The Stovebolt Site Forums The Shop Area Engine Shop 848 head

what year did the 848 head come on the 235 motor, and did it mattter what the motor application was? How do you identify the 848 head? I have a 51 or 53 235 that was an original powerglide motor and am wondering if i have an 848 head. i am installing a 60 261 in my 46 pu and would do the head swap for the added compression. thanks.

The most common 848 head found and used is the head from a 58-62 235. The head is identified by the number cast into the head on the left front corner as it sits on the engine block which ended in the numbers 848.
Find one of them and you got it!
Joe

thanks joe. somewhere along the line i had heard or read that you need to drill out steam ports? or something needed to be modified on the head for it to work on the 261. is this true for the 58-62 head? i was kind of under the impression that it was a bolt on and go swap.

Yes - the steam holes! I almost forgot. Thanks for the reminder. Using the 261 head gasket, you do have to drill the steam holes in the 848 head.
Joe

I just pulled an 848 head with a date code of K-1-3 off a 235 which makes it an early '54 model year I suppose. Not sure what the application would have been but that would be the first year for the high compression head I believe. You can identify these heads from the "848" in the last three numbers of the part number cast into the head.

thanks again for all the info. would anyone have a picture of the afformentioned "steam holes" so i might have a reference when i get the head and am ready to do the work.. thanks

Look at the photo on the bottom of page 16 of the Frank McGurk article in the May 1955 HRM. The steam holes were not mentioned in the article. Was Frank not aware? I know that I was not aware in August of 1958 when I put my 1954 235 head on my first 261. Maybe that was why it ran hot and was hard to start when hot.

Hoyt

I've always been told that the 848 head was the stock head on a 235 from 58-62. But, they were also sold as replacement heads. I'd be inclined to think that an 848 head on a 54 235 could or would be a replacement head. I don't think I would be looking at 54 235's for an 848 head, but instead I would look at the 58-62 models.
Joe

The first 848 high compression heads were cast in 1953 for the early Corvette.
The one on my 261 has a casting date of Feb'54.

There was also another lower compression 235 head in 58-62 with a casting number ending in 913.

Corvette Head Casting Numbers (235 cu in)

1953 - 3836066

1954/55 - 3836241

http://www.corvette-world.com/corvette_1953-1967_Cylinder_Head_Casting_Numbers.php

http://willcoxcorvette.com/product_...;osCsid=3375546612eec3eb41c8328fbdad689a

http://members.aol.com/thecorvetteplace/53vette.html

I didn't know this either, but learned from corvette guys that although the casting numbers were different, the heads were identical to the later 848 casting with the same compression ratio.
1954 was the first year this higher compression head casting got the 3836848 casting number.
The 29-57 master parts catalog also shows the 848 head as replacement for 53-57 corvette 235s.
These later heads also had more nickel in the alloy, which may have given them a different number. Just guessing.

The 1957 Chevrolet Master Parts catalog indicates that the 848 head unit was sold (for $47) as the replacement head for 53-57 235s, which includes the 18-bolt 235s. The catalog shows a different part number for the replacement head for a 53-55 Corvette six, but does not give a casting number. The catalog also does not give a casting number for the replacement head for a 261.

By the way, a knowledgeable acquaintance has told me that he has cc-ed the combustion chambers of an 848 head and a non-848 head from a 235 and they measured about the same, with the 848 head actually being slightly larger. Does anyone have any different information?

Hoyt

Here is a link to the page from the master catalog showing the 848 casting# for corvette 53-57.

http://chevy.oldcarmanualproject.com/1929_57chevyparts/57cmpc0136.htm

My 261 head casting# was 3836850 but it has lower compression than the 848 head.

Side by side comparison of the 848 head with others shows the smaller combustion chamber.
The shop manual of a 235 with non-848 head shows 7.5 compression ratio. The 848 head shows 8.25

A bored 261 with milled 848 head can give around 9.5 cr without further mods.
Mine came out to 9.3 and it burns lean and clean with 91 octane gas with plenty of torque and about 20 mpg on the freeway with a 3.55 rear.

On the road again,

Thanks for all the information.

Most likely, based on your postings, it seems the original 235 Corvette heads were high compression heads, similar in casting/design to the 848 heads. If that is the case, one major difference would have been that the 1953 Corvette 235 head would not have had the 4 valve-cover bolt-holes that would be found in the 848 heads?

I have an 848 head that I will one day put on a 1960 261 or on a 1954 235, depending on which engine is in my Suburban. The "folklore" value of putting a 261 camshaft and a 848 head on a 235, is now a much more interesting story.

Tim

I think all threaded holes are drilled and tapped later into the finished casting.

It appears the early corvette 235 cam and head setup was the model for the following 58-62 stock 235s.
All they need is a dual intake and exhaust headers to wake them up...

Interesting also that the master parts book lists the 261 cam for 53-55 corvettes as well as the 848 head up to 57 corvettes, despite 235s no longer being used after 55.

Did the stock 1958-1962 235s have the same cam as in the 261 (the 53-55 Corvette 235 cam was the same as the cam in the 261)?

Yes, the 57 master parts catalog shows that 235 trucks used the 261 solid cam, starting in 1956.
Cars starting in 1954 used a hydraulic cam with the same power curve as the 261 solid cam.
They had about 230 duration.

