If anyone is still interested in this kind of information. if stock heads are being used.
port entrance. tapered top and sides of runners. stock ports are 1.375" x 1.045". tapering the first inch or so out to 1.56"x1.17".
with entrance porting and port matching at head, the flow is 190cfm vs stock 150cfm

port matching to head. ended up going bigger than photo shows. just a little smaller than head port size.
this relatively easy to do. I would clean up the full length of the runner.

there's more that can be done, but it's a lot more work.

 

I did that to my crossfire back in the day and then later welded in some metal on port entrances to flare them some and ported further.Even the initial porting had a very positive effect.A 1/4" thick lidspacer was also added after 2nd modification.This setup is still on active duty

 

cool. great to hear about crossfire modifications
this is what I ended up doing.
didn't people would want to dd what I did. also ported full length of runner.


also did this to the top. the bumps effect the flow. especially the one with the allen plug in it.

 

That is actually almost identical to mine after round 2 modification except i kept my EGR channel in place and kept the swirl vanes. Very nice work there!. Back when i did round 2 in 1995,i also ported the #624 heads-those eventually developed cracks(was getting oxygen in cooling system,causing chronicly rusty coolant) so a pair of Dart Iron Eagles ended up on engine,raising compression one full point.

 

Thanks, it was a lot of work. I also have dart 165ss/summit racing heads. I did port the dart heads a little. bowl blend, unshroud the valves, gasket match and cleaned up short turn. I've been thinking about modifying swirl vanes to a larger diameter sleeve, because stock swirl vanes restrict flow above a certain cfm. they were restricting my manifold flow.
I destroyed a couple of manifolds before getting to this point.

 

I basicly destroyed my first manifold-breakthrough in several areas coupled with bad welding...it is salvagable though.My Darts are 165 also-right out of the box,valve job was good.Much better heads than the old '624s and fixed the rusty coolant problem. This is on '84 vette L83 shortblock.You may know,but '83-84 manifolds have the little crossover ports between runners and '82 manifolds do not. All the welding on my manifold warped it-got it straight again in a hydralic press

 

Very similar experience. Mine is also 84 vette. warped the second intake and also found the water jackets that are in-between port walls in two places, when porting. ended up buying older intake without the crossover ports, because they flow better on flow bench. last intake was skip welded. checked all gasket surfaces with machinist straight edge. I got lucky. minimum clean up with flat file. probable didn't have to file it. straightening a manifold with a press is a great idea. I imagine that took some patience.
If I do another, not going to weld it solid, not going to use round rod.
all the problems that come with welding is why I originally only posted porting the entrance and port matching. it's a 40cfm gain with minimal work. stock heads with stock cam flow about 185cfm and that simple porting job gets 190cfm intake manifold flow. Anything beyond that is a lot more work.

 

Interesting thread...Did either of you do a before and after dyno test to see how much of an improvement your efforts/cost made? That would be the real test IMO.

 

short answer is no,
I'm in the process of learning how to set up ECM for tuning. not going to be as good as renegade for sure. tried to buy one, but it was too late. It would be nice if they were back in production. I'm not afraid of trying and failing, so here I am. I like learning. All I have is, when the car was in stock form, it didn't do rolling start no brakes burnout. Now it does 20-foot long rolling start no brakes burnout. I know this means nothing, but that's all I got. On the flow bench stock flows 150-155 cfm. modified flows 213-220cfm. I was very conservative with wall thickness when porting, didn't want thin walls. got 225cfm on a junk intake, thin walls. I know this also means nothing.
I'm rooting for the renegade manifold to go back in production. would be perfect for my setup
some day it would be nice to dyno test

 

Big increase in S.O.T.P. performance with the manifold modifications,especially the added metal 2nd round that also included mild port job on the '624 heads-increased RPM capability enough to cause alternator belt problems:flipping over in pulleys or breaking-one incident belt broke at ~5500 and slapped a ~1.5x 5" hole in my SMC hood.A larger,deep groove alternator pulley meant for a '70.5 z-28 LT-1 fixed the belt problem. Still running original '82 ECM with Hypertech '82 vette chip '82 PC board ESC control box replaced with '83 module type because the '82 one was acting up.There is at least one guy on here that has installed a Renegade.

