does anyone know what lift the stock springs on a 86 lg4 305 will hold. and im even thinking less since the engine has 179,800 on it im just curious. also i see on edelbrocks sites the performer intake number 2101 and 3701 are both listed for sbc's but only the 3701 is listed for 305's whats the difference? a 2101 wouldnt work at all?

 

2101 is a small cam it works fine on a stock sbc, ive used 2 with good success

 

not cam i mean tintake i guess i had teh part number wrong.

 

Max lift on the stock Lg4 Springs...not enough to handle any decent cam...get new springs if you are changing the cam...

As for the intakes, the only difference is that the 3701 has the EGR port where as the 2101 doesn't.

 

Technically, the maximum lift they can take before coil bind etc is about .510" or so. However, by time you take worn springs, increase the installed height to allow that added lift, the seat pressures are so low, the valve will close and bounce right back off the seat with very little resistance (valve float).

Another thing to consider, factory springs are only about 85 lbs of pressure on the seat at the factory installed height. over time, they can only get weaker.I've seen Rimac'd springs check out to be 50 or so, give or take 5 lbs. Those were off of my old LG4 which, at the time, had 134,xxx miles. And, like I said, springs can only get weaker.

Lastly, even if you do increase the springs, rather, get springs that allow more lift before coil bind + safety clearance, you still are faced with the barrier of the factory guide bosses. Bottom line is this. At anywhere between .460 and .480" lift at the valve (actual numbers differ), and at the factory installed height, when the valve opens, the bottom of the retainer slams into the top of the guide boss. This basically halts any further opening of the valve. This leads to bent pushrods, ground down cam lobes, etc.

Match the springs to the cam and also consider the ZZ4 intake.

 

Agree completely with what Stekman says. My stock springs floated at 5200 RPMs.

I'll add that the stock springs have exhaust rotators, which are heavy and limit RPMs. Replace the springs and retainers.