400/406 Builds

[westie 666]

Last year I got a 406 that was built a few years ago and dropped it in my 77, it has Holley intake with Holley 750 dumping gas into it, I don't know what went into this motor but was told it was all good gear.
Now I have a big problem with it running on and pre ignition, was told it is also running backwards, to combat this I shut down with truck in gear, put it on the dyno to try and fix it but no joy.

Any ideas??

Cheers
westie

[Captainfab]

I have to disagree with your mechanic if he is indeed installing flat top pistons and the 'camel hump' heads. Not knowing the specifics on your parts I took an educated guess and entered some numbers in this online compression calculator and came up with 10.99-1.

http://www.summitracing.com/popup/ca...ion-calculator

That is definitely not going to be pump gas friendly especially with iron heads. Even if you install a wild cam, the dynamic compression is going to be way too high. I would suggest reading through this thread and see what Mike went thru with his engine, and he has pistons with a 12.5cc dish.

http://www.67-72chevytrucks.com/vboa...d.php?t=573986

I think there are a few other members here with more engine building experience than I, that will agree with me.

Originally Posted by nicks diner

Thanks Captain. My mechanic is building this 406 he assures me on the compression and that it will be on pump gas. I'm thinking of sticking with the camel humps which have the larger valves and are well ported. What are you thinking on the est power with my setup? Ignition is MSD 6al and like I stated full rollerr everything with a much more aggressive cam and full length headers and a 750 double pumper with a one inch spacer. Thank you.

The first thimg I would do is see where your timing is at. Not just the initial, but the total and also the amount the vacuum advance is adding. How is the engine built? what is the compression? What cam is in it? Is the carb in good condition and tuned properly? Depending on how the engine is built, it would likely run better with a smaller carb.

Originally Posted by westie 666

Last year I got a 406 that was built a few years ago and dropped it in my 77, it has Holley intake with Holley 750 dumping gas into it, I don't know what went into this motor but was told it was all good gear.
Now I have a big problem with it running on and pre ignition, was told it is also running backwards, to combat this I shut down with truck in gear, put it on the dyno to try and fix it but no joy.

Any ideas??

Cheers
westie