Problem with a 396 swap
Thread Starter
Heel & Toe
Joined: Apr 2006
Posts: 20
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Problem with a 396 swap
Need some help with my 396 swap. Swap out my 350 for a 396, some history on the engine;
The short block was running in a friends 67, the heads were alum. and he kept them and gave me the cast iron heads that his engine guy rebuilt. I assy. the engine with a Holley 750 double pumper, performer intake manifold. When I first started the engine it ran fine. A few weeks later the engine was getting more difficult to start and when it did the power was gone. This is a project car, so the mileage driven since the swap has not been more the 10 miles. It mostly sits in the driveway.
Now when trying to start the engine it takes a lot of cranking and I will get a back fire through the carb. It will eventually start and run for a while and then when you put it in gear it stalls and will not restart until the engine cools off. When it does not restart I have check spark and fuel and they are all there. The following is what I have checked so far;
a. timing is on 8 deg. BTDC and does not change at idle.
b. New cap, wire, rotor, plugs, coil.
c. Compression when cold is 150PSI per cylinder, +/- 5psi. Hot 120PSI.
d. Vacuum is were it should be, I believe 13".
e. No vacuum leaks.
f. The Holley is new and worked when it was on the small block.
g. I have changed jets, power valves, no real change in performance, runs very rich.
The short block has less than 30k on it since 1969. I look forward to any ideas before I roll the vette in the lake.
The short block was running in a friends 67, the heads were alum. and he kept them and gave me the cast iron heads that his engine guy rebuilt. I assy. the engine with a Holley 750 double pumper, performer intake manifold. When I first started the engine it ran fine. A few weeks later the engine was getting more difficult to start and when it did the power was gone. This is a project car, so the mileage driven since the swap has not been more the 10 miles. It mostly sits in the driveway.
Now when trying to start the engine it takes a lot of cranking and I will get a back fire through the carb. It will eventually start and run for a while and then when you put it in gear it stalls and will not restart until the engine cools off. When it does not restart I have check spark and fuel and they are all there. The following is what I have checked so far;
a. timing is on 8 deg. BTDC and does not change at idle.
b. New cap, wire, rotor, plugs, coil.
c. Compression when cold is 150PSI per cylinder, +/- 5psi. Hot 120PSI.
d. Vacuum is were it should be, I believe 13".
e. No vacuum leaks.
f. The Holley is new and worked when it was on the small block.
g. I have changed jets, power valves, no real change in performance, runs very rich.
The short block has less than 30k on it since 1969. I look forward to any ideas before I roll the vette in the lake.
