The Ultimate 235 Hop up Thread.......

There was a guy running a '40 Chevy coupe at the Jalopy Drags that hammered the car all day long. He was running the original column shift drivetrain in the car. He builds the transmissions himself. I wish I knew more about the particulars but maybe someone on the Hamb knows him and can get him in this thread. His knowledge about the early 6's and drivetrains would be invaluable.

 

When you buy pistons get the ones with the lump on the top to raise the compression, and get them with a compression height that will give you as close to zero deck as you want.

As to sinking the intakes, why? Your only hurting intake flow. You want as long a short side radius as possible. Like I said, look at the pictures in previous posts, it will give you the idea on the short side solution.

The combustion chambers on these heads were designed for an operating range in the 2k to 3k rpm area. If some one would produce a head with the chamber over the cylinder much like the GMC head we would all be happy. But they don't, so we are left up to our own abilities.

Carburation is an area along with exhaust where the most change can come from.
I have tried all the possibe combinations on the intake side. Unless you build your own there is not one with a long enough track to make full use of the torque of these engines. We added a minimem of 4in to the runners of 3 x 1 intakes for best results in out put.

Exhaust should be studied in the area of tube size per port and in how they are joined together in thier collectors and at what length. Do Not make them too short. Pipe size after the collector has a big effect on engine output.

More food for thought.

 

I had the block deck milled about .040 on my other 261 to get the piston about .020 down in the hole for decent compression.I didn't go for less deck clearance because of possible intake valve to piston clearance.Decking the block is about 100 bucks,set of stock type flat top pistons are in the 100-200 buck range.The stock pistons will survive ok if you keep the RPM's to 4500-5000.

Custom pistons can be very expensive,do you have a cost for them??? Set of 6 forged pistons from Venolia etc is 500-600 bucks. The bump used on 235 type heads to raise compression looks,in my opinion,like it will mess up combustion flame travel.

 

Great thread. I love driving my 50 Chevy 3100 with the 261. Mine was cast in late 1959, it also has a 235 head. Was this a old trick back in the day for more power? I was woundering if anyone knows how to swap a 5 speed behind the 261. Currently my truck has a 1955 1st series 3 speed trans and 1955 rearend.

 

So I guess a lot of talk on here about bumping compression on a 261 but what about the 235s? I got 235s up the wazzoo but no 261s and don't feel like tracking one down right now. Even the 54 1 1/2 ton truck I got that should've had a 261 my grandpa informed me they swapped a 235 into it.

My 54 needs the 235 replaced and wouldn't mind doing a mild performance build on it. I already got a Offy 2x1 and fentons.

 

I was wondering the same thing seeing how it is titled "ultimate 235 hop up thread"!

 

Considering that the 261 is the same motor with more bore, it just makes sense.

All the 261 stuff applies to the 235 as well.

It's like 305 vs 350. If you can get a 350, why bother with a 305?

GM was a little more friendly when it came to handing out 261's up here in the Great White North.

Shawn

 

We used pistons with and without the lumps and didn't see any difference in burn patterns or timing requirements as long as there were no sharp edges.

As to price, I guess today it might cost more because there are fewer requests for the high compression ones. Although they are still out there on request.

 

Hey Dude I was just reading a magazine today that had an add for an adapter plate to go from a 235/261/216 to a chevy s-10 5 speed. Il see if I can find where I saw it and il let you know who makes them.

 

found it.

http://hotrodworks.com/catalog/index.php?route=product/product&path=44&product_id=110

 

is this a all chevy tread? is gmc engines questions wellcome here?
i have a 1957 gmc 270 4-speed,i drive it almost every day in summer .i like the engine and is there any aftermarket parts for this engine,i want to build a spare engine with extra hp and strength.
ken sweden

 

http://www.patricksantiquecars.com/chevy_parts.html

Patrick is a heck of a ncie guy and very knowledgeable.

 

A Canadian Pontiac with a 261 was rated at 148 hp and the Corvette 235 with triple carburetors, dual exhaust, etc. came in at 150. Add up the cost of your multi carb system, exhaust headers, cam, etc. and remember the 261 makes that power without mods and costs no more to rebuild than a 235. Soooo,,, a 261 block is the ultimate 235 hop up.

