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Pontiac 1978 400 rebuild

  
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Pontiac 1978 400 rebuild

 
bassmstr28 bassmstr28
New User | Posts: 4 | Joined: 12/10
Posted: 12/19/10
08:55 AM

Recently bought a 1978 Trans Am with 66,000 original miles.I pulled the motor out with the trans to freshen up and do new gaskets,etc. Well the car has some burned sludge inside the block and heavy metal filings inside the pan. I suspect it was dry started as it sat from 1998-2007 in a garage. Oil was like mud... Anyways here is the plan I have a limited budget and a customer of mine own Tru Torque engines in Nashua N.H. so we may be trading work for the rebuild. here is what I have in mind and I am open to suggestions. Only looking for about 350 hp at the rear wheels.
pontiac 400
zero decked
flat top pistons
xe262 cam
connecting rods

Should these all be forged and not cast????

Stock 6X-8 heads rebuilt
milled .060

stock intake
rebuilt quadrajet that i will send out to have done and tuned to engine.

headers open to suggestions here

I have a new rebuilt turbo 350 that will get a tci or transgo shiftkit installed. maybe a mild 1800 stall

rear in the car is a awful 2.56 posi that will eventually be switched to a rear disc 3.73

2 1/2" dual exhaust not sure on mufflers yet.

so any thoughts i do not need 450 h.p. just looking for a dependable cruiser that i can have fun in And that sounds good.  

tuffnuff tuffnuff
Moderator | Posts: 2567 | Joined: 12/09
Posted: 12/19/10
09:47 AM

Your cam choice is mild,,, I'd go Ram Air III cam, or 268 duration .477"/.480" lift, for a better, lumpier sound.
Your stock converter is already 1800 flash stall, why change it.
Your stock rods are fine, just get them resized.
Full length headers will work best on your 400
Follow through with the rest of your plan, it sounds good.
Do a complete rebuild and oil pump
Smile  
When The Flag Drops.,.

tuffnuff

The Bull ***t Stops.,.
tuffnuff

P. Engineer, Engine Builder

Pontiacman8 Pontiacman8
Moderator | Posts: 5778 | Joined: 02/08
Posted: 12/19/10
10:14 AM

I would recommend a b&m shift kit for the trans.
Ya I agree on the converter some stock converters flash stall at 1800-2200 depending on the power that's put to them.

I would also recommend slightly more cam like this one.
http://www.lunatipower.com/Product.aspx?id=2477&gid=296

Your stock rods will be fine as tuff mentioned but before resizing them I would get ARP rod bolts for the stock rods installed then resize them.

I would never recommend milling that much off the surface of the heads.
Also you want to keep cr at or below 9.5:1CR for premium pump gas and iron heads.

A edelbrock RPM intake would be a nice addition to this build.  
Engine builder,self taught auto body guy.
Horsepower sells engines and torque wins races

Pontiacman8
Pontiacman8
Pontiacman8

bassmstr28 bassmstr28
New User | Posts: 4 | Joined: 12/10
Posted: 12/19/10
10:29 AM

Thanks for the cam advice I was afraid going to large would make performance problems with the size of the valves on those 6X heads. I will stick with the stock stall.

Any suggestion on the mill on the heads then? I was looking to get around 9:1 to 9.5:1

Also the b&m kit is that a stage 1 or 2 kit? I was going to install a finned trans pan with drain plug and a separate trans cooler.
Any suggestions on pistons or rods? I know my engine guy will give me his opinion. I assume forged is always better. Is there a good forged brand at a reasonable price you would recommend?
I also assume I need stainless valves should I have the heads cut to accept valve seals?
What do you think with this set up I could get for H.P.?

Thanks for the help just want to do it right the first time as I have had problems with these pontiacs in the past.  

bassmstr28 bassmstr28
New User | Posts: 4 | Joined: 12/10
Posted: 12/19/10
10:35 AM

Also I wanted to keep the shaker and will that work with the edelbrock intake? I have been told the stock ones are almost as good but again open to suggestions.  

tuffnuff tuffnuff
Moderator | Posts: 2567 | Joined: 12/09
Posted: 12/19/10
10:40 AM

Those heads should have 2.11" intakes, that's plenty to get 1 horse per cube.
Cast or hypereutectic flat tops will work, no need to get forged.
Your rods should be resized and will be OK for your build,,, you may want to consider ARP rod bolts.
No need for stainless, inconel, or titanium valves,,, that is overkill.
You can mod the valve to accept a variety of stem seals,,, your choice
With the RA III cam, you'll be at 400 honest HP
"IF" you do everything right and don't mismatch the combination.
Smile  
When The Flag Drops.,.

tuffnuff

The Bull ***t Stops.,.
tuffnuff

P. Engineer, Engine Builder

Pontiacman8 Pontiacman8
Moderator | Posts: 5778 | Joined: 02/08
Posted: 12/19/10
10:41 AM

The B&M that I would go with would be the trans pak and you could set it up for either stage.

