Laxity Posted February 26, 2018 Share Posted February 26, 2018 Nice stuff. I've got a HZ GTS in Atlantis Blue that I need to get around to fixing up nice. Link to comment Share on other sites More sharing options...
mckie1 Posted February 26, 2018 Share Posted February 26, 2018 Nice stuff. I've got a HZ GTS in Atlantis Blue that I need to get around to fixing up nice. Cool. We have a Palais White one ;) Link to comment Share on other sites More sharing options...
Laxity Posted February 26, 2018 Share Posted February 26, 2018 Cool. We have a Palais White one ;) Got any photos? I've only got a old one when it was garaged under a shed. https://www.shannons.com.au/club/enthusiasts/thresholdau/garage/1979-holden-gts/ Link to comment Share on other sites More sharing options...
mckie1 Posted February 26, 2018 Share Posted February 26, 2018 Got any photos? I've only got a old one when it was garaged under a shed. https://www.shannons.com.au/club/enthusiasts/thresholdau/garage/1979-holden-gts/ Ours is in similar condition unfortunately :( Will find a pic :) Link to comment Share on other sites More sharing options...
mckie1 Posted February 26, 2018 Share Posted February 26, 2018 Old photo. Have changed mags to honeycombs and removed lpg since pic Link to comment Share on other sites More sharing options...
Autosteve Posted February 26, 2018 Share Posted February 26, 2018 Got any photos? I've only got a old one when it was garaged under a shed. https://www.shannons.com.au/club/enthusiasts/thresholdau/garage/1979-holden-gts/ Nice car but that 600cfm Holley is miles to big for a 5 liter. I have a book called Holley Optimization printed by Holley with a graph that shows carburetor cfm, (cubic feet of air per minute) Vs RPM and for a 300ci or 5 liter motor, to use 600cfm the engine needs to be spinning at around 7200rpm something that is never going to be happening, about 5200 they hand grenade. Many believed bigger cfm meant better performance but it is the opposite. It makes the engine run lean sucking to much air at a lower speed and therefore less "Venturi effect" so the little fuel that is drawn isn't mixed efficiently resulting in poor performance and often poor fuel economy. Around 430cfm is good for a 5 liter to spin at 5000rpm but the closest Holley make is a 450cfm. Seeing as 450cfm is pretty close to exactly what you need then you can change the style of carburetor. I would say your 600cfm ATM would be a vacuum secondaries spread bore design which is ideal for a 350ci for mild performance but you will get that 5 liter dancing if you go to the 450cfm but change the style to mechanical secondary square bore design. Square bore means the carburetor is basically two carburetors in one. The front have is in this case 225cfm and the secondaries are also 225cfm instead of spread bore design which is about 1/3 front half and 2/3 secondaries. Mechanical secondaries means a mechanical link that is activated by your pedal position so when you push flat on the pedal, it "WILL" completely open the carburetor rather than vacuum secondaries that are reliant on engine vacuum to open them and when you plant it, engine vacuum drops resulting in slow takeoff because there isn't sufficient vacuum yet to open the secondaries. To overcome the low engine vacuum at take off, Holley come up with the "double pumper" setup. This is simply a quick injection of fuel down each of the rear secondaries when you open them hard. So to sum up your carby is miles to big for the size of the motor is bolted to. If you change it I would recommend a Holley 450cfm square bore double pumper with mechanical secondaries and then that car will perform as the name GTS implies. I've been down this exact same path with many mates that had 308 or 5 liter Holdens.;) Happy fast motoring..:) Link to comment Share on other sites More sharing options...
Defender Posted February 26, 2018 Share Posted February 26, 2018 Years ago I had an old 302 Clevlend with a factory four barrel. Too big. I put a two barrel manafold and 350 Holley and it went so much better, and way better fuel economy. So picking the right combination is so important. Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
gsr Posted February 26, 2018 Share Posted February 26, 2018 (edited) Nice car but that 600cfm Holley is miles to big for a 5 liter. my grandad had a holley 600 on his showroom bought xb gt and also on a ramsay ski boat with 327 from a corvette reckoned in the gt he outran the coppers along the hume at the time lol both were tuned by a drag shop probably wouldnt have been so bad in the boat with less load to haul either this was the boat and corvette the motor came out of http://i68.tinypic.com/9lbtzk.jpg http://i65.tinypic.com/ifo0o5.jpg corvette owner ordered a replacement hotted up one lol...crazy Edited February 26, 2018 by gsr Link to comment Share on other sites More sharing options...
Autosteve Posted February 26, 2018 Share Posted February 26, 2018 Problem is what rev range you want the engine working best at. The cfm rating is the most amount of air the carby will pass. If it simply is way more air than the engine can ever use, it simply is to big for that engine. That cfm chart was a damm good guide to put you in the ball park. The standard carby for that HZ GTS was a 730cfm vacuum secondaries Rochester which again is miles to big but being vacuum secondaries simply meant the secondaries simply never fully opened so you never really suffered from running to lean because it only partially opened to about 500cfm but the problem there becomes the lower half of the carby is still to big destroying good venturi action. They also have trouble pulling the skin off a rice pudding in stock form. Link to comment Share on other sites More sharing options...
