Clevo120Y

This right here is a huge compliment to me, cheers Tony. Yes you are correct that there is a big difference between just making a port larger for flow and making a port work properly using a smaller area and with a smaller valve, Once the head has the larger valve with backcut and a better seat profile there will be even more flow in it, I'm confident now that the shape of the port is correct for this combination so a bigger valve and better seat will only improve it. I grabbed the carb he was using on his race car to compare the flow with the carb I modified, as it turns out his carb is a 350 based 350 with a modified metering block and that's it, on a stock 84da manifold with just the top of the plenum chewed out to match the adaptor for the holley, The head he was using was a C1 casting with no port work and the chamber opened right up so it looks like a hemi chamber to drop the comp with his flat top pistons and a single seat cut and stock valves with some double springs, he was running this with the cam I mentioned above and big 2in primary headers, he was always popping head gaskets everytime he got off the gas and then back on it. I've been told by other drivers that he is a great driver and a few years ago had a good engine and won quite a few races, then he damaged it and has just had reliability problems ever since and could never get the combination to work again. So now he will have a carb that flows 58cfm more, a manifold that flows over 20% more and a head that will flow 208cfm at his lift point and will have 10.5 comp on 98 fuel. It should be a bit better ride this time and get him back towards the front so he can enjoy his racing again, He was just about to retire from racing before we got talking and now he is like a school kid again hahahahaha, Duckboy his name is Robert Wolf and is a local bloke here in Albany WA Wookie I don't know if you have seen it but in the DIY section on this forum I have a thread showing the build of my flow bench, This is the major tool I use to develop the manifold and head, the most important tool on the bench in my opinion is the velocity probe, it allows me to measure airspeed at any point of the port and I can map this airflow on the benches software and see were the air wants to flow and this guides me to the shape required for it to flow nice and smooth, the other things I use on the flow bench is cotton on a rod, when I put the cotton in the port it follows the airflow so I can physically see were the air is moving, it also shows me the airflows behaviour, the cotton vibrates when the flow is turbulent so you can place this anywere and you can see dead areas or areas needing work ect ect. Also when the air is moving through the port you can hear whats going on, turbulent air is very noisy so the sound is another tool to determine if your going in the right direction. Apart from that I have a collection of carbide burrs for alloy and cast in few different shapes and lengths up to 6in long shank. I use an air die grinder and a large compressor, a tip for porting is wear your PPE I have a full face mask with filters (cost me $400) long sleeve shirt, pants and gloves, the splinters from the alloy is sharp and when they stick in they sting, One in the eye and you done, as for cast iron and emory rolls the dust they produce isn't good for your health so that why I wear a full face filtered mask, I train in a sport that my lung capacity is very important LOL so health is important. I use a TIG for welding and all the other measuring tools to measure diameters and such, oh and a good flexible led light to put light in the ports as you work, that's about it hahahaha. Next week I will do a test on a stock port with the 3 angle seat and just chamber work and see how that compares to the rest and add it to the list.

Thanks guys, the port works very well and I'm happy with it for this engine. Sly, thanks mate I appreciate your comments, Yes from these flow figures a perfect cam can be calculated once I had the exhaust figures as well, as I have mentioned before this first engine is a compromise because of time and also the bloke has parts already that we have to use, a cam is 1 of those parts, he has a new cam already which has 542thou of lift after lash and just over 300 degrees of advertised duration with an intake centreline of 105 degrees from memory, I will have to check that. Pretty big cam and now that the head will keep up we can use all of that lift efficiently. I would like to do comparisons one day for sure, with this head port I believe you can use a cam of higher lift because this port stays stable even over the 600 thou lift mark it just doesn't flow any more air, his will most likely be a cross sectional area issue, the port is still reasonably quiet even at 700 thou. Ports that become turbulent over a certain lift point start to go backwards in flow by a fair amount and you can hear the air separate and go very noisy, this port doesn't do that. The texture on the port walls is to keep the fuel atomised and stop it from clinging and pooling on the walls like a smooth port, also it is the same theory as a golf ball, the grooves and dimples in the wall cause a pressure drop when air is moving past them and creates a sort of layer beyond my knowledge to explain but it works to keep the air running along the port shape and not separating but not actually ON the wall itself if that makes sense, anyway textured finish FTW I have been chatting to some very experienced porters both here and in the US including Larry Mauex and dyno tests have also proven a horsepower and torque increase, they don't look like artwork and it's hard to convince people but I'm into finding what works not what looks good so my port work might not be the prettiest but the results are there. Matt, the port work is required on the short turn and right hand wall for the port to be stable to 550 thou lift otherwise it falls over at 450 thou, you just don't have to work the valve guide or the bowl area very much at all, just open the throat to 1.615in diameter and do some blending to make the transition from bowl to seat nice and streamlined, it doesn't take much. Do the chamber work even if you leave the port standard and a 3 angle seat cut, there is so much low and mid lift flow to be had with just those 2 things.

