964 intake manifold to 3.0/3.2 port adapters

[Tom_in_NH]

As the title says, I'm hoping to find an adapter for 964 intake manifold to 3.0/3.2 intake ports. I can probably fab something, but time is precious, and talent is slim.

Thanks!
Tom

[Tippy]

Take a look at TurboKraft. Maybe they make adapters?

[gtc]

Rothsport makes them.

[impactbumper]

what is the benefit of this?

[Tom_in_NH]

The benefit, at least in my case, is that it eases the conversion to EFI from CIS. I was initially looking at the 3.2 manifolds, but was discouraged by the poorly matched flow characteristics of that manifold. The plastic 964 manifold is supposedly much more closely flow-matched from runner to runner.

The 964/early 993 intakes also incorporated a dual resonance flap that tuned the manifold for better torque over a broader RPM range. The possibility to take advantage of the resonance flap is intriguing. Plus, it's light-weight, incorporates almost everything I would need to go EFI, and is cheap compared to ITB solutions.

Tom

[Evan Fullerton]

Rothsport makes an adapter to use the 993/964 injector blocks or TurboKraft can make you new injector blocks. I went with the TurboKraft option because I didn't want to add any more height to the intake as it is already a tight fit using the later manifolds. The TurboKraft adapters are their 930 EFI conversion blocks with an extra adapter on top to fit the 964/993 rubber boot. Not quite as clean as a custome machined 1pc injector block specifically for the job but I really didn't feel like doing the CAD work for that. There is some sticker shock with the TurboKraft Kit as you are half way to ITB money but I want the midrange of the VRAM on my 3.0L build so that is they way I went.

[prschmn]

have you looked at the Bitz kit stuff?

[Tom_in_NH]

Thanks everyone. Evan, I see what you mean regarding the TurboKraft injector blocks. At $495, they're not too painful. But I would guess that the additional adapter required to get to the 964/993 rubber boot probably adds that much $ again (not found on their website). So, yup, including the cost of the manifold, I could easily be at $2k. I still think it's the way to go vs ITB though. With some tuning effort to get the dual resonance to come in at the correct time, it should be worth significant mid-range torque.

Tom

[Tom_in_NH]

I had looked at the Bitz stuff quite some time ago. It's a pretty clever adaptation of the existing CIS mainfold, and thats exactly the problem with it.
I'm building a 3.3 with fairly hot cams, higher compression, ported heads, etc. So staying with the very restrictive '83 SC intake (small port), is out of the question.

Tom

[Evan Fullerton]

Depending on what you are going for, RothSport makes an ITB Kit using Jenvey throttle bodies that accept a 964, '95 993, or GT3 single resonance flap intake manifold. This is supposed to be the best compromise of throttle response and midrange. I find that I don't really like extreme throttle response and appreciate the simplicity of only one throttle body from a maintenance standpoint but if you want midrange and throttle response, the RothSport ITB Kit with a 996 GT3 intake manifold is probably the hot ticket on a 3.3L big cam screamer motor.

[prschmn]

Jeff Gamroths stuff is great and pretty but not for the faint of wallet

[Tom_in_NH]

Yes, I've seen the Rothsport setup, it's gorgeous and reportedly very effective at building mid-range torque, while preserving the snappy ITB throttle response. But like Mark pointed out, it's fairly precious. So that's out for this build.
I was perusing some older threads and found that Clewett makes an adapter that would get the 964/993 manifold on the 3.2 ports, but I have SC heads. I think I can make 'em work if I don't go beyond 39mm porting them. Ideally, I'd be starting with 3.2 heads.
Tom

[gtc]

I understand the complete rothsport intake / itb assemblies are pricy, but are the adapters alone all that expensive?

[sp_cs]

Originally Posted by Evan Fullerton

Depending on what you are going for, RothSport makes an ITB Kit using Jenvey throttle bodies that accept a 964, '95 993, or GT3 single resonance flap intake manifold. This is supposed to be the best compromise of throttle response and midrange. I find that I don't really like extreme throttle response and appreciate the simplicity of only one throttle body from a maintenance standpoint but if you want midrange and throttle response, the RothSport ITB Kit with a 996 GT3 intake manifold is probably the hot ticket on a 3.3L big cam screamer motor.

