74 intake manifold ports vs 76

karhawk

karhawk

True Classic
Some here have mentioned that the 74 intake manifold flows better or has larger ports then the later models, I have a 76 intake manifold that has ports measuring about 24mm anybody know the measurements of the 74? Initially I will install a 34 DATR carb with a fast road/euro cam on a 1500 engine which may have the block deck shaved and or head shaved slightly. It will have a 74 4-2 exhaust manifold or tube header with custom exhaust. If the difference is minimal I can port the 76, everything with be port matched as well.

Thanks
Chris
Oakland, Ca.
 
24mm for emission manifolds, 26mm for the earlier 1300 manifold, 28mm for the euro 1500 manifold...

I have the manifold numbers (the cast in ones) in a thread over at turbo124.com/forum in the x19 discussions section.

SteveC
 
Euro carb manifold

I will measure the port diameter of the FI head. Where would one find a euro carb manifold? Sounds like I would be pissing into the wind putting on this emissions manifold.

Chris
Oakland, Ca.
 
Australian Specification X19 1500 (1980 casting) 4425193 128BS.2C.0, this manifold has runners that are 28mm at the face and are 28.5mm just inside. This is the manifold number Al Cosentino mentions in his book, in a dyno / engine build sheet as being the "prefered" stock manifold. IMO this is the best standard manifold for flow, but you guys in the USA don't see it as standard equipment.

Australian Specification X19 1300 (1978) manifold 4269347 128ASOC0025, this manifold has runners that are 26mm at the face, but just in they are 27mm

US spec 1300 (1974) manifold is Fiat part number 4320518, which is basically the same dimensions as the Australian spec 1300 manifold, but australian spec ones have a vacuum takeoff point to power a fast idle device (goes where a brake booster hose would fit on something like a 128)

US spec 1300 (75-78) is part number 4401817

US spec 1500 (79 -80) is part number 4409482 (which looks just like the 1300 australian spec manifold with the vacuum takeoff fitting but I've never had one in the flesh to measure or flow test)


There just happens to be a 1500 euro spec inlet on ebay right now....

http://cgi.ebay.com.au/Fiat-X1-9-X1...arts_Vehicles_CarParts_SM&hash=item1c1456b9d8

Maybe send the seller a message and ask him for the cast in number just to confirm...

SteveC
 
Thanks

Thanks Steve I have emailed the seller, it seems the second best intake over on this side of the pond would be the 74 1300l, with match porting to my head should work OK, but I do like those extra 1.5 mm much less work with the die grinder.

Chris
Oakland, Ca.
 
Ebay intake mani

Here is what the seller provided:

28mm diameter exactly and numbers on the manifold are 4425193 and 128BS.2C0

Chris
Oakland, cA
 
Jetting and choke sizes

Thanks for your help Steve, I put in a bid for that manifold and hope this seller ships to the US
I will be installing a new 34 datr, what chokes may be indicated (I suspect bigger then stock may be better?)for this build:

1500 new block
FI head rebuilt, standard size valves
may shave either or both to bump compression slightly
74 exhaust manifold with custom exhaust or after market header
careful port matching of intake and exhaust
regrind Delta cam to fast road specs NOT full race
4 speed trans.

Thanks again

Chris
Oakland, cA
 
Use the 74 exhaust manifold, make up a custom exhaust, look in another thread recently, I posted pictures of the 2.25" exhaust system I use on 1500's...even better would be an exhaust manifold from a 1500 as once again the ports are slightly bigger and will provide a larger anti reversion step to the stock exhaust ports.

IMO you would be best finding some small flycut pistons to go with the 1500, that's by far the best way to raise the CR, as there are no compromises with deck and head face thickness/ bolt threads / cam belt tension / cam timing etc etc... it's just a better way to acheive the same result.

There are lots of different 34DATR's... lots of different choke sizes ranging from 23/24 all the way to 25/27... so check what you have.

Depending on how you drive... F24 emulsion tubes might be a worthwhile upgrade from the F30 tubes that are standard...

If the cam duration is longish, you often need quite a large idle jet to compensate for the lower than stock manifold vacuum, but it depends on advance / retard setting of the cam... use a vacuum gauge (and prefereably measure the exhaust temps too) to set the cam in the "sweet spot"

SteveC
 
Good information thanks
The other engine I am doing is my daughters 74 128 coupe,
stock lower end w/60k miles
big valves installed in FI head with some port work
original faza 35- 75 cam
twin 36 DCNF carbs on PBS mani port matched
original 74 exhaust mani
custom exhaust
how would I measure the head thickness?
On the smog head from the 1300 X19 the piston circle is about 1.5mm
the big valve head is about .3mm
we have a stock Fiat head gasket to install

Thanks again
Chris
Oakland, Ca.
 
I have a spare Euro 1500 carb intake in the US

Sorry I didn't see this thread earlier and let you know. If you don't get the one you bid on, let me know.

Dave
 
$45US delivered to your door is good buying, and saves you hours of work enlarging the ports in that '76 emissions manifold.

SteveC
 
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