Another thing, this port isn't hogged out, the first part of the port before the short turn is the same cross sectional area as stock, the burr has just been run around it to clean the carbon off and give it some texture

Also thanks for you positive comments too mate, they are appreciated.

With a 3 angle seat and with just some reshaping around the short turn and the right hand side wall just before the short turn and leaving the valve guide basically alone and no chamber work I made 202cfm at 550. If you did the chamber work as I did it above you will gain throughout the low and mid lift as well on top which is what we want even more so with a shorter cam.

Thanks mate, yeah an 89% throat to valve ratio I used, the chamber work and valve seats are the big improvers over a stock port with a single seat cut, the port work is just the icing on the cake that keeps the flow stable over the normal choke of 450 thou of lift.

^^^^I agree, I would like to test the extreme top, being able to pull air from directly above the carb would be a benefit I think.

Yeah I will do comparison tests with manifold on and off, the flow figures quoted above for my manifold is with it bolted to a stock head that flows 184cfm so even on stock head the modified manifold is still a restriction but is even , still a lot better than the 135cfm it was pulling before when on the head, I'm hoping that if the port can pull more cfm that it will draw on the manifold harder and the manifold will be a percentage restriction instead of just capping flow at 165cfm if that makes sense. So my thinking is if the port can pull 220cfm and the manifold is a 10% reduction as it is now (184cfm down to 165cfm is a 10% reduction in flow) then I can still get 198cfm through the manifold if it works out that way. I didn't get time to work on the head today but I did some other testing today on some things I had in my head, the effect of aircleaners to flow. I tested a stock 350 holley again and my modified 350 holley, to start with I checked my notes and my first post I said a stock 350 pulled 325cfm but it was 321cfm so my mistake there too many numbers hahahaha, anyway I started with a K&N 9in x 2in filter assembly, the filter has done a few kms but in no way full of shit so I thought this was a realistic test filter. With this setup the stock 350 pulled 311cfm, a 3.1% reduction, the modified 350 pulled 365cfm which is a 3.7% loss. What I believe this shows is the low filter on the stock 350 is restrictive so close to the choke horn, it has about 1in clearance so the change in direction is more dramatic, I have come to this conclusion because the same filter pulls 365cfm on the modified carb which is less than what the carb can pull but I think that's about the limit of the smaller filter with some dirt in it. So I put another filter on top of that one and both carbs pulled to there full cfm values, what I think this proves is even with a small carb it needs plenty of filter surface area and some height above the carb for the airflow to settle and have room to change direction. I will probably make a suitably sized carb hat for the race car that is plumbed to an airbox in the cabin with a large panel filter, then duct some cold air from above the dash to feed the airbox. Don't choke your carb with small filters guys.

Thanks Tony, I thought the screws would give a couple of cfm but 6 is a good result, when you think about it that is like a 1.5% increase, and chasing the 1%ers is the difference isn't it. The valve is just a standard crossflow unit as is from the factory, just a single 45 cut on the valve no back cut and no skinny stem. The valve seats do have a 3 angle cut, 45 seat, 30 topcut and a 55 bottom. the valve seats are not new so are a little worn so redoing the valve seats again would give an increase in the low lift again plus I will be using a 5 angle on the race head, using the angles above plus a 65 and 75 on the bottom cuts. The race head will also have 1.84in intake valves and standard size exhaust valves, the valves are a single piece single groove for added insurance, they will also have a back cut, so getting good figures with the stock gear at the moment will hold me in good stead when we upgrade to the bigger valves and more angles. I haven't even touched the C1 chamber yet to unshroud the valve at all so some more flow should be there for the taking, I will do a full test on this port today and post up the results, I just did a quick test from 400 to 550 yesterday as It was getting late, the low lift should be up as well but I don't want to speculate until I prove it. Yes the valve guide will get some shaping next on this test head, I have asked for the race head to have the guides removed for when I do the roughing out of the port so I can shape the bosses easier, then I will go to the machine shop and get them to push the guides in until they just pop out of the bosses instead of hanging out so far as they do now. I was happy with the carb results, I was chatting to Zok from Zok race carbs and he said he gets 390cfm out of them so I'm not too far away from the pro's, not bad for my first real go at it, cheers for your input Tony, floating ideas around is brilliant, you can only try them and see if it works or not then you know what does what.

