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

Ok guys, I have been searching the web for a bit now and although I have found some very usefull info I crave more and I am sure that there are a bunch of others that do too!

I would love to see and hear about engine builds that are currently going on and ones that have been built. tried and true and any specs that can help. Also links to any good info would rule!!! lets see those performance goodies and hear how well they work. Lets see some cam specs and hear about the results. Some back yard tech would be awesome too.

I have really been looking into definate answers for head milling. and what guys have actually done and had work. I hear a lot of differeing oppinions but no real word on "hey I did this and it worked"

Should the valves be sunk in as much as the shave?????? I realize cam profile has a lot to do with it but what have you done and had work???????

Of course 261 stuff is welcomed as well.

I would call this the "Mother of all 235 inline 6 threads" but that name is copyrighted by Jefferey James. Damn him and his great posts.

So lets get this ball of wax moving shall we........

 

And here is my first contribution to the pot. A great article on why you need to "Heat" your intake manifold. It has been covered before but I would like to compile it all here if we can.

http://stoveboltengineco.com/index.php/2010/11/tech-tips/why-you-need-to-heat-your-intake-manifold/

 

Which 235 do you have. There are at least 5 different ones. Early one looked like a 216 with the tall side cover, then 1950 235 that came in a power glide babbitt rods, then the insert ones with pressure 1953, then 1954 235 with 4 bolts holding on the valve cover, the 1955 with the 3 bolt water pump.

 

If the compression is raised by milling the head or domed pistons, the valves must be sunk accordingly so they don't contact the pistons. Another way to gain compression is by filling the combustion chamber.


For me and my 261, here's my plan. Keep in mind, I am not building a race engine. I want something reliable for the street with occasional track type performance. More than mild but less than wild. I'll be rebuilding my engine soon and this is what I'm planning...

'58 261 block with 235 848 head. The block will be bored the next size up increasing displacement. Aluminum pistons for less reciprocating mass. The head will be milled a little with the valves sunk the same, raising compression a little. 3/4 cam for better breathing but decent idle. Fenton split headers with dual open exhaust for better breathing. Vintage dual point distributor for more reliable spark at higher rpm's. Triple Offy intake with three Carter W1's. Aluminum (hard to find) or shaved factory flywheel, again for less reciprocating mass (rotational inertia).

I already have the engine combo in my pickup and have collected and installed a bunch of parts. I'm only missing the dual points dizzy, cam and a lighter flywheel (besides installing the carbs and the rebuild coming soon).

A good reference for souping stovebolts is the old book "How to Hopp Up Chevrolet and GMC 6 Cylinders" put out in 1951. Although dealing with the older stovebolts, the theory is very solid and applies well to the later 235 and 261. This is available as a reprint from Amazon. I heartily recommend this book. Also, a killer article from May 1955 Hot Rod magazine, "Soup That Chevy". This has detailed dyno tests at each step from mild to wild. You'll have to search for one of these, it too me a year to find a hard copy. Feel free to save my images in the next post.







This combo should do pretty well to surprise some v8's.

 

Soup That Chevy! (thanks Squirrel!)...























/thread

 

This combo should do pretty well to surprise some v8's.[/QUOTE]

Yes it will surprise some V8s. Back in 1954 I was one of the first to run a 261. It was in my 1951 Chev hardtop. It beat many a V8, the only one that gave it a hard time back then was the Oldsmobile V8 coupes. It was a stock 261 with 1953 235 head, and a vette exhaust. It did have different gears in the three speed transmission.

 

Subscribed......future info for my 54

 

Now this is what I am talking about. a very strong start indeed. Thanks Turd that rules...and your Combo sounds like it will be a lot of fun in that troka of yours!

I have a 56 235 with an "848" head. it is a runner and I dont plan a rebuild but I was gonna regasket before installing. This is why I wanted to do the head cause it will be off and a great time to do so. I do also plan to "Chop" my flywheel for that little extra bump.

