Cast iron 4:2 exhaust manifolds

Discussion in 'Discussion Forum' started by Dr.Jeff, Aug 20, 2017.

  1. Dr.Jeff

    Dr.Jeff True Classic

    Location:
    Sin City
    There are several part numbers for the 4:2 cast iron exhaust manifold; various 128's, early US X1/9, Euro spec X1/9, and all of the other Fiat models with the same head configuration. The manifold spans a number of years and models, each with variances accordingly.

    Has anyone found either a listing of those part numbers and what they come from, and/or any specs on any of them (i.e. port diameters, collector diameters, flow values, etc)?

    Any information is appreciated. I've reviewed Steve C's classic SOHC document, searched the forum, and Googled it several ways. The most I can find are vague references that some are better than others.
     
  2. Hi Jeff,

    not a complete answer, but I can contribute the following. The 1300 manifold was centre aligned vs. the 1500 which was aligned to the left. The 1300 also has smaller ports.

    No idea about the US '74 manifold (which is 4310369 I think).

    In terms of part numbers, we have, for the 1500:
    For the 1300:
    • 4252518
    Also refer to the attached PDF for the 7554844.

    Cheers,
    Dom.
     

    Attached Files:

  3. Dr.Jeff

    Dr.Jeff True Classic

    Location:
    Sin City
    Thanks Dom, good info. Especially the part about the 1300 having smaller ports. Any idea what the measurements are for either the 1500 or 1300 manifold ports?
     
  4. kmead

    kmead True Classic

    Location:
    Michigan
  5. Eastep

    Eastep Dub-ing

    Location:
    PA
    Ill look tomorrow evening. I have a true Euro 4:2 manifold currently installed on my 79. Next time Im at the salvage yard, Ill have a look at the Yugo there, and take a pic of its 4:2 manifold part number.
     
  6. fiatfactory

    fiatfactory Steve Cecchele

    Location:
    Western Australia
    You can physically see the difference in runner size between the late style 1600 exhaust manifold and most of the other part numbers... just look at the proximity of the fastener counterbore on the outside runners... on the 1300 manifold there is a ton of room to the runner, the 1600 manifold the counterbore cuts into the side.

    The outlet ports on the 1600 manifold are a heap larger, it even takes a different flange gasket and allows for larger pipe sizes on the downpipes.

    1300 128 coupe/ x19 euro 1300 are the same thing ... part numbers for the 1300 euro , 74 USA , tipo 1600 and the yugo manifold are all listed in the 'ultimate sohc' thread... I have a euro X19 1500 manifold and another Ritmo/strada 1500 which I need to take pics of... I haven't got around to flow testing any of them yet, so I doubt anyone else has that sort of information either.

    SteveC
     
  7. Dr.Jeff

    Dr.Jeff True Classic

    Location:
    Sin City
    Thanks everyone,
    Given the number of years Fiat has used this manifold's general design, on a multitude of models, in world-wide markets, there are a LOT of them out there that fill the basic definition, but are also different in various aspects. Trying to get a handle on them has been a bit perplexing. Seems like the more I looked at all the related forum threads, on-line sources, Steve's SOHC book, etc, etc, the more I lost track of what was what.

    Part of the problem is a tendency to refer to various ones by language that can be vague (or even inaccurate). And part of the problem is I'm not well versed on some of the referenced models (especially the ones we don't see here). That's why I thought using actual part numbers might be a better way to identify them.

    Furthermore I have not found any quantitative data (actual measurements, test results, etc) on any of them to substantiate the claims made. Kind of figured someone would have done that by now given how obsessive we can be about these things.

    Really my goal was to get a feel for which ones (specifically) have a better design relative to one another, and to what extent that difference is.
    Thanks.
     
  8. kmead

    kmead True Classic

    Location:
    Michigan
    On the late 1600 manifold, which was used only on FWD vehicles, would the angle of the exit be appropriate for an X?

    The unit Eurosport sells shows the left offset described by others.

    I think know where DrJeff is going with this as I am also interested in creating a system using a cast iron manifold, a two pipe downpipe going to one outlet into the muffler(s) as close to the muffler entrance as possible.

    I am hoping to use the existing SS factory muffler with a resonator taking the place of the catylitic converter or use a high flow cat to manage resonance. This would be akin to the system TonyK developed for his "stock" engined X without the tubular header.
     
