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figulaz
11-25-2013, 01:16 PM
I have my original 92 stock heads and block I want to have machined for a 5spd roller I'm getting. I took it apart and had water pitting in one cylinder...deeper than a hone could handle. I figure I need to overbore .010. Since i'll be getting pistons is there a stroked piston/ rod combo worth doing?

For the heads I'm willing to go new valves,guides and seats with the heads...so might as well go bigger right? I won't do (can't afford) any porting other than a gasket match on the intake. Is there a valve size head and stem to request that works well. I'd be shopping for a cam with smooth idle and low end torque...maybe stick with stock? I'm looking for a reliable foundation for my ported late model blower that approaches 300hp and can pass CA smog.

short list of bolt-ons at my disposal as my 92 is now stock and will likely be my dads daily driver for the near foreseeable future.

ported late model (mpii attempt)
5% jackshaft
10% blower
stock ported inlet
75mm TB
C&L 80mm MAF
Dual intercooler w/fan
36# and 42# injectors
ported 94 exhaust manifolds.

jdsgallops
11-25-2013, 09:19 PM
I wouldn't waste your time with a port match. The intake to head mismatch is very minimal.the only thing you will gain is likely piece of mind. If you go to bigger valves this is even more true. You won't gain much airflow by adding bigger valves without addressing the "bowls" or the area behind the valve. This is the major bottleneck in the SC heads to begin with. You will also need chamber work to gain maximum airflow as the valves are already shrouded. Adding to the cost of the rebuild. That said IMO after doing a couple sets of SC heads the only way to do them "correctly" is to go with bigger valves. This will allow for the port to be developed properly, which is what any good competent head porter will look for not big flow numbers. These are my conclusions at least after doing 2 sets of heads for myself in the last few months. For what you will spend in upgrading to bigger valves you can have port work done that will likely give you more in gains and have a better overall port, which will makw the most power.

Other than that I would highly suggest you make the machine shop aware to radius the crank if it needs to be machined. My recent rebuild started with what was thought to be a bad crank sensor and turned out to be a broken crank. Being the engine had been rebuilt prior to my ownership by an unkown but appearing to be cheap budget engine builder and where the crank broke I am chalking it up to poor machine work and not radiusing the crank correctly as the bearing manufacturers and Ford suggests.

figulaz
11-25-2013, 11:22 PM
I guess there is no way around it. I had read around some older threads that pointed to small block Chevy valves but they either went unanswered or ended inconclusive. I was hoping a bigger valve combo would give me something. My machine shop is more of a production environment...they'll put in new seats and valves but don't mess with porting. My bearings had normal looking wear so i'm hoping i can get away with just polishing the crankshaft but I'm glad you mentioned radius. I had to look it up. In my dads shop (15-20 yrs ago)we'd send stuff to a machine shop and I never remember the subject of radius coming up. But i guess we did budget builds. I do have two sets of heads and a die grinder sanding rolls carbide bits...whats the worst that could happen? I did my blower,lower intake and intake ports on my other car and it still runs:D

Mike8675309
11-25-2013, 11:34 PM
Your machine shop should be able to determine the needed overbore. You can't know that until measurements are taken. Don't order pistons or rods until that is completed so you can be sure of the overbore necessary.

Any piston/rod combo will require custom pistons. Check with XR7 Dave as he has stocking of some common combinations. With the stock crank there isn't much room for longer rod/pistons and I don't know that there is significant benefit to going any longer on the rod. XR7 Dave could provide you some specific suggestions that match up with your goals for your build.

Bigger valves without some bowl work is unlikely to give you any advantage and might reduce performance. Again, XR7 Dave could provide you information.

jdsgallops
11-26-2013, 11:56 AM
If you have to confidence to do your blower you can do your heads. Just do some research on proper porting theory before you dive in. After that you will see things fall in place pretty easily. Even a backyard port job that "only" gains 30-40 cfm when combined with nearly 1 bar of boost should provide very respectable performance gains. The thing to remember though is boost is basically the measurement of the restriction to the airflow in the engine. Meaning if you run a 5% blower pulley which typically yields 14psi of boost it may only show 10-12psi. Even at that level you will be moving more air than the higher level on a stock head.It should also help keep inlet temps down. All of which help produce more power.

