New intake manifold modifications

[RallyBob]

In a quest to improve the performance of a later-model 'smog' style 1.9 litre engine, I decided to try to develop a series of modifications which could be implemented either individually or all at once, based on budgetary constraints.

One of the key items, as we all know, is improving airflow through the inlet tract of the 1.9 engine. The 1.9 CIH engine has an efficient exhaust port and exhaust manifold, while the intake port and intake manifold are less than adept for making decent power. Throw a Solex carburetor onto this 'mess' and it's no wonder they struggle to break 50 hp when measured on a chassis dyno!

So, I came up with a series of mods which are relatively easy for the DIY'er to replicate, and won't break the bank unless you pay someone to do everything for you.

*Modified 32/36 Weber (secondary venturi bored oversize)
*Welded and ported intake manifold
*2" exhaust system
*Compufire ignition
*Mild street performance cam: H284/H280-12 (426"/.420" valve lift - 212°/208° duration @ .050" - 112° LSA). Cam advance ground in to correct cam timing from head milling.
*2.0 litre intake valves
*Angle mill head .080"
*Bowls blended in head (no runner porting done)
*high-stall torque converter added (car is an automatic)

The eventual intent is to dyno this combination on a chassis dyno to see what kind of HP increase is seen over stock.

So here are the mods I did to the intake, with the primary focus being on retaining/improving low end torque. This is especially important with a low compression shortblock and an automatic tranny.

What I have done is taken an intake that was previously ported and modified it further. I did away with the epoxy originally used 15 years ago, and replaced everything with aluminum. I milled 3/8" off the top of the intake, cut the bottom off with a bandsaw, then notched it to allow for the 'tent' in the floor to be easily added later on. I also welded up some of the obvious holes produced by the porting work.

[RallyBob]

Here more welding is done to seal things up, the 'tent' is made from some .063" aluminum sheet, and I've made the new 3/8" 'spacer' from aluminum. The spacer in fact gets welded to the top of the intake plenum. Note the holes for the carburetor are now individual rather than open, and very closely match the throttle plate diameters in the Weber carb.

[RallyBob]

Things are getting blended here, the runners have been ported further, all the remaining holes welded up, the 3/8" spacer is welded to the plenum, the underside of the spacer is blended into the plenum area, the outside of the intake is smoothed out a bit, and the 'tent' is welded into the bottom of the intake once all the interior work is completed. I also fab'd up a 10mm thick spacer from phenolic sheet as a thermal barrier.

[RallyBob]

Note the continuity that the new 3/8" aluminum weld-on spacer and the 10 mm phenolic spacer provide for the carburetor barrels. They've artificially added over 3/4 more length to the carb barrels in the hopes to improve fuel atomization and signal strength. The intake is back from the powdercoaters, so now you can see the rebuilt and modified 32/36 Weber, the spacer, and the modified intake as 'one' unit. I did have to make some spacers for the underside of the Ascona throttle linkage bracket. This ensures perfect alignment of the throttle shaft with the throttle linkage.

I'll have some more show'n'tell when I discuss the carburetor mods at a later date.

[michaedo]

Nicely done Bob.
Clarification por favor.
I've got a 38/38 and went ahead and whacked out a
big oval hole in the manifold along with the spacer.
Am I causing vapor confusion when something like
that is done? I had to cut the littler hole bigger
anyway so went ahead and blended the two together.
It's all ground for a very smooth entry into the manifold
but I am all for eeking out anything extra that can be
found.
thanks,
Don.

[RallyBob]

Nicely done Bob.
Clarification por favor.
I've got a 38/38 and went ahead and whacked out a
big oval hole in the manifold along with the spacer.
Am I causing vapor confusion when something like
that is done? I had to cut the littler hole bigger
anyway so went ahead and blended the two together.
It's all ground for a very smooth entry into the manifold
but I am all for eeking out anything extra that can be
found.
thanks,
Don.

Don, I've found that a big open plenum works great when you are making some really healthy power up in the higher rpm range. Assuming you've got the supporting mods like a very healthy cam, high compression (10.5 to 11.5:1), big valves/headwork, you can see a big difference. But for most applications with a short-stroke 1.9/2.0, keeping the plenum area smaller really makes the car a bunch quicker around town (better low end torque).

[michaedo]

Tomorrow I check the timing. But at the moment
have extreme boginessity till 2500 then Katie bar
the door, the wagon takes off like a sexually
molested simian. After 4K it really starts a
hollerin'. Have yet to take it up beyond where
the tach shows red. Maybe tomorrow...
Got an SCCA solo event in Oakland, have to
see how the morning develops.
thanks for the response,
Don.

