Porting and Polishing question.

I'm surprised no one has jumped on this, as I too would like more knowledge. But I can tell you at least what I know, or how I see things at least. First of all I have always seen a Ferrari as a starter project. Not that its not a finished product, just that with anything in the world built by people, there is always room for altering things. Notice I didnt say improving. Thats because its so hard to actually improve something thats well designed.

Just porting your heads by themselves would probably at the least improve nothing, at most it could destroy your heads if done poorly, and destroy performance for the same reason. Porting is generally done only after other things have been done, or at the time other things are done. Bigger cams with higher lift, bigger valves, bigger intake manifold, more open high flow exhaust, in other words, what people are trying to do is flow more volume of air through the engine. More volume generally increases horsepower.

But a Ferrari already has a fairly high performance engine, and any real gains in power can be hard to find. The highest gains seem to be generally found with the later carbed cars and the early injected cars, as they were radically detuned at the factory to meet some rather silly emission standards that I dont entirely agree with. Putting them back the way "Enzo" would have intended restores a lot of lost horsepower. But to increase it beyond that takes more work. These 308 heads all seem to have a very nice finish in the ports right from the factory already. P6 cams can work, but generally require higher compression pistons. People have complained you lose a lot of bottom end torque and drivability, other says they work okay. Mine came with my car and I'll find out sometime this spring when it runs. Probably at that point, port "matching" would be of greater value. And you would most likely only see a gain from porting the heads in much higher rpm ranges than you would normally use on the street. Do you really want to rev it beyond 8K very often? The higher she goes the shorter the life expectancy of your engine. Up to 8k probably wont hurt it at all. But keep going up over 9k, or 10k, and see how long it stays together. Broken rods can do incredible amounts of damage. Ive seen blocks with large sections blown out by a broken rod.

I also dont see much room in my heads for bigger valves, not more than a mm or two at most. Remember that the head is water jacketed, and any metal you remove brings the outer surface closer to the coolant side. Puncture through and you either need to weld on the head to fill the holes, or find another head. thinner water jackets make more heat. higher performance makes more heat too, so do the math. You can either have durability, or high performance, but rarely both at high extremes.

If it didnt make the cars look so "unstock" I actually think turbo charging makes more sense than any other way of extracting more power while keeping the engine as durable as possible. It just needs to be approached with good knowledge and intelligence.

My intent at this point is to only port match my heads to the intake manifolds. However, I do not want to alter my heads by removing any metal at all. So instead, I will have metal added into the intake manifold ports on the sides that dont meet the heads ports, and will only remove metal from the manifolds. In other words, I will make the manifolds match the heads. I see places where they arent matching up that exceed 1/8 inch, and it seems to be almost all of them. So I assume it will make "some" difference.

Do you know, that on these 308 motors, the pistons dont come all the way up to the top of the cylinder bores? In conversations with Wiseco, they have seen every engine they looked at are down about .055 inch below the deck. I dont have a stock piston to measure, but I have 9.7 Borgos, the 7709 numbers for the LM engine. But in doing my calculations, and Wiseco confirms this, I did not have 9.7:1 compression. It was actually below 9! When I took out the .055 inch and re-calcualted, I found 9.764:1. Wiseco claims most of these engines barely have 7:1 compression, not the 8.8:1 as claimed. Mine were down .056".

Apparently Ferrari left some wiggle room for people in racing to find more power if they went looking for it, and to allow the engine to still fall within "stock" specs. You could concievable deck the block to bring the stock piston "above" the deck into the headgasket area, and achieve quite an increase in compression while maintaining a rather flat piston. My new Wisecos will protrude about .020" above the block, to basically achieve the same thing I could have done with stock pistons, although I will now be at a "true" 10.5:1. Actually about 10.46, lol.

 

In terms of money/horsepower, a properly designed exhaust system adds more to a car than just about anything. Porting and polishing, plus "cc'ing" the combustion chambers (cleaning up the combustion chambers so that each chamber is the same size) helps, as does boring and/or stoking, pop up, higher compression pistons, hotter cams, etc. It all depends how much driveability you are willing to give up for power, and how much money you want to spend.

 

Oh, yes you should remove the engine. I have heard you can get the heads off without pulling the motor, but it sure dont seem like the way to do it IMO. And you sure dont want to try porting them on the engine, for obvious reasons.

You can port them yourself for free, and if you read up on it can probably get as close as an expert. Or you can pay $$$. How much? Whats the guys name? I would imagine anywhere from a few hundred, to a few thousand, depending on who is doing it.

I was recently talking to a drag bike guy who runs nitro. Does his own porting. When I asked about flowing and matching the flows, he laughed and said it really didnt matter. Just port the damned things. He claimed his bikes were turning just as fast of times as the guys spending a fortune. Just remember, porting will start to wreck your low speed driveability.

