[MarkS57]

Hi all,

I am thinking about a Q-jet for my 400 w/ E-heads & Performer manifold. Attached is a picture of a 73 7043262 vent tube configuration. This will require a hole cut in my air cleaner for the vent tube. Is it possible to removed the cast vent (blue arrow); fashion a block off plate as a replacement and re-install a vent tube in the previous location (red arrow)?

Thanks,

Mark

[NeighborsComplaint]

Originally Posted by MarkS57

Hi all,

I am thinking about a Q-jet for my 400 w/ E-heads & Performer manifold. Attached is a picture of a 73 7043262 vent tube configuration. This will require a hole cut in my air cleaner for the vent tube. Is it possible to removed the cast vent (blue arrow); fashion a block off plate as a replacement and re-install a vent tube in the previous location (red arrow)?

Thanks,

Mark

Wouldn't it be easier to just drill a hole in the bottom of the air cleaner?

[F ROCK]

Originally Posted by NeighborsComplaint

Wouldn't it be easier to just drill a hole in the bottom of the air cleaner?

What he said.
...Or just use a stock dual snorkel?

[Skip Fix]

I drilled a hole in a generic drop base 14" air cleaner that is on the 81 TA that as a 73 Qjet.

I'm thinking if it is a "plain" Performer on E heads-even the D ports you are loosing a lot of flow. One killed the flow on my cleaned up RAIV heads.

[form74]

Sane as skip fix
Drilled a hole in The after market drop base bottom for my 74 Quadrajet

[steve25]

Mark your first issue is that Perfromer Intake !
It's a huge restriction on those E heads!

I just made up a adapter over the weekend to test intakes ( atleast Pontiac intakes) on my flow bench and on the short depth side of the Performers Plenum the best any of the 4 runners flow on that side is 205 cfm.
This is atleast a 28% restriction on those heads and will limit the motor to making no more then a possible 430 hp!

[Skip Fix]

When I got my RAIV heads and were building a motor for the old NMCA Top Stock class we bought a Performer as they advertised it as flowing "better than stock". My machinist had a flow bench (not all shops did back mid/late 80s) and stock RAIVs it dropped flow by 15% over my HO intake! I called Edelbrock and they waffled. Sent it back to Super Shops(told you it was a while back) and swapped it for T2. Kept the HO on that motor as less HP factoring hit than an aftermarket aluminum intake.

[Cliff R]

The vent needs to stay on those units. It's very well located and a better deal than blocking it off and trying to drill the airhorn further back for a vent....IMHO.

If you put a matching hole in the air cleaner base make sure you take steps to effectively seal it off as it's inside the air filter element and dirty air coming in there goes directly into the engine. If you don't end up with a really tight fit take a razor blade and make a custom seal from a piece of the correct size heater hose or rubber fuel line. Beats using a butch of RTV globbed up on the vent to get a good seal.....Cliff

[400 Lemans]

Drilled my air cleaner base for a 7mm size plug boot and it seals perfect. the lip at the bottom of boot keeps it in place and you can cut the top off for a larger hole.https://www.oreillyauto.com/detail/b...5824962?pos=12

[form74]

Originally Posted by Cliff R

The vent needs to stay on those units. It's very well located and a better deal than blocking it off and trying to drill the airhorn further back for a vent....IMHO.

If you put a matching hole in the air cleaner base make sure you take steps to effectively seal it off as it's inside the air filter element and dirty air coming in there goes directly into the engine. If you don't end up with a really tight fit take a razor blade and make a custom seal from a piece of the correct size heater hose or rubber fuel line. Beats using a butch of RTV globbed up on the vent to get a good seal.....Cliff

Thanks for tip on using a piece of hose to take up the extra space Cliff, the hole i drilled is just slightly larger due to being off a little on my measurement

[dataway]

When time comes to drill my base I'm going to put some modeling clay on the bottom of it, put it in place and use the clay marks for drilling.

[MarkS57]

Thanks for all the replies, much appreciated.
OK, I will leave the vent alone on the 73 carb if that is what I go with.
Regarding manifolds, I will break in the new cam with the Perfomer & the 750 Holley that was on the engine prior to the head swap. I know the engine will fire right away and should have no issue with cam break in. From there I was thinking of just going over to the 73 Qjet and leaving the Perfomer in place. My other option was to go back to my 69 iron intake & a 69 Qjet from a 428. I posted about that awhile back. I guess I can look at the Perfromer RPM or the T2.

