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#21
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I drove it last summer. It would pull good up until about 5000K and then it just runs out of pull. It's just not as quick and fast as it should be. All the parts in the build check out. Compression test shows good compression. I'm going to look a little closer at the timing and the distributor. |
#22
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The performer may be OK on a 400, a stock cast iron or RPM would be better...
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1977 Black Trans Am 180 HP Auto, essentially base model T/A. I'm the original owner, purchased May 7, 1977. Shut it off Shut it off Buddy, I just shut your Prius down... |
#23
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215 cranking pressure is about 8.5 DCR. Kind of high IMO for pump gas
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#24
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Took it out for a test and tune.
Added another bottle of 108 octane booster. Runs great up to 3200 RPM then it quits pulling. Some definite malfunction. Just don't know what it is. Everything is new. The whole fuel system is new. I switched the fuel pump again and did a volume test. Plenty of fuel. I tried adjusting the timing, didn't change the running out of pull at 3200. All I can think of is the distributor. I have had a lot of nice old Pontiacs and never had one built like this be such a dog. It gives hints of great power up to 3200 but that's it. |
#25
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I think the cam is too weak. I've run a similar cam (Summit 2800) in a 350, and it was a fun, yet tame, street motor. Those heads can take more lift.
702 or 703 Voodoo cam would be good - I run both. The 702 wouldn't take full advantage of the heads, but it has a little wider lsa for better management of the compression. Right now your cam is your performance constraint. I don't think you would have ANY complaints running a 702 Voodoo cam, especially in a lightweight 400 powered Firebird running 3.36's. Aluminum heads can take a little more compression. I think 72cc E-heads are fine. Just get a cam that isn't on such a tight lsa. You will be driving a convertible, which implies a large element of street cruising will be in play. You don't need a 550hp monster engine that will twist the body or frag the rear end. In summary? All you really need is more cam with more lsa. The rest of the package is completely usable, including intake and carb.
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"...ridge reamer and ring compressor? Do they have tools like that?" |
#26
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Once I figure out why it's not pulling past 3200 I will get to actually commenting on the build.
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#27
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If your timing is in the realm of "normal", then maybe your carb is not working right. Are the carb secondaries working? Throttle rod giving full open on carb? I can't imagine your valves would be floating.
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"...ridge reamer and ring compressor? Do they have tools like that?" |
#28
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What is the ignition? A decent HEI and eliminating points would be a good place to start eliminating electrical issues.
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77 Trans Am, 469 w/ported E-Heads via Kauffman, matched HSD intake, Butler Performance forged rotating assembly, Comp custom hyd roller, Q-jet, Art Carr 200 4R, 3.42s, 3 inch exhaust w/Doug's cutouts, D.U.I. Ignition. 7.40 in the 8th, 11.61@116.07 in the quarter...still tuning. |
#29
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I have the timing at 36 total advance. I have tried changing it on the test drive and couldn't get any improvement.
Carb secondaries are working. Goes wide open throttle. It does act like valve float. Seems like a long shot with this build, everything is new. It will rev high but there is no power past 3200 rpm. Once you hit 65-70 mph in 4th it's all done. If you shift before 3200 it will tear ass until you run out in 4th. It's definitely rpm related. The distributor is a new aftermarket 50K HEI. Could be that but it looks perfect. Vacuum advance works. |
#30
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Long shot here. Pull a valve cover and verify that the inner springs are installed. Given the history where the previous owner passed before things were finished, maybe he did a cam break in with inner springs removed (common practice), and never had a chance to get back to it.
BTW, what are the specs on the fuel system? I know you already checked the fuel, but mechanical pumps can sometimes have a diaphragm leak, giving poor performance that is short of a total fail. Other brainstorm is maybe a plugged filter or pickup sock, or maybe cracked soft hose on the suction side that is allowing air to suck in.
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"...ridge reamer and ring compressor? Do they have tools like that?" |
#31
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I replaced the whole fuel system last winter and it didn't change a thing. New tank and all new lines. New mechanical pump replacing the new pump that was on there. I will be checking those springs tomorrow. |
#32
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I second the cowl mounted fuel pressure gauge to confirm fuel pressure at load. A Q-jet that runs dry will just go dead like you turned key off. A Holley or other carb design may go lean and surge or just lose power and lay over without stalling.
It does need a cam with at least 15* more duration at .050 (and inherent later intake closing) to keep it out of detonation.
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I could explain all this to the girl at the parts store, but she'd probably call the asylum. White '67 LeMans 407/TH350/Ford 3.89... RIP Red '67 LeMans. 407/TH400/Ford 3.25 |
#33
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Set timing to 36 total all in, disconnect vacuum advance. See what that does for you.
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77 Trans Am, 469 w/ported E-Heads via Kauffman, matched HSD intake, Butler Performance forged rotating assembly, Comp custom hyd roller, Q-jet, Art Carr 200 4R, 3.42s, 3 inch exhaust w/Doug's cutouts, D.U.I. Ignition. 7.40 in the 8th, 11.61@116.07 in the quarter...still tuning. |
#34
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That cam is the Eddy Perfomer.
https://www.summitracing.com/parts/e...7/make/pontiac Are you sure you have Full battery voltage to the Dizzy. Appropriate spark plugs? Last edited by STEELCITYFIREBIRD; 04-02-2019 at 06:34 PM. |
#35
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That’s one itty bitty cam
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71 GTO, 463, KRE 295 cfm heads ported by SD Performance, RPM intake, Qjet, Dougs Headers, Comp cams HR 246/252 ...11 to 1 , 3.55 cogs, 3985lbs.....day three- 11.04 at 120mph ....1.53 60', 6.98 1/8 mile |
#36
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#37
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Tried the timing every which way.
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#38
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I have a new gas tank with one piece braided line all the way to the pump. New pump and new line to the carb. |
#39
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Is it possible the rockers were not set up right? Wouldn't I have more symptoms? It doesn't pop or backfire. Just acts like floating valves at 3200.
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#40
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Are they the single valve springs with no damper ?
p/n 5767 ? If they are then take a look at the valve lift capacity of those springs, assuming 1.800 installed height and 1.130 coil bind. Then consider he has only 0.420" lift, assuming a 1.5 rocker ratio. "Depending on the intended use and the spring and cam-lobe design, coil-bind safety margins can now vary from 0.015 to 0.120 inch, with tighter numbers predominating on very stiff valvetrains. Anything more than 0.150 inch may cause spring surge, which can greatly reduce the available spring load needed to close the valve." https://www.hotrod.com/articles/how-...rance-is-safe/ .
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'70 TA / 505 cid / same engine but revised ( previous best 10.63 at 127.05 ) Old information here: http://www.hotrod.com/articles/0712p...tiac-trans-am/ Sponsor of the world's fastest Pontiac powered Ford Fairmont (engine) 5.14 at 140 mph (1/8 mile) , true 10.5 tire, stock type suspension https://www.youtube.com/watch?v=qDoJnIP3HgE Last edited by Steve C.; 04-02-2019 at 07:42 PM. |
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