 

I didn't need a adapterplate on my 235. I run a '58 235 in my '51 chevy with the head planed and had no problems with valve interference. I also split the stock exhaust manifold and use a clifford intake with a holley 390 carb. It runs pretty smooth but I think has lost a little of the low end grunt it had (it could be because of the 4 barrel carb or maybe the rear axle ratio). As for the 4speed I bolted a saginaw to it with no adapters or anything. I only had to change to an open drive rearend instead of a troquetube. I believe all you need is a truck bell housing, Chevy made the manual transmission bolt pattern the same so you can use a 4-speed saginaw, muncie, and I think the t5 but I'm not positive on that.

 

This isn't necessary if the bellhousing and transmission have the same bolt pattern.
Any '48-62 truck and '55-62 car bellhousing is going to have the same wide bolt pattern as the '83-92 S10 or Camaro T5.

If using a T5 with the 7 1/8" input, then some trimming of the input and bearing retainer will be necessary, and possibly some grinding off the back side of the clutch disc hub or use a thin spacer between the trans and bellhousing.

 

I started with an all standard Canadian 261 out of a 1960 Pontiac, Canadian 261's were never full pressure so I did the conversion ala Inliners tech tip. Then had block cleaned and machined; bore .040, crank .010/.010, milled block .010 and head .070 recessed intake valves .070. Had hardened seats installed for exhaust and increase exhaust vavles to 1.6 (sbc) because I was going to GM TBI from Astro Van 4.3. Fenton dual exhaust Clifford 4v intake with TBI adaptor. Clifford 264 Hydraulic cam, kit and Aluminum gears, degreed cam and valve clearance checked. Machinist friend adapted 4.3 distributor and I rewired the 747 computer. port matched all ports and cleaned up the intake bowls and the also the bowls for now larger exhaust valves. Put it all into a 1950 Chevy Fleetline,used Pontiac bell housing and adapted T5 with 57 Chev 3.36 diff. Had Tony Sacher from Choice auto in Saskatoon reprogram the computer to Standard tranny specs and some other tweaks to deep for me to understand. Runs great goes good cruise easily at 70-75 with reasonable mileage.

 

You know I love the Jimmy sixes. And that info does apply somewhat here. Keep it on topic and I think the Jimmy's can fly here too.

That said I am still real interested in all the Chevy stuff we are talking about here. There is a lot of good info. I wanna see some of it put to the test. You guys have any Dyno sheets or real world numbers and experiance from your cars??????

 

Pics. of your fifty with the 261?

 

how to hop up chevrolet and gmc 6 cylinder i have the book.and i looked at patricks home page good stuff.trying to find a good block and do it like the did in book 1951.but i think i vill go with 4 barrel carb.and try to get a overdrive gearbox.ithink the pontiac v8 have same bellhousing as 270engine.then you have parts up to 1979
ken
sweden

 

+1

Subscribed.

 

Not exactly traditional but I'm playing with this right now:

 

You know as untr4aditional as it is I think it fits in just right. Some punk ass back in 1954 probably tried that exact thing then. Who knows how many really cool shit was built and did very well just to be put in a shed "for the right car" and it never materialized...

Id like to see more of it. I have always dreamed about turboing an inliner.

 

I have a 235 with powerglide still bolted to it FOR SALE if anyone wants it.

 

Subscribed.

 

The motor you see in the pic is a 235 I'm using for mockup.

The turbo system is being built for a 261 that is in my 1958 Pontiac Pathfinder (Canadian car) She's very rusty but still there enough to drive. I figure I might as well have some fun with the old girl before she returns to the earth.

These engines have a forged crank, forged rods and steel-strut pistons from the factory. Combine that with the low compression and you have a decent motor to add a turbo to.

The turbo is from a 1978 Buick Regal T-type, so is the carburetor. The intake plenum is from a 1980 Turbo Trans-Am (I have a few of these cars).

The Buick motor is a 231 so the carburetor tuning and turbo size should be just about perfect.

I'm going to keep the boost low, about 6 psi, to see how everything holds up. If it's all good, I'll see how it does with a little more.

The oil feed for the turbo is going to come from the oil filter, the turbo return line is made from 5/16 steel hard line and dumps into the valve cover.

The carb is a proper, turbo quadrajet. The enrichment circuit is ported outside the carb so it can see manifold pressure instead of turbo inlet pressure.

I hope to have everything together next month.

Shawn

 

Wow lotek that is really cool and really along the lines of what I have thought of as far as how to make it all work. id like to see it run.

 

Back up to the top

 

Thanks Man !!!! It appears to be a good way of doing the swap, and keeping the stock 3:90 gears out of the 55 1 st series rear.

 

Thanks for the reply. I believe the posting from the guy down under had something useful, that I may use.

 

How about Fuel Injection.... has anyone tried that?.... how?