I read somewhere that to port the stock manifold one would have to add more material top and bottom to get the runner diameters. Not a straightforward exercise. Probably beyond me.

 

I know.

Freight was going to be a killer that darn renegade intake you never received also.

 

Not having to pay the freight was was the only good thing about not getting one!

 

Beyond my abilities also.

Anyone can hog out or bore out a pair of sbc cylinder heads & an intake manifold with a air grinder or electric dremel tool.

Can they get them to perform better than stock GM or what the aftermarket supplier gave YOU ?

999 out of 1000 times I can answer that to YOU WITH A BIG NO.

People screw them up & they end up flowing worse than what they had to begin with.

Ron is honest.

More than I can say about most that do cylinder head & intake porting work.

And some people selling services & parts here on C4.

Brian R.

 

I got your back Steve............

watch mine for me.............

LOL

I like & trust Ron 100 %.

He is veteran mechanic like myself & a 100 % all American Hotrodder & Racer.

He fights for what is right & correct & slams the others that screw people.

He will fight with his bare fists just like You & me when push comes to shove.

Trust Ron.

 

No argument from me. I am sure it is a black art requiring a lot of skill.


What I would like to understand though is why GM designed the crossfire manifold the way they have. I thought I read somewhere that the runners had to be narrow for the manifold to work (port velocity at idle?). It then follows that by making them larger could be detrimental to performance.

 

They had problems meeting 1984 US Federal Emission standards with the CFI configuration in original form.

The compromise is what is on Your 1984 Right Hand drive conversion C4 Corvette right now.

Ron will make that lack luster CFI intake perform as GM engineers intended to begin with before they had go in neck ports down to meet emissions.

Its not a Black Art.

Its a science all its own........... cylinder head & intake airflow.

Great potential power to bad just waiting.

Takes a highly skilled & very knowledgeable individual to release that torque & horsepower for You.

RON>>>>>Cusinart>>>>>>>>>>>>>>>>>>

Cheers Steve

 

So who designed the Renegade? Is it simply about larger diameter runners? Is the Renegade essentially a ported cross-fire manifold?

 

The renegade intake was designed by dynamic crossfire solutions, to make an all new intake (for such a limited application) is a big undertaking & risk for a small company. Maybe there should have aimed higher on the price.
I wonder if the cfi intake could be cnc ported for a reasonable price? I had my intake extrude honed, but it seemed like they only smoothed the walls (glass smooth), it might be worth it to port your intake first then have it extrude honed.
Today all my cfi stuff is in a box marked 'For restoration only'.

 

From what I read that smoothing out the intake isn't good for a wet system but better for a TPI.

 

Is the renegade essentially the same design as the stock manifold? Appears to be to me. 8 runner wet system.

 

Your gonna smooth a manifold when you port, so theres no way around that.
The renagade is the same basic design as the cfi intake. If it was different you'd need different parts like t-body, fuel rails, & injectors to make it work. Its a basic swap over from what I've seen.

 

So that would explain why a well ported stock cfi manifold gets a similar improvement in 1/4 mile time (0.7 sec) as the renegade.

 

Still think the renegade is worlds better than the best worked over crossfire.
Now a worked Renegade, hmm. Too bad you cant get one!
On how far you can go thats hard to say without either going through one or having a sonic tester handy. One day....$$$

Brian thanks for the words, Im just a backyarder though. Appreciate it.

Those runners are long enough I wouldnt worry about airspeed or puddling, most that is old school thinking from the 60s of guys overjetting their Holleys and fouling plugs. Thats where the advantage of EFI/TBI comes into play bet you could polish them like mirrors and it will run the same as if they were rough. Just an opinion thats all.

 

I am not sure what you are talking about here. I presume this Xram that you put on is an aftermarket manifold and not the stock manifold. Any photos?

 

Wrong

From Hib Halverson ; respected C4 journalist

"Now, the final issue...why are the L83's intake ports so darn small?

In the mid/late-70s, with the new Corvette's powertrain under development, the state-of-art at the time was throttle body injection, however, Delco-Rochester did not have a throttle body assembly which flowed enough air to use on a Corvette engine.
So someone thought, "Why not use two of them?"

