The Stovebolt Site Forums The Shop Area Engine Shop 216 engine swap...to what?

Evening all

Looking for a little advise and have read some of the information on the forum. While I am well versed in twisting the odd wrench and fabbing stuff I am out of my element on the stovebolts.

I have a 1949 "3804" single wheel 9'box.

I am wanting to wind up with a very drivable vehicle capable of hiway (60mph) speeds reliably with a small camper and I can't see the old 216 being up to the job even modified.

I expect to use the stock trans but change the rear axle ratio to keep rpms in the 2500-2700rpms range.

But I want to keep an inline 6, make the minimal change possible to keep it looking as original as possible.

I was considering a 235 but I don't think it will do it. Thoughts?

Maybe a full oil pressure 261 with modifications? But all the 6 swaps seem to concentrate on the 235 and I am not clear on the difference in the swap.

The real big GMC's are too hard to find or get parts for in my part of the world.

Suggestions?

Tom

A 261 starts out nearly 30 cubic inches bigger than the 235, and it's a bolt-in swap with only minor differences to deal with. It will also respond better to "go-fast" modifications like increased compression, boring, stroking, etc. The later-model 292 six is another option, but there's a lot more work to making it fit in your early chassis- - - -different bellhousing, different rear crossmember, motor mount fabrication, exhaust changes, etc. The advantage of using the 292 is that it's a considerably newer engine, and parts aren't as hard to find. You've got another 30 cubic inch advantage over the 261, also. 292's aren't famous for fuel mileage, but they're very rugged, and they respond well to modifications like a 4-barrel carb, dual exhausts, cam changes, etc. For torque considerations, I think I'd choose a somewhat warmed-over 292 over a 305 small block V-8, or possibly a low-compression 350.
Jerry

Tom,

Most likely, the 261 is the easiest way for you to go, if you want a boost in power (for all the reasons Jerry stated). In Canada, you might be able to find a Canadian Pontiac 261. It is similar to the truck 261, except that the Pontiac has hydraulic lifters.

Tim

Thanks for the input Jerry and Tim

Spent alot of years racing but this stuff is new to me.

Sounds like the Pontiac 261 is likely the best route.

I want the swap to be reversible so I can go back to original eventually.

The idea of full pressure oil system and hydralic lifters really appeals to the reliability issue and 50 more cubic inches and the ability to "warm" it up a little more is right up the alley of my objectives.

Question though...

Will the 261 be happy with 2500-2700 on the hiway over the long term?

thanks again

Tom

Keep the piston and bearing clearances close to minimum, and do a pretty good static balance job, and don't worry about anything under 3,000 RPM. I think most of the inline sixes were horsepower rated at or above 4,000 RPM, so that should give you an idea what the engine is capable of surviving. My Motor manual lists the 1958 model car 235 at 145 HP at 4,200 RPM, with a torque peak of 215 Ft./LB. at 2,400. The 261 should beat those numbers by a noticeable amount, and since the stroke is the same as the 235, it should live happily at 3,500 or less for a long time.
Jerry

Thanks Jerry

Since getting the last input I am now thinking:
1958-61 Pontiac 261 with hydralic lifters
Full overhaul with:
- Boost to 9.0:1 compression ratio
- Static and Dynamic balance
- Ports matched, general clean up, bowl clean up
- Three angle valve grind
- Slightly stronger cam
(10 degrees more duration, 50 thou more lift)
- Header
(recommendations?)
- Better induction
(triple singles, high flow air cleaners,in part for nostalgia)
- Stock ignition with high grade coil

I would think that would boost things a little, allow for steady 2500 to 2700 rpm cruise speeds and a little more umpf for general driving.

I am more than open to ideas on the intake side as I am just guessing at this point.

Thoughts or suggestions welcome.

Tom

The 390 CFM Holley 4-BBL carb will add plenty of airflow without dealing with all the headaches of multiple carbs. I seem to remember that there's a bigger intake valve available, but I can't recall what engine it comes from. If you open up the port under the valve and blend it in right, the breathing with the bigger carb will be improved considerably. A modest increase in cam timing and lift will also help, but don't go ovdrboard on duration. A relatively short duration, high lift cam is what builds torque for trailer towing, so try to get someone to grind an "RV-cam" profile onto a 235/261 hydraulic cam core if possible. I wouldn't go over 260 degrees duration, but get as much lift as your cam grinder can supply. The 261 engine can handle an .080" overbore without getting into cooling system problems, but be sure and run a good radiator and plenty of fan if you go overbored. There's a thread somewhere on this site that describes an offset stroker modification on a 261 using a 292 Chevy connecting rod that will increase the displacement, also. I believe it's possible to get the cubes up to 280 or more with the right bore/stroke combinaation. With an 848 casting number cylinder head modified with the 261 head "steam holes", the compression you're looking for can be achieved with just displacement increases, I think. These types of modifications get pricey in a hurry, however.
Jerry

Advise well taken Jerry

No plans on going to a stroker or big bore.