figulaz
11-30-2013, 11:54 PM
I'll give it a shot. I've just been comfortable removing casting marks. I gasket matched and felt conflicted because of talk about bigger cfm at the expense of velocity. My car is stock and feels better but I'll never have flow numbers...it felt pretty good even with the early blower on it. i just bought a junkyard engine so now I have 3 sets of heads so I'm going go a little more aggressive. i plan to unshroud and gasket match but i need a little clearer idea In terms of bowl work raising the roof anybody have pics or hand drawn diagrams? Up close pics of runners , bowls...center cyl?(#2&5)

jdsgallops
12-01-2013, 02:51 AM
All the talk about velocity is kinda hype when dealing with stock castings. Ford makes there ports so small that even when you grind on them they aren't going to get too big to kill velocity unless you really mess something up. In a N/A engine you look for a velocity around 300 ft/sec at peak torque. Very easy to achieve at low rpm with stock castings. Don't worry about hurting velocity.

Head porting basics 101

1) the ideal port shape is that of a funnel
2) you do not want to lower the short turn radius under any circumstances
3) to aid airflow at the short turn radius you want the port "D" or trapazoidial shaped to help slow the velocity at the short turn radius to help it make the turn
4) the bowl should be 85% the diameter of the valve. What I have found is if you find a good shop that knows how to do a proper 3 angle valve job the bottom angle goes from the seat to the bowl at 85%, the middle angle is the seat and the top angle blends into the chamber. For best results find a shop that still cuts these by hand!
5)aim to make the port as straight as possible
6) tear drop or remove valve guide bosses in the bowl area. In all but the most extreme cases there is enough guide in the head that a street cam will have no problem with valve control. I believe I took out the guide on Intake and Exhaust on my sc head.

If you use these simple rules and your finger as a guide to feel high and low spots the port will fall into place. A vacuum cleaner can also show you flow patterns when cleaning out the port. Or use water. Observe the port and how and where the water comes out of the port. As you move along the steps you will see changes in it's behavior.

Finally if you have extra heads and don't mind sacrificing one of them, find someone with a band saw and have them cut the head straight through the center of the valve guide. This will help you see thin spots or where to becareful because of a water jacket close by. It will also show how much straightening the port will need.

If you have a dremel feel free to use it. Yeah it removes less material quickly but that is the whole point when beginning. Once you know what you are looking for jump to the die grinder and get it done quick. Just a few things I have learned over the last 20 years.

XR7 Dave
12-01-2013, 01:41 PM
All the talk about velocity is kinda hype when dealing with stock castings. Ford makes there ports so small that even when you grind on them they aren't going to get too big to kill velocity unless you really mess something up. In a N/A engine you look for a velocity around 300 ft/sec at peak torque. Very easy to achieve at low rpm with stock castings. Don't worry about hurting velocity.

Head porting basics 101

1) the ideal port shape is that of a funnel
2) you do not want to lower the short turn radius under any circumstances
3) to aid airflow at the short turn radius you want the port "D" or trapazoidial shaped to help slow the velocity at the short turn radius to help it make the turn
4) the bowl should be 85% the diameter of the valve. What I have found is if you find a good shop that knows how to do a proper 3 angle valve job the bottom angle goes from the seat to the bowl at 85%, the middle angle is the seat and the top angle blends into the chamber. For best results find a shop that still cuts these by hand!
5)aim to make the port as straight as possible
6) tear drop or remove valve guide bosses in the bowl area. In all but the most extreme cases there is enough guide in the head that a street cam will have no problem with valve control. I believe I took out the guide on Intake and Exhaust on my sc head.

If you use these simple rules and your finger as a guide to feel high and low spots the port will fall into place. A vacuum cleaner can also show you flow patterns when cleaning out the port. Or use water. Observe the port and how and where the water comes out of the port. As you move along the steps you will see changes in it's behavior.

Finally if you have extra heads and don't mind sacrificing one of them, find someone with a band saw and have them cut the head straight through the center of the valve guide. This will help you see thin spots or where to becareful because of a water jacket close by. It will also show how much straightening the port will need.

If you have a dremel feel free to use it. Yeah it removes less material quickly but that is the whole point when beginning. Once you know what you are looking for jump to the die grinder and get it done quick. Just a few things I have learned over the last 20 years.

Most of this is generally true and follows standard cylinder head porting rules and guidelines. However, not everything that is generally accepted applies directly to the SC cylinder head situation.

For example, most people think of ports #2&#5 as being the worst but in reality those are the best port designs of the set. I know that throws a monkey wrench into everyone's thinking, but there is a specific reason why the center ports are superior, and to really do effective porting you have to be aware of that first.