If you are not going to put any forced induction on the engine cast or hypereutectic  pistons will be fine.
I would be careful of how much power you pull out of that 1978 block because they had widowed mains from 1975-79 on the 400's which weakens the block.
If you really want to go forged on the pistons summit has rebuild kits with speed pro forged pistons.  
Engine builder,self taught auto body guy.
Horsepower sells engines and torque wins races

Pontiacman8
Pontiacman8
Pontiacman8

tuffnuff tuffnuff
Moderator | Posts: 2567 | Joined: 12/09
Posted: 12/19/10
10:41 AM

Icon Quotebassmstr28:
Also I wanted to keep the shaker and will that work with the edelbrock intake? I have been told the stock ones are almost as good but again open to suggestions.



You can bolt the shaker to the hood for added clearance.
Grin  
When The Flag Drops.,.

tuffnuff

The Bull ***t Stops.,.
tuffnuff

P. Engineer, Engine Builder

Pontiacman8 Pontiacman8
Moderator | Posts: 5778 | Joined: 02/08
Posted: 12/19/10
10:45 AM

No I think with the rpm intake the stock shaker will not work the rpm intake is a good improvement over stock intake but the stock intakes do perform well.
Stock valves if in good shape will be fine.  
Engine builder,self taught auto body guy.
Horsepower sells engines and torque wins races

Pontiacman8
Pontiacman8
Pontiacman8

Pontiacman8 Pontiacman8
Moderator | Posts: 5778 | Joined: 02/08
Posted: 12/19/10
10:48 AM

With the cam I recommended and a 9:1CR good set of headers and with a proper tune 380-400Hp is well within reach.
I would have a 3-5 angle valve job done when you have the heads reconditioned.  
Engine builder,self taught auto body guy.
Horsepower sells engines and torque wins races

Pontiacman8
Pontiacman8
Pontiacman8

tuffnuff tuffnuff
Moderator | Posts: 2567 | Joined: 12/09
Posted: 12/19/10
11:15 AM

Icon QuotePontiacman8:
The B&M that I would go with would be the trans pak and you could set it up for either stage.

If you are not going to put any forced induction on the engine cast or hypereutectic  pistons will be fine.
I would be careful of how much power you pull out of that 1978 block because they had widowed mains from 1975-79 on the 400's which weakens the block.
If you really want to go forged on the pistons summit has rebuild kits with speed pro forged pistons.



Pman, my block is a 75 and there are no windows in the mains of the 400,,, are you thinking 403 Oldsmobile Confused
Grin  
When The Flag Drops.,.

tuffnuff

The Bull ***t Stops.,.
tuffnuff

P. Engineer, Engine Builder

Pontiacman8 Pontiacman8
Moderator | Posts: 5778 | Joined: 02/08
Posted: 12/19/10
11:27 AM

Ok not all 1975 400's had them if I remember right it was in mid 75.
what is the casting number on your block??  
Engine builder,self taught auto body guy.
Horsepower sells engines and torque wins races

Pontiacman8
Pontiacman8
Pontiacman8

tuffnuff tuffnuff
Moderator | Posts: 2567 | Joined: 12/09
Posted: 12/19/10
11:34 AM

I'll have to look and post them,,, I know the last 4 numbers at the bottom of the block match my numbers on the dash plate,,,
So my T/A is a numbers matching 4 gear with air and posi.
Smile  
When The Flag Drops.,.

tuffnuff

The Bull ***t Stops.,.
tuffnuff

P. Engineer, Engine Builder

Pontiacman8 Pontiacman8
Moderator | Posts: 5778 | Joined: 02/08
Posted: 12/19/10
11:36 AM

Two numbers were used 481988/500557.  
Engine builder,self taught auto body guy.
Horsepower sells engines and torque wins races

Pontiacman8
Pontiacman8
Pontiacman8

Pontiacman8 Pontiacman8
Moderator | Posts: 5778 | Joined: 02/08
Posted: 12/19/10
12:09 PM

I know the later blocks were weaker.

1975 - 488986(early), 500557 (late, thin main webs, weak)  
Engine builder,self taught auto body guy.
Horsepower sells engines and torque wins races

Pontiacman8
Pontiacman8
Pontiacman8

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