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 68 Catalina Intake and Carb
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D1onysus
Tribal Scout

9 Posts

Posted - 24 Aug 2017 :  12:58:53 AM  Show Profile  Reply with Quote

So, my Cat came with an Edelbrock P4B intake and a 1406 carb. I was always planning on ditching the carb because I just plain don't like Edelbrock carbs. The intake I misidentified as a Performer, so I was going to leave it and switch to a Holley carb. It also came with a Triangle of Death air filter, which I had planned to swap to a regular, normal, circular air filter anyway, but it melted, so now I have to. When it melted, it may have messed up my carb, I haven't pulled it apart yet to see, but the car has been running like crap recently.

There's also excessive blow by and possibly low compression in the #2 cylinder, but I'm still troubleshooting that, the ceramics on the spark plug pretty much shattered as soon as I put a socket on, so I'm waiting to do my compression tests until I'm replacing all the plugs anyway.

Anyway, back to the intake side of the equation. I was thinking I'd swap to either a performer or performer RPM paired with a Holley Double Pumper, I was thinking somewhere north of 650 CFM, since the 600-650 range was what I usually ran on smaller sub 360ci engines. Does anybody have experience with this set up? Would the RPM cause fitment issues? Is a K&N filter worth the hundred bucks for a simple round air filter?

I'm planning on also adding headers (still looking at brands) and a true dual exhaust (I have a 1-2 in the trunk that came with it). I'm not planning on going a lot more aggressive with it, just some mild street performance. It is a 4 door sedan, so it's not exactly going to be rocketing down any quarter miles.

1968 Catalina 4-door Sedan "Hispaniola"

Bill Boyle
Horse Feathers (Charter Member)

USA
4794 Posts

Posted - 24 Aug 2017 :  08:12:17 AM  Show Profile  Visit Bill Boyle's Homepage  Reply with Quote
You could probably replace that intake with a stock OEM 4 barrel unit pretty easily. I'm almost certain there are guys that visit this board that have one to sell for a fair price. The stock units are very good and hold their own against aftermarket aluminum intakes very well without modification. I'd also contact Cliff Ruggles and see if he has a carb that will perform for you for a reasonable price.

Unless you plan to upgrade the engine with forged pistons, balancing, ported heads, simply go with a log manifolds and a good 2.5" true dual exhaust system. No need to spend hard earned cash on a K&N filter or RPM intake, because it's overkill on a near stock or mild engine.

"Dedicated to keeping the classic Pontiac engine alive."

----
400 bored +.030, forged TRW pistons, ported 62 heads, Hedman headers, 2.5 SS dual exhaust X Pypes, Comp 276AH10 cam, Scorpion 1.65 RR, 850 Q-jet, stock intake & tuned HEI; original owner.
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cortcomp
Coyote

USA
5335 Posts

Posted - 24 Aug 2017 :  08:51:50 AM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
Adding to what bill says, i don't think anyone is running anything under a 750cfm on a pontiac engine here. I ran the edelbrock 750 (and still have it on the shelf) on my 455. I had an issue where it'd bog and hesitate when going from cruise to fast WOT. Came to find out that it's a common issue for these carbs in the BOP engine crowd, and you really can't tune it out. Went with a quadrajet and never looked back. Only thing i had to adjust was the APT and full throttle mixtures. Cliff walked me through it, the phone call took longer than the settings adjustment.

I need to get my parts up for sale here. 99% sure i have a stock intake, and an edelbrock regular non rpm performer intake with separated water cross over, a rebuilt qjet that had a slight whistle when idling through the idle air holes and that performer 750.

I'm not a holley fan for a street car, i just don't think it's the most efficient for sub 2500rpm cruising. But, others like them so there's something there.

Of course if you want to burn money, the coolest setup to cruise is the pontiac tri-power, they look great in the big cars too.
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D1onysus
Tribal Scout

9 Posts

Posted - 24 Aug 2017 :  4:32:22 PM  Show Profile  Reply with Quote
Would I get any performance boost from running an OEM 4 barrel manifold though? I have the original manifold and carb if I every feel like putting it to something resembling stock, so I'm not terribly worried about being period correct, which I guess the P4B is period correct aftermarket. If there's no performance gain from switching to the cast manifold, then I may as well keep the P4B, but I was kinda looking to get something that would give me room to expand over time. I have a habit of falling down the "just one more thing" trap.

I was thinking a 750cfm sounded about right for my 400, but that's just based on guessing from my experiences with smaller engines. I always had good luck running a double pumper in the past, but it was also the main carb I had. I found it in a scrap metal yard, took it home, rebuilt it, and put it on a couple different things, so it could just be a matter of "when all you have is a hammer". I've been thinking about the q-jet since I started researching this car, but it seems like they're hard to maintain/tune and expensive in every direction. I've seen quite a few for sale between $20 and $200 on craigslist in varying states of repair, but I know I can rebuild a Holley, Carter, or Edelbrock; I'm not as sure about the Q-Jet. It also doesn't help that people selling the q-jets almost never list CFM.