    Dr.Jeff likes this.
  9. rocco79/138

    rocco79/138 True Classic

    Location:
    Fairview nc
    If I understand correctly the angle would be critical on the intake manifold and less so for the exhaust. The intake manifold angle has a direct effect on how the carb is sitting and thus how the float is situated. I get the issue and realize that it may in fact cause some problems but I also drive up and down pretty steep grades on a regular basis without an issue whatsoever. Perhaps the problem would reveal itself if I had a 128 style manifold and drove on the steepest of roads. If the manifold was 3° off and I am on a 6° incline that would make the carb 9° off. I have never experienced any problem in this regard so I can't say for sure.
    With the exhaust I would not think a degree or several on the exit flange would have that much of an effect. More a matter of any adjustments needed while fabricating everything down stream... A factory downpipe for a 128 setup may have clearance issues on the X1/9 setup. But if custom fabbing the whole thing this should not be an issue?
    The only thing I know is aftermarket headers are super duper performance! Off the chart compared to anything out there... :) JUST KIDDING Steve! They may function better than the Uber restrictive NA exhaust stuff and marginally better than a properly sorted euro exhaust but again I am not certain and I don't think there is much in the way of comparison out there. I have had a couple IAP style headers and they seem fine, butt Dyno felt some improvement.
    My Yugo really lit up when I dropped a cam in it and that was the 4-2 manifold so from that I would say I agree with Steve and the SOHC thread about the factory 4-2 being better breathing and responsive to upgrades in other areas.
    The cost and effort needed to set up all the various parts in every conceivable configuration for testing just won't happen so I don't think we will unequivocally "lay this one to rest". I feel comfortable knowing that the 4-2 can provide better performance than stock NA system and a header may or may not do better yet? I have no idea whether the cost of the header is justified nor do care.
    My own experience would indicate that the factory stuff is more durable if mistreated... i.e. exhaust hangers missing or failed and not replaced = stress and a cracked header. Perhaps the same is true for the stock setup but it was not in my experience...
    Regards
     
  10. Angle is not so much an issue as whether let vs. centre offset. That said, this is only really an issue if you are using an exhaust that is designed to work with a specific manifold.

    I'm running a 4:2 cast iron header connected to a 2:1 down pipe (from a CSC exhaust) which then connects to the standard SS factory muffler (US and Aus). The sound is better and the power is equivalent to what I had with the CSC 4 outlet exhaust (which was obnoxious). I'll post pictures when I'm back in Munich.

    What does prove difficult is to run this configuration and retain the cat. There is simply not enough room for a very tight turn. From what I could determine, one would need to invert the muffler / cat to do a 4:2:1 system that retained the cat (i.e. mount the cat above the muffler).

    Cheers,
    Dom.
     
  11. Dr.Jeff

    Dr.Jeff True Classic

    Location:
    Sin City
    Is part number "7691880" the 'late 1600 manifold' we keep referring to?

    To Karl's point about the various outlet locations/positions relative to the original stock manifold...and how it will mate up to the rest of the stock system. I assumed that would likely require the down-pipe (between the manifold's dual outlet and the muffler's single inlet) to be custom made if the manifold exit is positioned anywhere other than the original stock location. But it sounds like Dom's set up using the CSC pipe worked with the factory muffler; however I think that might be a function of the particular manifold and muffler he is using (his is all Euro spec I believe?). So it may be different for us in the US, especially if a manifold from either a 128 variant or late 1600 variant was used. In my case I intend to make a complete custom (non-stock configuration) system after the manifold so this is not as critical. However if it can be done the way Karl describes with "bolt-on" parts (eliminating the custom fabrication) then I would consider it.

    Frankly the manifold's outlet positioning is something I was leaving unaddressed until after I determined which manifold I ended up using. In addition to the considerations I listed earlier, price is also a factor. Most of the (limited) listings I've found for 4:2 cast manifolds are either the more restrictive models (e.g. 1300 variants) or have rather high pricing (in my opinion). Honestly if the cost is going to be equal, I'd consider going to a good tube type header instead of the cast manifold. Although I am not too thrilled by the current offerings there either. I would prefer the more 'torque' oriented design like the old ANZA 4:2:1, but in stainless steel, and well built. In my opinion no one has ever made a good 'street' header that meets those requirements. This was discussed at length on Xweb a couple years ago but it kind of died out. I am considering the possibility of having one made, which could be produced for the market if there is any interest. But first I wanted to explore the 4:2 cast manifold option as we are discussing here.
     
  12. AKimball92

    AKimball92 True Classic

    What all key measurements are needed to accurately compare the different manifolds? Is there a way to create a Google Docs spreadsheet through this forum where we could all contribute our P/Ns and clearly laid out measurements? For the measurements needed, some pictures showing lines of what to actually measure would keep the data consistent. If anything we could provide the requested data to this thread and someone can compile the data then later post it to the wiki. I have one 4-2 sitting in my garage ready to install. A similar table could be done with the cams, cylinder heads, etc.

    Also what do you mean by left vs center aligned?
     
    Dr.Jeff likes this.
  13. Dr.Jeff

    Dr.Jeff True Classic

    Location:
    Sin City
    I like your idea to form tables with some standardized data. For cams, heads, and both intake and exhaust manifolds. Someone would have to assist with forming the actual spreadsheet/tabulation.

    For exhaust manifolds as we are discussing here, I think at a minimum the diameters of the inlet ports and outlet ports will help to give some comparative performance perspective. That may not necessarily correspond with actual gas flow rates, but at least it gives a base-line of easily determined data to help assess each model. And as you say, the corresponding part number for the measured manifold will need to be included.

