[68fostreet]

Alright guys who has broken in a rebuild chevy with a blower?
ive pulled the inner valve springs. got some fancy oil and what else, any good carb tips?
thanks
miles

 

[camaroman7d]

One of the main things is to make sure your timing curve is right. You want ~20* initial and limit the total to about 32*. If you have the timing retarded it's going to run hot and your headers are going to get red hot. You don't want to have to shut it off during break in if you can help it.

Other than that it's just like any other engine. Don't expect it to run perfect when you are breaking it in, just get it to run well enough and stay cool enough so it can maintain 2500 RPMs for ~25 minutes. Then you can change the oil and filter and start tuning.

What type of carbs are you running?

 

[68fostreet]

Im running two Pro systems 950 dp's

 

[Nolowrider]

If I were you, I would lock out the timing for the break in. Makes it much easier. Blowers like a lot of initial and not too much total. You can always go back later and dial in the curve. FWIW I run my blown BBC locked out all the time.

Also jack up the front of the car and fill the radiator, this helps get all the air pockets out.

Have an extra person to help check for leaks and set the timing while you are working the throttle.

 

[forcd ind]

im guessing its a flat tappet cam, and its a roots blower
nothing real diff than a NA engine, have no idea how things are set up, but as said sneak up on the timing, also ck the belt tension when its hot, esp if a fixed idler(non spring loaded)
beyond idle, ck your AFR's
i used to run 10 degs in the dist(20 at the crank) and the rest int. timing, whatever it will take, all in by 1800-2000

 

[Nolowrider]

Forgot to mention this, but the best way to break it in is to do it with a normal intake and carb, then once the break in is done slap the blower back on. Last thing you want it a timing or rich back fire through the blower. That can damage the rotors. The blow out valve should catch it, but if it doesn't it can be bad. JMO

 

[77 cruiser]

Make sure it's not lean & have plenty of timing or your headers will be glowing for sure.

 

[ironhead]

Banging the blower rotors and cyl wall fuel wash would be my high on my list of no no,s.Nothing less than 20* initial and baseline the idle mixture screws 3/4 turns out from seat.
If its a 3" gilmer belt with a fixed tensioner..at least 1" of belt deflection on the drive side to compensate for thermal growth.
Do not crack the throttle while cranking.Better to hit the accel pumps a few times and then count to ten prior to engaging the starter.
Once she lites off..you can use the curb idle screws to play with rpm while your wing man checks the gauges and looks for leaks.
:beers:

 

[camaroman7d]

Excellent point on the belt tension George, this is very important.

Fill the carbs through the vents, before starting if you don't have an electric pump.

OH, here is another important thing that most people new to blowers don't know, DO NOT pump the gas or hold the throttle open when cranking. For the initial start I would suggest pumping the gas 1 - 2 times and then take your foot/hand away from the accelerator until it fires. If it doesn't start, stop cranking, pump the gas again then try to start. NEVER open the throttle while cranking, this will create a lean backfire through the blower every time.