As the title says, I'm swapping the heads on my 305 from the 614 casting to some remanned 601s. I'm also planning on polishing the important parts as, with most remans, the quality really isn't very good on most of the intake and exhaust surfaces. Having already made several costly mistakes in the process of putting this engine back together, I want to make sure I do this part right. I'm also swapping the cam and rockers, giving me near .500" lift on the exhaust and somewhat less than that for the intake. I know these heads have problems with that, and I've heard of a few solutions, so I need advice on which route to take here.

Starting off with the valve lift issue, I know that the stock valve stem seals will hit the retainers somewhere near .470" - .480". Since my exhaust is going to be traveling about .496", I'll need to make more space. The two solutions I've heard of are:
1: Get a set of +.050 keepers, which will move the retainer up by that amount. This would also require me to either buy new springs (complete overkill for the 5600rpm this engine will see at maximum) or shim the springs I have, as well as pinning the rocker studs to prevent them from pulling out of the head.

2: Cut down the valve guide on the exhaust side by .2" or so and use a different seal. I'm kind of wary of this method, as I don't know how well a different seal would work here.

As for the polishing part, I'm not really clear on how this works. As far as I can tell, I mark out the excess material on the head by placing the gasket over it and using a paint pen on any metal the gasket doesn't cover on the face of the head. Then I remove the valves and just go at the thing with a flapper-disc on a dremel? If so, that part should be fairly easy, but I feel like I'm missing several somethings here.

 

I'd recommend, in 2020, just using stock LS6 springs, with the Comp "adapter" retainers (727) for putting them on 11/32" valves. Gives an extra .050" clearance AT LEAST, and dodges the whole machine work thing altogether.

There are a number of individual actions one can take when working up a set of heads. Each of them does something specific. Some of them need to be done in a particular order; for example, "gasket matching" does ABSOLUTELY NOTHING WHATSOEVER for performance unless The Low Hanging Fruit has already been picked. "Polishing" is somewhat similar; largely ineffective in and of itself, but is a nice finishing touch on castings that have already been seriously massaged.

Apply the Pareto Principle to your mental image of what you're doing. That's an economic concept but applies WIDELY in a vast array of real-life situations. In this case, it would mean something like, you can spend 20% of the total possible time and money working on those heads, and get 80% of the results. Maybe even closer to 10% of the input in exchange for 90% of the results. The closer you want to get to 100% of the results, the closer to 100% of the inputs you'll have to spend.

The Low Hanging Fruit is, first and foremost, a multi-angle valve job; "bowl" work, which consists of smoothing out all the weird steps and angles where the different parts of the casting process met right behind the valves, and what's left over from the factory just jamming their cutter into the midst of all that; and smoothing the guides, reducing their diameter as they descend from the roof of the port, and making them into a "teardrop" or "airfoil" shape.

All that "polishing" in the chamber does, is help reflect all of the heat (energy) from combustion, back into the chamber rather than "leaking" into the casting and the coolant. It marginally increases the amount of energy in the fuel that gets extracted into useful work by the expansion process. "Polishing" accomplishes nearly nothing in terms of flow.

One HIGHLY USEFUL thing that can be done in and around the chamber though, is the removal of ALL sharp edges from everything. A common place for these to be created is where the chamber meets the deck: if the deck gets machined, it will often throw up a burr all the way around the chamber. That little tiny very thin bit of metal can glow red-hot in there, and cause all manner of pinging, pre-ignition, and even detonation. Take your sanding rolls and smooth off that entire transition. And any other sharp protrusions of metal into the chamber that you can find.

"Polishing" is sometimes done to exhaust ports, once the port shape has been carefully optimized using a flow bench, a template, and so forth, to get the last CFM or 2 out of them. Largely useless on an untouched stock port, simply because there are so many other things that limit the flow, that the surface roughness is insignificant. Best thing you can do in exh ports is to raise the roof SLIGHTLY at the header flange surface (making the port "flare out" in the upward direction slightly, so to speak), and smoothing the "short side" radius WITHOUT lowering the port floor AT ALL.

In general, one should always try to remove as little metal as possible. The goal is to streamline flow and reduce turbulence, while retaining constant or constantly-changing air velocity all the way through. It is NOT to "hog em out" no matter what you hear in the McDonalds parking lot on Friday night.

 

You sure about the 727 retainers? That's $300 just in spring retainers.

 

Sorry, brain cramp. Try 787. https://www.summitracing.com/parts/cca-787-16

These springs. https://www.texas-speed.com/p-9573-g...laced-ls6.aspx

 

Thanks! Was wondering why the spring retainers were worth as much as the heads, lol.

 

I can see why you'd wonder that.

And my last comment about exh ports up there BTW, applies to them AFTER they've had a good valve job, the bowls are cleaned up, and the guides streamlined. I wouldn't bother with those other things unless the basics are covered first. Otherwise it's just putting lipstick on a pig and calling it a supermodel.

 

Alright, springs and retainers ordered. Now I just have to... wait... for the money to buy the heads. Oh, well. Suppose I can get the timing and everything else done.