 

Well, good. Glad you are happy and it will perform better than stock for sure. I run a Renegade and mine runs well. Maybe that is two?

 

Yes- KITT1983 would be the other known user

 

at 6 seconds in.
looks like the first 3/4" of the top of runner at entrance has a radius taper. I find it interesting that my welding, grinding and testing lead to similar shape. I was going on the theory that if the entrance had turbulence and flowed like a smaller sized runner. making the entrance bigger would compensate for that.

 

Interesting video. Is that the ~ 1967 z-28 302 "over the counter"GM crossram or something else ? Has that mid-1960s-earlier breather pipe and did not notice a "Winters"casting mark Didn't Smokey Yunik design a crossram manifold?

 

Edelbrock str10 intake. smokey yunik made one and Offenhauser still makes one. there all different. showed edelbrock because of the entrance. can clearly see at 6 second mark on video. that's all.

 

got 230cfm with new port entrance design

hitting the limit for my little flow bench. Just wanted to see what could be done. can get back to this manifold sometime in the future. I have another car project, different brand of car, but what was learned on this project will help the next project.

 

just can't leave it alone.
can't believe this worked!
bumped out radius piece out of 3/16" piece of aluminum. rounded leading edge. was getting 232cfm until raising the top with 2 washers.
raising the top .14", now the runner flows 240cfm. still not max ported runner. starting to believe a max port job can flow 250 cfm with top raised 1/4" and raise the bell mouth another 1/8". I'll show a photo of bell mouth when the actual one is made.

 

What's the best method of blocking the hole where the EGR runner was ??

 

get early crossfire intake manifold 14031372. they don't have the egr holes.

 

lost a few CFM after welding. still rough, need to be cleaned up. need to order some cartridge rolls.
next step is to port #6 runner

 

Curious to see how this turns out, I have a renegade manifold, I removed it and returned to the original after a polishing off the rough castings on the original. I can tell you the longer intake runners and small ports help the engine build torque at low RPM. The renegade didn't get me the performance it promises, after removing and polishing the original the car felt much stronger on the low end, upper end sure, it is choking. The polishing also brought much better idle with it.

 

stock intake flows about 150 to 155cfm no matter what's hooked up to it. stock runners are 1.375 x 1.0625, but can be smaller. port matching helps and tapering the entrance is all that's needed for stock heads and cam. put on header and free flowing exhaust if more power is desired. stock exhaust is restrictive.
this is the manifold I have on car now. 1.4"x 1.1" runners with taper and radius entrance. 215 cfm average bolted up to head. 212cfm head, intake and TB's.
Runners on this manifold is only slightly bigger that stock runners, but more efficient.

this intake is to see how much cfm I can get from stock intake. #8 is pretty much done. #6 is in the process. still not that big of a port 1.56 x 1.1, port matched and tapered entrance. #8 with no spacer flows 236cfm and 238cfm with 1/8" spacer. not worth using a spacer unless #6 needs it. I imagine the middle runners will flow more than the end runners.
this is a lot of work to do, but its less work than the other manifold

 

this is as far as I got today. tested with sloppy clay entrance just to get preliminary flow numbers 234 cfm. should be better after welding. can contour entrance and smooth out transition. this is runners 6 and 8. 1 and 3 should be the same. middle runners should flow more.
I'm projecting middle runners all flowing over 240cfm.
It's very possible this intake will flow 240 cfm average.
sonic test helps a lot.
For me this is plenty of flow for a street car.
I've come to the conclusion that this design works, but current method isn't practical. disappointing! way too much work. too much welding. Needs to be simple with no or minimal welding. back to the drawing board.
To be honest, I don't want to spend weeks porting and welding.

 

Added another vacuum to flow bench. now I can test above 240cfm at same inches of vacuum.
did some testing today.
the one max out runner 1.53 x 1.3 = 250cfm with bell mouth. Not a very efficient runner.
ends runners 1.53 x 1.13 flow 238cfm with bell mouth. I'm sure I can massage runners to get 240cfm
1.53 x 1.13 middle runners will flow more, for sure 240cfm. most likely 242cfm +. middle runners flow about 5 cfm more
this will be at least a 240cfm average.
I think 240cfm is respectable.
wasn't satisfied with this result until now. Just have to do it now.
If someone wants to max out runners and is ok with the possibility of using epoxy. 250cfm is most likely possible. I'm not going there.
going to start making parts next.

this is how I'm cutting or milling, if I had a mill. top of runners. will add pcs. will show progress as I go.