 

If it is not a 4 valve then it would a good time to get rid of the sodium filled exhaust valves. Expert opinion has it that they are time-bombs

 

Over the years I have probably spent about 500-600 hundred hours on the flow bench. I can promise you that the very last thing in the world you would ever want to do is just "port the damned things". That will get you mismatched cylinders and screwed up mixtures as a minimum and probably result in less hp and torque too.

The cylinders need to match each other, the close the better. I like to keep everything within 1%. The engines I've messed with like the exhaust to be about 92% the intake flow. I flow the intakes thought the entire intake system and with the head mounted on a cylinder. The exhaust with the heads at least and preferably with the whole exhaust system. I also like to do the flow work at the pressure the engine runs at, about 10-12 in water for a multicarb or big throttle body setup.

The flow numbers need to be matched to the rpm, the cam to the rpm, the compression to the cam. When they all match, the low end power will not suffer and the engine will produce a nice broad torque curve. The more mismatched things get, the peakier the engine will be to the point that the peak power will even start to drop.

I really would recomend not just jumping into it with at least doing a bit of research and buying or building a flow bench.

That said, I don't mess around with it much anymore...I've discovered the joy of just adding boost....you'd be amazed how much air 308 heads will flow at 22 psi

 

Has anybody extrusion honed their intake manifolds?
I'd bet the TR has some hidden HP in its intake system i.e.: in the manifolding.... not the head.
Rgds,
Vince

 

Experts use flow benches for good reason.

 

1) Not really , but head removal is easier if the engine's out.

2) Few thousand

3) Nothing signifigant. The heads flow fine from the factory. If you want power, you aint gonna get it from porting. Period. Try cams, or some better tri y headers.

4) All engine gaskets, seals, o rings, and T-belts.

 

I've just finished a 308 job where I've had the heads ported and flowed. And I've done several before now too.

The engines respond well to matching the inlet ports to manifolds as they are TERRIBLE as std, and they also seem to respond to flowing. My guy swears by actually disturbing the exhaust port a little as it's too efficient. Mikes 92% rule is about right I think.

On a carb car, the surface should NOT be polished. On an injected car it doesn't matter so much as the fuel gets better atomisation anyway. Polishing a port does the same as polishing your paintwork. When wet with fuel/water the droplets will bead up on the surfaces, meaning fuel separation/bad mixtures for a carb car.

Definitely change the exhaust valves due to the sodium, but also the inlets work better with a more widened "Tulip" design. Basically widening the window for a given lift and creating better swirl. It also lightens them allowing less stress to springs and less effort to turn the cams at speed etc.

I always do heads in situ, unless there is a specific reason to remove the whole engine. I've never had to back track yet. My reason is that I run a business and try to avoid snowballing as much as possible, but if it were my own car with free labour and no time pressure, I'd use the opportunity to freshen the whole thing up. It'll take at least 4 times as long to do it by engine removal with associated "while I'm at it" jobs. I am well over 6ft though, so if you're a stumpy you may have to stretch a bit!

Extrude honing is a very good thing too, for long track inlets like a TR or any exhaust systems. There is less to gain from doing exhausts though, as it's going to get pumped out no matter what, but efficient scavenging on the inlet is worth chasing (a turbo is of course best here!).

FWIW, the car I've just done fires up from cold instantly and idles immediately at about 750 rpm with no throttle and no fast idle. Once warm it settles at 1000rpm and is VERY sweet all the way to 8000rpm....on stock std points and condensors with twin std Dizzies......

 

Yes the ferrari port is very efficient in stock form, but gains can be had by an experianced hand. These gains can mostly be had by paying close attention to the bowl area, say the first inch and a half, where the airflow has to make its turn. In this area the three main spots for improvement are: the short side (radius) turn, this requires blending all sharp ridges and smoothing the radius into or out of the port or combustion chamber.
Next is the area around the valve guide. This area around the guide must be sculpted a little pointed at first and gradually tapered out and around the guide. Make a little more space to the sides of the guide in the port wall. This gives the air a little more room to get around the guide and valve and make its turn.
Third on the short list is the area around the the sides of the port adjacent to the short side radius (Intake) This area if done right opens the bowl area and gives a little better shot at the valve with a lot less restriction. All areas must be blended and smoothed clear up to the valve seat itself.
Above all make your porting job a fine sculpture carried out with finesse and the ultimate of care. Think of it as massaging rather than heavy metal removal.
The nice thing about going through this exercise is that while youv'e got the heads off you can go ahead and port match the intake manifold and the exhaust headers. Significant flow gains can be realized by doing this. gary

 

The following represents some of our conclusions regarding the 308 head that has been completed in conjunction with the 4-liter project.

