Crossfire dual carb
 

Hello everyone,
I am new here and have recently purchased a 1983 Z28. The car is very clean but the fuel tank and pump were trash. I have done quite a bit of work to get it running well, but I need more power. I like the crossfire setup but would like to use dual carb on a 383 build with a renegade intake. I want to keep the breather and scoops functional for that nice slow Camaro look lol. Has anyone tried doing dual carbs on the crossfire intake?

Re: Crossfire dual carb
 

I see the other threads on this topic but no one mentions the renegade or Offenhauser intakes

Re: Crossfire dual carb
 

I’m not aware of anyone who has converted the Renegade to carbs. But here’s some trivia for you. The Crossfire intake base reused the 67-69 Z/28 Crossram intake tooling. They had to reduce the size of the of the runners and ports to keep velocity up while using two Iron Duke 175 CFM throttle bodies though. Didn't quite work as well at 4500 rpm as it did with two Holleys at 8000 rpm.

Re: Crossfire dual carb
 

No need to go carb for mild 383-just upgrade the CFI and it will be good enough for a "warm"street 383-if you want "hot"street 383,better to just go carb with a standard manifold.

Re: Crossfire dual carb
 

Idk, but someone should mount 3 bbl TBIs on a V8. Just because. Or, turn a LU5 intake into a wind chime... Wonder if an oldschool crossram intake with two Holley 4bbls would fit under a thirdgen hood, and how far off the hood would be from being able to be made functional... Hmmm...

Re: Crossfire dual carb
 

There's several low-profile crossram intakes that were intended for carbs that could be modified for multi-TBI use.
Offenhauser is probably the least expensive other than an OEM Crossfire with a modified top plate. Offy had dual-four, single-four, and three Weber top plates. What is currently available is anyone's guess. Offy hasn't been a "real" company for years if not decades. It seems they produce parts when they have enough orders pre-sold, so inventory is sketchy and back-orders are common.
Edelbrock Smoke-Ram was intended for single-four barrel carb, but of course you could fabricate a different top plate to accept dual fours or dual one-barrel TBIs.
Edelbrock STR (Street Tunnel Ram) was intended for dual fours, would accept dual TBI with adapters or a different top plate

Seems like a waste of a specialized manifold.

What tooling? The manifolds are VERY different, not just in runner size but also in terms of EGR. I don't know what would be salvaged from the original crossram tooling to produce the TBI manifold except maybe the aluminum-melting and pouring equipment.

Far as I know, the original crossram was made by Winters. Who made the Crossfire manifold?

Re: Crossfire dual carb
 

Don't remember. It was from a book, "Chevy Smallblock" or something like that, where they were interviewing the CFI developers and they stated that GM forced them to reuse the crossram tooling. They went into detail on the air fuel distribution problems that caused them. They also stated that with a little more development they could have fixed it, but they had already moved on to TPI by then.

Re: Crossfire dual carb
 

Compare the "racing" dual-four crossram manifold
http://www.camaros.org/crossram.shtml
http://www.vintagemusclecarparts.com...-302-crossram/

https://cimg6.ibsrv.net/gimg/www.thi...88edd6a8b6.jpg


To the emissions-choked dual-TBI "crossfire" manifold:
http://www.technovelocity.com/chevyh...rt_polish.html

https://cimg2.ibsrv.net/gimg/www.thi...9fb8832042.jpg

There's very little that is the same--from the thermostat housing angle in front, to the overall shape of the top cover, to the EGR in back. I'm having problems finding a photo of the underside of the older crossram, but the way I remember it, it didn't even have an exhaust crossover.

I can't imagine Winters re-using any tooling from the Sixties cross-ram on the TBI cross-ram.

Re: Crossfire dual carb
 

I see a lot of similarities. Furthermore, he also stated that the biggest distribution problems were caused because the front TB was on the passenger side. He said, if they could have done it the other way around, ie., the front TB on the driver's side, they could have solved a lot of air/fuel distribution problems, but they weren't allowed to deviate that far from the old Crossram design. He explained the reasons why, but I can't remember them.

Maybe I'll search for that book and get the engineer's name. It's in my basement in a box somewhere.

Re: Crossfire dual carb
 

I can't believe I found it. The book is: CHEVROLET SMALL-BLOCK V8, by Anthony Young. Really an interesting book.

The engineer is Louis Cuttita. If I'm not mistaken, it was him and his team who quickly hotrodded the LG4 into the L-69.


Standby....

Re: Crossfire dual carb
 

https://cimg3.ibsrv.net/gimg/www.thi...a7056ee9d9.jpg

https://cimg6.ibsrv.net/gimg/www.thi...881d4ff0af.jpg

https://cimg3.ibsrv.net/gimg/www.thi...45026fc8d4.jpg

Re: Crossfire dual carb
 

For grins, here is a pic I made comparing an original crossram intake (left) to a Renegade intake (right). Notice how the Renegade's runners point straight into the port vs the more curved crossram runners.

Compared to the original crossfire intake above, the Renegade has more angular corners to help the flow of the outside runners.

https://cimg4.ibsrv.net/gimg/www.thi...b4be5c542a.jpg

Re: Crossfire dual carb
 

When we decided to create the Renegade manifold and started doing a lot of testing with one of the worlds largest custom manifold manufacturing company's we found a lot of issues with the stock CF manifold and was rather surprised and so were they. So, as the better mouse trap was being designed we kept that data handy and made some significant changes to the design to reduce the issues we found. To the average person looking at it doing a side by side comparison as depicted here, all you see is the way the runners look and the "bell" lip which IS a very important detail of the design. There IS a lot of improvements to flow not including making another 20% more plenum area gain over stock. If we could have gone up/higher on the manifold, we could have made more power, but was restricted by all year stock hoods on all CF cars. Everyone back before we started this project said that the old XRam manifold was the bomb and the company building them said they made 100hp more gain than stock. I called BS! I had one along with my partner Jim and we NEVER saw 100hp gain, not even close on a 383, but it was better than stock, kind of.

