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#1
02-09-2020, 08:07 AM
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Valve springs or something else?
Took the T/A to test and tune yesterday. Ran the usual #s with e.t.s between 12.12 and 12.18 but on the last pass I noticed that the rpms flat lined at 5300-5400 at around the 1100 ft mark. I shift at 5500 and usually go through the traps at 5700. The springs have a lot of passes on them and I had to shim them back into spec several months ago when I had the heads off to replace the head gaskets. I might suspect fuel delivery except that I have never had a problem in that area and no changes have been made. I run a HP150 pump, 1/2" supply, sumped tank and a Q-jet. Any ideas?
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69 Bird w/1970 400 block(409 cubes), #64 heads, hyd. roller, Q-jet by Jeff E., original interior, ps, pdb, th350, and 3.73 gears. Pump gas, street driven muscle. 3800 lbs. race weight. Best, 11.39 @118, my son's car. 79 T/A w/463, Scat crank, Eagle rods, Icon pistons, Lunati solid roller, 262/270, KRE 325 heads, Northwind intake, QF950 carb, full interior, ps, pdb, th350, and 3.73 gears. Pump gas, 3650 lbs. race weight. 10.68 @ 126 so far... no tuning yet. |
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#2
02-09-2020, 08:38 AM
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were the conditions generally a lot better than a normal race day for you? If so it may have been flat because the air was so good it went a little lean. was your MPH up or down alot?
where you know you have already had to service the springs, i would expect this to be the most likely factor. just need to look for anything else that may contribute. was trans or motor hot?, lash loose or tighter than normal? different fuel? have you checked retorque on the head gaskets? same size tires? etc
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1969 carousel red firebird 455, richmond 5 speed 1964 540 gto 1971 lemans sport convertible 1972 Maverick under slow construction |
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#3
02-09-2020, 08:52 AM
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The air was very good and the times seemed a bit off for the conditions. MPH was down a bit but we did have a head wind. I thought about a lean cond. so I made a pass with richer sec. rods. Car actually went slower on that run at 12.18. Also the fact that my best run ever of 12.01 at 111 was in similar air with the same setup as now. 60 ft. times were very good yesterday so I would have expected a bit better e.t. and mph.
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69 Bird w/1970 400 block(409 cubes), #64 heads, hyd. roller, Q-jet by Jeff E., original interior, ps, pdb, th350, and 3.73 gears. Pump gas, street driven muscle. 3800 lbs. race weight. Best, 11.39 @118, my son's car. 79 T/A w/463, Scat crank, Eagle rods, Icon pistons, Lunati solid roller, 262/270, KRE 325 heads, Northwind intake, QF950 carb, full interior, ps, pdb, th350, and 3.73 gears. Pump gas, 3650 lbs. race weight. 10.68 @ 126 so far... no tuning yet. |
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#4
02-09-2020, 09:02 AM
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Put some new plugs in and see what it does?
(been better if done the day of testing though) 
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John Wallace - johnta1 Pontiac Power RULES !!! www.wallaceracing.com Winner of Top Class at Pontiac Nationals, 2004 Cordova Winner of Quick 16 At Ames 2004 Pontiac Tripower Nats KRE's MR-1 - 1st 5 second Pontiac block ever! "Every man has a right to his own opinion, but no man has a right to be wrong in his facts." "People demand freedom of speech to make up for the freedom of thought which they avoid." – Socrates |
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#5
02-09-2020, 10:17 AM
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John, the plugs are fairly new buy it wouldn't hurt to put in a fresh set. Unfortunately it will be 2 months before I can back to the track. Hope to have some 'fixes' in place to try out.
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69 Bird w/1970 400 block(409 cubes), #64 heads, hyd. roller, Q-jet by Jeff E., original interior, ps, pdb, th350, and 3.73 gears. Pump gas, street driven muscle. 3800 lbs. race weight. Best, 11.39 @118, my son's car. 79 T/A w/463, Scat crank, Eagle rods, Icon pistons, Lunati solid roller, 262/270, KRE 325 heads, Northwind intake, QF950 carb, full interior, ps, pdb, th350, and 3.73 gears. Pump gas, 3650 lbs. race weight. 10.68 @ 126 so far... no tuning yet. |
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#6
02-09-2020, 10:23 AM
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Hey Gates,
When was lat time you popped your cap off your dist to make sure it's all moving as it should? Jeff
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Carburetor building & modification services Servicing the Pontiac community over 20 years |
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#7
02-09-2020, 02:34 PM
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Hi Jeff,
Good point. One of those 'out-of-site', 'out-of-mind' things. It has been forever since I did anything with the dist. Will give it a look.
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69 Bird w/1970 400 block(409 cubes), #64 heads, hyd. roller, Q-jet by Jeff E., original interior, ps, pdb, th350, and 3.73 gears. Pump gas, street driven muscle. 3800 lbs. race weight. Best, 11.39 @118, my son's car. 79 T/A w/463, Scat crank, Eagle rods, Icon pistons, Lunati solid roller, 262/270, KRE 325 heads, Northwind intake, QF950 carb, full interior, ps, pdb, th350, and 3.73 gears. Pump gas, 3650 lbs. race weight. 10.68 @ 126 so far... no tuning yet. |
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#8
02-09-2020, 07:37 PM
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I vote valve springs are weak
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62' Lemans, Nostalgia Super Stock, 541 CI, IA2 block, billet 4.5" crank, Ross, Wide port Edelbrocks, Gustram intake, 2 4150 style BLP carbs, 2.10 Turbo 400, 9" w/4:30 gears, 8.76 @153, 3100lbs |
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#9
02-11-2020, 06:12 PM
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I've got a set of SD ported heads and they have chrome valve springs
who makes these chrome valve springs does anyone know? Thanks GT. |
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