47ford

As the title states I'm having a boost spike issue. Just got the car running a few months ago and wanted to turn it up a little bit. Ran it with the 7-8 pound spring with out issue. I then bought an 11 pound spring and started having this issues. Under full boost it is spiking to 16+ psi. Only thing I changed was the spring and took out a little more timing. I checked everything over and found all the fittings are tight and I replaced the line going from waste gate to the intake. Second fitting on side of wastegate is plugged and tight. On the wastegate I have the top fitting un plugged to the atmosphere and the side fitting plumbed into the unported fitting on the carb. Running out of ideas any help is appreciated.

Car is a 1947 ford coupe under 3k with me in it
Stock 5.3, cam, valve springs, hardened push rods
Vic Jr with CSU blow through carb
3800 stall th350
On3 78/75 with on3 44mm wastegate

47ford

Also running a msd 6010 box for ignition

Forcefed86

iTrader: (4)

The spring rating alone doesn't designate boost level. SYstem back pressure, WG placement, etc all play a big role.

Put the lighter spring back in and use a boost controller of some sort to hit your desired boost. You can easily make 16+lbs on a 7-8lb spring.

47ford

Thanks for the reply..... Pretty simple set up I'll just buy a manual boost controller and go that route

47ford

So put 7 psi spring back in and still having spike to 16+ psi. Faulty wastegate or gasket inside of wastegate blown?

Forcefed86

iTrader: (4)

Sounds like it. It's pretty easy to pinch the diaphragm. Maybe you did it when you installed the heavier spring? What gate is it? Put air to the top port and it should be an air tight seal. I like to use a clamp to reassemble them.

47ford

It's an on3 44mm wastegate. When I took it apart to put the 7 pound spring in I looked at the diaphram gasket and it looked ok but I will try to put air to it and see if it is sealed once I get off work