The Cat Is Back But With Issues

chromebumpers

chromebumpers

solid fixture here in the forum
Staff member
My opinion of the new exhaust w/crossover. I can’t say there’s any difference in sound at idle. Still sounds loud in the car at idle. Apply moderate acceleration - somewhat better, drone gone but I was really looking forward to a high performance sound and it’s not there.

The choke wasn’t working the way it should. I found I installed a spring wrong, choke side.

Puzzled about the kick down switch - on the transmission it’s a single wire connection. On the switch above the gas pedal it is 2 wires? See photos*

The car starts great, fast and runs pretty good. Idle doesn’t seem too fast but when I put it in drive it hits hard!

About 5 miles driving I stopped at a light and now the car is stumbling and wants to stall out. Accelerate away and it runs fine.

Get home - pull in to park and it stalls. Restart and it’s great, does’t stall. Turn the car off and back on again, fine, not going to stall.

Raised the hood checking for visible defects. I noticed a small slow leak around the T stat neck around gasket. I kinda expected I’d have a problem.
When I swapped intakes I installed a new TStat. No real recess/grove that the T stat can sit secured into position like on a Chevy. I centered the TStat best I could on top of the new Felpro gasket and placed the TStat neck over top and tightened down VERY securely. Should I remove and re install, this time use “Form A Gasket?”

Ideas?98B47EB0-9B6C-45EE-A715-B40781331387.jpeg
 
A Switched on with Ignition key Power lead hooks onto goes into the Turbo 400 kickdown switch one side.
Other Side of the switch hooks to the Turbo single Lead of the Turbo 400 kickdown solenoid .
I seem to recall Pontiac got the Power into the the Turbo 400 kicksown switch from the lower drivers side fuse block an added on assembly line power lead ignition keyed on .
Have to look in the 1968 Pontiac GM Factory Service manual.
I don't have for 1968.
Have one for 1970 should be similar same.
 
The Rochester Quadrajet Fuel Level is too high at 1/4" inch.
I found in past on the street it would cause engine stall out out on Abrupt take offs and then instant off the gas.
Also Wide open throttle High speed runs then hit the brakes super hard to slow down back to stops 0 mph.
Engine died flooded out.
If you use 1/4 " float setting it must be used with a .110" needle and seat inlet.
9/32" float setting works much better on the street with .110, .120, .135" needle and seat fuel inlet valve.
.135" I used because I was at 550Hp + in the 70 TA.
With todays pump gas it boils easy with engine water temps 190,-210F then the gasoline expands, too high of float level it floods the engine out with raw gasoline from the float bowl vent(s).
Engine stalls dies out .
Vintage Mallory Comp 110 or 140 fuel pump with a Mallory 2-port Regulator is the best for low budget Street engines I have found.
Provides best steady Dead Head Fuel flow.
Set to 6-1/4 psi for street cruising.
Wide open 1/4 mile drag streets 6.5 psi to 7psi with 9/32 " float setting.
Edelbrock and Cartter made the best Mechanical stock style Fuel pump for a Pontiac V8.
Holley also made a nice one but has been discontinued, I used a Holley Mechanical back in 1998 on the 63 Gp with its 1st 1973 455.

Cliff switched to a Holley 4150 Double pumper on his Race car Ventura 455 I read a few months back.
No issues flooding out like Q-jet .
They have own issues on pump gas I found.
Hot summer time heat soak car running or long idle periods.
Need a Full Drag Race Car Fuel return system what I ended up doing in the 63 Gp. Do it right it's very expensive I spent over $2500 cash to do it.
Earl's PTFE lined Race Race Stainless steel hose #10AN all . Only Earl's Speedflex fittings can be used.
AN Fittings $50- 75 Each.
 
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There is only 1 muffler for Vintage cars and Muscle cars that will not Drone.
Original Walker Super Dynomax 2-1/2" and 3 inch.
Were discontinued but they brought them back under another name.
Seen recently have to go look for them for you.
 