 

I considered adapting or building my own upper when I owned a crossfire car. Flowed nearly 250 cfm untouched and right at 300 cfm ported. Also would have used the largest bore TBI units I could get without the injector pods in the way. With the marine upper and 80mm TB my 383 made 412 whp and 430 wtq through a 4L85E and GM 10.5" 14-bolt.

 

Even the ordinary aluminum L30/L31 truck base has the material to easily hit 300 cfm and will flow 220-230 cfm even with GMs horrible factory port shapes.


Here is the stock port shape.

 

very impressive. that's more than my engine will ever make. thanks for info.
I realize other manifolds can flow more. My goal is to see how much the stock manifold can flow. stock intake flows 153cfm and modified it flows up to 250cfm. walls get pretty thin to get 250cfm. 240cfm is enough for current heads and cam.

 

passage side.
[img alt="will weld vertical walls, but wait until after porting to weld tops on. easier to port runners
drivers side"]https://cimg3.ibsrv.net/gimg/www.thirdgen.org-vbulletin/2000x1504/20241104_135800_1__7ceb70db5c9fe1a4e17756b9ad6393e2892628a5.jpg[/img]
will weld vertical walls, but wait until after porting to weld tops on. easier to port runners drivers side

used a router to finish mill the top of runners
looks pretty rough now. will look pretty after clean up and radius. Have the 4 middle runner figured out now. welding shouldn't be that hard. the wall thickness will be thinner after porting and that welds easier.

 

the harder of the pair of middle runners to add onto. needs some little clean up welds. good enough for now. other pair should be easier.
tested flow with no other porting. head side stock. stock is 153cfm. 170cfm with bell mouth. done this enough to know that port matching head side the flow should be 203cfm. So basically, with bell mouth CSA x 140= cfm. up to a point. I didn't consciously do this. was just following the best flow.
Ended up making port dimensions, entrance 2.06x1.1875, 1.53x1.1+/- middle. head side 2.06x1.1 and get 240 cfm. this seem to be the sweet spot for this size bell mouth. efficiency goes down from here. could go wider, but not without grinding hole and welding up hole and grind again. I don't want to do that. that's get frustrating. If there was epoxy that was gasoline proof, then no problem. that's my progress to this point

 

not done yet. little more welding

porting goes under top mounting flange
not finished. more welding to do. beveling help make the welds a little easier. welding doesn't really take than long. most of the work is porting.
takes about 6-8 hrs for each pair of runners and that doesn't include porting the rest of the runners. not a very practical and most people can't weld. I must be a little crazy to do this. the welding is much easier with this design. beveling is helping.
usually take me longer because I keep changing and evolving as it goes. haven figured out a fast way to do this.
doing this intake takes time. I do enjoy learning
having a crossfire intake manifold that looks stock and flows 240cfm, is pretty good to me.

 

bell mouths added. now port the rest of the runner. entrances are not finished yet. do that when testing. intake manifold didn't warp. that's a good think. the end runners, a pain to do. easier that the last manifold though. all 4 sets are custom fit. I couldn't figure out an easy way to do this. that I could personally do.

 

started porting #7 runner. right now, size is about 1.5 x 1.1 and it flows 236cfm. 1.53 x 1.1 should flow 240cfm. little different design for bell mouth this time. more efficient. in theory 1.56 x 1.3 could flow 250cfm. not sure.

