Rebuilding a 65 273..I need some help.

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pishta said:
Yup, the Y headpipe, extension and muffler had a different part number.
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My 66 had the 2 barrel stuff on it when I bought it. Dang it was small. Like you said almost 1 1/2"
 
there are some excellent utube vids on rocker arm geometry to get the correct pushrod length if you need custom. the one from straub industries/ scott foxwell is the best. its real easy to grasp.
 
Rapid Robert said:
off topic, what about scoring a good used 318 or 360? More power/cheaper than a rebuild.
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Well, I have this engine which is original 1965 casting and was rebuilt by a service manager of the local Chrysler dealership to do some racing but the heads he put on it were too big a valve for that little engine so he took the heads off and stored the engine, minus heads and cam , under his workbench it has forged crank, high-performance connecting rods and TRW pistons already installed in an engine block that hasn’t seen much wear since it’s been rebuilt last.. as a matter fact he told me the other day there probably was not even 10 hours of running time on that engine..
 
2465315 – 1964-1965, 273 LA-series small-block, 1.78/1.50 valves, 57cc

2532080 – 1964-1965, 273 LA-series small-block, 1.78/1.50 valves, 57cc

4323302 – 1985-1986, 318 LA-series small-block, 1.78/1.50 valves, Fast Burn, 56cc -65cc

The 302's have a "slightly different" eyebrow chamber and induction hardened valve seats.
 
65TerrorCuda said:
I wonder what he means by big valves.
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Good question. All the 273-318 heads had 1.78/1.50 valves You would need to use a 340/360 head to get bigger valves. For a low compression 273 you don't need a big open chamber and can't use the larger valves and larger ports.
 
If it has TRW pistons in it, they may already be hi-compression.....what do the tops look like, 2 or 4 valve reliefs? hi-comp should not be flat but have one side raised. I dont know if TRW made a replacement low comp 273 piston. That would change the cam profile radically.
 
pishta said:
If it has TRW pistons in it, they may already be hi-compression.....what do the tops look like, 2 or 4 valve reliefs? hi-comp should not be flat but have one side raised. I dont know if TRW made a replacement low comp 273 piston. That would change the cam profile radically.
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They did make forged flat top pistons with 4 valve reliefs.
 
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The original heads on my 273 had closer to 65cc chambers and CR with the stock replacement flat top pistons (0.055" below deck) put it right around 8.2:1, 25 years ago. 2 or 4 valve reliefs I don't remember. Just fyi
 
65TerrorCuda said:
The original heads on my 273 had closer to 65cc chambers and CR with the stock replacement flat top pistons (0.055" below deck) put it right around 8.2:1, 25 years ago. 2 or 4 valve reliefs I don't remember. Just fyi
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65cc chambers sounds about right. Not sure of replacement pistons though.
 
Sorry to hijack this thread but these seem to be the guys to ask. On a 67 273 2v head. Can 1.6 and 1.88 valves be installed and used and does the block need notched? My engine is .060 over. I have a 2v engine that's been rebuilt. It has dual ext and a 4v manifold. I'm thinking of swapping in a cam, and port matching the heads, intake and adding the bigger valves and some port work to pep it up some. Also thinking about milling the heads in an attempt to get closer to 9.5 comp. Your knowledge and exp is much appreciated. Thanks guys.
 
Dmopower said:
Sorry to hijack this thread but these seem to be the guys to ask. On a 67 273 2v head. Can 1.6 and 1.88 valves be installed and used and does the block need notched? My engine is .060 over. I have a 2v engine that's been rebuilt. It has dual ext and a 4v manifold. I'm thinking of swapping in a cam, and port matching the heads, intake and adding the bigger valves and some port work to pep it up some. Also thinking about milling the heads in an attempt to get closer to 9.5 comp. Your knowledge and exp is much appreciated. Thanks guys.
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Best to do a dry run and check first. It should clear but may cause some shrouding.
 
that 273 at .060 over, is now a 283.6, rounds to 284/ 4.65liters.
The bore is 3.69. I don't think you can put a 2.02 in that hole, at any desirable lift.
A big-valve head is better-called a big-port head, which comes with either 2.02s or 1.88s .
IMO, and that's all it is; I'd rather use an intake valve that doesn't get shrouded at a higher lift, than a shrouded big valve at a more normal lift. With the advent of 1.6 arms, it's easy to get up over .500 lift.
But I also can't see a good reason to run big-port heads on your 284, for your street application.
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I forget the distance between the valve centers but 1.6 +1.88 is already 3.48 which doesn't leave much room on the bore centers . Allowing say .10 between the valves, is now 3.58. From 3.69 this leaves just .055 to each of the cylinder walls..... if the chamber is centered. If. Good luck getting all 4 of them centered.
If the valves do not open on the center-line of the bore you got problems.
Would I try it?
I plead the Fifth.
 
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AJ/FormS said:
that 273 at .060 over, is now a 283.6, rounds to 284/ 4.65liters.
The bore is 3.69. I don't think you can put a 2.02 in that hole, at any desirable lift.
A big-valve head is better-called a big-port head, which comes with either 2.02s or 1.88s .
IMO, and that's all it is; I'd rather use an intake valve that doesn't get shrouded at a higher lift, than a shrouded big valve at a more normal lift. With the advent of 1.6 arms, it's easy to get up over .500 lift.
But I also can't see a good reason to run big-port heads on your 284, for your street application.
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I want to use my 273 heads. I just want to know if I put 1.88 intake valves in the 273 heads will the block need notched. I don't want to use big port heads. I just want to make these 273 heads very effecient and figured someone already used the 1.88 in the 273 and could or couldn't and will tell me why. If They will work. I'll hunt down a set of 1.88 1.6 prep them now and put them in this spring when i pull them and freshen them up.
The cam I'm looking at is .475 .494" 220 226 @ .050 with the factory adj rockers.
 
I figure if the valve is .1 larger then that's .05 closer to the cylinder wall. with .060 overbore divided in half i get .030 of that back getting my valve .020 closer to the cylinder wall then factory. I have not even looked at the room between the valves. What should that min clearance be?
 
Dmopower said:
The cam I'm looking at is .475 .494" 220 226 @ .050 with the factory adj rockers.
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A 220*cam might power peak at 4800.
1.88s compared to 1.78s? in a 5000rpm engine? IDK if if it's worth it, not to me anyway. But if I did the swap I would for sure notch the bores to eliminate shrouding. Else you may lose more than you gain. Notching is not a hard thing to do; just stay out of the ring-sealing area, and the Fire-ring area. But yeah, IMO, the engine will need to be torn down and thoroughly washed afterwards.
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If you do not yet have heads, consider a pair of Magnums. They already have the big valves in them, and a better port is the bonus. You can run hydros, and adjust the preload with the adjustable arms, to the minimum required to keep them quiet. Jus saying.
toolmanmike said:
Oops, Magnums don't have adjustable rockers.
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AJ/FormS said:
A 220*cam might power peak at 4800.
1.88s compared to 1.78s? in a 5000rpm engine? IDK if if it's worth it, not to me anyway. But if I did the swap I would for sure notch the bores to eliminate shrouding. Else you may lose more than you gain. Notching is not a hard thing to do; just stay out of the ring-sealing area, and the Fire-ring area. But yeah, IMO, the engine will need to be torn down and thoroughly washed afterwards.
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If you do not yet have heads, consider a pair of Magnums. They already have the big valves in them, and a better port is the bonus. You can run hydros, and adjust the preload with the adjustable arms, to the minimum required to keep them quiet. Jus saying.
Click to expand...
Oops, Magnums don't have adjustable rockers.
 
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