Still I havent heard a "Yes Eric you dumb ass if you mill the head and dont sink the valves they will hit when you use that 3/4 cam" But I have heard people say you need to and not.so i am back to confusion. I assume that if you dont sink em and can get away with it, it will net a slight bit more bump in compression. correct?

That book on hopping up 6's is good but a bit vauge in some areas. plus there have been a few more tricks to come along since it was published.

Thanks again guys lets keep this goin.

 

Two of you guys are running a 235 head on your 261's. Is it better than the 261 head? Or just what you had. My 261 is bone stock, so far...

 

It was my understanding from reading that book and my buddy's hot 235 that if you shave the head, you must recess the valves. Otherwise they will hit the pistons. Likewise if you use domed high compression pistons, the valves would need to be recessed.

I have a 235 "848" replacement head. These are factory replacement parts from "back when" for warranties or breakages. The "848" designation is the important part of this equation. This particular head on the 261 will bump up compression by approximatly 1/2 point. If you can find a good one cheap, its worth the swap.

 

in the magazine article that terd posted there are more than a couple references to recessing the valves. I would err on the safe side and sink em!

and honestly you'll know for certain the first time you turn the engine over!

oh and a side note that I learned the hard way,
MAKE SURE YOU USE THE STOCK COIL BOLTS!

I used some fancy stainless ones that were less than a 1/16 too long and for some ding dong reason GM made one of those holes go all the way through.

yeah, so uh, bent pushrods, and a whole bunch of sucked up upholstery and a pretty expensive "fresh" 235 that sounded like a tractor/helicopter later, it turns out that the bolt just gently rubbed the pushrod and one got a weak spot and broke and bent 2 others.

scared the nine hells outta me!

I thought I had just wiped out a brand new fresh engine...

 

Unfortunately there's no stock answer to your question due to several factors:

Has the block been milled before?

Has the head been milled before?

Cam lifts variation

The only real way to get the answer you need is to mock up the engine with the cam you're planning on running, pushrods, lifters and head in place, and put some modelling clay (or Play-doh) ontop of the piston. Rotate the crank slowly and if you feel interference stop!

If it rotates fully you can take the head off and measure the squished clay to see how close you are. It will give some idea as to how much to mill off of the head and if the intake valves need to be sunk.

There are probably way better explanations elsewhere for this but it gives you the general idea.

 

Just finished my 235 rebuild for my 41 Chevy. Ran it on the dyno last Fri to break in the cam and see what kinda power it had. Several friends and buds on other forums asked me to start a blog with details about the build along with pics. The blog is started with about 4 entries. Haven't put up the engine build details yet but you're welcome to take a look and follow along if you want to. No disrespect, but I know some folks like to make wise ass comments just cuz they can hide behind a keyboard and monitor. Please keep the foul language and Mr. know-it-all stuff for here on the H.A.M.B. not as a comment on my blog. Besides, I'll just disapprove your comment if I don't like it anyway.

http://41chevy2drsedan.blogspot.com/2011/01/why-blog.html

 

My 52 Bel Air is running a 54 235 with an 848 head. I believe the 848 was introduced in the 56 model year. My motor was bored 60 over and the head was shaved. I'm running a 3/4 cam and have no clearance issues with pistons to valves. I have to believe as long as the valves are up inside the plane of the deck of the head you would never hit? I got to think that the machine shop that does the machining should know the answer to that question. I also had my rotating assembly balanced, which made a big difference in the way the motor runs. Very smooth.. I'm also running a Tattersfield dual intake with a matched pair of Carter WA 1 carbs. My intake is heated and I'm using water and not hot air from the Fenton headers.

 

Does anyone remember a three carb manifold for the 235 that was three individual manifolds connected with balance tubes. Each manifold mounted a two barrel Stomberg 48. The only identification on the manifold that I can remember was the word "tensalloy or tenzalloy" which probably referred to the material used. I had this manifold on a 53 Chevy in 1960. I bought the manifold used. Any comments would be appreciated.

 

Holy shit... I totally did that!!!!!!! Like 10 years ago with my original 235. i hit it just enough to cause a rough running issue. now that I think about it I don't remember how I figured it out. it's crazy the things you forget about.

