How much did you gut out of the chambers? Just curious, +X cc's less means less compression.

Good job, and thanks for all of the info and pictures!

 

Actually, I think at the most, I might have removed maybe 2 or 3 ccs from each chamber, all told. I've learned today these heads have been milled twice already, so the compression is still going to be fairly high. They likely have come off a 1984 Z28. That certainly fits their 601 casting number.

You're welcome! I hope it helps you with your heads

 

Hey I am off work by 6pm Sunday I wanna go too! Sitting Bull call me on my cell or whatever and we can all go for a brew! -TS

:lala:

 

You got it Teal Shark

 

And finally some pics of the assembled heads, ready to be installed

As you can see, they are painted an aluminum colour. It is good to 1000* Farenheit.

 

A shot from the opposite side.

 

The combustion chambers and valves, showing those nice new 1.94" intakes

We also planed the heads by .007 just so I could be James Bond. Just kidding, about the Bond part

 

A couple closeups of the combustion chambers. I made sure to chamfer the sharp edges of the chambers, in order to remove any possibility of them causing detonation. Sandpaper and your thumb is all that is required for this.

 

The second shot.

 

Head on one end.

 

A pic of my Crane PowerMax 260 cam.

 

Hmmm, the intake valve seems to stick out into the quench area a little bit, eh?

Are you going to check piston to valve clearance?

 

The Crane's spec card.

 

The info stamped on the end of the cam. It says 11-06-02. I wonder if that is its date of manufacture?

 

And a pic of the cam with its fancy stickers--worth at least 20 more hp, eh?

 

Yeah, it isn't completely flush but I'm pretty sure it is going to be OK.

Hey, where's some pics of your port job? Still haven't seen any at all!

 

Yeah, the pistons are dished a little bit so the valves ought to clear OK. I hope.

 

And finally some pictures of the assembled engine with the cam and heads installed. All stickered up, too--can't toss away 20 free hp, eh???

 

Another one.

 

Mmm, mmm, good

As you can see, I painted the headers with a high heat aluminum paint that is rated for 1000* Farenheit. Not that I expect it to last, that's why I took the picture

 

Last one!

It really has a lot more power above 3500 rpm now. It is like another passing gear when the secondaries kick in--you really feel it coming on! Pins you to the back of the seat! And a wicked barking rap to the exhaust, too.

I estimate it will now do mid-14s in the quarter mile, especially since I put 3.42 gears in, as well.

So there it is. About 65 or 70 more hp from the heads and cam, and maybe another half second off the ET from the 3.42 gears, too.

That's one horsepower per cubic inch. A REAL 305 High Output smallblock Chevy, the way the factory should have made 'em!

The job is done. And if I can do this (with the help of my buddy Stewart Baldwin twistin' wrenches), any of you can port and polish your own heads, too!!!

 

And this is what the hp and torque curves look like, comparing the final engine to the engine before the porting and polishing, and the new cam.

Like I said, hang on when you hit around 3000 rpm!!! :hail:

 

looking great!!

 

Bull,

You could probably get about 30 more HP with a slightly hotter cam, around .460-.480 lift. Did u change the valves as well?

 

I don't want a radical cam because this is my daily driver, and around here that means -30* in the winter. It is very hard to keep a car running well with a lumpy cam at those temps

Yes, I installed all new valves. 1.94s to replace the 1.84s but I left the exhaust valves at 1.5.

 

Those heads came out looking pretty good. If I ever take my engine back apart, I am going to go heavier on the porting on mine. The compression is on the high side of 11:1 and I'm not to fond of it, so that may be an excuse to tear into it now!!

