67mustang302

When the header primary tube is slightly larger than the port, if the gasses on their way out at the end of the exhaust stroke begin to stall, the slight step impedes them trying to flow back into the chamber before the valve closes. I believe this assumes that the pulse tuning isn't scavenging at the end of the exhaust stroke.

There are headers (or there used to be, not sure about these days) that had slotted bolt holes so you could move the primary tubes up/down on a dyno and see how moving the step location around changed the power band.

I doubt it's enough to worry about on a street engine, but since most headers are not custom to the engine itself, but generally work well on most applications; I can see where a slight step into a larger header primary can help in the areas where the header happens to be sub-optimal.

But yeah, #1 concern is max flow of the gasses out of the chamber/head and through the exhaust. That's why I run the JBA shorties, give me the ground clearance I need and flow really nicely (they use the Firecone collector, or whatever JBA calls it). I don't even worry about pulse wave tuning, my only concern is an unobstructed flow.

boogerschnot

There is a guy on Craigslist here in SD selling some 351w heads, rebuilt, stainless oversized valves and other goodies for cheap.. Check craigslist..

4reboy

Looks like it's gone now, or I can't find it. Thanks for the heads up though!

On that note though, after some thought I think it will be best for me to stick with my stock heads and get them serviced. However, I still think I want to put in a different cam to get more power.

How does the Weiand Stealth intake and Xtreme Energy XR270RF-HR with stock heads sound? It should open it up more than my RV cam, right?

I will order the needed springs for my cam and bring them into the machine shop when I get my heads serviced. What else can I do to these stock heads to squeeze more power out without much cost? You mentioned the stainless oversized valves which is a fairly common upgrade from what I know.

67mustang302

That cam will be too big for the stock heads, you won't really benefit as much from it because the heads will be a big choke point. It won't hurt you, but won't help nearly as much as with heads that breathe.

If you plan to swap heads later then putting that cam in now isn't a bad idea.

4reboy

If it won't hurt me I think I'd rather have something I can grow into if I get the itch for more power and find some used aluminum heads. As long as I'm not losing power compared to my RV cam by putting in a cam that would be better for new heads... The better intake and roller setup should help as well

I'll talk to my machine shop and see what kind of work can be done to get them to flow better and see if it's worth it. It looks like I'm at a slight advantage having 69 heads that already have bigger valves than the later years.

67mustang302

No point in spending money on the heads you have, you'll spend almost as much as buying used heads and get half as much in return. Depending on the cam you have now, you might lose a bit of power at lower rpm and gain some in the mid range, or pick up power everywhere. It'll still generally run better.

With that cam and stock heads you're leaving about 75-100hp on the table though. So it's worth spending money on heads later, or now, whenever you have the money.

Starfury

I agree completely. I jumped from '68 302 heads (big valves, exhaust port-match) to a set of Trick Flow Twisted Wedge heads and picked up a lot of power above 4k (my cam makes power from 3-6k). The updated cam will definitely help, mid- and high-range power, but the heads are still a choke point.

4reboy

Got it, thanks guys. I'll simply have the machine shop surface the heads then as well as replace anything that looks bad (including the 1 damaged valve). I'll ask them if I should bring them the cam/valve spring kit or if they can source it for me for a better price.

I still really want aluminum heads but to do everything properly just isn't in my budget yet. Since my car is down and out I'd like to fix it now and upgrade again later. I'll keep browsing the forums and craigslist for some used ones though!

Edit: These kits often come with new timing chain sets, do I need to bother with this with a rebuild that only has 10k or so miles on it? It looks like I also need to degree the cam, that's new to me so I've been reading up on that.

67mustang302

If it doesn't have a double roller timing chain, upgrade to one. Comp and Cloyes both offer excellent and affordable double roller setups. Their **** doesn't stretch and lasts forever. My Comp set is on it's...2nd cam? In it's 3rd engine? Stopped counting the miles a long time ago.

Just get the cam and matching Comp springs from Summit, that'll be your best bet. Get the heads surfaced and have the valves replaced and seats reground if needed. If valves need to be replaced, it wouldn't hurt to go to larger ones since the price is pretty much the same.

Spending money on the right stuff now so you can upgrade properly later will save you money in the long run.

Comp should have some videos on YouTube somewhere on how to degree a cam, you can get a wheel for cheap from Summit. You'll need a dial indicator though, which ain't cheap...but if you plan on doing a lot of engine/transmission work in the future, you'll need one anyway. I've used the hell out of mine over the years.

Starfury

You can get cheap dial indicators from Harbor Freight for like $20. They won't stand up to shop abuse, but for the DIY tech they work ok.