ando76

That's some impressive figures there Jason - especially considering the year. No wonder the corty runs the numbers on relatively low comp. Great stuff but gee look at those figures from the BA crowd. No wonder they go so good with just a cam upgrade and a set of extractors...

multiply by 1.67 - yes I finally remembered.......

Hey don't forget Wazzy is running those numbers on a flat tappet camshaft!!!!! AND a car that is heavier (but not by much) than a bloody little corty with a roller cam. P.S I have met, spoken with and respect both Jason and Ken and their efforts. One only has to look in street machine to see big dollar, big cube clevo's doing 10.7 to realise how quick these times are.

Well that's it. Only one way to work this out. I'm going to back to back these extractors with the modified (extended secondaries) pacemaker extractors I've got on the burnout beast on the dyno. I'll just modify the collector on the 6-3-1 extractors as it is god ugly. Anyone want to lay bets????

That port with an individual runner manifold like the webber one Rob is running would go off. Straight entry into the chamber and optimum fuel air mix on each port. Hold on Rob .. Yahoooo. The figures look good, especially with the intended lift. I can't help but thinking that a bigger inlet valve would be better tho - provided we could lift exhaust flow to match - which I reckon would be a piece of piss. Why not undercut the inlet valve stem while you are going to see if there is a high lift gain there - I'm confident there will be. Easy for me to say - I don't have to do the lathe work. LOL.

See that feeling through the seat of the pants seems to contradict the theory that the 6-3-1's are better in the top end. If the 6-2-1's are still making torque at the high rpm then that means that the HP ceiling is also raised. Anyone that's spent anytime on a dyno knows that HP takes over when torque drops off. Hmmmm me thinks two sets of pipes back to back on dyno and track only way to settle this. Time and Money once again. See how the secondaries stop short on the 4.0l set. I reckon that has more to do with ease of fitment up to the Cat convertor than actual exhaust design. I'd like to see a bit more length in that secondary before they meet the collector - especially as they have all just done a tight 90 to get to the collector. One area where pacemaker are well ahead of the others is the pipe over cone design. when I up my secondary pipe sizing I take the secondaries to the exhaust shop to have the ends expanded so that you get that same pipe over cone thing happening.

This is exactly why I am trying an X pipe on the roller cam engine. 6 into 2 into an X pipe. Look at the configuration of an off the shelf set of extractors. Look at the firing order. Correlate that to the extractor design. Pulse - pulse. Exactly the same as a V8 and X pipes have been proven to make more power on V8's for years. Just look at Vizard's exhaust studies. Call me mad - many have - but I'm cool with that.

Going into the shed (toy store) in town tomorrow so I will have a look and take a pic.

Perhaps the short turn could be improved a bit (hard to tell from the photos) and maybe a little bit of work in the combustion chamber might improve flow. Are you happy with the size of the bowl???

I have a set of old genie 6 -3 -1 extactors to suit XF here if you need something to copy off. I am led to believe they are a bit rare and someone once said they were genie 'speedway' extractors. I'm not sure on that one. I have never tried them. The boys run a custom set of 6 into 1 on their speedway car and I know of one other top XF competitor who runs the same set up. Awesome looking set of pipes, all same length and HPC coated with EGT probes. very horn. EGT probes are good for tuning - but then again so is your AFR gauge and with an individual runner manifold EGT's should be pretty even.

Thanks men. Joined up to that GT site so maybe they can assist.

Well I think your primary sizing is spot on, as to length well I reckon pacemaker know their stuff. I would highly recommend 2 1/4 secondaries at the length I prescribed. After that I don't really care as long as it is no smaller than 3.5", mandrel bent and as long as you can before it sees a muffler. I like the idea of rear exit if it is achievable without too many bends - but then again you don't have a spare wheel recess to worry about anymore. If you want to knock the noise down run a muffler in the original location and then a moroso spiral flow muffler at the very back. Gonzo used to make his own resonator very similar to the moroso units. I highly recommend the Borla muffler if you can afford them. They make MORE power than open headers - proven time and time again in the US.

seems we are on the same page - both students of Vizard it would seem???? Diameter of exhaust valve, inside diameter of current extractors and exhaust port I.D. while your going Sly.......

For a high rpm engine like yours I reckon 2 1/4" secondaries, long enough to give you the cubic inch volume of your engine (250 = 2 pipes with 125cu in in each pipe) then merged into a 4" expansion chamber (3.5 if space is tight) down to the original muffler position where you taper it back to 3" and into a straight through maximum flow hookers or if you have the coin a Borla straight through circle track muffler - dumped at the diff. It may sound OTT but it works and is quiet. You will have to do it yourself as most exhaust shops will look at you as if you have two heads. Another option would be twin 2.5 with a narrow x pipe at the gearbox extension housing back to twin 2.5" straight throughs at original muffler location dumped at the diff. This is the set up that I will be running on the roller cam speedway engine. I run the above set up on my current flat tappet motor. Both these are well and truly out there designs but they are built on sound theory and not just what makes a street car go fast or what is easy for the exhaust shop.