 

Sitting bull- I think I might have some relevant info to share about these heads and your port job:

The heads are slightly improved versions of the old 70's era 305 heads. They have the same spark plug location where the plug is basically flush with the chamber wall. Officially, they are still 58cc. The reason they don't look like 58cc, and the reason they don't have that familiar squared-off look to the chanbers is that they basically took some of the volume around the exhaust valve away and then did a modest job adding it back in around the intake valve, slightly unshrouding it. This was necessary when they bumped up the 305's intake valves from their original 1.74" size (70s era) to the larger (thank Goodness) 1.84" size. On other designs they made even more changes and pushed the plug further into the chamber (that sqaure, intrusive plug boss you see on that one comparative photo you posted) and then added the volume BACK IN around the exhaust valve again to bring it back up to 58cc and again make the chamber look "squared off". The intrusive square plug boss might hurt flow SLIGHTLY but it puts the plug tip in a more optimum point in the chamber for better combustion. Later Vortec castings still use this intrusive plug location, which should give you an idea how important plug location is in making good combustion. Whew! That was a mouthful. Re-read several times and I think it will make sense.

The "hole" in the roof of the intake port under the rocker stud is on all Chevy SB heads. It's part of the casting process. They cast in a hole and then machine it out a little more at the top for a real tight fit on the rocker stud (pressed in rocker studs) or machine it for threads (screw in studs). Totally normal, doesn't seem to hurt flow any.

Don't sweat about unshrouding the exhaust valve too much. It doesn't hurt and it doesn't help. "Shrouding" as a flow-limiting phenomenon seems to be far more important on the intake side than the exhaust. (Personal experience). Opening up aroung the intake valve all the way out to the bore-limit is almost always a good thing to do on a little 305. It looks like your chambers were almost there in stock configuration and you took them about as far as they can go- good job on that, I think.

A REAL IMPORTANT THING TO BURN INTO THE BIO-COMPUTER WHENEVER YOU'RE DOING PORTING..... 80% of the flow potential of any head happens 1/2" before and 1/2" after the valve seats!!! Can't stress this enough (also, professional head porters will agree and live by this rule, even Mr. Vizard). My personal experience with home port jobs (done about 8 or 9 successully over the years, don't ask about the failures) proves this to be true in spades. That's where all the power is. First-time porters like you and me don't want to get close to the seats for fear of slipping and destroying them. Sorry, but you're gonna have to get up-close-and-personal with them if you want to make serious flow. I notice what I beleive to be a "lip" on some of your intake and exhaust bowls between where the machined seat area meets the cast runner. IT'S GOTTA GO. Lots of flow left there.

About the "short side radius" issue..... Like was said before, you want it to be just that- a RADIUS, not a series of sharp angles. Don't change it's general shape- jsut take the sharp edges off. This applies to both the intake and the exhaust.

Last one......larger valves. DON"T do it! Unless you are ready to port them all over again. When you install larger valves you change all the shrouding relationships (inside the chamber) and seat-to-port relationships (inside the ports). In short, you install the larger valves BEFORE you go porting. Even then, their effect is not predictable on power unles you have a flow bench and dyno to test out the changes. And remember, 99% of all 350 Chevys use that same 1.50" exhaust valve and exhaust port. Something to think about.

Last one (really this time)..... Use back-cut valves (or have stock valves back-cut). Don't shove untouched stock valves back in there unless you back-cut them. You want a nice gentle slope on the back of the valve head down to the seat contact area, not a sharp angle with a lip like stock valves have. The air has to squeeze down past the seat real smooth, so having a nice smooth port on one side but a sharp nasty angle on the other side (back of the valve) you're giving up flow like crazy. Undercut stems look real cool, but properly back-cut valves will make a much bigger difference in flow.

 

Damon, thanks for the info! I appreciate it. Even the Mortec site has next to nothing to say about these 601 castings. Do you think our current high voltage coils make up for less than optimal plug placement in the chambers? I ask because I'm using top notch components in the ignition; MSD cap, rotor and wires, Proform 50000 volt coil and Bosch Platinum plugs gapped at 0.45. I really like the chamber shape a lot better than the ones I took off, and the engine runs like silk with this new setup.

The guys at the machine shop were able to unshroud the intake valve a little more, as you can see when you look at the closeup shots of the finished chambers. That is even after they enlarged the seats for the 1.94" intake valves.

