Hey guys, I am gettin world torquer 305 heads for my 91 z and I want to know three things...

1. Why do people say that these World Heads need to have some "bowl work" done.

2. This might sound stupid but what is bowl work and how do you do it.

3. Does anyone know how much of a HP difference it will make if I do the bowl work and then put the heads on or dont do the bowl work and put the heads on.

Thanks for the help.

 

Ice,

Sorry, but I can't answer the first part. I've never had a World head on the bench.

Typically, "bowl work" means bowl porting, or enlarging the valve bowl area. It may also include some short side radius blending of the bowl to the runner, and trimming the excess material around the valve guide boss.

It may be that the World heads are not as open behind the valves as they could be, or that some of the finer details are not that well executed, like valve guides or radius blending.

The third part is just as much of a mystery to me as the first, for the same reasons. However, small details can make a difference. I do know that radius added to the front faces/margins of intake valve in SBC heads can add as much as 5 HP in short track engines that run lower RPMs (5,500-7,000). That seems like a little detail to me, but five ponies can make a difference. It's all about the flow, which is probably why you are thinking about new heads in the first place.

Hopefully, someone with a spare World head with the valves out of it can offer a little more insight as to some of their potential shortcomings, if any. Either that, or send me a pair and I can "evaluate" them for a couple of seasons.

 

Thanks for the explanation.
Grant

 

I took some pictures of mine before I started working, unfortunately the camera & flash didn't sync quite right, so only half the frame came out...

But,

Even World told me bowl work is a good idea. For whatever reason, they leave a lot of material cast into the ports below the valves. Their CNC stops pretty high, leaving large steps and sharp edges along with the restricted port. The guide casting is also very large (not sure why they do that), so trimming it down is a good idea, especially on the exhaust.

The recent Popular Hot Rod (I think - both PHR & CHP arrived on the same day) had an article on "normal" S/R Torquer 2.02/1.60 heads, with bowl work done by a novice and before & after flow benching. The exhaust improvement was substantial at .4 lift, intake was not too impressive at any lift, and even exhaust improvement fell off (but was still higher) at .5 lift. Of course, they didn't smooth out the guides (and I don't think even did port matching - don't have it in front of me so not sure on that), and didn't do the "complete" Standard Abrasives DIY guidelines job.

I don't know either how much difference it makes from a HP standpoint, but if the rest of the system (intake, cam, exhaust) is also improved, the improvement from the porting will be even greater than if it is the only improvement. If you haven't done so yet, look at the Standard Abrasives guidelines (also don't have the URL in front of me - cleaned out the briefcase last night) and consider their "full-up" job. I'm convinced that porting work is a substantial part of why my car runs as well as it does now (sorry, no 1320 times until at least April 13th...).

 

Five7kid,

I am DYING to see what that 305 of your's turns!!!!!!!!

 

No earlier than April 13th, I'm afraid...