Defender Posted February 26, 2018 Share Posted February 26, 2018 As long as they still sound like a v8, it’s good.[emoji12] Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
jason1 Posted February 26, 2018 Share Posted February 26, 2018 Years ago I had an old 302 Clevlend with a factory four barrel. Too big. I put a two barrel manafold and 350 Holley and it went so much better, and way better fuel economy. So picking the right combination is so important. Sent from my iPhone using Tapatalk the old clevo must have been a bit tired to only have a 350holley, I had a mild crossflow and she was too small for that. was good on a stock crossy though, I did use a 350 to run in my fully worked Crossflow as it pretty much stopped me from being able to give it a good bootfull Link to comment Share on other sites More sharing options...
oldhank Posted February 26, 2018 Share Posted February 26, 2018 I had a 390cfm holley on my old slant six that went plenty well enough for what it was Link to comment Share on other sites More sharing options...
Defender Posted February 26, 2018 Share Posted February 26, 2018 It was, but it worked and it was to drive around, so the fuel was a reason too. I had a mate with a 250 crossflow with triple 48 mil delortos and a massive cam. It was a monster in his TC cortina. So it all depends on the work done to things as well. I also had a mad 302, top loader, nine inch disc Capri in the eighties when you could get away with more. So much fun and so broke because of it. Ha. Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
jason1 Posted February 26, 2018 Share Posted February 26, 2018 It was, but it worked and it was to drive around, so the fuel was a reason too. I had a mate with a 250 crossflow with triple 48 mil delortos and a massive cam. It was a monster in his TC cortina. So it all depends on the work done to things as well. I also had a mad 302, top loader, nine inch disc Capri in the eighties when you could get away with more. So much fun and so broke because of it. Ha. Sent from my iPhone using Tapatalk fair enough, would have drastically improved fuel economy. as for crossflows, this is my Baby, spent to much money and time building this thing, a v8 would have been a smarter choice but I do have 347stroker in our XR8 but I wanted to see what I could do to a crossflow this is my nitrous injected, custom fuel injected Crossflow in our XF, uses full counterweight crank shaft from a later e-series 4L, with custom made pistons, so revs like a mother and should handle 180hp of nitrous, but ive only ever run 150hp of nitrous as Im a sook, the nitrous is integrated with my aftermarket ECU and it can adjust the air fuel ratio as the nitrous is being injected so Its pretty safe, but still I play it safer by not pushing it. Link to comment Share on other sites More sharing options...
Defender Posted February 26, 2018 Share Posted February 26, 2018 Very cool. I don’t have that sort of money now I’m divorced. A rust free xp with a mild 289 is all I have now, which needs to go. Never gets used. I love your cars.[emoji3] Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
jason1 Posted February 26, 2018 Share Posted February 26, 2018 Very cool. I don’t have that sort of money now I’m divorced. A rust free xp with a mild 289 is all I have now, which needs to go. Never gets used. I love your cars.[emoji3] Sent from my iPhone using Tapatalk yer an XP would be nice to have. Link to comment Share on other sites More sharing options...
hotty Posted February 26, 2018 Share Posted February 26, 2018 Are we talking a coupe? Link to comment Share on other sites More sharing options...
Defender Posted February 26, 2018 Share Posted February 26, 2018 It’s a four door, not two. Couldn’t afford it at the time Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
hotty Posted February 26, 2018 Share Posted February 26, 2018 Damm...... I could see money coming your way. Link to comment Share on other sites More sharing options...
Defender Posted February 26, 2018 Share Posted February 26, 2018 Yep, a few have said that. Ohhhhh Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
Laxity Posted February 26, 2018 Share Posted February 26, 2018 Nice car but that 600cfm Holley is miles to big for a 5 liter. I agree. It came on the car when I bought it 20 years ago :) swapping the 4:11 rear would make a big difference too. The motor will probably be a lot hotter when I get around to rebuilding it. 355 with VN heads etc. Haven't really thought about it too much just yet. Got to many projects. Link to comment Share on other sites More sharing options...
oldhank Posted February 28, 2018 Share Posted February 28, 2018 my old slant six with 390cfm Holley Link to comment Share on other sites More sharing options...
Jed Posted March 4, 2018 Share Posted March 4, 2018 Not my ride, but used to be Jack Brabham's ! I came across this today - and found it a bit hard to walk away from and stop looking at. What a little jewel/death trap... Link to comment Share on other sites More sharing options...
vintage Posted March 8, 2018 Share Posted March 8, 2018 basically a rocket on wheels lol Link to comment Share on other sites More sharing options...
Super Moderator Foot Posted March 8, 2018 Super Moderator Share Posted March 8, 2018 I had a hq with a 308 stroked to a 327 that used to run a 700 double pumper. Very streetable, my daily driver in fact and used to run 13 flat at 109 mph at willowbank. (I was cranky at my mate in his LH 308 who wan 12.7s, I wanted his 750DP to try) I upgraded from 600 double pumper I was running and gained several 10ths The size of the Carby is all relative to the compression, cam size, head porting, valves and of course how you tune the carby. Would I run a 600 DP on a stock 308? most likely not, I also had a HJ ute running a 202 with a small cam and extractors and only ran a Holly 320 econodyne, I miss my HQ and Im not likely to be able to afford on ever again, friggin crazy bucks for one now Link to comment Share on other sites More sharing options...
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