 

Howards, Isky, comp etc.
You need to research proper homeand effective porting cylinder heads. "polishing" with a dremel is not going to gain anything. The meat and potatoes is in the bowl under the valves, the valve guide boss and the roof and short turn into the bowl. The port opening only needs minor squaring up. Deeper in the push rod pinch wall can be opened up.. pass on the polish.
cams Isky 201271, Howards, 110991-08
Lunati UDHarold 301A6Lun, 301A3Lun Comp xe262-10, Xe256h-10 comp CS260AH-8 #12-310-4

 

Use a 350 .015" steel shim head gasket when you reinstall your 305 heads or the cr will be less than stock.. The wrong direction.

 

The cam I'm running is a Lunati Barebones 280-290 with .443" intake and .465" exhaust, but I'm running 1.6 roller rockers.

The block mating surface isn't in the greatest shape. I've cleaned it up as much as possible, but I'm assuming copper form-a-gasket spray is still recommended for this.

 

You only need the 1.6 rockers on the intake side.
sbc's do not respond with 1.6 exhaust rockers the ex side is more responsive to event and duration changes..
The intake side is what gains wiyh 1.6 rockers, especially if the heads are ported.
use a 1.6 in/1.5 ex rocer set.
Install the .015" shim gasket clean and dry on clean dry surfaces.. Its the head deck flatness that counts.
The block just needs to be clean and reasonable.
No copper gasket spray is needed. they either seal up or they don't.
New GMPP head bolts are cheap.
Comp 265deh-10 is another good one.
Your 214-224-.443-.465 112 (107-117) cam is fine needs compression. DO NOT USE 1.6 ROCKERS ON THE EX SIDE.. just on the on intakes.. The slot in the head needs to be made s hair longer towards to stud.. not wider, longer (pushrod clearance)

The #601 heads need agressive full porting not polishing.. Get in there deep and get dirty.

 

Seems like I'm getting some conflicting advice here.

 

Also, I'm probably going to be using the 1.6 rockers on the exhaust anyway, as I don't have a set of 1.5 roller rockers and I don't want to re-use the old rockers.

 

Single pattern grind with a tighter LSA is better on the little 305s in most cases. I tend to stick with no more than 220° duration and no wider than 110° LSA on a 305 that is under 10:1 compression. As for rockers I had used a mixture of 1.5s, 1.6s and 1.7s on the same engine with the same heads and cam. I have even tried 1.7 intake and 1.5 exhaust. Had noticeable power gains stepping the exhaust up to 1.7s over 1.5s or 1.6s. Vortec headed 350 with a mild cam at the time. On a 305 head the exhaust valve is already proportionally larger than it is on a 350 so that is why the square duration aka single pattern cam works well. Its not the lift that makes the engine perform better from the higher ratio it is the increased lobe intensity and longer duration that makes it breathe better.

Rhoads lifters also perform very well on the smaller cubic inch engines. They shorten the cams duration 10-15° for the original design and 15-20* for the V-Max. Both of which tame the idle and keep your low-midrange torque. Around 3,500-4,000 rpm full lift and duration is restored and the top-end power of the bigger cam takes over.

 

I've got a set of 1.6 roller rockers. I'm reeaaalllly trying not to spend another several hundred dollars just to squeeze a few more horsepower out of the thing. Only reason I'm even getting the heads is because I didn't pay enough attention when buying the E-street 5089s and can't use them.

 

Alright, so the regular 601 heads weren't available, but after A LOT of searching, I found these ones on the same website. Not advertised at all, no links to them from the stock 601s, but supposedly they're the "SS" version, whatever that means. Apparently better valves and springs. Only $30 more than the stock ones, so we'll see. Here's the link in case anyone else wants a set: https://www.alliedmotorparts.com/pro...35037896114334

 

Aaannnd they sent me 993 heads. Great.

 

Not good. 76 cc chambers, OR MORE, instead of 58 or whatever.

Send em back.

There are other places to try where you can specify the casting you want. I've used www.headsonly.com before. www.cylinderheads.com is another you could look at, haven't ever used them myself though.

 

They say they're sorry for the error and they're going to correct it, so we'll see how it goes. But yeah, the feeling when I opened the box was not a good one.

 

Well, I've sent the wrong heads back (they provide a free return shipping label on each box for core returns) and I'm told the ones I ordered are shipping out tomorrow. I'm actually really happy about how this has turned out, as the last few 'wrong part' orders I've had have been an absolute slog to get what I ordered. These people always responded almost as soon as I'd sent the text/email, every time, and were very apologetic the whole time. Probably helps that I wasn't a dick about it. Allied Motor Parts, for anyone who wants to order stuff from them.

 

Heads are in! They came with upgraded spring retainers, too. Probably still gonna swap them out for the LS springs and adapted retainers. The valves are definitely slightly larger than stock, so that's nice. Looks like they made them as large as possible without seriously affecting chamber size/shape. They did come in a little dirty (I think it's leftover lapping compound stuck in the runners- grey and gritty) but that's alright as I'm going to be disassembling them for cleaning anyway. Overall pretty pleased so far, it appears to be a decent upgrade for only $30 markup over the regular 601 heads.

Edit: It's oil. They put oil on the head to protect it from rust. I'm an idiot.

 

Got a picture here;


No idea what those little 'dimple' looking marks are for, but they're perfectly flat with the rest of the head so who cares, really.