THAT was the reason we created a no BS good CF manifold. We only said that you would gain at least 30hp more to the rear and have seen a little more than that on a good running stock CF vette motor. Ben73 who probably has the fastest 84 N/A CF 383 motor on the planet right now running 12.20s ran an XRam manifold and he could only get best time of 12.55 out of the motor at the 1/4 mile track and only did it once. Look him up, he is on this forum. We sent him our manifold to test it. He installed the Renegade and did not touch his tune which was one of our stipulations and went to the track and made a 12.30 pass the first one down the track and ended up with the fasted pass ever at 12.24 I think it was. So, if the XRam was giving you 100hp more, what is the Renegade giving you? Maybe we should say it will give you 150hp more. LOL, just kiddin'. I think the numbers put out by Pat Oney in TX the builder of the XRam were off a bit, but ours can be backed up with real data from various sources including real track results. We NEVER lied about its gains or boosted/inflated the numbers.

My CF 383 is running about as good as Ben's motor before he replaced his manifold at mid 12s, but I think I can get it down a bit more with a couple more tweaks to 12.40s or better, we shall see. I would throw a set of bored TBs on the manifold with larger injectors and boost the FP a bit with an external FPR and start tuning. You may be surprised at the results. My TBs are 2.13" and Ben's are 2.20" Most people bore to 2". We also tested on a flow bench the different TB configurations from stock to 2.13" and was surprised at the flow rates, this was also to include the different tower heights with injector pods. The manifold will support up to 2.25" TBs. Who does that? We did, because we wanted o know and it cost us plenty of cash to do all of this research way back when. Now you know the real story and there is actually tons more that I haven't told here, but that is somewhat proprietary info.

Re: Crossfire dual carb
 

I've always wondered about tower height. Just thinking out loud, I'm sure the injectors were positioned at a specific height for spray targeting purposes. I've wondered if you should raise the injector height when you bore to get the proper relationship back.

Re: Crossfire dual carb
 

Here is an idea for you: combine the Smokey Yunick SY-1 intake
https://i40.tinypic.com/v6ulcn.jpg

and instead of a carb, use a 4BBL throttle body style self-learning fuel injection unit like the FITECH or Holley Sniper.
https://www.jegs.com/images/photos/5.../546-30002.jpg

https://i.ytimg.com/vi/DdogK82voYc/maxresdefault.jpg

Re: Crossfire dual carb
 

I've thought about having a custom top made for my Renegade and switching to a 4-bbl EFI unit. Would probably go that direction if I want significantly more HP. I would be worried about fuel distribution though.

Re: Crossfire dual carb
 

Yeah, you have to contend with "wall shear" in the TB if bored, but it all works when you raise it up about 3/8" or double gasket. You are limited by fittings hitting the base.

If I were to do a EFI system, I would go with a Holley setup of some sort vs FiTech. The FiTech IMO is a bit iffy vs Holley. Both are 4150 base plate gaskets, standard Holley four barrel.

Re: Crossfire dual carb
 

Hey Buc,

Question on your combo - why do you run such a high RPM stall in your converter? I wouldn't think that a 383 combined with a relatively long runner intake would need it. I'm definitely no expert in this area, just asking. Possibly cam related? I remember seeing DCS had a custom cam for sale.

Re: Crossfire dual carb
 

It's all the above on the combo I'm running and the current package works pretty good, but I want to drop my 60' at least another tenth at the track to 1.60 possibly lower. To do that, going to a SS3,600 should do the trick and still drive like a stock converter. My 3,200 now drives just like a stock 82 TC with no extra gas needed to get it going, very responsive, but I am running a 9.5" TC, not the 10.5 or 11" that a lot of company's are selling. I've talked with Dave the owner at Yank a lot about this and he agrees with me about mving up to a 3,600. I'm only running a 3.31 gear as well, not the typical 3.45, 3.73 that a lot of people run.

The cam you are referring to is... suggested to use with the Renegade manifold and 2 inch throttle bodies and 80ib injectors. This cam works well with a 383 cubic inch motor and produces good low end torque and excellent mid range. If I remember correctly, the cam spec Erson: Dur: 229 @ .050, Lift: .544/.544 with 1.6 rockers LSA: 113. A stall converter of 2,400 - 2,600 is recommended along with a gear of at least 3.23 or higher, headers and dual exhaust. Note: This cam requires a modified 1227747 or 1228746 ECM with HAM board for laptop tuning and we suggest using the EBL Flash II.

Re: Crossfire dual carb
 

Just a bit of trivia here, but that looks like that is serial number 0084 which I hand stamped myself. Only the first 100 were stamped and serial number 0001 was never sold. I have serial number 0001 of the pre-production manifolds which were numbered differently. So, to the person that has serial number 0002, you have the second production manifold produced and the first production Renegade manifold ever produced and released to the public. :thumbsup:

Re: Crossfire dual carb
 

Yeah, I was in the first group that paid for the intake up front. It was well worth the wait.

Re: Crossfire dual carb
 

Oh yeah, I remember now. Thank you for the purchase, believing in us and the manifold, it does work well. :thumbsup:

Re: Crossfire dual carb
 

Dave::
If you made this CFI to carb swap, do you still have the 1225550 ECM and white 24 pin female connector to the ECM?
I need them for repair of ECM short on my '82 vette.
Thanks,
Cliff H.