Ok , here's my question! The stock MAF flows aprrox. 550 CFM's of air and the stock throttle body flows approx. 680 CFM's of air!! Now, since the air flows through the MAF on the way to the throttle body wouldn't it make sense that if you removed the screens on the MAF to increase the CFM's to approx. 711 CFM's, that would also increase the CFM airflow of the throttle body because the MAF is allowing more air to get to the throttle body quicker??

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1986 Trans AM
305 TPI
4 Wheel Discs
9 bolt Borg Warner Rear
Completely Stock
Soon to upgrade to a 383 stroker w/TPI, Hedman Shorty Headers, 64cc Pocket Ported Worlds Product Sportsman-II heads, ported intake, comp cam, TPIS air foil, Adjustable Fuel Pressure Regulator, and 24 lb/hr SVO injectors!
Current project: Keeping my car running until I get the money for the above mentioned project! :-)

 

Modding the MAF isn't really necessary for a 305, only for a high flowing 350, (unless u are planning heavy mods) it might give a few HP, not that much, but instead of modding, maybe have it give codes, and maybe having to buy a new 1 because of the modding, a Wells MAF flows more than 700CFM and its not that expensive, something like $80, compared to buying a new Bosch MAF if u don't do the modding correct. More airflow at a better price, and u don't need anything more than a 48mm TB.

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Looking For:

87 IROC-Z 350 TPI
84 TRANS AM 305 H.O.



[This message has been edited by IROCZTWENTYGR8 (edited January 31, 2001).]

 

Actually, I've priced out the Wells MAF from two sources, and the price was closer to $200.

Pulling the screens off yourself is not that difficult. You'll need a pair of fine-tipped needle-nose pliers. Go slow and be patient and carefull.

Removing the screens will not set codes. I have done this to both of my MAF's and had no troubles. By the way, if you want a little insurance, used MAF's come up on ebay occassionally and sell for around $75.

If you want a little more insurance, you could send the MAF to <a href="http://www.tpis.com/welcome.html">TPIS</a>. For $45, they will remove the screens and fins for you. They claim with these mods, the MAF will flow 750+ cfm.

 

The answer to your question is: NO

The flow rate of the MAF and the TB should have been conducted as separate units but at the same test conditions, such as, vacuum.

If you test both together as a single unit, you are likely to get 550cfm or a little less.

If you modify than MAF so that it flows 711cfm, you are now TB limited to 680cfm.

Note that I'm using your numbers assuming they are correct.

 

I see what you're saying! So the airflow will only be the lesser of the two (TB and MAF)! So right now I'm flowing about 550CFM because of the MAF....by removing the screen to get approx. 711 I will then get approx. 680 CFM's because that's the smaller of the two (the TB airflow)! Now, by removing the screen and the fins, the MAF will flow 750+ CFMS so by upgrading the TB to a 52MM that flows 750CFM, I'm guaranteed to get at least 750CFM's! Gotcha now! Thanks doc for clearing that up for me!!

*Posted by 86TpiTransAm*

Wrong username because my friend was on here and I forgot to change the username!


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1989 firebird formula

Mods: converted from T.B.I. to a carburator 305 to a 350. Flowmater exhaust,hedman shortie hedders,202 heads,350 horse cam,bored.40 over, Edlebrock torker2 and a 600 edlebrock manual choke.

Future mods performer rpm air gap intake (polished) comp roller cam, and way better headsa 400 defintely in the works!

[This message has been edited by burnoutrpm (edited February 01, 2001).]

 

You can mod the MAF and buy a larger TB, but once the air is past the butterflies it will almost all be for nought.

A 350 running at 100% V.E. would need to get only 506 cfm to the cylinders(63.25 cfm/cyl) to be able to run at 5000 rpm. However, a L98 reaches it's highest V.E.(<80%) at peak torque(about 3000 rpm). At 3000 rpm a 350 only needs to get 304 cfm into the cylinders to reach 100% V.E. And a stock L98 would need only 243 cfm. So obviously, even the stock MAF and TB aren't limitations at this point, both components are capable of double the required flow. Removing the screens and fins will however allow denser air to reach the plenum. However, most of the extra density will be lost before the air hits the runners, as the plenum tends to heat the incoming air and cause a LOT of flow losses.

If you really want to increase flow, spend your time(and money) on the components behind the TB, not those in front of it.

 

Almost everything in that post is what I'm trying to say.

