[kzooman83]

Quick question for you head-porting guys:

I am looking at buying a set of head porting templates from Mopar Performance for big block chrysler heads. My only concern is that the kit is intended for stock valve sizes (2.08/1.74) and I would like to eventually install larger valves (either 2.14/1.88 or 2.20/1.81). Would it still be a good idea to use these templates, or would the larger valves mean the whole bowl would need to be ground again?

Thanks!

*Also, I did not see porting templates for small block heads on Mopar's website; have those been discontinued? And if so, can I get them anywhere else?

 

[dana44]

Use the templates if that's how you have to do it, and if you go ahead with larger valves later, after the seats are cut, simply blend the bowls at the bottom edge of the new cut seat into the already ported pockets. This actually works very well.

 

[valiant67]

I don't recall ever seeing small block porting templates in the Mopar catalog. I may have missed them, but I'm not sure they were ever offered.

 

[stroudtom]

Porting templates were avaible from Mopar for the W2 head but I think that was it for small blocks.

 

[kzooman83]

Thanks for your replies. I will do that with the big block heads.

The small block heads are #302 swirl port castings with small ports. I want to open the runners up to 360 size (gasket match more or less) and add 2.02/1.60 valves. I would like to blend the bowls also, though; could I just have the seats for the bigger valves cut and then blend the bowls to match, like with the big block heads?

 

[dana44]

Yes, simply blend the bowl.

 

[kzooman83]

Awesome. I will probably get started with the small block heads in the next couple of weeks (I have to have them inspected first and cut for the bigger valves); I will let you guys know how it goes. Thanks!

 

[dana44]

What are you going to use to cut them? I highly recommend using carbide burr cutters, there is one about the size of your index finger, rounded on the end, it works best for the angle to open the bowl. It is not a matter of hogging it out as large as possible but contouring casting marks and better flow, then leave the texture the burr cutter makes, it is amazing how much cleaner the ports remain when they aren't polished with sandpaper rolls, really works good on the street and there is no way you would ever be able to tell the 3cfm difference lost with the texture, but does prevent the engine from loading up at idle the way polished ports can do on the street. Tear the heads down 100,000 miles later and the surface will look like you ported them the week before every time, just very efficient.

 

[kzooman83]

That's what I am planning on using. I have heard that polishing with sandpaper rolls does not accomplish much on a street engine; I think I will leave the finish rough knowing this. This is the first time I have done this, so I am kind of using the small block heads to learn on. Provided I don't mess them up too bad, I want to use them on a relatively hot 318 for my cousin's pickup (posted another thread about that swap). Am I on the right track with having a machine shop cut the valve seats and then blending the bowls?

 

[dana44]

I personally have done it the other way, ported the heads to the bottom edge of the seat, then cut the seats. This way you know you have a good bowl to start with and you will not tend to overport the pockets. You can think of it as once the heads are ported and the new valve seats cut, then simply flare and blend the existing ported bowl into the new cut seats, it will help prevent wanting to just hog the bowls out that way. The flare (I call it tulip shape), does really good because the way it flares out it packs the fuel/air behind the valve and then bursts out faster when the valve opens, then really flows outward when the rpm goes up. Kind of a ram effect, and it works.

 

[kzooman83]

Good to know. I guess I will start sooner rather than later, since I can do it before the valve job. Thanks!

Off topic: Can #452 big block heads be opened up to match a max wedge intake and exhaust gasket? I have heard yes and no, I am wondering if you or anyone else knows for sure.

 

[dana44]

It's kind of one of those yes you can, but no, they don't last, the walls get a little thin and don't last, valve springs tend to push through the port, things like that, so I don't personally recommend it. At the same time, you want to go to this extent, aluminum castings out there match the volume of the Max Wedge heads (like Indy).

 

[kzooman83]

I was also looking at the stage III cast iron heads from Mopar Performance with Max Wedge ports; I just wondered if it would be possible to save money by hogging out the 452s. I won't put Max Wedge heads on my little 400, but I would like to EVENTUALLY stroke it to 500 or 512 c.i. I am debating going with Max Wedge ports once i stroke it so I can keep the power band about where it is with the 400 (torque peak around 5000 rpm, based on port cross-sectional area). My intent is to keep it streetable but maybe make 500 rwhp.

