The Stovebolt Site Forums The Shop Area Engine Shop 261 engine build questions

I'm preparing to build a 1959 261 engine for installation in my 1959 38 (1 ton) and have few questions for the engine experts here.

(1) I know that many 261 engines have had a 235 "848" head installed. Nevertheless, Is the power increase to be had by switching to the "848" head substantial?
(2) Could I obtain similar results be milling the 261 head?
(3) Is it correct that the 261 engine oiling system is such that hydraulic lifters can be used instead of the stock solid lifters (assuming a compatible cam)?
(4) Is the stock 261 cam okay to use with hydraulic lifters?

I know, lots of questions in one post. I just want to get this build right.

Thanks,
Steve

I am not an expert, but I did recently finish a 261 build for my '50 3600. I'll give you my .02

I found and installed an "848" head. It required drilling steam holes in it to fit it to the 261 block. I have no idea whether performance was enhanced by using an 848 head, as the engine still has (relatively speaking) very low compression (higher compression pistons are not available, unless you want to pay $$$$ for custom pistons). Someone had already milled my 848 head before when I got it, perhaps as much as .040. With my cam (Langdon "Bulldog" cam), it ended up driving the intake valves very close to the piston (.075 measured clearance, using valve checker springs).

Milling the block or the head is not a great idea IMHO, as you will never get any appreciable increase in compression, and you will have to sink the intake valves further into the head, creating even more problems with valve train geometry. If you run even a mild performance cam, you may find yourself right up against, or beyond the limit for intake valve/piston clearance. The stock 261 cam is an ideal cam for the 261, and it's the same cam (Blue Flame) GM ran in the Corvette 235.

There are no replacement hydraulic lifters for this engine, as far as I know.

The best way to build the 261 is to build it stock with the single carb and stock head and 261 camshaft. It's a great engine, just like that. But easy to make a mess of by attempting to hot rod it. If I had it to do over, I'd have left everything completely stock. The very mild gains in performance were not worth the expense or the hassle, especially with my dual carb setup. The 261 is an old stovebolt engine that performs better than any of the others, even in stock form. If you want more, I'd look at building different engine.

That said, the HEI setup is kinda spiffy, but I need to first put some serious miles on my truck before I am completely sold on the idea of throwing out the old distributor.

Others here have far more experience with this engine, and I am sure they will chime in shortly. Good luck!

You would probably need a Canadian "Pontiac" 261 block to use hydraulic lifters. I don't believe the American truck engines had the oil gallery drilled for oil supply to the lifters, since all the trucks ran solid lifter cams. No, you CANNOT run hydraulics on a solid can. The lobe profile is all wrong, and cannot be compensated for by adjustment.

Yes, it is possible to mill a 261 head for more compression. Get ready to spend at least 3 times the money you would on an 848 head job to correct the piston to valve clearance and valve train geometry problems that doing that creates. The compression gain is minimal either way.

I'll be doing a 261 engine assembly job over at Stovebolt headquarters with about half a dozen observers/helpers next weekend. Fun times! We're using a new stock-specification 261 cam made by Elgin, and I'll be doing a timing, lift, and degree check like we did on the NASCAR engines during the installation. After that, I'll have the measurements to prove why hydraulic lifters on a solid lifter shaft is a really bad idea- - - -something the rest of the world other than self-appointed stovebolt gurus has known for the past 60 years!
Jerry

Here are a additions/clarifications to Dave's helpful/informative post/list:

The 1958-1963 USA 261 blocks had oil passages that allowed hydraulic lifters.
Canadian Pontiac 261s used hydraulic lifters.
My guess (warning-warning : this is a guess) is that 58-and-later 235 hydraulic lifters should/might work.
Maybe Pre '68 Dave and/or others will comment.
Nonetheless, I'd stick with mechanical lifters.

Another way to describe the 1954 and later Corvette mechanical-lifter camshaft is to say it is the same camshaft designed-for (and introduced in) the 1954 261 truck engine. This camshaft can also be used in high-pressure truck 235s
I wonder if this is the same camshaft that the Canadian's use with hydraulic lifters?
(does anyone know the Canadian 1956 and later truck (and Pontiac) camshaft part numbers/numbers?)

I agree about keeping the old distributor if you are thinking about going to an HEI unit. The original distributor works fine at the RPMs you'll most likely be reaching. It is also reliable. I carry a tested distributor as a spare (on long trips).

I have used a few dual-carb set-ups on my 1960 USA 261. As Dave posted, they might be more trouble for minimal improvement.