Those inset ridges in the valve seats, both intake and exhaust, were machined out by the guys. They did a really nice job for me, mostly because I ended up waiting patiently for them for two weeks to get around to them because one of the guys was having bad back problems. (I can understand that, since I have the same troubles.) They even knocked the price down to $390 Canadian from the regular $470 because of the wait

When they machined the intakes to accept the 1.94 valves, they solved a problem I was worried about. I thought I might have been too extreme on the bowl blending at the seat area, perhaps exceeding the 91% rule the experts warn about. But after they enlarged the seats and even machined down into the bowl area abit, I could see that I had only gotten out to around 85% of the seat diameter and was A-OK there. What a relief! They then removed the lips under the seat for me.

The short side radiuses turned out just like you recommend. I only worked with what was there and didn't remove massive amounts of iron. It just wasn't necessary at all. By far the largest amount of material came out of the bowls. Man, were they ever rough as cast and machined from the factory! When I was done with them I was sweating from all the fierce grinding I'd been doing. I spent hours and hours on the bowls, blowing out metal dust and running my fingers over the contours until I was satisfied they were smoothly shaped and nicely enlarged. Like I said, I was worried I'd grossly overdone them until I saw how they looked after the enlarging of the seats at the machine shop. The final appearance was very nice, just like in the pictures of the ones the pros do. It just takes a lot of time and effort. Interestingly, they were not ground down from the cast finish in all areas--I only ground out what didn't flow from one area to the next. Some of the bowl area at the junction of the runner was simply untouched because it fit nicely in with the shape. And I thought the rougher surface would encourage a better aeration of the fuel/air mix.

I decided not to enlarge the exhaust valves from their 1.50 stock size. It would have been another $80 and I didn't think it was necessary.

All of the valves were treated to a nice three angle valve job, so they should be flowing nicely. It sure has a lot more power than it did before!

Other than that, the valves are just plain old stock replacement valves, not stainless steel or anything exotic.

 

Plug location is one of those pieces of black art in head design. I'm not the most knowlegable about it but the general idea is to start the flame kernel as close to the center of the chamber as possible. I think having a killer ignition and running afairly wide gap might make up for a little of the bad plug location but probably not much. End of the day, however, flow is what really makes power, regardless of where you put the plug.

Next time you have those heads apart make sure you back cut the valves. It'll give you another ~2-3% more flow (esp. at low lifts) with no other changes. Just use the diagrams in "How to Hotrod Small Block Chevys" to give you an idea the cuts that need to be made. Any head shop has the tools to do it.

I'd say overall, a damned fine job for a first-time home port job. Much better than the first set I ever did.

 

And finally, here are the latest flow numbers that F-Bird'88 has gotten from his ported and polished 305 heads.
______________

October 17, 2002

The latest set I did with 1.94 x1.60" valves flowed 238@28" in
and 189 ex.

Thats not too shabby for something that you'd throw in the garbage.
Even my friend with the flow bench was shocked. "This thing must be leaking or something!!"

We flowed a set of Brodix -8's and a set of 2.02 Vortecs
at the same time so we know the bench was operating right.
Outflowed the unported 2.02 vortecs and a set of mildly ported
041's.

If it ever stops raining here:
I will be getting them on the car (with a few other mods
single plane intake .550" lift solid cam, 12.65:1 cr)
and will report on their performance.
My vortecs (Set A) are coming off. Flow was 228@28" on these vortecs and it runs 13.05. Won't be a direct comparision but...

Looking for a 12.6? et at about 108mph
I'm curious to see what these 305 heads would do on the dyno
also.... maybe some day.

In my opinion these 305 heads have a little more potential
than the common open chamber smoggers if you're willing to
put the work and bigger valves into them. The combustion chamber size and shape is better especially after a lil reshaping (unshrouding). The ports are about the same.

Note: These 305 heads are not lightly ported. a lil pocket port
will not cut it. Plan on removing some metal.
_______________

Just by way of comparison, stock L31 Vortec heads flow 228 cfm at .500 lift on the intake side, and 140 cfm on the exhaust side.

So let's see how much hp F-Bird'88's recently ported 305 heads can produce.

