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pontiac 1967 400CID manual engine rebuilding

melsg5

Staff member
SUSTAINING MEMBER
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I don’t know if anyone said anything about the date code.its a 1966 block 389 355 hp 10.75 to 1 with 67 heads
Hi Fred, I dont understand your post. The first post in this thread stated "Production date seems to be D158". Which is April 15th 1968. Combined with the WT code which eliminates any other year ending with 8.
 

Dedek963

The European guy
51
1
8
Prague
Hi Fred,
The fact is that the engine is with no doubt 68.
On the other hand is fact that we were not able to find out why the bore was smaller than it has to be.
Thank you for trying.
 

Dedek963

The European guy
51
1
8
Prague
Now I am finally so far I can consider the break in the engine.
As the engine is raw I am hesitating to just start the engine and let the self-learning injection unit to start learning.

Just to refresh the memory:
Everything inside the engine is new. Cylinders honed, new pistons, new rings etc…
461 stroker, Pontiac Comp Custom Grind Billet Roller Cam (HR) (Std Firing Order/ Std Journals) 282/288, 230/236, .510/.521, 114LS

Among all the modifications there is new injection from Holley which has a self-learning unit.

The self-learning includes some idling, some mild driving, some performance driving and a pedal to the metal cycle.
I do not want to let the engine break in idling speed of the engine, because of the oil pressure (and I don’t know how long it takes.
The same with the performance driving of new engine, not to mention pedal to the metal part of the learning cycle.)

For the very basic break in I firstly decided to attach the engine to the external source of power -> i.e. electric motor revving the engine at 1500 RPM for several hours.

All components (alternator, water cooler, water inside,) would be in place – except for spark plugs.
If I let the engine to run by the electric motor for 10 hours it would be an equivalent of driving some 300 miles.
Even if I do so for 24 hours I don’t think it can be enough for performance driving cycle.
To make a full break in it would be about 100 hours at the external power unit.

The negative of this solution is that the engine is powered externally, so the forces inside the engine are different from the internal combustion reality.
On the other hand some automobile companies used to use this way to brak in new engines before the car was released to customers.

So I asked Holley what they think about it.
Here is the answer:

"When breaking in a new engine it is not recommended to use the Sniper EFI. We suggest fully breaking the engine in with a carburetor and then installing the EFI once its broken in. Trying to break in a fresh motor with the Sniper is a bad idea because it adds another component to have to troubleshoot in the event something isn’t working right."

Well, back on the tree and change the EFI for a carb.

Let this be information for somebody doing similar engine restoration. :)
______________________________
 

melsg5

Staff member
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Actually that is what I would have sugested. You can not break in an engine without the expansion caused by heat and for the cam and other components to be exposed to varying engine speeds so that the splash pattern of the oil on internal components changes based on engine speed, the speed cannot be 1500 rpm for the whole process. Look at the instructions that came with the cam for a new engine. Any mention of light valve springs for breakin, that was a requirement for flat tappet cams with heavy springs and may no longer apply to roller cams.
 

Dedek963

The European guy
51
1
8
Prague
Of course I would have had vary the RPM, that was the smallest problem.
The forces and processes generated by internal combustion were the second one.
The second issue was the trigger why I decided to go back to carb.

There were no instructions coming with the cam. I suppose that this is because the forces are reduced due to rollers.
 
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