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Looking For:

87 IROC-Z 350 TPI
84 TRANS AM 305 H.O.

 

Thanks everyone who replied! I completely understand what you're saying now!! That's good too because I've already replaced my MAF once because it went bad and I wasn't looking forward to replacing it again if my mods messed it up! I plan on buying a dremel to port the plenum and I will probably have a shop port match my intake!!

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1986 Trans AM
305 TPI
4 Wheel Discs
9 bolt Borg Warner Rear
Completely Stock
Soon to upgrade to a 383 stroker w/TPI, Hedman Shorty Headers, 64cc Pocket Ported Worlds Product Sportsman-II heads, ported intake, comp cam, TPIS air foil, Adjustable Fuel Pressure Regulator, and 24 lb/hr SVO injectors!
Current project: Keeping my car running until I get the money for the above mentioned project! :-)

 

Port-matching all the intake components is a good place to start(don't forget that pesky casting wall behind the TB openings). One word of advice: Dremels are nice to use on soft materials, but they lack the torque and speed to do metals with any finesse. Invest in a small compressor and a die-grinder(I like one that has about 40,000 rpm). I guarantee you will find other uses for the compressor and grinder(like blowing out all the metal filings you create when you hog-out those openings).

Once you've port-matched the intake, there's no reason you can't do the same to the manifold and heads(and remember by now, you've already got the tools you will need). And after that mild porting and polishing on your heads WILL yield good results. It won't hurt to practice on a set of junkyard heads($25) to work on technique.

A lot of the 'hot rodding' magazines have done good articles on porting heads, most of which are available as archives on their websites. There's also some good books out there on the subject. Most of what it will require from you is: time, effort and patience.

 

88IROCs is correct. People worry too much about what's in front of the plenum, instead of what's after. The TB and MAF only show their "stuff" after you get rid of the bottle necks after the TB. Think of it like a "constipated pancake eater".

As for the die-grinder, yes, it is the best tool. People have used a Dremel, but this is not what they are intended for. You'll be there a long time, go through a ton of grinding bits and possibly burnout your Dremel. If you don't hava a compressor and/or it is not feasible (say you live in an apartment), they do make electric die-grinders at a fairly reasonable price. Not as good as a compressed air driven die-grinder IMO, but much better than a Dremel. Very convient for people in places where a compressor is not feasible.

 

Glenn,

After a thoroughly miserable weekend(some @sswipe tried to destroy the #1 IROC with his 1/2-ton while I was in the bank), your post actually gave me a reason to smile. Imagine grinding any metal in an apartment. If you were friendly with the neighbours before, you won't be afterwards. Then again, if you never got along with them,....

One very good reason not to use a Dremel,... safety! It's very easy to have any grinder take-off on you, if you hit a rough spot(this happened to me with the Dremel on plastic) or lose concentration. The Dremel will continue spinning, possibly damaging your work piece and/or causing injury. Die grinder have a spring loaded trigger and a mechanism to prevent inadvertent activation. Thus if you do lose control, the grinder will stop and you will not accidentally restart it by hitting the trigger in a panic.

Speaking of safety, invest in a good full-face shield. I've tried using goggles and a mask(to prevent chewing bits of debris), but invariably some material always gets around the goggles(maybe I'm just a clutz?). And not having to wear a mask makes breathing a lot more comfortable. A reversed ball-cap(or a bandana I suppose) is also a good idea. The bits that go flying will always find any areas of yourself that are exposed.

[This message has been edited by 88IROCs (edited February 05, 2001).]

 

Well, this topic has obviously turned into a dremel/die grinder discussion (probably caused by me), so I'm giving my two cents here!!

Look at this site! http://www.tribal-treasures.com/cars...-port/port.htm

Dremel is recommended there and it's cheaper mind you! Also, my best friend has a dremel and has ported his intake just fine!! The dremel only runs 10,000 RPM's less at 30,000 RPM which is PLENTY of speed for porting!! And about losing the dremel while porting...just hold on to the damn thing tighter and take your time!

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1986 Trans AM
305 TPI
4 Wheel Discs
9 bolt Borg Warner Rear
Completely Stock
Soon to upgrade to a 383 stroker w/TPI, Hedman Shorty Headers, 64cc Pocket Ported Worlds Product Sportsman-II heads, ported intake, comp cam, TPIS air foil, Adjustable Fuel Pressure Regulator, and 24 lb/hr SVO injectors!
Current project: Keeping my car running until I get the money for the above mentioned project! :-)