In the February 2002 issue of Car Craft, on page 54, under the "How to Port Cylinder Heads" article, they state that AirFlow Research has quantified the question of Air Flow = HP with a formula, which they claim is "fairly well established." It reads thusly:

hp = cfm x 0.2575 x number of cylinders.

So just plug in your numbers and it should be pretty close.

238 cfm x 0.2575 x 8 = 490.28 hp!!!!!

WOW!!!!!!!!!!!!!

That is well beyond any stock set of Vortecs

And he was selling these heads a couple of weeks ago for a MERE $375 US, plus shipping!

You can duplicate what he has done by following the instructions laid out in this thread, and only spend about what he is selling them for

So who says you need to spend serious coin to have an excellent set of heads, eh???

If this thread has made you rejoice in new found hp and torque, drop me and F-Bird'88 a line and let us know. It makes us happy to see YOU happy :hail:

 

1. there is alot of flow to be found there, its on the roof where the most flow can be found, by using a flow bench we have seen an increase of upto 15cfm (882 heads). You can expect an increase of 5 to 10 cfm by filling that area on most chevy heads....by head numbers 10 cfm is alot

 

Here is a copy of my machine shop bill for all the work on the heads.

On top of this would be the $40 for carbide cutters, $48 to rent a die grinder and $30 to build a speed control unit. Add another $25 for some wrecking yard heads.

sub total = $532 Canadian, or about $340 US.

They knocked $80 off for my two week wait, so let's add it in just to be accurate.

Total = $612 Canadian, or about $390 US.

You can't find another set of good performance heads for anything close to that, I'm sure

 

Yeah and how much did the bare heads cost?

 

What, you don't remember?

I added $25 to the total to account for that

 

Looks like you done a hell of a porting job though. You may do better than mid 14's.

 

this would be a great tech artical, take out some of the posts that ask questions and some other non relavent posts and it would be a lot easier to read and print out.....

 

Aron213: Your absolutely correct and I stand corrected,
We retested my 305 heads today, with and without the void in the port roof filled in with puddy and picked up and additional 6cfm at high lift by filling in the void. Not bad.

 

now you have to find an epoxy that can withstand heat and can withstand fuel!

 

Anybody have any pictures of what needs to be filled? I understand that the roof needs a little extra meat, but not too sure where.

 

the area in this photo where the arrows are pointing

 

Just go to File>Save As and save the whole thing to your hard drive. You must save both pages, however.

 

Have to keep this in perspective. The other set of heads
I did flowed more air without the void filled in than these heads
did, with it filled in.

 

if you have two different sets of heads you cannot compare the two. Your ports are not identical therefor the flows will vary from head to head

 

Isn't that interesting! I remember in the Super Chevy mag "How To Port Vortec Heads" article I emailed to F-Bird'88 that they found no increase in flow by filling in that cavity on the L31 Vortecs. It must be casting series specific, eh?

 

considering that void isnt on the L31 heads you cant fill it.

Dude I do this for a living, Ask Jester from the carb section who I am, he will inform you that I just might know what Im talking about.

 

Let's not misunderstand each other. I'm not questioning your qualifications :nono:

I'm only stating a bit of info that I found in a Super Chevy article on porting Vortecs. The hole in the top of my 601 castings was fairly large, too. After all, that is a pic of my cylinder head that you linked to a little ways back.

I'll take your word for it that the one in a Vortec isn't as large.

So, would you use JB Weld to fill it in? Is that stuff gas and heat resistant?

 

we use an "A" "B" epoxy, Im not sure about JB weld.

 

so who wants to port n polish my heads

 

JB Weld says it's good to 400 degrees F. Fine for intake ports, no good for exhaust.

Worlds don't have that rocker stud hole going into the intake ports. Another reason to go with them. And, you still don't have screw-in studs, which would increase the cost of "fixing" stock heads (although pinning would seem to be a reasonable, inexpensive alternative).

The whole idea of this post is, "You can port your own heads."

 

has anyone actualy got any real data on HP and track times with the ported heads?