87-'95 350mag (and also the 5.7 260) had 76cc heads with center bolt valve covers and the more vertical center intake bolts. They were of the same performance as the pre 86 heads with perimeter valve covers and traditional intake pattern.
In '95 they had a TBI 350 mag, I assume these had the 64cc TBI heads, are these the ones you have? Aside from the compression bump I don't think you will gain much.
In '95 they had a TBI 350 mag, I assume these had the 64cc TBI heads, are these the ones you have? Aside from the compression bump I don't think you will gain much.
#9
Registered
Thread Starter
Join Date: May 2014
Location: Buffalo, NY
Posts: 1,053
Likes: 0
Received 0 Likes
on
0 Posts
^^ The 64cc combustion chamber heads are what I will be picking up^^
They are an iron copy of the L-98 TPI heads that came on the Vettes and some Irocs.
http://www.gmpartsdirect.com/perform...CATID=671.html
They are an iron copy of the L-98 TPI heads that came on the Vettes and some Irocs.
http://www.gmpartsdirect.com/perform...CATID=671.html
Last edited by Jonesyfxr; 10-23-2014 at 01:49 PM.
#10
Sorry wasn't trying to make it confusing.
If you don't have heads or an intake right now, go with 64cc VORTEC heads with a vortec style intake gm marine intake (or edelbrock rpm or rpm air gap). You will be much happier with the performance.
If you don't have heads or an intake right now, go with 64cc VORTEC heads with a vortec style intake gm marine intake (or edelbrock rpm or rpm air gap). You will be much happier with the performance.