 

[dana44]

Seems a little high for peak torque, it is usually best when kept down in the 3500-4000rpm range, so it must be a pretty big cam to do this. For racing, larger than 325cfm flow through the ports is fine, for the street, bottom end is quite bad, idle quality gets bad because there is so much dead air an automatic tends to want to drop out so idle quality in gear gets bad (I have had this happen in the past, my 283 in the Nash suffers from this when she is cold for the first couple minutes, but it may also be the cam itself). 300-325cfm is basically a set of ported Edelbrock heads, and for street engines doubling the cfm is right at max of what the hp can be for any engine up to around 7000rpm (it goes up from there, but then you are talking about a really big cam that won't work on the street, as in Nascar engines and does not include turbo and supercharged engines, that's forced induction). So with a stock set of heads running in the 225-235cfm stock, ported to hit the 300cfm is quite close to the limit of the castings but accomplishable, there is actually added capability of the flow with the carbide surface which really increases the fuel/air suspension and keeping it from separating below the 3000rpm range (where you drive the most), and above that rpm the surface doesn't essentially matter because the speed overcomes the imperfections and port design problems, but limits itself through volume. Kind of like an engine that all the sudden comes alive above the 3000rpm, port wall interference slows the flow below that, and then the guy says, yeah, she isn't all that impressive but when she hits 3000rpm, hold onto your seat because she jumps and will squish you in the seat. Well, it's that way because flow moves from the walls to the least path of resistance, skipping past imperfections, below 3000rpm it goes around and fills the voids and causes eddies behind those imperfections, so ported heads have a more consistent increase in power and the jumps are smoothed out better.

 

[kzooman83]

The idea would be to run a less radical cam and get the flow I need from the big ports. I have experienced the effects of a cam that is too big for a combination before, and I am trying to avoid that. If the larger ports would cause the same problem, though (lack of low end torque, poor throttle response, very tempermental around town), then I will probably stick with standard ports. The car is primarily street driven; I don't mind putting up with a motor that is a little tempermental, but I don't want to have to run a 3500 stall converter and 4.56s to keep it from stalling at every light.

440source.com has flow numbers for their heads posted (I am told they flow similar to Edelbrock rpms) and they reach peak flow at around .600" lift. As far as off the shelf cams go, the only way to get that lift in a street cam is a roller cam, and cams with that much lift tend to have a lot of duration (like more than 250 degrees at .050). My thoughts were that Max Wedge ports would allow similar flow with less lift, i.e. a milder cam that would have better manners on the street (well, in a 500 inch motor, anyway). Would porting and leaving a rough surface on the Max Wedge heads alleviate some of the low rpm issues associated with the big ports?

 

[dana44]

It will definitely help, but a street engine just doesn't like the large ports. Think of it this way. Think of water flowing through a one inch pipe is equivalent to an engine running smooth. If the same amount of water flowing through a two inch pipe, there is dead space (the water of a one inch pipe doesn't fill a two inch part, so this would be dead space), so what happens with the water in the two inch pipe? On a street engine it becomes unstable, stalls, flashes, doesn't do as good as you want, no amount of porting is going to work at low rpm. At the same time, high rpm is great because the port fills whatever the engine can pull, but on the street, there are more guys that don't understand porting that say they won't buy another ported head because they had ported race heads for the street and they suck. With this in mind, 440 Source and Edelbrock aluminum heads flowing he way they do at .600 inch means you can suck all the air at rpm you want to that lelvel without a problem, and the larger cubes simply pulls harder through the ports at lower rpm (its a volume suction thing, nothing more), and they will still produce power to redline, larger ports simply produce more power, but unless you run at that high rpm during racing, you wouldn't know how much more power could be made (out of safety really), so, the 440 Source heads with the ports simply improved from the sand casting to the carbide burr cutting surface will improve the flow characteristics by being able to suspend the fuel in the air better, and then the location you want to make the real power is in the combustion chamber. Case in point, I was reading a comparison of seven aftermarket and stock LS6 heads,(stock comparison, ported stock, then five aftermarket ported heads). Flow was from like 280cfm stock through 385cfm ported, and when it was all said and done, all dyno'd, the difference over stock was not greater than 50hp over stock (everything else being the same block and intake). At this point, there is around 75-100hp/lb-ft torque lost through the burn inside the combustion chamber itself. I proved this on a dyno simply porting the heads and intake for a 4.9 Cadillac engine, dyno sheet proved it, other ported 4.9 Cadillac engines never came close to the numbers I produced through combustion chamber porting. If the guy didn't have the dyno sheets, a guy that had been professionally trying to build this engine never would have believed the numbers we ended up with. Statistically, the 4.9 runs 275lb-ft torque at the flywheel, I got 349.7 at the rear wheels with porting and combustion chamber porting (this is where the most power is lost on most stock heads, but I will say, the 906/452 and similar open chamber combustion heads have very little work to make slight improvements, it is the lack of compression that keeps them down on power)..

 

[kzooman83]

Cool. It sounds like I would be better off sticking with the standard port heads. So the next question is how far can I push the iron 452s (in terms of improving flow) before it becomes a better option to invest in either performer rpm or stealth heads? I know the 452s have an open chamber and are iron, so they will tolerate less compression before detonation. Other flaws in the factory castings? Areas for improvement? Thanks again for the advice.