 

keep in mind that I'm no expert. I enjoy learning. Always been drawn to problem solving. These results only shows that this design increases flow on a flow bench. should also have good velocity, because the CSA is still relatively small. I think this design is very promising and should work. I notice watching engine master's, that Edelbrock cross ram has similar entrance to runners. its new design to me, but not to edelbrock. only time will tell if this design works on a running car.
the problem was how to get more flow out of a small CSA that doesn't have room for radius entrance on all sides. This is my solution.
too bad it takes so much time to do. If parts were lazer cut and the use of a fast-cutting burr, the build time would come down. But I only need one intake manifold.
shared my journey on this forum in case others could learn from this. For me 240cfm is a win and 250cfm is possible, but not necessary for me. truth is, I'm not a racer. I build cars to drive, but don't drive them hard. once in a while get on it. I enjoy R&D of this project. I wasn't happy with previous result; it felt like an unfinished project. I'm ready to move on to next project.

 

not a finished product. runner
#7 flows 253.4cfm with top plate off, with top plate on 240.37 cfm. runner #5 flows 245cfm with top off and with top on 233 cfm. little low. could have a narrow section.
#1 flow 252cfmm with top off, 239 cfm top on. #3 250cfm top off, 232.5 top on. going to port all the runners and then start working on entrance to improve. I think that can be massaged a little to get higher average. already good enough for me, but I think there's some more to get.
the porting is much faster now.
# 8 249cfm with top off, 239cfm with top on.
need to make spacer for top.
236.77 average at this point
checked an un-ported runner, it measured 1.31" x 1.03"= 1.349 CSA. it's also inefficient.
removing .22" of material to get 1.53 height, mostly from the top of runner.

 

learned today, that widening and using a smaller burr on corner radius on top of runner flows better. seems obvious.
runner #1, #3, #5, #7, #4, #6, #8 are all 240+cfm now. not finished yet, could go up. I'll have to check wall thicknesses. can't really go higher, maybe go wider. still have #2 runner to port.
1.53"x 1.13" = 1.7289 CSA. I don't know how much to subtract for radius corners.
this manifold will flow more than port matched air gap and the same as stock Victor Jr.. Of course, both of these manifolds can flow more with port matching and plenum porting. My intake will never flow those big numbers. good thing it's just a street car. surprised to get it to flow this much to be truthful.
Chevy Intake Manifold Porting - The Manifold Man - Hot Rod Magazine

these numbers are from porting service company. I notice some of the numbers are different
SBC CHEVY INTAKES: stock port matched port M and plenum full porting
1 EDL-2925 SBC Edlebrock Super Victor (SBC) 271 CFM 296 CFM 357 CFM 382 CFM

2 EDL-2975 SBC Edlebrock Victor Jr. (SBC) 237 CFM 262 CFM 316 CFM 341 CFM

3 EDL-7501 SBC Edlebrock Performer RPM Airgap (SBC) 210 CFM 235 CFM 308 CFM 320 CFM

4 WP-061040 SBC World Products - Motown (SBC) 255 CFM 280 CFM 320 CFM 360 CFM

5 HOL-300-25 SBC Holly Street Dominator (SBC) 283 CFM 308 CFM 333 CFM 351 CFM

 

I really need to fire up the welder and finish up my intake manifold then dyno it and see how it runs against the renegade. As usual, good work sir.

 

thanks. lots of experimenting and failures. rediscovered what edebrock knew in the 60's, but I had never seen their intake until after the fact.

 

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Posting here as a marker; I want to come back & read thru this whole thread when I get some time. I know next-to-nuthin' about the Crossfire stuff, but I'm pretty interested in reading thru this thread so I can learn a little.

keep up the great work !

 

previous tests were made with clay added to divider and I didn't consider both runners when testing. My mistake. have to add weld and shape it like the clay now.
New numbers
----top off--- top on---- top on with .25 spacer
# 1 247.3---- 234--------- 238
# 2 251------ 237.54----- 240.75
# 3 255.84-- 236--------- 240.11
# 4 251------ 238.19----- 240.75
# 5 253------ 240.37----- 238
# 6 251.74-- 233.23----- 239
# 7 251.5---- 237.8------ 238
# 8 248.54-- 234.15----- 238
-----------------average cfm
----------------237.31----- 239.07
with .25 spacer the cfm is more even. got close to the 240cfm number
going to put a stock top with diffusers. see how much they choke.

