94brick

I have decided to go with the GM Hot Cam on my 94 LT1. Now that the cam choice has been made I need to find the best head package to utilize this cam and frankly I am confused. I hear about porting my LT1 heads...good. THen why not ported LT4 heads...better yet? What about aftermarket heads, trickflow or AFR...are they even better or just more exspensive? And is there a limit to the size heads that can be used with the Hot Cam.? I am looking for the heads that flow/work best with the Hot Cam. Thanks, I hope that makes sense.

Corvette Kid

Talk to Bob at Precision Porting & Coating. He can optimize a set-up for you using the factory heads. Even at Stage II level they'll out flow LT4 heads and cost you less.

http://www.precisionporting.com/highlights.html

727-365-1451 Tell him I sent you.

Nathan Plemons

It's a perfectly valid question with a perfectly confusing answer. As for genuine GM parts, the breakdown goes like this.

Stock LT1 Heads - least optimal but will work well with Hot Cam.
Stock LT4 Heads - fairly costly to buy, requires LT4 intake
Ported LT1 Heads - can use stock castings cheaper than lt4 heads and intake
Ported LT4 Heads - initial purchase + porting costs makes this the most expensive option.

For a Hot Cam car, the best bang for the buck will be to get your stock LT1 heads ported. There are probably a few more horses to be found by going with the LT4 stuff, but it's probably not worth the effort. A really good set of ported LT1 heads can be just as good as a really badly ported set of LT4 heads, so it's really hard to tell.

The same goes for aftermarket heads as well. Some of these have really large runner volumes or flow numbers that look good, but they're out of the usuable range of the Hot Cam. A head that flows 350 CFM at .600 lift is useless to you becaues the hot cam only goes to .525 lift. What you really need to do is look at the flow numbers for all the different heads you are considering. Find the setup that has the highest flow with the smallest runner volume and that'll be the winning ticket.

94brick

Great advice. So I guess there is a limit to the head size/flow you can go with the Hot Cam. And from the responses It looks like porting my LT1 heads will work best with the Hot Cam, correct? I will talk to Bob, Thanks guys.

jimbomill

I spent a couple of weeks this past month doing the same thing of researching what heads to go with my selection of an upgraded cam on my LT1, deciding to go with Bob's work at Precision Porting, Corvette KidNC gave you sound advice. Of course, Bob just had ababy and may have a abnormal sleep pattern

Nathan Plemons

There's no real limit, but there is a practical limit. You will eventually reach a point of diminishing returns. Most of the time when you see really big flow numbers they are peak values. If that peak is above your maximum lift then you can just throw it out the window. What you're looking for is maximum area under the flow curve for your lift.

What I like to do is take the flow data given and plug it into my TI-83 graphing calculator and it it make a plot. What you get typically is a decent looking parabolic shape, but it's just a lot of points, fairly useless. The calculator can take those points though and calculate a quadratic line of best fit. Plot that line and you suddenly have a very good representation of the cylinder head flow characteristics, represented as continuous function.

So what good does that do us? Well with a continuous function I can integrate it over a given span and figure out the total area under said curve. Integrate from 0 to .525 and you have a representative number of how much flow can be utilized by this head and the hot cam. You can compare that to other flow numbers and see what you come up with. The head with highest number flows the most air which means it should make the most power.

Alas though there's one small technicallity, and that's the runner volume. A head with a really large volume can flow a lot of air but do so at a low velocity. This effectively kills the low end torque of the motor so it must be considered too. As such head with a slightly lower flow area but a much smaller runner volume may well perform better than one with bigger flow curve and a large runner volume.

So basically for all calculus tricks it allows me to make an educated guess as to how a head will perform. It's far from perfect but an educated guess is better than a non educated guess.

SouthernSon

94brick, this link gives you a very good article in the evolution of GM head designs. Although it is mostly about the LS1, it compares the evolution of the Gen 1 and 2 heads (LT4 specifically) to the LS1. Very good article....enjoy

http://www.idavette.net/hib/ls1c.html

comp

on the link

94brick

good read southern_son