 

[dana44]

It and I have proven the myth of the aluminum heads and compression levels, several articles out there talk about it. The advantage of the aluminum heads comes down to weight and ability to handle when installing, they are simply lighter, and from there it is then improvements made by aftermarket companies over factory castings, period. Aluminum heats up more easily and maintains temp a little better in early running (cold engine), and they dissipate heat easier, but they also warp easier, more prone to head gasket problem if overheated, causing more damage when they have a problem. On the street the extra 75 lbs of weight aren't going to be fealt when driving around, and pop the hood you have the looks of aftermarket heads. So then the question is, what causes pinging? It isn't just compression, because if an engine doesn't ping at idle and cruise, why does it ping at throttle? I had a Chevy 350 I ran from Washington to Guadalajara, Mexico running 13.3:1 compression and travelled 17,000 in six months and ran it on 75 octane unleaded Pemex in Mexico without any pinging, ran on 87 octane all day long without a problem and pinging was not an issue until I got to pushing hills on the Mexican gas, but it was not dangerous pinging, made me slow down a little bit, that's all. One advantage was going from 9mpg to 13mpg with the raised compression. But to run this compression on 87 octane all the time without a problem, great. I have also run 10:1 big block 361 on 87 octane all day long without a problem, the whole issue of pinging with cheap gas is the combustion chamber and hot spots, something aluminum heads are capable of doing just as well as cast iron heads, so get rid of the sharp edges inside the combustion chamber and make sure the edges of the intake and exhaust valves are also rounded. The open chamber big block (and small block) heads have a sharp ridge all the way around the combustion chamber, this is your ping zone. The next thing is, if you notice, Mopars (of the past) always run less total advance compared to the competition (35-36 degrees, sometimes 37degrees), which is up around 38degrees from the factory. Basically the less advance an engine needs to use the more efficient it is because the fuel is burning better. A 10:1 compression that runs slower advance (I used a heavy and medium spring on the 350 and 361) because I didn't need the spark to run so early, my combustion chambers burn faster, similar to the open chamber heads (and Hemi heads), just have to take care of the ridge around the head gasket ring. Do that and she will run as high a compression as you want, use a flat topped piston, have at it. As far as opening up the heads, gasket match and ensure you have smooth as possible transitions and you will be happy. As good as the eyeball can tell and a set of dividers can measure, from intake to the valve, a smaller cross section will be the max flow available, meaning just ensure you try to maintain equalness all the way through and a flare at the valve guide boss to the valve seat itself. For the combustion chamber, place a head gasket on the head and mark each cylinder ring. whatever is inside the ring needs to be blended into the combustion chamber (this is your open chamber ping location).

 

[kzooman83]

Awesome. Thanks for all the advice. I totally forgot about edging the chambers; I had heard of this before, mostly on this forum. I will definitely be doing that also. I will be starting with the 318 heads soon, since I have them in my garage and off the engine already. I will see how that goes and then start looking at porting my big block heads.

Regarding the 318 heads, I have one final question: If I open the ports up to 360 size, do I necessarily need to put 340/360 valves in it to see the benefits of the porting, or would I still see improvement even with the stock 1.74/1.50 valves?

 

[dana44]

Truthfully, I wouldn't open the ports to 360 size, the casting will get thin in critical locations and may not last on the street very long. Adding the 1.88s from a 340/360 will make the ports of a 318 breathe just fine, even if you step up to guides from a Magnum, which are 1.94s, which work really well on a 3.9 that is then ported (yeah, I know that one, it was worth the time to do it when I freshened my Dakota). Now, the 1.94s have a different valve stem diameter but the guides themselves should be able to work in the heads since they would need to be punched out anyway, but not real positive on the valve length for this operation, whareas adjustable rockers from a 273 or aftermarket would fix that problem in a heartbeat. Gasket match the heads and intake to the 318 and they will run fine without having to try to get a 360 port out of the 318 casting, really not enough material to do it on a stock head, 1/8th of an inch of cast iron in some spots does not like to seal very well.

The conversation has mostly been about "bigger better?", and there is a way to make large ports work well on the street. There is first the porting and leaving the carbide burr surface which dramatically improves fuel suspension at lower rpm, to which doing a port match and carbide surface on a torker single plane intake manifold, you know, straight runners from carb to head, can actually be run on the street with the same results as a dual plane because the fuel doesn't puddle when there is slow velocity (low rpm). This is kind of a kicker given the size and straight angle of the flow, no control of air movement at low rpm, so, at the same time, large ports which maintain curves, so the fuel/air is controlled, keeping a fake velocity within the ports, works, too, but this is difficult because most ports don't have a lot of curve to begin with so one has to be creative in order to make this work.