Besides the general port design, on any cylinder head the most critical area is that which is within 1" of the valve. For the beginner, the most important thing is starting with a properly sized valve and the properly formed seats. Then you can do minor work from there and surpass the end result of a full on ported but stock valve head. The stock valves are indeed the biggest bottleneck in the heads, but just putting in bigger valves doesn't accomplish the result because it's not so much the bigger valve as it is what you can now do with the added area under the seat that counts.

I have pictures on my facebook page of some extremely effective, yet (what I call) unported heads. What we do underneath the seat and within the first 1" of the port is the same on a stock head/big valve combo as what we do on our all out street heads. The biggest difference between the two is just what we do beyond that 1". ;)

jdsgallops
12-01-2013, 10:49 PM
Good to see Dave says "most" of what I said is accurate.

You are correct though Dave each head design does have it's own intracancies. I have cut my teeth on SBF heads in search of budget performance when I couldn't afford aftermarket castings. This yielded results of stock cast iron heads flowing as well as early edelbrock aluminum heads at all data points. But if I were to take what I learned to a SBC head I would need to do everything backwards as the SBC heads flows differently.

I do disagree to a certain extent on the bigger valve not helping flow though. Bigger valve equals lower velocity which should provide a small gain, at least in theory.

Bottomline is to not look at peak numbers but flow at all data points and then compare over all flow with the theoretical max flow the of the valve diameter used. This will tell you how well developed the port is. Until the law of diminishing return rears it's head the need for larger valves is really just a matter of spending money that could be spent elsewhere to get a bigger gain in power.

XR7 Dave
12-01-2013, 11:57 PM
I do disagree to a certain extent on the bigger valve not helping flow though. Bigger valve equals lower velocity which should provide a small gain, at least in theory.

Bottomline is to not look at peak numbers but flow at all data points and then compare over all flow with the theoretical max flow the of the valve diameter used. This will tell you how well developed the port is. Until the law of diminishing return rears it's head the need for larger valves is really just a matter of spending money that could be spent elsewhere to get a bigger gain in power.

I didn't mean to imply that simply installing a bigger valve won't help anything, but what I meant is adding a bigger valve sets the stage for much bigger gains beneath the seat. You will pick up about 5% over most of the range, but mostly at low lift with just putting in a bigger valve. Forming the seat and bowl area appropriately after installing the bigger valve nets about 2x additional gain. Clearly one goes hand in hand with the other.

figulaz
12-02-2013, 11:45 AM
Thanks Dave and jdsgallops..Dave--I saw your facebook. You do awesome work. Do either of you guys have recommended reading or youtube subsciptions. I'm definetly a visual learner. I found Headbytes Porting. I hopped a round a few vids and he seems to know what he's doing. Since this my 1st attempt I'm using what I got. If I'm happy then I'll go with bigger valves.

jdsgallops
12-02-2013, 08:52 PM
I am much the same way. I was fortunate enough to have a friend send me the head off his 10 sec 66 Mustang to view the port work provided I got flow numbers for him. I unfortunately do not have anything sitting in the garage right now that I could do the same with.

that said I think you are over thinking what you need to do with your heads. Dave is a professional who makes his money off people who don't want to or have time to do the work themself or are looking for every last ounce of power. That means he has spent the time and money to get all the details right. That is what he gets paid for. That does not mean you can't achieve 50, 75, or 90% of what he can at a lesser out of pocket expense. It is all dependent on how much time you want to devote to it. If all you are looking for a a little more performance or to maximize the potential of your parts while they are disassembled then does it really matter how much gain you get? And best of all you will be able to claim you did the work instead of paying someone else. To me that is the best kind of personalization you can do to your ride. Dive in head first and see what happens. If you put them on and you aren't happy with the results you have spares to try again or replace the others. SC heads are dirt cheap. If you ruin a set it isn't a major financial loss or not easily and cheaply replaced. You aren't talking about a $1000+ set of aftermarket heads here.

There is a reason I labeled my above post "Head porting basics 101". If you can visualize what I posted there while looking at the port then you will yield good results and a respectable increase in airflow and power. What I listed there is far from being everything you need to know but will get you well on your way to respectable gains for your time and money spent. I just don't want Dave and I's conversation to deter you from giving it a try. We all started somewhere.

figulaz
12-02-2013, 10:31 PM
Yup. It's time to jump in. I'm getting real comfortable wrenching on this car. Porting and tuning are a natural progression. All my cars I've just done repairs and moved on. It's helps this forum has great contributors. Thanks guys. I'll post pics in a couple days.