[opelwasp]

What size emulsion tubes are you using? If it is the originals(F50) that is your problem. You need an F66 E tubes in there or it will bog like crazy down low then run like raped ape in the upper band.

[RallyBob]

What size emulsion tubes are you using? If it is the originals(F50) that is your problem. You need an F66 E tubes in there or it will bog like crazy down low then run like raped ape in the upper band.

Good call Chris. I forgot to mention or ask about that. Could also be a mixture of two or three things, like the emulsion tubes, the carb spacer, and the ignition timing. DGAS's like a little more initial timing I've found.

[blancojp]

Note the continuity that the new 3/8" aluminum weld-on spacer and the 10 mm phenolic spacer provide for the carburetor barrels. They've artificially added over 3/4 more length to the carb barrels in the hopes to improve atomizations and signal strength. The intake is back from the powdercoaters, so now you can see the rebuilt and modified 32/36 Weber, the spacer, and the modified intake as 'one' unit. I did have to make some spacers for the underside of the Ascona throttle linkage bracket. This ensures perfect alignment of the throttle shaft with the throttle linkage.

I'll have some more show'n'tell when I discuss the carburetor mods at a later date.

I want one!!!!!
I have a similar drawing of what I would do to the manifold but never got around to doing it. I can't weld anymore, the Optometrist told me that I would lose my sight if I continued so have too find a good welding shop here in Acworth.

But to further the previous statement, I want one!!!!! I want one!!!!! I want one!!!!!I want one!!!!!I want one!!!!!I want one!!!!!I want one!!!!!I want one!!!!!I want one!!!!!I want one!!!!!I want one!!!!!I want one!!!!!I want one!!!!!I want one!!!!!I want one!!!!!I want one!!!!!I want one!!!!!

[RallyBob]

I want one!!!!!
I have a similar drawing of what I would do to the manifold but never got around to doing it. I can't weld anymore, the Optometrist told me that I would lose my sight if I continued so have too find a good welding shop here in Acworth.

But to further the previous statement, I want one!!!!! I want one!!!!! I want one!!!!!I want one!!!!!I want one!!!!!I want one!!!!!I want one!!!!!I want one!!!!!I want one!!!!!I want one!!!!!I want one!!!!!I want one!!!!!I want one!!!!!I want one!!!!!I want one!!!!!I want one!!!!!I want one!!!!!

Well, I'm not making any promises for Carlisle, but I have plans for a fully fabricated 'sheetmetal' intake for my wagon at some point. In theory it should take less time to fabricate than it took to modify a stock intake as shown here.

But I have to source some flanges for the head, for the carburetor, and have to make the wooden hammerforms first, so that adds to the overall time of building the prototype. First one always takes forever, the second one usually takes half as long and turns out nicer!

Bob

[wrench459]

Nice work Bob
Ok very nice work .. please keep us in the loop with the sheet metal intake.

[broszzy]

Bob, can you show the work you did on the carb?
Thanks Pat

[RallyBob]

Bob, can you show the work you did on the carb?
Thanks Pat

You can either look up the photos on my Flickr photo page for now, or wait until I'm ready to do a write-up here on it. Don't know when that will be, when I'm a bit more rested I guess.

Start at this pic, and scroll to the right.

[RallyBob]

Pat, I just made a bunch of updates on the Flickr site with subtitles and explanations about all the carb mods.

HTH,
Bob

[broszzy]

Pat, I just made a bunch of updates on the Flickr site with subtitles and explanations about all the carb mods.

HTH,
Bob

Thanks Bob I'll check it out
Pat

[wrench459]

OOO thanks Bob
for the details on the main jet sizes. I did go a little lean on the top end with my jetting 14:1. I might be able to crack the century mark now. Without spending a small fortune on jets.

[Redskinsjbs]

Pat, I just made a bunch of updates on the Flickr site with subtitles and explanations about all the carb mods.

HTH,
Bob

I Want One!!!

[RallyBob]

OOO thanks Bob
for the details on the main jet sizes. I did go a little lean on the top end with my jetting 14:1. I might be able to crack the century mark now. Without spending a small fortune on jets.

I think you'll need more fuel still. At least 175 on the secondary, thanks to that camshaft.....

[wrench459]

I think you'll need more fuel still. At least 175 on the secondary, thanks to that camshaft.....

Ok Bob
I've got an open Sat. for some testing and tuning planned. Now how fat do you think I should go with the A/F ratio? I've got two carbs to play around with. The 32-3X and a 38. That I can mix and match.
BTW I came back to this post for a whole other reason...err what was it?