425 day dreaming
Thread Starter
Registered User
Joined: Dec 2010
Posts: 143
From: Columbia MO
425 day dreaming
Going in a 65 B body. Since no one makes headers that fit this combo, how far could/should one go in building a 425 using starfire exhaust manifolds? I want all the power I can reasonably get, but don't want to spend money on anything that is just going to be negated by the exhaust manifolds. Kind of a starfire spec. plus build I guess. Any thoughts opinions would be welcomed, and yes I'm hoping some of you engine builders chime in...I don't have the budget to do it yet and so am not going to waste your time with a phone call just yet. Not looking to go cheap either, just want to spend the money on the best I can get that will add power, reduce friction, etc.
Registered User
Joined: Feb 2013
Posts: 15,436
From: Phoenix, AZ
Did you see the post about a new piston for the 425 engine? Lightweight forged piston with 8cc dish and modern thin ring pack. Sounds like a great part for the base of a performance build.
https://classicoldsmobile.com/forums...25-piston.html
https://classicoldsmobile.com/forums...25-piston.html
I am pleased to announce that I have received a verbal commitment on a new forged 400E and 425 piston. Sizes will be 4.100" and 4.155" respectively and have the following specs, although not carved in stone quite yet.
4032 material
.980 pin
1.620 compression distance
8cc D shaped Cup and the most modern ring pack available today, 1.00mm, 1.00mm, 2.00mm all steel ring set.
Price would be in the $600.00 range which would include pistons, pins, clips AND rings. Overall piston weight would be significantly less than all the current pistons available.
Compression would be in the mid 9 range on a 400 with stock heads and the pistons approx. .020 in the hole. A 425 will have upper 9:1 compression.
The goal is one configuration for all applications.
4032 material
.980 pin
1.620 compression distance
8cc D shaped Cup and the most modern ring pack available today, 1.00mm, 1.00mm, 2.00mm all steel ring set.
Price would be in the $600.00 range which would include pistons, pins, clips AND rings. Overall piston weight would be significantly less than all the current pistons available.
Compression would be in the mid 9 range on a 400 with stock heads and the pistons approx. .020 in the hole. A 425 will have upper 9:1 compression.
The goal is one configuration for all applications.
Thread Starter
Registered User
Joined: Dec 2010
Posts: 143
From: Columbia MO
Did you see the post about a new piston for the 425 engine? Lightweight forged piston with 8cc dish and modern thin ring pack. Sounds like a great part for the base of a performance build.
https://classicoldsmobile.com/forums...25-piston.html
https://classicoldsmobile.com/forums...25-piston.html
BZZBRand
Joined: Jan 2017
Posts: 38
I just rebuilt my 1965 425 Starfire motor and did just what you are wanting to do. What I did was make all the stock style items work better. Added a small cam from Mondello, all new valves, seats & springs then Balance & Blueprinted the thing. Also added a good 2 1/2 inch Flowmaster exhaust system with the stock manifolds, etc. This thing wants to rev like a mother and runs pretty darn good, especially with the stock 4GC Carb.
Registered User
Joined: Aug 2005
Posts: 1,972
From: Braceville, Ohio
This is Just My Opinion. If you want the most torque for your money get a 455. While the 425 is a good engine, pistons and possibly the valve train if it's an A headed 1965 engineand the camshaft could be a little more pricey if it is a 45 degree. Because rear gearing is limited you want all the torque to move the heavier B Body. So a 455 will give you more torque and be cheaper to build. My Turquoise 98 is 461 cu in, 3:08 posi, home made Toro 2.5" exhaust, 4680 lbs and best 1/4 time was 14.13 @ 100 mph. Shifts at 4800. Just going into 3rd before the traps.
Registered User
Joined: Mar 2011
Posts: 558
Going in a 65 B body. Since no one makes headers that fit this combo, how far could/should one go in building a 425 using starfire exhaust manifolds? I want all the power I can reasonably get, but don't want to spend money on anything that is just going to be negated by the exhaust manifolds. Kind of a starfire spec. plus build I guess. Any thoughts opinions would be welcomed, and yes I'm hoping some of you engine builders chime in...I don't have the budget to do it yet and so am not going to waste your time with a phone call just yet. Not looking to go cheap either, just want to spend the money on the best I can get that will add power, reduce friction, etc.
Registered User
Joined: May 2011
Posts: 3,688
From: Delta BC Canada
Fyi
Your car is an A body. His car is a B body. There are no headers for his car because of the steering box location.
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steve walker
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