I may stick to replacing the Carb, exhaust manifolds and exhaust first and see what my butt dyno tells me from there. The 600cfm carb on this thing is smaller than I'd like anyway.

1968 Catalina 4-door Sedan "Hispaniola"
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Bill Boyle
Horse Feathers (Charter Member)

USA
4794 Posts

Posted - 24 Aug 2017 :  5:11:03 PM  Show Profile  Visit Bill Boyle's Homepage  Reply with Quote
A stock OEM cast iron 4 barrel PMD intake manifold from 68 is superior to the P4B.

"Dedicated to keeping the classic Pontiac engine alive."

----
400 bored +.030, forged TRW pistons, ported 62 heads, Hedman headers, 2.5 SS dual exhaust X Pypes, Comp 276AH10 cam, Scorpion 1.65 RR, 850 Q-jet, stock intake & tuned HEI; original owner.
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D1onysus
Tribal Scout

9 Posts

Posted - 24 Aug 2017 :  5:56:50 PM  Show Profile  Reply with Quote
I'll keep my eye out for one then. From a quick cursory google search, it doesn't look like one in good condition is going to be easy, or cheap, to find, but if it performs better, that's what I want. It's always kind of fun upgrading with parts off another car anyway, reminds me of my Grandfather's hot rods.

Looking into the Q-jet in a bit more depth, it appears they came in a whole lot of different configurations for different applications. Would you, in general, suggest sending it in to Cliff Ruggles and waiting the four months or so to have it purpose built until I'm more familiar with the things, or should I be fine with experience rebuilding other carbs, a rebuild kit, and possibly the book?

Sorry for all the questions, old Pontiacs are new territory for me. I know I'm a tad skeptical of the cast intake working better, but that's just my knee jerk reaction to putting a stock part in place of a "performance" part. It feels somehow morally wrong, lol, but I'm here asking questions especially to learn stuff like this and benefit from others experience. There's only so much reading about stuff helps before you need to just ask somebody that knows.

1968 Catalina 4-door Sedan "Hispaniola"
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cortcomp
Coyote

USA
5335 Posts

Posted - 25 Aug 2017 :  10:00:13 AM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
So many aftermarket performance parts are really to brag about the money and upgrades you spent on your car at cruise night, and less about actual performance. Even worse are mis-matched performance parts, easy way to kill a good combo (so maybe 4.11 gears with a motor that doesn't rev or runs out of breath at 3k, or high flowing heads and a stock cam...)
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D1onysus
Tribal Scout

9 Posts

Posted - 25 Aug 2017 :  4:31:11 PM  Show Profile  Reply with Quote
Yeah, I'm just used to working with classic imports, since that's been my main focus for the last few years. With them there's not really the big names like Edelbrock with a style of intake, for example, that fits everything, it's a lot more brand and car specific, especially older Toyota's. Usually there's like two people that make a part for whatever car, and they're well known, and you know if you can wait and pay for one of those two guys, you are getting a quality part that will perform above stock. Not that you can't get a lot out of stock parts, but, well, I think you get what I mean.

If you do come across that intake and q-jet, let me know, depending on how pay day is falling, I may be interested.

1968 Catalina 4-door Sedan "Hispaniola"
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D1onysus
Tribal Scout

9 Posts

Posted - 25 Aug 2017 :  7:11:01 PM  Show Profile  Reply with Quote
Well, the point is moot for the time being anyway. Ran a dry compression test on Cylinder 2, 4, and 6. two was at 60psi, the other two were at 150+. I didn't even need to finish it at that point, pretty sure the rings in #2 never seated right after the previous owner rebuilt it and that they are now shot. Not having a garage, cherry picker, or engine stand, I'm probably going to have to have somebody else do it. That's going to take all the money in the world.

1968 Catalina 4-door Sedan "Hispaniola"
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cortcomp
Coyote

USA
5335 Posts

Posted - 25 Aug 2017 :  9:18:28 PM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
You might have a head/valve issue. Put some oil in the cylinder and see if the compression comes up. If it does, it's rings. If it doesn't it's likely head/valve related and you can yank the head(s) and take to a shop.
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D1onysus
Tribal Scout

9 Posts

Posted - 26 Aug 2017 :  03:42:25 AM  Show Profile  Reply with Quote
I've had pretty hard core blow-by, which is why I'm leaning rings. There is a valve issues, because for some reason the previous owner could not find new valves for this thing. It took me one google search. He's bad at internet though, I've been finding parts for the bike I traded him for online, so might just be that. The blow-by is what makes me really think rings though. I would have done a wet test if I can a good way to get oil in on hand, but the plugs are almost horizontal. It's like 50 bucks to replace them all again too, but you're right. I just hate going through the whole tossing plugs stage. I think I can modify an old spice bottle to squirt some oil into the cylinder.

1968 Catalina 4-door Sedan "Hispaniola"
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