 

SO it looks like my answer is to set it up and get out the play-doh or suck it up and pay the extra to sink em in. I think I will do a little port work then too.

That 52 in your avatar looks great.. I would love to balance my rotating assembly but it will have to wait untill I either get another inliner to build up or when this one gets tired and I have to rebuild it.

 

Sounds like a Harper. I think Heathen on here had one for sale a while back with Strombergs. Killer looking set up!

 

Sounds like a killer set up. Valve clearance also depends on how much you mean by "shaved". Just having a head trued is one thing. hotdamn had his shaved .0125". That's 1/8". No way around recessing the valves on that one.

And incidently, hotdamn has one of the hottest 235's around. That thing is FASSST! Quick details are bored, shaved head, Howard rough idle cam, McGurk intake w/2 Cartr YF's, Fentons, engine painted candy gold. Its a piece of work for sure! His engine is what made me fall in love with the stovebolt.

 

http://www.youtube.com/watch?v=2dPT1j1OLfk

This is my motor on the break in stand. It has an original edmunds what they listed as 2 v8 carberator manifold (holly 94s) I got a little fancy with the tubing. A delta 265s cam and sure seal hapless rings. We smoothed the block and striped it. Other than that it is stock compression and stock distributor.

 

stop it terd you're making me blush!!!

My 235 is peppy but I would still like to do a whole lot more to it.

if I had to do it all over again I would definitely build a 261 and as the gentleman with the sweet 52 hard top did, get it BALANCED!

stovebolt harmonics suck!

get it balalnced and track down a aluminum flywheel ( for some reason I am drawing a blank on the name... I know it like I know my own?)

and possible one of those expensive fluid dampeners.

makes everything so much smoother.

I have learned a great deal from mine.

dont get me wrong I love it and it runs like hell I just have an astronomical amount of moola tied up in it and could have gotten a little more bang for my buck with better research...

now that cam...

I think I read somewhere that the howard rough idle cam is something like a 292 lift... pretty hoss.

but make no mistake about it, it lopes...

know that when you are sitting at a red light your rearview will vibrate a little

 

Wow! I had no idea (while worshipping at the alter of Flathead V-8s for 60 years). Did everybody notice the numbers that came in at 4000-4500 R.P.M.in the last 3 tests?

 

Subscribed.

hotdamn why would choose to do a 261 next over the 235. Is it just for the extra cubic inch .

Also does anyone have any tricks to free up a 235 that has been sitting with the head off for 10 years or more. I have put multiple oils and penetrant on top of the pistons for about a month or more and can't budge it.

 

Some of the things that we did to these engines;
-angle milled the head .060 to the plug side,
-off set the head to the manifold side to get more of the chamber over the cylinder,
-used a balancer from a sbc for smoother high rpm use,
-used an Al flywheel,
-cut pistons to reduce weight,
-pocketed pistons for intake valves,
-used a carb jet to restrict oil to top end,

This should give you some things to think about.

 

Please elaborate on the hows and whys of this part.

 

Subscribed.

 

That is cool stuff that you did. Do you have any pictures or more elaborate info????? I am really curious about the angle milling. I totallo get it but would love to know all the details.

 

I was thinking that same thing Terd.....

 

Zero decking gives the same result as milling the head but without polluting valve geometry and for true performance builds use a torque plate.

 

That yellow book that Terd posted is by Roger Huntington. It's still available new. There is also a Speedy Bill book (still available) that has the same basic info as Huntington's, but also includes GMC and Buick inline motors. Both of them have excellent info on all the specs, and what you gain by doing each step. Basically, you get the biggest bang for your buck by improving breathing: adding carbs and headers. After that, you'll pay a lot (or spend a lot of time) for very little pay off. Those details are limited to what was available in 1953-54 though.

I have a 261 that will be bored and stroked to 290 using different rods and Caddy pistons and an overbore. I also have a 2x1 Tattersfield intake, Carter W-1 carbs, a split manifold, and an 848 head for a 0.5 increase in compression. One of these days I might actually get around to building it. *sigh*