Hi I’m new to this site, but have been stocking it for years. I know and have read a lot about this topic but will bring it up again. I have a 1957 Chevy truck with a 265 and Hydramatic. I just took the engine (block 3781548) (heads 3731554 69cc low compression) to the machine shop to be rebuilt. I am thinking to keep it stock with the original 2bbl, but wanted to know if I should add any modifications like raising the compression some how, putting a better cam in or am I just wasting my time. I heard this block can be bored to 283, should I do that so I have more piston options? What cam should I go with? Pistons? thx mark
Since most modern machine shops dont do 265"s make sure they know they need to use a 265 type cam ,or there wont be oil going to the top end.This engine used a milled notch on the rear cam lobe to get oil to the top end.There was a thread on 265"s about 10 days ago so do a search.One of the guys showed how to cut a groove in the rear cam bearing bore to over ride the need for the 265 cam.Dont go too wild with duration on a 265 cam they dont like alot. As for boring to 283 back in the early days the block would go that far.Theres been 65 years of rust in the water jackets so it may not go that far now.A good shop can check the thickness/ soundness of the walls for you.Myself I wouldnt bore any farther than needed.I have a 265 in my 55 Cameo. I used a Edelbrock intake,and 500 cfm carb,and tube headers.It runs well.When you break it in run Zinc in the oil.Modern oil doesnt have it,and you could loose the whole engine at break in if you dont. You will find that it cost way more to rebuild a 265 than it does a 350 so unless you love the early engine now may be the time to go bigger.
Definitely make sure the cam used is correct or that the oiling issue is addressed. The more experienced HAMB guys can help ya with that. What heads are on it now, if it’s non -power pack heads, a set of those would up the compression by themselves. Those can usually be found cheap. A non power pack 265 was rated at 8:1 while the power pack equipped one were rated a 9.24:1 (ish) Along with a factory 4v intake from the same time frame. Remember, a cam recommendation for a 350 is not the same for that small cubic inch engine. Wonder if the corvette solid lift cam is still available? https://www.jalopyjournal.com/forum/threads/lets-build-a-265-chevy-v8.416175/
As already mentioned, there are some differences between the 55 - 57, 265's / 283's and the later small blocks. There was a book by Don Francisco called "How To Modify Chevy V8 Engines". It has alot of info on these early small blocks. To find a copy, you'll have to look around on Ebay, or in a vintage book store. My copy was printed in 1957.
Thanks for all the replies! From what I read the 57 265 may already have the oiling change done from the factory. Once he gets the rear cam bearing out I’ll know for sure, I’m crossing my fingers. I know for sure the cam that came out did not have that oil grove in it (bit since it was not running when I got it, not sure if it’s the correct one for the block. The block is a virgin 265 so still debating on having it cleaned up to the nearest size or to bore it out to a 283 (more piston options, as I don’t see many choices for a 265) after having the walls checked for thickness. I’m thinking about putting the 3896929 cam in it, anyone running that one? What do you think?
I seem to remember that the cam notch was only '55 and early'56. That's no guarantee that yours is the new design, but it's a good sign. I looked up the casting #s you gave; I found 3731548 block ('57 283 only) but could not find 3781548. 3731554 head came up 55-63 dual quad Corvette. I couldn't find the c.c. volume for that casting. In 57 I don't think there were any 69cc combustion chambers. I definitely could be wrong. Anyway, my family had a '57 powerpack 283 that I installed an L79 factory hydraulic cam. It worked great. BTW measure the bore in your block; you may already have a 283.
Just curious how you know, for sure, that your engine is a 265. The 265 was the baseline V-8 engine in 57 that came is 3 speed manual transmission cars (I can't say about trucks), and then only with a 2 barrel carburetor. Any other V-8 setup, 4 barrel, automatic transmission, dual four barrel carburetors, fuel injection, was a 283. Even a 2 barrel 283 was an option. True, the 57 265's and 283's used the same casting number blocks. If your engine is a 265, and does't need to be bored, I can help you out with a NOS set of Jahns, standard bore, 2 valve relief, flat top pistons, for CHEAP. They will help to bump the CR up very slightly. Also have 2 sets of NOS, Thompson, 265 + .030 over, forged, Any piston, to really step the CR up, will be expensive, as they will have to be specialty made.To keep things fairly cheap, I'd go with a pair of 305 engine, casting number 601 heads, with 53 CC chambers; they will have hardened seats, and accessory holes if you want to add air conditioning, power steering, etc, at some point. You can get aftermarket, cast iron heads with 49 CC chambers, but no where as cheap as 305 heads will be. I always say, it's really hard to build any kind of CR with these small bore, short stroke engines; the performance parts for them just is't out there any longer. The 57 V-8's, the 265 and 283, both have the improved oiling, so you don't have to worry about having a rear cam journal "notch". The 57, V-8 blocks, also have a provision for a block mounted starter motor if you ever decide to go with a more modern automatic transmission, although the Hydra-matic is a pretty cool deal. Does your engine have pistons with valve reliefs? I know the 55-56 265's had true, flat top pistons, without any valve reliefs. Chevrolet did a lot of warranty work due to piston-to-valve contact with missed shifts, over revving, etc, early on. I am Butch/56sedandelivery.
If I remember correctly, you can tell by looking at the rear cam plug area of the block. The early design, (with the groove in the cam), looks slightly different from the later design. If the back of your block looks exactly the same as 283's 327's etc. it doesn't need a cam groove.
Hi Butch, Thanks for all that great info! From what I’ve read the small v8 trucks got the 265. When we pulled off the heads we measured the bore and it appeared to be 3.75, and the pistons were flat top GM pistons. I’m still on the fence on whether to build it back to stock, the high cc heads and 2bbl. I’ll know more when the machinist checks the wall thickness etc. what kind of compression boost would it give over the stock flat top pistons. The only pistons I see on eBay are the silv-o-lite 1410’s. I’m going to stick with the Hydramatic, not sure how it will drive, but i think it will be cool to drive. thx mark
The casting on the block is 3731548 not 3781548.[look closer] Chevy designated the same block to 265 and 283 so you can safely bore it out to 283 [without sonic testing] The 265 blocks were painted Chartreuse and 283's Chevy orange This is the only 283 block without side engine mount bosses [all 265's were the same] The 3731548 block has full flow oiling [from the rear cam bearing] so no oiling mods are required I did exactly what you are planning. My engine had a crack so I chanced onto a block with the same casting #'s [but it turned out to be a 265, so I bored it to standard 283 bore] To get the compression up, it is better to deck the block than mill the heads. But be warned 283 "rebuilder" pistons have 0.020" less compression height. I had to deck 0.050 off the block to get zero deck clearance. If I had time, and was to do this again....I would hunt down a set of STD bore 283 pop up pistons [10.5:1] This would net an honest 9.5 to 9.8:1 compression with your heads and no milling or decking needed. Don't go too wild in the cam......a 3.00" stroke dies with too much duration .
That cam is a stock product for the 275HP 327 and several others. I have one in a restoration 327 300HP from 1965. Nothing special about it. Idles smooth and quiet. I believe they were also used in 283's.
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