If you do not need Eye-Candy duals or triples, you might want to consider a larger/bigger-CFM single carb. If you can find the correct adapter-plate/base, a single GMC Zenith 270/302 carburetor with adjustable metering jet/jets works very nicely. My 261 is over-bored to around 270 ci, and a 2-barrel AA1 Zenith (from a GMC 302) with available/adjustable jets performs real nicely. When I am just cruising on highways, I get around 18mpg. If I open the jets for high-speed or better acceleration, I can get some impressive oomph at high speeds (and, the gas mileage falls).

I ran hyd lifters in my 261 for a while until they got noisy so switched to solids, (must keep solid cam with solid lifters), now days there is a fix for this prob. see pre68daves blog for all this info (also can check with Langdon's Stovebolt for lifters). Word is that there are some inferior hyd lifters out there and nos ones are really pricy, that said I really like the quiet running of that motor. Today I'm running Bulldog solid lifter cam from Delta Cams, like it a lot, very mild easy to set lifter, engine sounds great and pulls strong.

I am also running the 848 head which has combustion chamber volume in the 70s vs 83 or cc or so, can look this up if you need. 848 is a bolt on swap if you have one but don't thinks is that big an issue. My intake valves are the bigger Powerglide just under 2", just surfaced the head vs a mill job. I've run several different sets of single and dual carbs on this motor if you want to go that route, currently have a new 390cfm Holley on a 235 that is really nice. I wouldn't run an old carb unless its in perfect shape, will drive you crazy, get the best one you can find, again check with Langdon's.

I would highly recommend the HEI distributor, that alone made my motor run better and start easier.

Here's some good info re. 261s from Jim Carters, oiling system on these motors is a bit different but very important to understand.

http://www.oldchevytrucks.com/blog/index.php/2010/02/the-forgotten-261-6-cylinder-engine/

Best of luck
Jim

Note, See lots of good 235s for sale cheap, on sites like trifive.com, many of those folks pulling good inlines and usually sell for not much money.

So I have often wondered if the lift is a little enhanced on the hydraulic cam to make up for some give in the lifter?

If the lifter "gives"
1. bad lifter
2. not enough oil pressure

Without getting too technical, the transition from the base circle of the cam lobe to the area where the valve begins to lift is much shorter on a hydraulic cam since there's no need for a "clearance ramp" section of the lobe to take up the valve lash. The hydraulic lifter stays in contact with the cam lobe at all times. The cam profile on a hydraulic cam is completely different than a solid lifter shaft- - - -different lift rates, possibly different height and duration of the lobe lift, etc. Hydraulic cams can be ground mild to wild, high torque to high horsepower, depending on what the intended purpose of the cam happens to be.
Jerry

Thanks to all for your input. I never intended for my 261 to be a hot rod engine as its going into a working truck that I want to look period correct. Ideally, I'm hoping that be replacing the somewhat tired 235 with a "new" 261 I will gain enough extra torque that I can change the rear gears from the current 5.13 to 4.57 and still tow a trailer. So, it looks as though I will be rebuilding to stock specifications except for the "848" head and possibly the carb. I know I don't want multiple carbs or a four barrel. In the distant past I built a chevy 250 with high compression, high lift cam, headers, and aluminum intake with a Holley 390 cam carb. It was a bear to get the jets, power valve, accelerator pump springs, etc setup correctly. Although in the end it made a nice runner and surprised a number of people that it wasn't a v8.

Jerry,
Are you familiar with Wright's machine shop in Fayetteville? Three generations of machinists in the shop and the owner is very familiar with building 261s. I plan to have them do the rebuild.

Steve

I've always used Lincoln County Auto Parts in Fayetteville, owned by Alan Holmes, for machine work I can't do myself. Where is Wright's located? I might want to go by and get acquainted, since I've got a few oddball ideas about reconditioning 216/235 splasher rods with Massey-Ferguson tractor bearings. That requires a non-standard rod journal size, however. I've been accumulating Babbit rods for quite a while and I've got about a hundred of them stockpiled.

Another project I've got on the back burner is a 261 "Cadillac" stroker 261 that will end up somewhere close to 300 cubic inches. The Carter YF carb for a Ford 300 inline six might be just right for that engine.
Jerry

Wright's Machine is south of Park City on Lincoln Road approximately 1/2 mile east from Hsv Highway 231/431.

Steve

Thanks- - - -I'll drop in and visit with them sometime. Do you know if they're set up to do line boring on stovebolt engines? Those 4 different size main bearing bores get most modern machinists a little spooked.
Jerry

If I remember correctly, I don't believe they have the capability to do line boring on stove bolt engines.
Steve