Just want to keep it simple reliable and original looking.

For regulare driving I am a big fan of really well built stock engines...with maybe a little warm up.

I've always found headers a great efficency as well as power enhancer so its a definite.

But other than "balancing and blueprinting" the long block will be stock. Don't mind spending money on really good machine work, balancing and good head work, but don't need the big valves, stroking and boring for this project or budget.

I think the Holley 390 you recommend is likely the best choice, but I want to build a nostalgia style triple set up because I want to see if I can and it's period looking.

Thanks for the 848 casting recommendation...I would like to bump the compression, but if I don't make 9.0:1 without going overboard I won't be heart broken (well maybe a little).

Appreciate the advise.

Thanks Tom

I seem to remember that there's a bigger intake valve available, but I can't recall what engine it comes from

The Powerglide valve is 1/16" bigger, direct fit, but it won't do anything unless the bowl is enlarged etc.

I believe you'll find the triple carb setup presents some pretty formidable clearance problems unless you modify the firewall contour, or eliminate a core support brace rod. If you choose that route, definitely go for the smallest venturi carbs you can find, and/or use a progressive linkage setup where the end carbs don't open up until nearly full-throttle is reached with the center carb. The Buick straight 8 twin-carb setup worked that way, and it was pretty reliable. I think Hudson also used a progressive linkage 2-carb system on some of their hotrod engines. With a progressive linkage you can also disable the idle system on the outboard carbs and eliminate a lot of idle synchronization headaches. The Chevy, Olds, and Pontiac TriPower 3-2BBL rigs did that, and also the Corvair Spyder engines with the 4-carb system. Good luck!
Jerry

Thanks for the advise again Jerry

I raced imports with multi carb set ups for about 10years at one point so I am pretty familiar with most of the issues in general.

Planned on using(3) very small single barrel down draft webers
(going to the 261 I will have to redo all the math and sizing) with a straight linkage.

They are very low for a downdraft and with selectable venturis it should allow the intake charge velocity to remain high while allowing better flow and distribution.

Still guessing but the direction I thnk I would like to go.

Tom

Doing the 235 swap myself right now. If you can find a 261 that will provide ya more ponies as stated. Patricks has a good article on the swap in their catalogue, http://www.patricksantiquecars.com/
call them and request it. Also found Patrick to be helpful info. wise and very good with his prices on the engine rebuild kits.

BTW, saw a 235 for sale in Canada in the swapmeet section, not sure how close you are though?

Hank

For what its worth, MikeE (Stovebolter from Green Bay) is driving a 1Ton panel with a 216 and 4-speed. With the tires he is running, he is getting 55-57mph (based on my GPS) all day long.

The point is, a gear change with minimum power increase will be all that is needed to get to 60mph if thats your goal.

Webers- - - - -good choice! I raced a Datsun 240Z with three DCOE 40 Webers on it, but it was an all-out competition setup that never hit the street. I'm also planning to build up a Triumph Spitfire with a GM 2.8L V-6, and I'll use a single Weber 48IDA downdraft carb on it. Most of the guys on this site are locked into Rochester or Carter 1-bbl's when they go with multiple carburetion, so they end up waaaaaay over-carbed. The oldtime 235 Corvette 3-sidedraft setup was effective, but very maintenance-intensive, and a working-condition one is outrageously expensive now.
Jerry

What have been people's experiences in fitting a 3-carb set-up (down-draft carbs or side-draft carbs) on a 216/235/261 in a 47-55 truck engine bay?

Tim

I've heard that there are some serious firewall clearance problems, at least with the downdraft setups. Don't know about the side drafts, since they're so scarce, and the Corvette restorers keep them scavenged up every time one comes available.

Here's a pic of the Corvette 3-carb manifold:
http://www.53classicchevy.com/images/corvette-sidedraft-carburetors.jpg

Jerry

Morning all and thanks for all the great input

Jerry
Nice to see you too have been down the multi carb path with the 240Z series. We raced Alfa Romeo, Fiat, Dat 510, 240/280Z and Suzuki (not bike) all with Webers...nice carb once you get them right.

The single barrel downdrafts are quite short and have similar range of adjustment to the DCOE's, not the cheapest though.

I have built a number of multi carb set ups for auto engines I converted for aircraft use so I am aware of the joys of custom designing and building intakes etc.

You are right in your earlier post...for best power and easiest route to go would be the right 2bbl...but part of my choice is nostalgia and part I want to see if I can do it.

I think combined with the right cam, again we agree, bunch more lift/not much more duration, a good header/exhaust system and a well built bottom end it should get me a strong runner to about 4500rpm and strong, reliable cruiser for the 2500-3000rpm range.

If I get lazy or impaitent...on will go a 2bbl.

Thanks everyone

Tom