[steve25]

Unless you have 3.73 gears out back then with your 400 cid motor the rpm Intake is the only way to go!

[Cliff R]

The Performer intake has small runners and very quickly becomes a restriction on these engines. It's probably OK to about 400hp but I've tested them back to back on high HP set-ups and they can induce issues that you can not tune out.

On my first 455 installing one immediately caused a severe hesitation/stumble/bog going quickly to full throttle. This simply amazed me at the time because I was doing some intake manifold testing and wanting to swap a bunch of intakes at a private track rental. I was NOT able to use the Performer intake as the stumble could not be tuned out.

On the subject of intakes I also back to back dyno tested 3 intakes on a 500hp 428 engine we built here. We ran my "modified" iron intake first and it made 497hp. Installed an RPM port matched to a stock Felpro intake gasket and it made 491hp. Then I installed a 455 HO intake, one of those Chinese re-pop's and it made 487hp.

That testing makes me about how many folks with 350's and 400's have swapped in RPM intakes then had to do a lot of "cobbling" to get them to fit and they probably made more power with the factory intake they removed.

The other kick in the nuts is that raising the carb an inch higher often involves having to use some sort of drop base air cleaner. I've also tested air cleaners and different lids and you'd be surprised how much power is lost when you move the lid too close to the carburetor.......FWIW.......Cliff

[MarkS57]

Originally Posted by Cliff R

The Performer intake has small runners and very quickly becomes a restriction on these engines. It's probably OK to about 400hp but I've tested them back to back on high HP set-ups and they can induce issues that you can not tune out.

On my first 455 installing one immediately caused a severe hesitation/stumble/bog going quickly to full throttle. This simply amazed me at the time because I was doing some intake manifold testing and wanting to swap a bunch of intakes at a private track rental. I was NOT able to use the Performer intake as the stumble could not be tuned out.

On the subject of intakes I also back to back dyno tested 3 intakes on a 500hp 428 engine we built here. We ran my "modified" iron intake first and it made 497hp. Installed an RPM port matched to a stock Felpro intake gasket and it made 491hp. Then I installed a 455 HO intake, one of those Chinese re-pop's and it made 487hp.

That testing makes me about how many folks with 350's and 400's have swapped in RPM intakes then had to do a lot of "cobbling" to get them to fit and they probably made more power with the factory intake they removed.

The other kick in the nuts is that raising the carb an inch higher often involves having to use some sort of drop base air cleaner. I've also tested air cleaners and different lids and you'd be surprised how much power is lost when you move the lid too close to the carburetor.......FWIW.......Cliff

Hi Cliff,

Excellent points. The increase in carb height with the RPM did concern me. Spent some time last night looking at drop base air cleaners then figuring they could be a problem as well. Right now, I am considering sending my 69 iron intake to SD as he has CNC programs to help the factory iron (you are mentioned in his web page). As a side note, one of the unforeseen side effects of the aluminum heads is the reduced weight over the front end and now the car sits up noticeably higher in the front so going to the iron intake helps a little in combination with the added weight from the RA exhaust manifolds.

[goatman1970]

RPM intake with the same Q-Jet with that pesky front top vent tube inside the cleaner, used a drop-base cleaner, drilled hole and installed a grommet to seal around the vent tube, and put a K&N filter top on the air cleaner. All issues resolved.

[dataway]

Did the OEM air cleaner bases use a grommet? I have to do this same process on my engine and was wondering if there was an OEM part or repop grommet for the hole.

[Grand73Am]

Originally Posted by dataway

Did the OEM air cleaner bases use a grommet? I have to do this same process on my engine and was wondering if there was an OEM part or repop grommet for the hole.

It's not a grommet in the hole. I believe it was like a soft rubber gasket, sort of a square o-ring, that you slid over the vent tube so it sat at the base of the vent, so when you put the air cleaner on, the hole sealed against the gasket. Easy enough to make something, maybe from some gasket material or rubber sheet. I've seen an o-ring on one before, but most o-rings don't compress, so might not seal as well as something softer.

[dataway]

Good idea, thanks, I've got a ton of foam and stuff here.