Technical Help. It sounds the same as a faulty U- jointwithout the ringing. The clunk occurs from too much freeplay in the differential pinions and wheels,. Mopar Head Porting Templates. These Mopar Performance cylinder head porting templates are. A small block Chevy V8 head with 1. Raising the port location in.

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>>>DIY Port Matching and Porting (combined thread) User Name Remember Me? Wouldn't cubic inches play a large part in using this? It's important to note that I said power potential, not how much power you will get. ( sorry I got called away before I could finish) 200 cfm SBC heads could be bolted on a 283 or a 400. The actual results will depend on many factors. At an efficiency of 1hp per CI you could get 283hp or 400hp but the same heads won't flow enough AIR to support 450 HP even if they're on a 500 CID engine. Best Hp is the result of burning 1 part fuel to 12.7 parts of Air (by weight).

You need to supply about 1/2lb of fuel per hour for every HP. For 450 hp, that's 225 lbs of fuel per hour or which is only.008 gallons per second (2 table spoons).

Getting enough fuel into an engine is easy. You can get it rich enough to blow black chunks out the tailpipe. However, you also need 12.7 lbs of air for every pound of fuel. For a 450 hp engine you need 2,857 pounds of air per hour. That's a lot of air!

Getting a lot of air to go in by itself is hard unless you force it in with a supercharger or introduce it chemically with Nitrous Oxide. It takes about 60 hp to run the supercharger on a 450hp Ford Lightning. Cramming over a ton of air is a lot of work. A tank of nitrous is cheaper than a supercharger but it doesn't last very long. An hours worth of continuous spray would be very expensive, indeed. In a normally aspirated engine, heads are the key to power production. The bowl and valve is the most restrictive part of the path so port matching often doesn't give the best gains.

If you have a lumpy idle cam with lot of overlap then it may be more productive to leave the manifold smaller than the port to act as an anti-reversion ledge. The actual benefit depends on how bad the before was and how good the after gets.

Heads, intakes and carburators are not superchargers. A bigger CFM rating doesn't mean the engine will get more air, but generally speaking improvements in head flow improve power output.

Here's one final comment on head porting. The 5 axis CNC machine has revolutionized head porting. Porting heads is nasty, grueling, exacting work. It's also very difficult for even the best head porters to duplicate good ports consistantly. It's also hard to train and keep head porters. Most quit to do something else.

I'd bet there are less than 100 expert head porters in the country and surprisingly, the demand for more isn't really growing. These days once a good port is developed it's mapped and programmed into a CNC machine. A head is done overnight instead of weeks later and very little hand finishing is required. Fotoba Digitrim Manual Woodworkers. It really cuts down on labor intensive skilled work. Aftermarket CNC ported heads are a bargain compared to expertly hand ported heads. I think the new 505hp Z06 even has CNC ported heads from the factory! A big change from the old crappy heads from the last century.

Hey DriveWFO. One of the many experienced 'engine gurus' will have a much better qualified response. But I will go out on a limb and say no more than 3% - 5% improvement. But my response is based on a 3/4 to 1 inch clean-up into the runners to the selected gasket combination. I am only basing this on reading material and theory - since I just started my first real adventure into porting (really only very careful clean-up work to stock parts). Just completed a gasket match on Victor Oval Port intake.

Getting set-up to start some mild clean-up on the '781 BBC heads. I think the real answer is a bit more complicated and depends on a few more variables - but I am anxiously waiting responses to this thread. Now we can wait for the better qualified to respond and see how wrong I am.

Wouldn't be the first time though. Im not all that experienced in this myself but I have researched it for my own knowledge. Generally you want your intake and heads to be port matched so to elliminate any turbulence through the intake path that would hurt flow. For instance you want it to be matched depending on whatever the head port size is. Say you have a stock head matched to a felpro 1204 gasket. You will want your intake to be the same so the intake charge is evenly passed through.

