it was 85 up 318s got a comp bump to the 9.0 to 1 with a taller piston comp height and the closed swirl port chamber #302 heads. from the few police 85-up 4v318 engines I owned, I found they had the 9.0 to 1 piston comp height but the open chamber 360 heads drops it down almost a full point of comp. what is really different is the cams the 4v 318 use to maximize the 360 head flow.

so if you take a 2v 318 with the #302 heads 9.0 to 1 comp ratio and drop on a set of 360 heads/intake it does 2 things. 1 it drop comp ratio, 2 it still has a whimpy 2v cam with less than .400" lift

THIS is why most people say it kills effort. and say it sucks.

IMHO this is why a whiplash cam does so well in a low comp engine and works well in a street engine.

the early intake closing build cyl pressure so it does not kill off torque.

the larger valves/runners and high lift flows more in the upper rpm range. these 2 things alone make up any loss from the swap in over all performance you really feel in the seat of the pants in traffic.

example... if a stock 360 head max flow is around .450 lift any cam with more than a .450 lift is a waste as you can not get the max flow of cam due to head restriction.

so the right cam is KEY to swapping 360 heads/intake onto a lopo 318 remember though it is easy to over cam a 318 as well. so pick a high lift & short Dur @ .050 cam like the whiplash line of cams.

look at a 340 cam sheet .420/.443 lift range with x heads. so lift is right around max flow of the heads. THEN add some cubic inch & 10.5 comp with a 6-pac 4 speed 3.91sg and it becomes a high rpm legend on the streets. yes I remember in 68 when 340 A-bodys ruled the streets.

another reason I have always used a 340 cam in most 318 with the smaller heads. makes a fun daily driver. but I am hooked on the whiplash roller cams now and cant wait to run my 5.9 magnum whiplash roller cam in my home ported, back cut, #302 heads on a backward piston 318 next.