Stock 308 Head Airflow:

The stock 308 head airflow is not up to contemporary port design standards. Steve Demirjian has quantified the limitations of 2-valve head flow in the “Nick's 308 to 4.0 conversion” thread. This information includes airflow test results for the 2 valve head.

In a causal conversation between Steve and a high level representative from Air Flow Research, Steve showed him the Ferrari 2-valve head. The result was a lot of laughter. Then one of them commented something to the effect, “I guess they didn’t have airflow benches back then.” The 2-valve head is not very good. This fact is plainly visible to the training eye; they really don’t need an airflow bench to understand the problem.

Intake to Exhaust Flow Ratio:

I have provided some literature from Superflow’s shop manual regarding the ratio of exhaust flow to Intake flow. The general target is approximately 75 percent. That is why both exhaust valves and ports are generally smaller than their counter parts on the intake side. Our test shows that the stock exhaust port flows about 90 percent of the intake and at some lift points the flow approaches 100 percent. This can cause some problems that I will differ discussing to another time.

Vacuum Standards for Flow Testing:

Most people now use 28 inches of water as the standard pressure drop to test airflow. In fact, it is my understanding that Ford Racing goes all the way up to 40 inches of water. The newer, high-end flow bench manufacturers all sell equipment that is consistent with the 28 inch standard. A greater pressure drop between the flow bench and the ambient air accentuates variation in flow within the port. This is done to avoid leaving any horsepower on the bench. Published airflow numbers by automotive industry are generally listed at 28 inches, but this can vary.

Do it yourself?

Please don’t. For the reasons already mentioned, this is not a good idea. The learning curve is just too steep and too long.

Where to port?

I have attached information that shows where most porting gains generally can be achieved. I hope this is helpful.

One of the by products of the 4-liter project is that CNC porting services will shortly be available to remove the guesswork from this process. This will insure repeatable results and help drive down costs.

Thank you,

Mark Lewis
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While we are on this subject a couple of questions:
Before porting heads what is the process of improvement?
My car has no cats, K@N and a tubi, its also running a single
distributer and MSD. Its a 77 and will keep up my friends
QV (honestly). Before opening up the engine and adding cams
etc can the carbs be re-jetted for more power and is it worth
while adding some kind of crank fire system etc. I have also
seen things like lightweight, resized pulleys etc. Exactly what
is the next worthwhile stage if you want to improve engine
performance in a progressive manner?
I also find it fun changing thins around a bit, must be crazy!!!

 

Jon,
Rejetting and fine tuning on a dyno might net you a few extra HP.

From what I have read the best bang for your buck without removing the heads is cams and rejetting with fine tuning on a dyno. The next step is to pull the heads and pan to install 10:1 pistons. A lot of bucks for that additional bang.

The 308 engine is only 8.8 compression ratio and your MSD ignition should handle that just fine. Maybe go for a hotter coil.

A $1500.00 crank trigger/direct fire system is great for high compression and higher than normal RPM ranges but impractical for the price on milder modifications.

I run Crane XR700's on mine with both distributors and stock coils. It revs easily to 8,000 RPM without skipping a beat.

I am assuming you are talking about underdrive pulleys in place of stock. Light weight pulleys in themselves offer no HP gains. Underdrive pulleys reduce rotational drag by driving your water pump and alternator at a slower speed. As challenged as the cooling and charging system is on these cars I would NOT do it unless it was a track car and you were turning over 4500 RPM
continuously.

Be happy you can keep up with a QV. It's better than most 308's can do.

DJ

 

With dohc and one choke per cylinder, my guess is that the old 308 is still flowing fairly well. I don't dispute that it could flow more by porting, but porbably not that much.

My limited sense is that more cam and more compression is going to do a lot more for you. particularly considering that the stock cams were developed and compromised for ........"emisions", ditto compression.

I also have a 77 and am looking into finding someone who can recurve the distributor for better power/economy, as well as set up two crane pickups.

Someone once pointed out that the otto cycle engine was an ill conceived air pump and that anything that you could do to improve the ease of inlet or outflow would yield more power.
Compound this with the counterproductive crimes against naure that are done in the name of emisions and you have a vast area of opportunity, e.g.
compression, more favorable advance curves, for sure more cam, reduced exhaust restriction, (mufflers and cats), and reducing intake restrictions.

sorry, I ramble a bit. All of these things are less costley and more productive than porting, (as romantic as it sounds).

Clearly, vastly more hp could be gained with with turbocharging, (have done that), or by supercharging, (Tried that).

My preference is for a low mass, high compression, quick revving, simple, carbed car. I think that the 308 is fairly close to that and am willing to really look into doing it better.

How can I do it better??

???
chris

 

Sam,
The sad fact is that you purchased a 2-valve injected 308--the dog of dogs--slower that most 6 cyl mustangs. I know my friend-cause I was right with ya for a loooong painful time.