Rather than use two on an in-line intake manifold and create a hood clearance problem, deep inside Chevrolet Engineering, some genius remembered that back in the late 1960s, the Camaro's '67-'69 302cuin had a factory dual-four-barrel, low cross-ram that Chevy homologated for the SCCA Trans-Am series. They took that idea and figured since it worked great on a race track, the same type of intake manifold would work great on a Corvette street use if fitted with two Rochester throttle body injectors.

Bad idea.

As the system proceeded from design to development, Chevrolet soon found that while the system made pretty good high rpm power, it had terrible throttle response and awful low-speed driveability.
What these wizards had forgotten is that the long runners, the huge plenum volume and the throttle body injectors so far from the intake valves, had fuel condensing out of the air stream and puddling on the runner floors when the velocity of the charge air dropped as the throttles were opened quickly.

What GM should have done was either stick with the Q-Jet 4ME for another two years or use a time machine to bring TPI from the future. But, most likely, for political, marketing and perhaps cost reasons, Chevrolet continued to try and put lipstick on a pig.

The development of CFI was long and difficult. I interviewed a GM Engineer back in the late 80s who told me he knew personally two powertrain engineers who paid for new homes with the overtime it took to get the CrossFire Injection to run well in the 82 Vette with an automatic trans and tall gearing.

The biggest problem was low port velocity at tip in. The eventual solution was to drastically decrease the port volume so that, when the driver whacked the throttle open at low rpm, port velocities remained high enough such that the air/fuel mix remained a vapor and little or no fuel condensed out of the air flow onto the port floors.

Of course, the end result of the tiny, high-velocity ports was significant restriction and poor performance at high rpm."

 

Ref post # 5

If you need something to put you to sleep , read these entertaining discussions started by 84cfi ( AKA Nelson 84 , 85L98-84L83 ) where he promotes and argues the Perf benefits of the Renegade before it went into production

http://www.corvetteactioncenter.com/...D-more-hp.html

http://www.smokinvette.com/corvettef...light=RENEGADE

 

GM solved the throttle response problem by having small ports. Enlarging the ports will improve high rpm performance but low rpm performance will again suffer as the throttle response problem would surely come back.

"Any low cross ram manifold has never worked on the street. Too much plenum volume and too low intake velocity such that, sure, you get a lot of power and a sharp torque peak but lousy driveability and no low end.

At the time GM did that, it didn't have big throttle body injectors and port injection was still 2-3 years in the future so some fool, who must have been looking at old SCCA Trans-Am engines, got the hots for a 2x4 TBI on a cross ram.

Once protos were running they found out what others knew back in the 60s that low-rise cross rams don't work on the street.

The solution....they made the ports freakin' tiny to get the velocity up. A pal of mine, who used to work at GM for Herb Fishel's old group told me that he knew two engineers who paid for new homes with the overtime it took to get that system to run right and pass emissions.

If the goal is to keep those two nasty looking throttle bodys and have horsepower, as long as your willing to give up a good torque curve, any low cross ram with big ports will make power!"

 

I've got tons of photos on Photobucket of everything that has been done to the car.
Back in the day when I had first bought the car I was trying to figure out what direction I wanted to go as well as far as intake. I had no experience at all with porting, there was no Renagade. There was however the Xram. So with my lack of experience porting I decided to go the Xram route.

This is the base manifold of the Xram


Base manifold with the plenum of the Xram


After putting on the Xram I ran the dyno


Got these results


Now a Stock Crossfire puts out about 170hp at the wheels. This dyno clearly shows a 37hp gain over stock with just an intake change. Trying to find someone to post the results of a Renagade over stock is like pulling teeth, its a big secret for some reason. Any route you go over stock will show a good hp gain. 30-40 hp, whether its SY-1, Offy, or a well ported stock intake. Aftermarket intakes will always flow way better on a stock bottem end and actually will flow to good. This is why I'm a believer that the best bang for your buck on a STOCK bottom end is going the route of a well ported stock intake.

You can help compensate your low end by putting in a 2500 TC.

 

Why don't you recommend the Xram? Seems as good as anything else. I suppose putting in an 2500 TC was out of the question for GM?