Increasing the port to say a 1205 will probably gain very little or even hurt flow and be pretty pointless. Unless you actually do a full out port to the entire intake path of your heads or go with stock race port heads to really see any gains. Im not so sure it would be gaining flow but more so getting your heads flowing optimal to whatever your heads should be flowing without any obstructions. I guess it all depends on what exactly your trying to match. I mean if your trying to put a 1205 port intake on a 1204 port head then I would think it would be needed.

Hogging out a 1204 intake to a 1205 fully ported or stock race port head would probably give you some good HP gains but probably affect torque in some way. There may be lots of variables depending on intake design like runner length or intake volume.

I would imagine some porting actually may not gain anything but actually move the power band in different rpm areas. Ive actually been comparing a couple of intakes one was a 1205 intake the other a stock 1204 intake. The 1205 intake actually created slightly more horsepower and levels that were farther up on the rpm scale while the 1204 had slightly less but similar power levels but lower on the rpm scale. Even though the intakes had similar power levels the 1204 intake created lots of low rpm torque and power that was better for the street while the 1205 made better high rpm power more suited for the track. Both intakes seemed to do similar 1/4 mile times which is kind of shocking because you would assume the bigger intake would totally outrun the smaller intake no matter what.

Im sure the bigger intake would eventually out flow and do better than the smaller intake when head flow increased but this is what helped me decide what I wanted. Download Anime Naruto Shippuden Episode 334 Sub Indo there. On a 400hp 350ci, what kind of hp/tq gains (on average) could be expected from port matching the intake manifold? Don't think you'll feel the change from the seat.

Just match them up exactly or make the intake very slighly smaller is ok, on a single plane you can look down in an see the match, if they misalign an there is a step up to the head or the head is smaller now ya messed up, that will cause bad turbulance an flow in that port an may cause the fuel to puddle there an hurt power. I'd let those small vortec's alone an get some good heads on that 400 if power is what your after, much easier!!! Port Matching For many years I've thought intake port matching was not worth the trouble. In fact, for some intake manifolds you can end up ruining the 'aim' of the intake runner design and negatively affect cylinder fill.

Some years ago I read that it was definitely not recommended to port match the Edelbrock Torker for this very reason. Looking at a Torker it is obvious that some of the runners are shaped such that a large portion of the intake port on the head is not being fed. Why would they design it that way when they can do most anything they want with a new design?

To positively affect flow efficiency is my guess. Lo and behold there is an article in this months Car Craft (see, that C*evy biased rag is good for something) where they dyno tested a big block engine before and after port matching. Bottom line - no significant difference.

Something like 2 HP and a couple lbs-ft of torque. Glad I haven't wasted all that time and money over the years. Forget about port/gasket matching your intake/heads UNLESS the intake has larger passages than the heads. Then, and only then, is it worth it to even consider this expensive (if you pay someone else) and time consuming exercise. And I don't care how careful your are, how do you know that after everything is torqued down, run and re-run a couple dozen times, that your 'port match' is still perfect. You could easliy introduce edges that can mess up the flow as much as help it.

Waste of time for sure on a street driven car and probably also for 99% of race engines. [ Thanks to Bob Handren for this information.

] Here's an from Circle Track. And one from Note that they also say the gains are 'insignificant' in the CHP article. However, I know pro race teams spend a lot of time lining up intake runners with head ports to make sure the flow vectors are aligned. They don't go to all that trouble because it's a waste of time. Stock rules often allow port matching within 1' deep of the opening.

There's a good reason for that rule restriction. True port alignment needs to extend all the way to the valve. If you just match the opening to the gasket hole, without considering the flow alignment you probably haven't really helped the flow. I use special aluminum templates from Brysinski Racing instead of a sloppy fitting gasket and bolts. They have close tolerance alignment dowels and are double sided to get a precision anti-reversion step, if required. I searched out and merged together some of our threads on DIY porting subject and put it in Best of Tech.

I've read a few online blogs where gasket matching was attempted, but never found any scientific results to prove the gains. I searched out and merged together some of the threads on the subject and put it in Best of Tech. Here's an from Circle Track. And one from Note that they say the gains are 'insignificant' in the CHP article. Thanks Paul - great information (as usual).

Back to reading and glad to have some practice at least - and hopefully don't hurt anything by staying really conservative.