DO NOT go over board trying to milk horsepower out of it.

There are several options and you need to weigh the costs carefully.
a) go to carbs, hi comp pistons, new cams--308 2-valve motors and a snap to hotrod once you dump the injectors.--$4000-6000
b) pull th emotor and swap it out with TRutland for a 308v4 motor.--6-7000.00
c) take the 7k--add your existing car--upgrade to a 4valve car or 328.

THE POINT BEING----do not get sucked into the endless spiral of looking for power in that car--fix it ONCE or it will live in the garage more than on the road--DRIVING IT IS A LOT BETTER THAN LOOKING AT IT IN PIECES!!!!!

 

I reread what I wrote and I need to quantify something. I wasnt saying to just "port the damned things", that was what this crazy bike guy was saying. But I also believe, that like someone pointed out about it being done artistically, some people have experience and talent that go beyond what we think is possible. Looking at his yard full of bikes and parts, one could assume he has spent his life wrecking heads looking for power until he no longer needs a flow bench. As he said, his bikes never really need to idle anyway.

That all being said, I absolutely believe you need and should use a flow bench. Better yet, I think the heads should be left alone. When you port a head you remove metal that cannot really be put back, and you weaken the head. I am 46 years old. My car is 27 years old. If I can still drive 30 years from now, my car will be almost 60 years old. How many heads will be around for my grandson in another 30 years if they are all used up?

22 psi you say eh? Wow, that would make some ponies the cheapest way possible if done wisely.

 

Thanks for all this. Is it true that early 77 308 have different cams already and put oput a bit more HP and do you know a specific cam that would offer an improvement. I seem to have read somewhere once that Ferrari actaully offered a high performance kit for 308s in the late 70s.
Yes I mean't the underdrive pulleys, Nicks website also advertizes a harmonice balancer that is mean't to add a few HP.
Again as others have stated I love my car and would be happy with a motor producing a genuine 275hp whilst still be manageable in traffic. I figure that will result in a performance at least as good as the early Euro models. If this can be done for 4 or 5k then that is great.

 

As I stated earlier, the stock 8.8 pistons do not come all the way to the top of the bore. The compression of 8.8 is only theoretical and would only be accurate if the piston came all the way up to the top of the liner. Wiseco seemed to feel the actual was only slightly above 7:1.

My engine had 9.7:1 pistons, but after measuing and cc'ing the combustion chambers and piston dome, the actual was just over 8.4! If the 308 engine is rated at 255 HP in original form with the original cams, then its only because they probably decked the block the .055" that the pistons are below the deck.

When I bought my GTB, I found it had P6 cams. These are Ferrari factory performance cams that they used in the 308 GT/4 LM racing program. I am making some assumptions based on other posts and and other peoples dyno run results made with simular engines, that when I put it back together with my new 10.4:1 actual compression, that with those cams and the engine tuned well, I should be close to 300 HP at the crank. Using the 18% loss figure through the gearbox should leave me with about 246 HP at the wheels.

As I already have all the big parts, and as everything is measuring out within factory specs, I dont need much machining. I don't know yet how the heads will come out, but I am planning to replace all the exhaust valves, and probably all the springs. I am hoping to have the heads done within a $500 budget. We'll see how I fair on that. I may get buy with $2500 parts and only some minimal labor I cant do myself. We'll see where I come out in the end. I think if you shopped around to have cams welded up and reground and hardened, you could have simular cams for maybe $500. I know a cam shop south of me that I know could do them and they are well trusted. But I have never spoken Ferrari with them. But I am sure they could duplicate my cam profiles.

 

Are you serious!!! I've never heard this before. Our engines only have a compression ratio of 7:1.....well that just plain sucks. Me thinks I should do an engine out "service" next winter!

 

I am absolutely serious. My pistons stop .056" inch from the top of the cylinder. Wisecos figures were .055" and are from all the 308 engines they have made pistons for, which include both 2 valve, and 4 valve engines. They all apparently stop short at about .055" from the top. Wiseco felt that the reason was so someone who seriously wanted to race could gain an advantage by decking the block while remaining stock and using stock components. This obviously leaves everyone else running stock motors with rather sick performance I would think, and also probably explains why no one has ever seen the cars make dyno numbers that match factory claims. When I calculated out the .055", my figures fell at 9.76:1 using my Borgo 7709 pistons, which are supposed to be 9.7:1. My new pistons will not only be .055" taller above the wrist pin, but will protrude into the head gasket area a few thou so as to keep the piston flatter for better combustion. This was Wisecos suggestion and follows other 308 pistons they have made and had good results with.

 

I short, porting and polishing is probably the most labor intensive and most expensive operation out of all of the other options for the smallest gain in horsepower.