360 heads on a 318. good idea?

[slipyoke]

So i have been building a 318 shes nothing to fancy. got a mild cam, intake headers, bored 60 over and i droped 360 heads on her. now the 360 heads thing should be fine right? i thought they would justy drop on and go but i got to thinking and thought i should ask first.

 

[C130 Chief]

This has been done since 1971 when the 360 was introduced (using basically a 340 head). There are some pros and cons to the swap.

Pros:
Larger ports and valves have significantly more flow and horsepower potential.
360 heads cost the same or less to rebuild making them an economical upgrade.

Cons:
Larger combustion chambers will reduce compression.
Larger ports may hurt low RPM throttle response.

The loss of compression on the street will more than offset any gain in flow, so add the cost of milling and shorter pushrods or domed pistons. 300 horsepower is about the point with a 318 that the bigger heads make sense, but you can certainly make 300 hp without them. If your cam is less than 230 degrees at .050 lift, you likely won't see much gain.

 

[Claudius]

There are a number of intake manifolds that are able to accommodate your suggested configuration. I am putting a set of 340 heads on my 318 and I got an RPM Air Gap (7576) from a FABO member that he was not using. What a huge difference in the size of the ports compared to the 318 intake!! Edelbrock specifically identifies the combination that you are talking about using. My 650cfm Thunder AVS carb arrived in the mail today and that will make a nice addition...

 

[rumblefish360]

IMO, I'd look for a LD4B or a Performer intake, both from Edelbrock. Even a stock iron intake is OK.

Claude, you think the RPM has large ports, check out a LD340 or Strip Dom. from holley, or a Mopar single M-1. Darn near gasket sized allready. Bigger than the RPM's ports.

 

[stroker mike]

Strip dominators are awesome! I gave my M1 to my brother, but I have the holley sitting on my engine right now till I can pull the performer off my other block. Very cool intake. Too bad I can't really use it's potential, with only a 270 cam. I was gonna use some 340 heads on my 318 but I talked to guys about it here and decided to sell them and got myself some ported 302's. I want it to pull hard from the stoplight, and I really won't be revving past six at the most. A performer or LD340 seem to be the best choices for a street engine. Good luck with your build.