This is a well documented mod done to the PPG cars. It eliminates the runners inside the plenum closes the gaps between them and enlarges the neck right at the choke point. The increased air volume from the mod is significant. With a 3.4 pr swap it will significantly reduce the choke out due to lack of air after 4500 rpm. Yes don’t have specific specs on the improvements but they are out there here on PFF.
This is a well documented mod done to the PPG cars. It eliminates the runners inside the plenum closes the gaps between them and enlarges the neck right at the choke point. The increased air volume from the mod is significant. With a 3.4 pr swap it will significantly reduce the choke out due to lack of air after 4500 rpm. Yes don’t have specific specs on the improvements but they are out there here on PFF.
The hogging out of the walls between ports at the bottom of the middle intake did more for >4500 rpm power than anything else. ;-) You can almost keep the entire intake stock and benefit just from that one simple mod. I see you left the EGR port on the intake. Did you at least deepen the neck area to allow more flow volume there? That is a huge restriction overall.
EDIT: Ah with that latest picture I now see that you did deepen/enlarge the neck area! Nice work!
[This message has been edited by lou_dias (edited 05-19-2020).]
This mod is a good one and will undoubtedly work to improve air flow especially at the high end of the power band. While the peak torque and horsepower will be better you may lose some torque and horsepower at the lower end in the 1000-2800 RPM band.
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
The hogging out of the walls between ports at the bottom of the middle intake did more for >4500 rpm power than anything else. ;-) You can almost keep the entire intake stock and benefit just from that one simple mod. I see you left the EGR port on the intake. Did you at least deepen the neck area to allow more flow volume there? That is a huge restriction overall.
EDIT: Ah with that latest picture I now see that you did deepen/enlarge the neck area! Nice work!
Can you recommend an affordable welder for aluminum intake work like that shown above? I've got a keen interest in learning this skill for the rest of my semi-retirement.
[This message has been edited by sourmash (edited 05-19-2020).]
I have been modifying an 87-88 upper for my 85 w/ 3.4 F-body longblock.....Have it done and installed but need to test it. The 3.4 with L44 induction system would pull 4500 RPM going up hill with a friend and me in (Getrag) 4th gear...Next sunday I am planning on testing it again with the modified manifold....
[This message has been edited by cvxjet (edited 05-19-2020).]
cvxjet, how did you cut the intake? Also, what diameter Aluminum pipe did you use for the piece to weld on? It's nice to see a design like this retaining the EGR for purposes of smog testing.
[This message has been edited by Notorio (edited 05-20-2020).]
I believe it is 2 ID 1/4" wall tubing but I will go check........I used a number of tools to do the cutting- Did some drilling, and also picked up a couple of carbide cutting wheels for my B&D "Dremel" tool.......Simply put, it took time and patience...
Notorio, here is some more pics......The tubing was 2" ID/ 1/4" wall and 6" long. Also, when I did get done removing the section out of the manifold, I cut out and saved the PCV nipple, because anything you can find to take it's place will stick out so much it tends to interfere with the fuel rail. I drilled a hole that was tight and then tapped it in with some RTV around it to make sure of a good seal.
[This message has been edited by cvxjet (edited 05-21-2020).]
Notorio, here is some more pics......The tubing was 2" ID/ 1/4" wall and 6" long. Also, when I did get done removing the section out of the manifold, I cut out and saved the PCV nipple, because anything you can find to take it's place will stick out so much it tends to interfere with the fuel rail. I drilled a hole that was tight and then tapped it in with some RTV around it to make sure of a good seal.
That's excellent .... thanks! I just wondered if you could offer a simple 'kit' consisting of the pre-cut tubing and a template that can be applied (idiot proof) to the intake to transfer cutting lines? Do you think JB Weld could stand up in place of getting the welding done?? I'd buy a kit like that b/c now one is just dealing with regular tools in the garage and won't destroy the paint by heating. Perhaps all you'd need was a splash of paint and you're good to go.
I don't think JB weld would hold up....and I'm kickin' myself for not taking a pic of the pre-welded manifold in place with a ribbon holding it together....would have been hilarious!
I am going to do a whole post on this mod as soon as I test the car next Sunday....Maybe I can do a pattern and place it on graph paper in a pic that can be printed..
I did take it for a drive yesterday and it seemed to be a bit better above 4000 rpm- in 2nd it revved out to 5200 and was still pulling......
I’ll be installing mine this weekend. My mod will Have the plenum hold 25% more air capacity than just the neck mod and the air will get to the middle intake runners faster as there no runners Inside the plenum to channel the air. I’ll take some pics and video of before and after.
[This message has been edited by jjd2296 (edited 05-22-2020).]
So I forgot to take a before video and o still have to take the after video but I can tell you this made a huge difference! Pulls all the way to 5500! Big improvement. I can cruise at 140 in 4th! And pull to 160 easy. The extra air intake and the 3.4 results in great 👍 improvement but it will need a chip burnt to have it run perfect.
Glad to hear it! The stock Fiero programming is overly rich >4100 rpm... What cam did you use? That's probably what's limiting your power >5500...and perhaps your throttle body... Also - I assume you ported the heads...
260h cam but have 1.6 rollers to add at some point. Ported everything. Any suggestions for leaning it a bit? I do have an adjustable fuel pressure reg.
I wouldn't do anything until you get it on a dyno. I would only adjust the fuel pressure if you had an immediate problem that showed up on the dyno, other than that just tune it with TunerPro and a chip burner. Anyway, it's your cam limiting your power as far as the rpm goes...
No mine is a custom grind. Little bit more than a 260h I was told. And o didn’t push it more than 5500 rpm it’s a fresh build still. I do have 1.6 rollers which would give me so me more lift