    The "left" or "center" reference is to the positioning of the outlet end of the manifold. For some models (e.g. 128 vs X1/9) that had to be moved to one side or the other to clear other obstacles on the engine or around the engine bay. Also there may be minor differences in the angle (fore to aft) of the outlet as compared to the inlet side of the manifold, due to the difference in engine mounting angles. These types of measurements will be more difficult to gather with consistency. But perhaps we can devise some ground rules with a fairly simple way to collect that data?
     
  14. kmead

    kmead True Classic

    Location:
    Michigan
    My point about the angle of the outlets for a FWD only app is that there can be times where the angle might interfere with the rear bulkhead or other elements. For example you cannot put a 128 Coupe 4 tube header on an X (for a variety of reasons).

    Beyond that yes the connecting part, which will be made to fit the application, would be the mediator between the manifold and the muffler etc.

    I like the cast manifold as it reduces noise, some heat and is more durable over a complete header application.
     
  15. rocco79/138

    rocco79/138 True Classic

    Location:
    Fairview nc
    I agree! The header is a problem going either direction because most drop down to the bottom of the bay and for the 128/Yugo it turns out toward the rear of the car as does the X. But the angles are different and the X(IAP style) then turns 90° to meet factory muffler at the end of where the cat would have been. I had an X header failure near the collector and considered cutting and placing a new collector at the first turn for use on the Yugo... I did not go far with it but I felt like it was not going to play nice if I had tried. You can see from a photo that the X and a 128 header will not appear to interchange.
    I think either manifold would work but not if you had to use the down pipe... The Yugo had some emissions valve hanging off the back of the manifold but if removed and blanked I am pretty sure it would have plenty of clearance in the X engine bay...
    Regards
     
  16. Eastep

    Eastep Dub-ing

    Location:
    PA
    Sorry, I have been unable to check the PN on my exhaust manifold, as Ive been very busy with work. Ive used modified exhausts on all of my X1/9s, throughout the years. The best exhaust Ive ever run, is my current setup. It flows, and you can actually "feel" the engine is breathing as optimally as allowable, with a stock camshaft. Ive run tubular header, in thr past, cat deletes, custom exhausts, etc... none flow as well as a Euro 1500 manifold, into a Yugo dual DP, into a Vibrant Racing 10633 muffler! Brayden Brannon, is running a very similar setup but with a tubular header. Id be very interested in hearing his or Matts thoughts on this setup. Im sure they will both argee, that for the street, youd be very hard pressed to find a better flowing system.
    BTW, a Euro manifold into a Yugo DP is essentially a 4:2.1 two piece header and should flow & perform similarly. Where a traditional header is one piece, and better performing up top. My car pulls hard from 1500 to 6k. After that it drops strait off. I suspect the Brannon's similar setup pulls
     
  17. Dr.Jeff

    Dr.Jeff True Classic

    Location:
    Sin City
    It occurred to me if we make a list of manifolds by part number, we should try to also include any/all known applications for that part number for reference.

    Unfortunately the most "data" I've found so far, which does not fit all the criteria I've suggested, is as follows:
    1) 128 Rally 1300, part number (as given to me) 1612182, inlet ports 30mm, outlet ports 34mm
    2) 1974 Euro spec (as I understand), part number 4392487, inlet ports 28mm, outlet ports 33mm
    3) 1974 US spec X1/9 (I believe), part number 4310369, dimensions unknown
    4) Late 1600 (??), part number 7691880, no dimensions

    As you can see the information I've found is vague, incomplete and likely not very accurate...hence my reason for starting this thread.
     
  18. GregS

    GregS ProjectX

    Location:
    Australia
    I've put a 4:2 manifold on my road 78 X1/9 1500 engine (from a Fiat Regatta in Australia, same SOHC engine as X1/9), I was told it came off a 128 Sport Coupe, part no. 4392487, head side ports are 28mm diameter. The exhaust ports in the head are also 28mm. I enlarged the manifold ports slightly at the entrance to make sure there was no interference. I was told some X1/9 manifolds have 29mm ports, but have no further info on them.
     
  19. So I'm using an Australian muffler which is exactly the same as the US one (stainless, hanging from a spring mount). The only difference is that in Australia the "test pipe" was factory ;-)

    Here are some photos of the 4:2:1 config I'm currently running. Basically, the cast 4:2 manifold, a stainless 2:1 down pipe from a CSC exhaust (that was far too loud) and some flex stainless exhaust that connects directly to a US style stainless muffler (because I don't have a welder).

    Cheers,
    Dom.

    IMG_8786.JPG IMG_8798.JPG IMG_8799.JPG
     
    kmead likes this.
  20. AKimball92

    AKimball92 True Classic

    I cannot remember who set up the latest Xwebforums being really terriblewith names. Is there a way to embed the excel doc into the site and make it easily accessible and modifiable to all members? Is that within the capabilities of the Wiki or a major pain? I also have done some similar research in cams and cylinder heads, collecting many pieces of the puzzle one piece at a time.
     
    Dr.Jeff likes this.

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