Only 1 loud Race Car Muffler that wont Drone, Hooker Aero Chamber Race Mufflers.
Meant to be loud throaty.
You dont want loud
 
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Permatex Aviation gasket sealer is the only to use on Pontiac V8 and Oldsmobile V8 Thermostat housing paper gasket to coat seal with for Zero water coolant leaks
 
High Performance sound you only get in a Pontiac V8 with a right chosen camshaft.
Isky 280 Mega I have in the 1976 455 is like the Pontiac RAIV Cam but better makes way more power.
Low intake manifold for power brakes.
Just barely works power assist in the 63 Gp.

Isky 270 Mega Hydraulic cam be a good choice for the 1968 Catalina 400 Convertible.
Comparable to the The Pontiac RAIII 3 400 camshaft, also used in SD455 Trans Ams.
SD455 Most famous for Race Car sounds stock.

Iskenderien the Only I can Guarantee not to wipe out camshaft lobes, no Lifter failures.
All 100% USA.
You must buy the complete Iskenderien install kit.
Set aside $900 for.
All The Summit cams copycat clones Pontiac V8 are China.
Worked while USA Crane lifters still around. Get China junk now with.
 
Also if you run Zero exhaust system like I do there is no Drone issues any.
Just Race Car Loud all the time.

The 87 Corvette Convertible drones too with the exhaust system it had.
No more Cut sawzall all off right up to the Head pipes left a few inches to dump on the ground clean.
Loud now still Love 3 years later.
Zero drone behind my head driving.
 
https://iskycams.com/shop/index.php?main_page=product_info&products_id=1430

Isky 270 Mega Hydraulic.
The Largest cam profile that can be used with a stock torque converter.

Pontiac and Chevy TH400 Torque converters stock only had a foot brake stall of 1400 Rpms.
High stalls only used in L88 Corvette ordered with a TH400 , Pontiac RAIV 400 with TH400, SD455 Not going to find any today for sale.
Aftermarket premium Race type torque converter needed, Use an aftermarket standalone transmission cooler as Grumpy talked about in past and plumb all with Areoquip #6 or #8 PTFE Lined Stainless steel braided race hose and use special Aeroquip Steel fittings for Hose ends.
Stock GM hard lines not up to tasks any with Performance Race torque converters.
Also need to set aside $900-1500 for it alone.
Did it Grumpys way #6AN Aeroquip PTFE Trans lines and Moroso Finned Cooler, Grumpy doesn't like my cooler but it works.
I agree #8AN lines be better, Fan powered cooler be better yet.
$950-$1000 into my 63Gp Hughes HD Pontiac 455 specific 2500 rpm stall rated TC , Trans cooler, Aeroquip PTFE Lines, And steel fittings.
Steel Fittings Ultimate strength I wanted.
 
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I have to look in my Paperback Isky Catalog for Master Cam kit part number # all parts supplied zero hassles for 270 Megahydraulic Pontiac V8.
Iskenderien builds these kits as orders come in now.
1 at a time.
Nothing slapped together China any.
 
All the Pontiac stock is no good for Performance cam swaps as many others will tell you it's Ok.
Isky supplies Billet 4140 Chromemoly Retainers and Billet 4140 valve locks.

Stock Rockers Ok to reuse if in good shape zero wear.
Same high quality found on Big block Chevy V8.
Pontiac V8 is unique.
 
You never stated what cylinder head casting numbers you have, so I can state if pressed in or screw in Rocker arm studs used on them.
Isky 270 Mega compatible with Factory pressed in Rocker studs because with stock 1.5:1 ratio Rockers you will have .465 " lift at the valves.
1.65:1 RAIV Rockers will give .503" lift at the valves, but past .480" valve lift limit of Factory pressed In studs.

The stock 2-bbl #254 Pontiac cam you have now has only .410 " valve lift with stock 1.5:1 rockers.
 
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I had to convert the 1971 GTO #66 casting heads to Screw in Rocker Arm studs.
Pressed in stock, strange best flowing D-ports with large valves 2.11" & 1.77" with pressed in Rocker studs.
I did the work myself on a drill press I bought and modified the table custom to do it.
Used extra long (.875" - 7/8" long) Helicoil inserts for 7/16"- 14 tpi Lower screw in Rocker arm studs threads.
 
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