 

this is what the entrances ended up looking like. added more material to radius.
top on, with no spacer
#1 235.65
#2 240.58
#3 241.38
#4 242,04
#5 240.05
#6 240.72
#7 240.56
#8 239.38
average= 240.045 cfm
done!
ran out of wall thickness. the only way to get more would be to cut off water jacket so the floor could be thinner. gain another .125" in height. #1 and #8 runners would still have water jacket shrouding problem. would have to modify that. I'm not doing any of that. It could possibly get to the 260cfm range. this manifold is done. I might try making proper spacers .25" and .5". not sure about hood clearance.
This side shows finished product. other side is done now. not perfect, but good enough. nothing more to gain. no more wall thickness to work with.

checked for warpage, no warpage. the reason I didn't weld the ends of radius to thick walls on #1 and #8, was to prevent warpage. should be a descent manifold for my purposes. If I had a cad file for a stock intake manifold. the file could be modified to have taller runners, get the water jacket out of #1, #8 runners and get egr port out of #5 and#7 runners. would have to experiment to find max useable height, because there is a point where larger CSA doesn't help any more. bottom line, this is good enough for me. don't want to change heads and camshaft.

 

I love it. I love what you've done and documented. I can't wait to hear a report about how it does on the car. FBA, man....strong work!

 

WOW! That looks so Renegade looking for a stock manifold. I would be very curious to see the before and after dyno results. Also, would love to actually port my Renegade at some point and see how far I can push it. It's kind of funny to see that we are copied to some degree on the port entrances that we found out and did a lot of research on back 18 years ago. Thanks for the efforts on your project and documentation. I hope it performs great for you. GL

 

Your runner mouth entry solution was very creative. It's not surprising to me that Mike eventually came to the same solution. Why didn't GM seek out those types of essentially free power nuances to the original casting? 200 hp was "good enough"...I guess.

 

Thanks, I have no idea how it will perform. I think it will. never know. the biggest gain was the bell mouth shape on the roof of the runner. the runner are still small. end of job, had tig torch in my hand and added material to radius. I think a more pronounced radius looks better. It did gain 2 to 5 cfm on some runners.
Renegade is a much better design. Renegades are so rare. never seen one in person.

 

thanks. I can get a little obsessed. I'm going to make a mold of the runners to get accurate dimensions to share. it's not the same as original drawing. been a fun learning experience. I have found 2 dyno's within 20 mile of where I live. there's one at the racetrack. pacific raceways.

 

When we first started the renegade project the racing manifold company we used did some testing on those runners and the "bell" openings and found that the flow got rolled into the runners faster. So, with that info, we redesigned the internal runner shape as well to maximize the efficiency of the runner into a ramming effect. It does a good job and the numbers you got are pretty good for flow, better than I originally thought. It should make a good difference in performance that you will feel IMO. You also got the flow pretty close to each other which is nice. I have talked with a guy in OK about doing some porting on my Renegade, we shall see what kind of numbers I get down the road. Again, GL on the dyno and waiting for the results.

 

thanks for the encouragement. I hope you hit your numbers on porting. I'm kind of in shock after hearing how you developed your manifold. I stumbled onto this design after weeks of porting and welding I noticed better flow when tapering the entrance. than studied fan bell mouths and velocity stacks. as soon as I saw the airflow simulation, I got a better understanding. not an ideal design.
good luck with your porting job.

 

ported manifold no top--------------------------- runner #1 247.3 cfm---- runner #7 251.5cfm

stock top with mixer blades and TB's---------------------211.4 cfm-------------------217 cfm
stock top no blades and TB's-------------------------------228.5cfm--------------------233.3cfm
stock top no blades 1/8" spacer and TB's---------------230cfm-----------------------235cfm
stock top no blades 1/4" space and TB's----------------230.4cfm---------------------236.83cfm
stock throttle bodies could be restriction.

 

Maybe. It doesn't seem likely that one runner would be restricted by the TWO TB's. To me, it seems more likely that it's turbulence under the lid, w/the lid on. You picked up CFM by adding the TB's.

The results are awesome, IMO. Isn't that nearly 100 CFM over stock? Don't stockers flow ~140 per runner?

 

I see your point. I have a modified top but only showed improvement with clay radius. should have been testing with TB's. must have gone too far with this top. good thing I have 3 more tops.
yes its 95-100 cfm gain over stock.