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#1
06-27-2026, 05:12 PM
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Oil Cap
I have a chrome push-on breather cap but the diameter interferes with the fuel pressure and oil pressure gauges that sit just above the oil fill tube.
Does anyone know the diameter of the correct cap, linked below? Hoping it might be a little smaller. https://www.amesperf.com/parts/36516/
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1968 Pontiac Firebird Sprint 1991 Pontiac Firebird Formula LS2/6-speed 1977 Jeep Cherokee 401/TH400/Quadratrac |
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#2
06-27-2026, 05:50 PM
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The Closed PCV system uses the "Top-Hat" style cap.
like the one in your link. The Open system, Vented cap is larger. Depending on how the gauges are set up you'll either have to modify them or use a removeable plug of sorts in the tube.
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When I die, I want to go peacefully like my grandfather did, in his sleep. Not screaming like the passengers in his car. 
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#3
06-27-2026, 07:26 PM
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Jeff-
I was a little confused because Ames calls the "top hat" a breather cap, which it really isn't if it is used in a closed system. Ames also has this one (link below) but calls it a "twist-on." Looks like a "push on" to me, and like your photo. It does look smaller than mine. Can you measure the diameter of yours? This one might work. https://www.amesperf.com/parts/1301/
__________________
1968 Pontiac Firebird Sprint 1991 Pontiac Firebird Formula LS2/6-speed 1977 Jeep Cherokee 401/TH400/Quadratrac |
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#4
06-28-2026, 06:59 AM
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The "Twist" type are for the V8 Valve covers and have ears to twist and lock.
You want the Push In. I use the '64 offering and they are close to OE, I just blast them and repaint with High Heat Black. If your Cammer is a CLOSED system you don't want the Larger Breather style.
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When I die, I want to go peacefully like my grandfather did, in his sleep. Not screaming like the passengers in his car.
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#5
06-28-2026, 08:25 AM
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68-9 used the closed system only
66-7 Calif A.I.R. used closed system
__________________
Everything comes and goes Pleasure moves on too early And trouble leaves too slow |
| The Following User Says Thank You to Cammer-6 For This Useful Post: | ||
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#6
07-03-2026, 03:49 PM
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Jeff - the 64 cap from Ames works great. It looks tight but there is enough space to remove and reinstall. Thanks for the tip!
__________________
1968 Pontiac Firebird Sprint 1991 Pontiac Firebird Formula LS2/6-speed 1977 Jeep Cherokee 401/TH400/Quadratrac |
| The Following User Says Thank You to scotty54 For This Useful Post: | ||
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#7
07-03-2026, 04:48 PM
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Im trying to figure out the need for 2 regulators
what pressures are they set at?
__________________
Everything comes and goes Pleasure moves on too early And trouble leaves too slow |
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#8
07-03-2026, 08:04 PM
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The fuel pressure regulator is set to 3.5 psi, the other regulator is for the oil line to the rear of the head, set at 6 psi.
__________________
1968 Pontiac Firebird Sprint 1991 Pontiac Firebird Formula LS2/6-speed 1977 Jeep Cherokee 401/TH400/Quadratrac |
| The Following User Says Thank You to scotty54 For This Useful Post: | ||
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#9
07-03-2026, 08:17 PM
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I didnt think about one for fuel pressure.
You have no problems with valvetrain at only 6psi? Ive never gone that low.
__________________
Everything comes and goes Pleasure moves on too early And trouble leaves too slow |
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#10
07-04-2026, 09:20 AM
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The Weber DCOE works best at 3-4 PSI. This I learned from TR6 owners, the best resource so far for learning how to tune the carbs. Other than a rough idle (which I am troubleshooting with their help) the carbs are working nicely.
I must have gathered somewhere that 6 PSI was a good setting for the oil pressure. What should it be? Still learning . . .
__________________
1968 Pontiac Firebird Sprint 1991 Pontiac Firebird Formula LS2/6-speed 1977 Jeep Cherokee 401/TH400/Quadratrac |
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#11
07-10-2026, 07:24 PM
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It appears that my oil pressure regulator is a standard Holley which has a range of 4.5 to 9 psi. I now have it maxxed out at 9 psi.
__________________
1968 Pontiac Firebird Sprint 1991 Pontiac Firebird Formula LS2/6-speed 1977 Jeep Cherokee 401/TH400/Quadratrac |
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