Early 273 intake problems

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jedrattle

jedrattle

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First things first. I have read all the stuff on early 273 intake bolt sizes and angles. I’m looking for a solution/suggestion to my problem. My 273 used the 5/16ths intake bolts.

I have a ‘64 Valiant 2dr ht Valiant with a 273/4spd setup. I’ve had nothing but problems with 3 different 2bbl carbs. I’m over it! I want to put on a brand new small 4bbl carb and a 4bbl intake. So I bought this Offy intake manifold from a member (for the record I’m not mad). This is what I got...

00966862-1812-4285-BBC4-3399F53327BC.jpeg
BE660E30-9684-40FE-B181-8C06492B9A37.jpeg


Fast forward about 5 weeks and I finally get time to install it. Nothing but problems. The front bolt holes won’t line up at all. The rest are at a weird angle. The bolthead will not sit flat, when it touches the intake. The stock one was the same way but this one is way worse! Here are pics I took of the bolt angle in relation to both manifolds

288589A4-2351-4C3C-B7DB-8690ADDEFAEE.jpeg
0F563573-75A7-40F0-8B83-0B2803426700.jpeg


And here is the front bolt holes. Yes, there is a gasket in there.

24B4F531-C929-4029-B001-7FD5D0A127DC.jpeg


I checked the intake mounting bolt hole angles the best I could and discovered the stock one is 3-4 degrees higher then the Offy. Also all the bolt holes in Offy are 3/8ths. Now I’m thinking that this is for the later models. The are no model numbers on the Offy to confirm it.

So I’m at a cross road as to what I should do. I’m on a time and budget crunch. I think these are my options...

1. Mod the holes on the Offy and make it work. But I feel like I’m ruining a beautiful intake by doing that

2. Sell it and buy another early manifold that fits correctly. Time and budget is not my friend on this one.

3 Find a used performer and mod it to fit and be done with it. I would grind the angles of the holes and the mounting pads to work correctly

What would you do? I’m leaning heavily toward #3!
 
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grimreaper said:
You must have later year heads on your car. Is it actually a 273? Blue paint raises question.
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Exactly. Look on the intake ports and let us know the part/ casting number'
 
toolmanmike said:
That's a 64/65 intake. It is possible the heads were machined causing some mis-match. I don't understand the difference in angle. How does the stock bolt angle compare to the Offy intake?
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Pics 3 & 4 show the difference. It’s a little bit off between the 2. Enough to cause problems. That’s what is making me think it’s possibly for the latter engines.
I’m lost too! Lol
 
Do You have access to an engine machine shop. They can mill the aluminum intake to fit. I can’t imagine it would be costly or take a lot of time.
These engines and parts are only getting older (50+)it’s not hard to believe they have been machined a time or two.
 
tubbedamx said:
Do You have access to an engine machine shop. They can mill the aluminum intake to fit. I can’t imagine it would be costly or take a lot of time.
These engines and parts are only getting older (50+)it’s not hard to believe they have been machined a time or two.
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Yes there are a few locally. The intake looks like it sits correctly on the heads. I need to double check it.
 
I don't recall which has the steeper angle 65 - older or 66 - newer.

Is there any chance that there are inserts in the heads? Changing the 3/8 bolt thread to 5/16?
 
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That is indeed a 64-65 intake. Put some hardened washers on it and call it a day. I ran a Performer on the 65 heads with washers and it never leaked. AS for the holes that dont line up, take all the bolts out and manually line up the intake again. I bet they all line up with 5/16 bolts. I got to question the wrench needed to tighten those '5/16' bolts. If its a 9/16 hex then they are 3/8 bolts. 5/16 take a 1/2 wrench as those head angles are 3/8 for sure. Whats head casting number?

2465315 – 1964-1965, 273 LA-series small-block, 1.78/1.50 valves

2532080 – 1964-1965, 273 LA-series small-block, 1.78/1.50 valves

My pic of a real deal 65 intake and 64 heads, note skinny 5/16 bolt face angles and casting line on head that follows bolt angle. 66+ heads are at a 90 to the intake face. Check your head(s)for this line, buck says they don't have 'em.
early2-jpg.jpg

early-jpg.jpg
 
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pishta said:
got to question the wrench needed to tighten those '5/16' bolts. If its a 9/16 hex then they are 3/8 bolts. 5/16 take a 1/2 wrench as those head angles are 3/8 for sure. Whats head casting number
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That's where I was going, later heads on earlier engine, or later engine and heads, with earlier intake. The bolts look larger to me too, but there is no perspective.
 
I used an Edelbrock Tarantula intake manifold on my '65 273 with washers on the smaller bolts and a lot of wiggling around to get them all started by hand.

65 Valiant5.jpg
 
self deleted, not self defeated! Cuz I didn't beat myself......
 
dibbons said:
I used an Edelbrock Tarantula intake manifold on my '65 273 with washers on the smaller bolts and a lot of wiggling around to get them all started by hand.

View attachment 1715424295
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Wow! What did that TM-5 rpm at on that? Sorry to hijack, just imagining it had the torque of a weedeater mini with bad rings until it reached 4 or 5 grand...
 
Launch was 6000 RPM, Shift Points 6000 RPM, Trap RPM was 6400 RPM but still pulling strong (four-speed with a 4.56 rear end). I never had an engine failure and wore out one pair of slicks down to the belts/cords. Was afraid to wind it any higher, but the Isky cam was advertised good to 8000 rpm. Used to cruise Main Street Salinas on the weekends.

First used the 3.09 first gear A833 four-speed then switched to the close ratio 2.66 first gear A833 four-speed.
 
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