Well I think so, I run the correct size bore for the engine in the bore adaptor to give realistic flow figures including any shrouding from the bore. To come to the conclusion that the bore alone is causing the shrouding would be quite difficult I would think, if you start upping the valve size too much it can lead to other problems like the short turn can become less effective as the valve face becomes more tucked in under the turn itself, putting a 4v inlet valve in a 2v clevo head has this problem, using a smaller valve can flow more efficiently, the trick is to find the biggest valve that doesn't lead to you going backwards as well as adding weight to the valve train. Here are some pics of the bore adaptor I made with inserts for the crossy to give the correct bore size.

Had more of a play today, I removed the choke horn and smoothed it all out, put the carb back on the bench and it made zero difference to total flow of the modified carb. Saying that, it made no difference on the bench but I believe the difference would be noticed when an air cleaner assembly is installed, the top of most aircleaners are very close to the top of the choke horn and would be a restriction, that restriction would be gone with the choke horn removed. Next on my list was to skinny down the boosters, I probably made the walls of the boosters half of what they were so I could probably remove some more material if I wanted, doing this made a 13cfm gain bringing the carb up to 373cfm at 28in. I then shortened the throttle plate screws to be flush with the shaft, this amazed me as it was worth another 6cfm on the next test for a total of 379cfm. I also did a bit of port work today playing with some shapes with pretty good results for minimal material removal, cracked the 200cfm mark with 202cfm at 550thou of lift, the cfm number isn't super impressive but what I'm happy with is I have moved the choke point of the port up 100thou in the lift range, the port is nice and quiet all the way up to 550thou then falls over, so this tells me that the shape is on the right track, so during the week I will work on it some more and get velocity readings in the port to tell me were the air is and were it wants to be. All of this is with a stock sized intake valve.

Thanks Gary, that would explain why I couldn't find it. Admin can delete thread if they wish.

Thanks for that mate, I think I will have to get a few more runs on the board before the inbox starts lighting up but I hope it happens.

I would be happy with $1000, that is charging my labour really cheap plus some consumables, now that I have done 1 I could repeat the process for maybe $700. Your manifold that you developed with Mark may work better than mine and probably better value in the long run, I'm having fun mate and this is only the first stage of development, all your above suggestions are certainly on the list and when I get some more time I will be trying them all and record the results.

Agreed, that's why I changed the shape to reduce the centre runners and boost the outer runners,1 and 6 flow the most at 165cfm and the centres flow 162cfm now, a priority of mine was to keep the airspeed up to the outer cylinders as well so they taper down nicely to increase airspeed with no reduction in cfm flow.

Thanks Clint, this job is my one and only freebie, more sponsorship really, it works well for both of us, he owns the local wreckers and I now have access to as many parts for research purposes as I like for nothing, plus if the car performs well he will put a big sticker on his car for me and spread the word that I may have some idea LOL. Your right about the hours, there is a solid 2 weeks of work in that and it's just about taking it slowly, remove a bit of material, put it on the flow bench and map the airflow, change the shape with some playdoh to get an idea of the radius needed to stop the air from shearing off the corners then put the shape into the alloy, test it again, some shapes helps some runners but not others so a happy medium for an even flow across the 6 runners is needed, I can get the 2 centre runners to flow over 170cfm but the other runners don't keep up, so a change in shape reduced the centre runners and picked up more flow in the others to get an even 164cfm average over 6 runners. Great fun but the alloy splinters in the socks get old real quick hahahahaha

Looking for peoples feed back, I just bought a digital valve spring tester and wanted to just make sure it works, put a stock crossy spring in it, compressed it to 1.8in and got a reading of 30 pounds, that is seriously low, has anyone else tested them before, also I tried a stock Windsor spring and got the same result.

Is your car a manual?

TFI module on the dizzy or an ecu fault possibly.

Not bad, just spine tingling lol

I'm a dumb arse LOL had it set to kgs, and Clint I agree with your findings, stock springs ranged from 56 to 64 pounds at 1.8 inches.

That's good to hear mate, happy motoring

She drives a lot better now then?

I've got my fingers crossed for you mate.

You need to do some tests, first I would do a compression test to make sure a valve isn't been held open, then a check of the ignition system, make sure the leads are in the correct order and no cracks in the dizzy cap, then check the timing. Make sure there are no airleaks around the base of the carb and the inlet manifold to head gasket. In regards to the converter freezing what the others have said is spot on, the converter needs hot coolant to flow through it to vaporise the gas, when there isn't enough temp in it she freezes. Removing the choke was not a good idea in my opinion, it will be a bastard to start without it, if the mixer doesn't fit then it's the wrong mixer or you need to make a spacer to raise it up to clear the choke. I don't want to come across as rude but having personal convo's with you, you might be better off finding a new mechanic as I feel he has let you down a bit if the car left his garage running the way it is. Not having a go at you personally Squid man so please don't be offended by my comments.