There's a post on Rennlist by *Rsscotty where he states the GT3 is too big for anything under 3.6, and recommends the 964/993 intake for smaller displacements.

* I think Rsscotty works at Rothsport ?

http://rennlist.com/forums/993-forum/758109-how-to-remove-clutter-from-993-964-engine-compartment-2.html#post10540045

[Evan Fullerton]

Build a 3.3L in the spirit of a RSR sprint motor and it will exceed the air flow that a 993 manifold can deliver. For 340hp+ I think you will be better off with a GT3 manifold regardless of the engine displacement but it's all beyond my budget.

[Steam Driver]

For anyone's information (although this may be superfluous; there seems to be some knowledgeable people on this thread), adapters for going from the 3.0 and 3.2 heads will not be interchangeable. The injector boss/bore on the 3.2 goes in a much steeper angle than the CIS injectors and if this is installed on a 3.0 head you will find (as I did) that the injector relief in the port shrouds the injector bore. This is with the big port SC heads; the small port versions would be marginally worse. Not that it matters; neither would be compatible.

I know this because when we were doing Supercharging of Knoxville we had CNC adapters for going from the 3.2 heads to our own manifold for using the Auto Rotor blower. I am currently wanting do exactly what you are proposing, on a 3.0. When I was doing a trial fit I found that out. But except for the "minor detail" about the injector bore being partially covered they would have worked great.

So, if you want to do a 3.2, I can fix you up with those (we have some left over laying around). But they won't do a 3.0. However we're working on that since I want them and my partner might also. Particularly since it seems there might be a market.

I'm going to use the 964 intake plenum with (at least initially) the 3.0 TB; it will bolt up to the 964 plenum directly but does require an intermediate piece to account for the difference in diameters to account for the (very slightly) differing seal diameters. I made one out of phenolic. Doesn't look as sexy as ITB's, but as they say "if it was good enough for Porsche," etc. I initially was going to use the CIS intake, gutted, but the 964 parts turned up in my partner's garage (more SoK leftovers). It's obviously has (or at least should have) a lot "slicker" airflow than the 3.0.

If anyone is interested in the 3.2 parts I can send you pics of them and see about a price. Just send me your e-mail via PM.

[Tom_in_NH]

Great heads up there Steam. I knew that were potential issues with port matching the SC heads to the 3.2 manifold, but was unaware of the injector being partially shrouded. I would imagine that it would cause some low speed tuning issues, especially if batch triggering the injectors.
So, the smart thing would be to source 3.2 heads....but that adds considerable to the build cost. Keep me posted with your progress on the 964/993 maifold adapters for the SC heads.
Tom

[Steam Driver]

There is another, more minor, issue that I forgot about. The adapters for the 3.2 are a slightly larger diameter than even the big port SC heads, which would make an undesirable "step" in the airflow. That can be easily corrected by using a tapered sleeve to fit inside the 3.2 adapter; no chance of it coming loose since it would sit on the aforementioned "step." But the injector port differences are a major item that make that a moot point.

If you want to look at the 3.2 adapters and the fit up with the SC heads go to:

964 Plenum To 911 SC Heads Adapter Project by Paul Burch | Photobucket

The order isn't what I want, but stupid Photobucket doesn't seem to want to custom arrange them!

I will keep you posted. Our CAD/CNC guy had a major computer crash last week that he's just now recovering from.

[Tom_in_NH]

Great photos Paul. Makes the issue pretty clear. So machining the SC port to provide clearance for the 3.2 injector path is not possible? Not enaough wall cross section?

[Robbbyg]

Hi Tom,
I have Limited knowledge so im Not sure if the mechanics are the same, but i matched a 3.3 x51/993 Manifold to a 3.0 block without any adapters, i decided against them partly for cost also for higher pressure in the manifold by keeping the containment area as small as i could, what i did was matched the Top of the Factory Manifold blocks to fit the larger diameter 3.3 head ports/tunnels? and put it together as is leaving the bottom of the blocks matched to original 3.0 head, I havent driven her yet to see how this worked but will post results

Is it possible to take some pics of where your at with it?
photos help a lot when brainstorming