I have noticed no loss in performance with a drop down base and extreme top filter on the dyno. Mine makes the same with or without aircleaner but it does richen up the idle a fraction. Properly done I doubt anyone would even notice if you lowered the engine mounts. I would suggest that you bevel your cuts and fill and then sand/ linish them on the outside. The chassis mounted engine mounts I am talking about. You could also run a nice weld around the inside of these mounts and no one would ever know. There is also plenty of room to set the engine back a bit while you are going - if you have a custom sump. Some racing classes frown on that but hey rules were meant to be pushed/broken. Most 'racing' classes require some form of engine mount strap or chain anyway but I would be modifying the rubberised engine mounts. I'm a big fan of solid engine mounts on cars with big torque as in my opinion they help transmit all the torque, but there are plenty that will disagree. it's just my thing I guess. You can just weld a 4mm strap on the top half of the engine mount and drill a hole in the strap so that the engine mount bolts passes through it. This ties them down but still provides a small amount of dampening. Choice is yours.

how sweet does that sound!! and lift those front wheels and gone. Having seen this car in the flesh and heard it sit at idle it truly is an amazing beast, driven and owned by a top bloke to boot. Yeah cammed up LS1's run as quick but this is old school technology going seriously fast. Perhaps we all just smash a certain magazine with emails demanding a write up???

that's not good Jason. I know where there is a really good cylinder head in Brisbane that is almost done - but it owes me too much now. lol. I hope you get it sorted man. hard luck.

a drop down base air cleaner may help. You can also lower the engine significantly with a custom sump and cutting the lower engine mounts that fix to the chassis. You would be surprised at how much you can get the engine down with these two mods. you can also elongate the engine mounts to the block and get the engine a bit lower again. all these little things add up and may well give you the clearance you need.

grimmy you have some seriously big gonads my friend. Most cam manufactures recommend run in on outer springs with seat pressures over 120lb. I would think that at 140 you are pushing the envelope and run the risk of wiping a lobe at some stage. but hey if you get away with it all well and good.

they do not require machining of the springs seats. If you run single groove valves you can buy the 707-sta steel retainers and 255-vsl locators. You may need to shim them up depending on your installed height. If you run multi groove valves you will need comp cams 744-16 retainers and about an hour on the lathe to make them suit the 295D/ 235D springs. Yes you can run the cam in with them as is as they are only a single spring with a damper and with low spring seat pressures you will not wipe lobes.

That is a bit unusual for an Isky spring. I find that I can get four years out of the 235D's. At four years they lose 5lb of seat pressure but I'd still be happy to use them with 105 on the seat. I usually replace them, the bearings and rings at that time and its good for another 4 years of flogging. That's in speedway. They would probably last forever in a street/strip engine as they just don't see the constant high revs like speedway engines do. It's all dependant upon how many cycles they go through.

If you want to rev it with confidence,have no harmonics issues and have less than .600 lift, then there is only two springs for a x-flow. Isky 295D Tool room springs with 115 on the seat. For lift at .584 I use the 295Ds little brother the 235D at 110 seat. Tried - tested - proven. I have never fucked a cam bearing - pulled a shaft mount roller rocker out etc. with these springs and they will go to 7500 all day, every day. My engines are used in speedway but this spring is equally at home on the street. People will say I'm crazy and have no clue running such low spring pressures and a just a single spring with a damper that is ' way to small to do the job' and that's cool - cause they are the same people that have there engines apart, miss meetings and have constant failures and that is good for me. I must say that I did not come up with this spring. The late great Geoff TRUSCOTT was my dear friend and he discovered this spring and he loved it because it does not create valve train harmonics. I am using the 295D on my roller cam engine - Yes roller cam. It does have less than .600 lift tho.

Gerg - good to hear that you have had success. they truly are an awesome piece of kit. Interesting on the rotor phasing thing, but no real surprise as they do say to check it in the instructions from memory. Happy motoring for you now and stunned looks to come when the 'griswald' is hooked up to the laptop.....

Never to pretty to skid - especially when you could fit some au 16's and they would tuck right in. Clevo I'll send a manifold down once I get my stuff together. Just waiting for the other new one to arrive and then I'll be out playing.

your dead right. Both my burnout and race car have AEM's in them and I would not be without them. an absolute god send.