Power estimate, mildly modded 305?

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

Logbed

Member
Joined
May 31, 2022
Posts
39
Reaction score
31
Location
Finland
First Name
Juha
Truck Year
1985
Truck Model
c10 Fleetside Silverado
Engine Size
305
Hi,
I'm new here, cool info everywhere, thanks!
I just installed 1,5in longtube Flowtech headers to my 1985 305+TH350 Fleetside. The engine is a 305 from a 1986 Caprice. The car has no smog equipment and in addition to long headers there's a free flowing 2 1/4 double exhaust, Edelbrock Performer 500 manual choke carb, Ederlbrock Performer-plus cam, Performer intake and MDS HEI distributor. It runs already well, but I'm going to take it to have the ignition and carb adjusted just to make sure I get everything out of the super expensive gas I pour in it ;) There are guys who do the adjusting on the street and others who do it in the dyno. If I get to the dyno I'll learn the power figures, I'f not what's your hp guesstimate for my setup?
 

Vbb199

B-rate Hillbilly Customs
Joined
Jan 12, 2018
Posts
9,042
Reaction score
15,333
Location
Salisbury NC
First Name
Vince
Truck Year
89, 79
Truck Model
89 Suburban R1500, 79 C10
Engine Size
350, 502
Maybe 250-350hp

The stock 305 is like 150-180hp

So maybe closer on the end of 250
 

Rickf

Full Access Member
Joined
Jul 29, 2017
Posts
571
Reaction score
713
Location
Grafton NH
First Name
Rick
Truck Year
1974, 1954 & a 1937
Truck Model
K20
Engine Size
350
225 to 250 would be my guess. I always thought the flow of 305 heads were the limiting factor for more HP. There is no substitute for cubic inches.
 

Octane

Full Access Member
Joined
Dec 31, 2019
Posts
2,038
Reaction score
3,629
Location
Atlanta
First Name
Eddie
Truck Year
1977
Truck Model
K10
Engine Size
350
At 180hp,maybe 205 now.Cam and intake peps it up.Cylinder heads would wake it up.At 8.0 compression is low.350cid is 8.50:1: compression,which aint much,but works a little better if only doing these mild upgrades. We owned a brand new 1986 Caprice with the 305
 
Last edited:

Rusty Nail

Full Access Member
Joined
Jan 29, 2015
Posts
10,041
Reaction score
10,134
Location
the other side of the internet
First Name
Rusty
Truck Year
1977
Truck Model
C20
Engine Size
350sbc
True dat! ^
Power IS limited by what the cylinder heads can flow.
Want more power?

Rebuild the right set of #416 heads (H.O. 305) They WILL accept 1.94 and 1.60 valves - then it will be a runner.
Winky face ;)
 

bucket

Super Moderator
Staff member
Super Moderator
Joined
Aug 3, 2010
Posts
30,445
Reaction score
28,347
Location
Usually not in Ohio
First Name
Andy
Truck Year
'77, '78, '79, '84, '88
Truck Model
K5 thru K30
Engine Size
350-454
I also would guess in the low 200 range.
 

Matt69olds

Full Access Member
Joined
Jan 8, 2018
Posts
2,451
Reaction score
3,819
Location
Central Indiana
First Name
Matt
Truck Year
81
Truck Model
GMC 1/2 ton
Engine Size
455 Olds
Whatever the number is, you will want more. Just a fact of life for a gearhead.
 

Latest posts

Forum statistics

Threads
44,166
Posts
950,718
Members
36,282
Latest member
Doug Hampton
Top