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Old 09-30-2011, 10:02 PM
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Pontiac 1965 389 w/ 400 heads - Won't Start

Hello,
Recently, my father and I started working on his 1965 GTO which has the stock 389. We had the engine redone and decided to go with the 400 6X Heads from a 1976 Pontiac. We are having a lot of problems getting it started and we have exhausted all ideas we both have tried.
So far we have tried the following:
- Setting the Timing via putting #1 on the top of the compression stroke and making sure that the distributor is pointed to #1
- We have verified that the cam timing gear and crank timing gears are aligned
- We have tested the distributor

We are using the 400 electronic distributor to get away from the points system.

Now, we are at a loss of what else to try.

Does anyone have any ideas or suggestions?

Thanks!

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Old 09-30-2011, 10:13 PM
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What pistons are used? Were the heads milled?
The likely issue is large chambered heads, flat or dish top pistons which put the compression ratio around 6.5:1 or lower. Providing you got it to start if this is the situation it wouldn`t have enough power to spin on vaseline.
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Old 09-30-2011, 10:55 PM
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What is the secondary code stamped on the head? See the attached thumbnail.
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Old 10-01-2011, 12:28 AM
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The normal 389 pistons were used, flat top pistons. The engine was bored 30 thousandths (and pistons matched)

The heads were milled 30 thousandths as well.

As for the codes on the heads, I will look this information to you tomorrow sometime.
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Old 10-01-2011, 02:46 AM
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Quote:
Originally Posted by Spiney
Hello,
Recently, my father and I started working on his 1965 GTO which has the stock 389. We had the engine redone and decided to go with the 400 6X Heads from a 1976 Pontiac. We are having a lot of problems getting it started and we have exhausted all ideas we both have tried.
So far we have tried the following:
- Setting the Timing via putting #1 on the top of the compression stroke and making sure that the distributor is pointed to #1
- We have verified that the cam timing gear and crank timing gears are aligned
- We have tested the distributor

We are using the 400 electronic distributor to get away from the points system.

Now, we are at a loss of what else to try.

Does anyone have any ideas or suggestions?

Thanks!
The HEI distributor cannot use the same coil positive wire that was used for the points distributor to power the HEI distributor. The reason is the stock wire has a built in resistance that lowers the voltage to the original coil. For that reason you need to use a circuit that's "ON" when the key is in the "ON" and "RUN" position, that will supply the full battery voltage. The original wire can be replaced w/ordinary automotive insulated 12-14 gauge wire or a circuit can be chosen from those in the fusebox. Usually there are accessory circuits to allow the use of aftermarket equipment that can be used if removing the original wire isn't done. You can do a search for "wiring hei ignition" or similar terms for a more detailed discription of how to proceed w/this.

The distributor needs to be grounded as well. The coil ground terminal is the center terminal between the "TACH" and "BATT" terminals at the coil cover on top of the cap. Ground this center terminal as well as run grounds from the engine to the chassis and firewall/fenderwell sheetmetal and from the battery to the engine and battery to chassis. Again, a search for "grounding engine electrical system", etc. will get you more info.

In case you and Dad are more used to a Chevy engine than a Pontiac (one member here calls it a "Chevy-centric world" lol), you do remember that the firing order is just like a SB/BB Chevy, BUT that the distributor rotates- and the cap is wired- in the reverse of a Chevy (CCW on a Pontiac), right?


Last edited by cobalt327; 10-01-2011 at 02:59 AM.
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Old 10-01-2011, 07:09 AM
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You don't want the rotor pointing directly at a post when it is at tdc on compression stroke. You want the rotor slightly after the post. You want the initial timing 10 or so degrees before tdc on a first fire.
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Old 10-01-2011, 07:47 AM
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I'd put the stock Delco points and coil back in... Those motors came from the factory with an excellent ignition system..

Did you take a compression reading?
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Old 10-01-2011, 09:21 AM
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Quote:
Originally Posted by Spiney
Now, we are at a loss of what else to try.

Does anyone have any ideas or suggestions?

Thanks!
I forgot to ask you what the engine was doing when you try to start it. Is it popping through the carb or exhaust, or does it just crank over w/o any sign of trying to start?

Is the HEI distributor from a running engine?

Are you absolutely positive the valves are correctly adjusted? If you are still using the stock 6X bottle neck rocker studs and tightening the lock nut down to 20 ft/lbs, the valve adjustment/lifter preload could be causing the valves to not all seat as they should if the heads or block was milled, or a different thickness head gasket is used, or a different cam, valve job, etc.

Or if you have it set up to have an adjustable valve train, if the lifter preload is too tight the valves could be off the seat as well.
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Old 10-01-2011, 02:07 PM
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valve reliefs from the 389 pistons were made for heads with 22 degree angle valves the 400 heads you have are designed with a 14 degree valve angle.Milling the heads .030 may have put the valves close enough to the piston tops to bend them, slightly as the valve reliefs on your combo dont match the need for the 400 heads
I would do a compression test.
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