I went with a 254 duration in/ex cam grind for my 261 bored .060
The larger displacement can handle more duration and lift, without getting poor idle and low rpm performance.

On the Road: your 52 has a 54 grille....right!?

Yes and 54 front fenders as well.

Fellows, I will agree, yes, there were some "other" higher compression heads made and used by Chevrolet throughout the 53-62 run. Not all were "848" heads, some had other casting numbers, BUT for the sake of walking thru a bone yard and looking for a high compression head, you will never go wrong if you pull a head with the casting number ending in "848". If you want to look for others, fine, but considering we know the "848" head is the one we want and considering that the "848" head was a replacement head, maybe the only replacement head used by Chevrolet, I think that the "848" head is the animal you want to hunt. If it sez "848" on it, what else could you want? To go a step further, when I was last at the local bone yard, just walking thru, I saw about three or four of them on engines with the hoods raised up. They are easy to find and quick to recognize.
Regarding the 261 cam, yes it is the same cam used in the 53-54 Corvette 235 engine. The cam fits and works fine, BUT that cam is not the best choice out there, considering the fact that they are not that easy to come by without a partial engine tear down. Even in a 261, you can do better with several other aftermarket cams that will help your engine breathe even better and also give you a good rump-rump sound. I'm runing an Isky track cam in my engine. It sounds good and moves along nicely, especially with some higher RPM's. It's a good in town on the street cam because there is good low end power on it. It works very well on the road,also. There are some others out there that I don't have personal experience with, but Patrick sells them. Another I do like is a McGurk cam. True they don't make them any more, but the specs are available to have your stock 235 cam or 261 cam reground to match the McGurk specs. Very good performance and great rump-rump.
I'm sorry - I didn't mean to ramble, and I am just trying to help. I'll shut up now!
Joe

Are the 1955-57 848 heads different from the 1958-62 848 heads?
What would make the 1958-62 848 the most common and used head for the 261?

Joe,
Any idea what the lobe lift would be on those performance cams? I'm wondering exactly how much more lift a performance cam would have had over the 261 cam I bought. Any idea why is there no performance cam specified for the 261 exclusively?


BTW,

GM Canada put the 848 head on the Pontiac 261 strato-six from 1955-1962.

According to old postings on the VCCA chat site:

The 1958-82 848 head produced an 8.25 to 1 compression ratio

The earlier (1956-57) 848 head produced an 8.0 to 1 compression ratio

I don't believe that GM factory castings with the same casting# were different from each other.
I compared all my 848 heads and they were exactly identical.
Btw: The difference from 8.0 to 8.25 cr would come from the type and thickness of the head gasket or as little as .02 milling.

The master catalog shows only two heads available for 1954-1962 235s:
3835913 with 7.5 cr
3836848 with 8.25 cr

I drove my late 235 daily with the 913 head for years until I switched to a milled 848 head a few years ago.
The differrence is noticeable in power and sound.

Some info about cams and grind patterns...

Delta Cams in Tacoma WA has several different 235/261 cam grinds to choose from.
Patrick's and Langdon's cams are from Delta.
Delta will regrind your existing cam to any spec for $50.
Very good phone customer service.

They recommend 254 duration max. for 3500 rpm and less, either 235 or 261.
The same cam in a 235 will move the power band a few hundred rpm higher compared to the 261.

McGurk's road and 3/4 race cam grinds always had longer duration for exhaust with shorter duration for intake.
They were all great at high rpm, but even the milder grinds lacked power at the lower rpm range.

Delta offers a similar but less extreme asymmetrical grind pattern with their popular 'Bulldog' grind giving much better low end torque.
Their cam grinds have different valve event timing with less overlap than stock and early performance cams.
These guys have ground cams for decades and really know how to get the best performance from these engines.

Cam grind depends on the rpm range the motor is supposed to give most power.
For mostly city driving and hauling, the stock cam grind will give highest torque.
For frequent freeway trips, a mid-range cam gives better performance.
Race cams get maximum hp starting at 4000 rpm.

The 261 link in my signature has some graphs I made showing the dyno results of the famous McGurk Article in Hot Rod magazine 1955.

Very interesting thread!!

So, I've got a 848 head on my '54 235. How can I tell what year it was produced? I know it has a date code on it but how do you read it?

Thanks

The date code is between the 2nd and 3rd spark plug on the passenger side.

There is a letter followed by 2 or 3 numbers.
The letter's sequence in the alphabet is the month, next number is the day and the last number is the year's last digit.

Examples:
B 47 = February 4th, 1957
D 232 = April 23rd, 1962

Both of my 1954 235s have 848 heads on them. Yes, I know where to look.

One of my 1954 235 blocks has an 848 (3836848) head on it. That had what I guess is a date code 8 16 8, so I think that someone put that head on the block after 16 January 1958 (is that how the date code is translated)? (That code is under the valve cover on the top of the head, a little to the right of the block casting code).

The numbers under the valve cover are not casting date codes.
The date code is right between spark plug 2 and 3 on the outside.

At least that is what some have posted on the inliners and chevytalk forum.

Thanks. I'll check it out. Where are the date codes for the block?

Here are some photos and questions about a 261 engine's codes.

I'll add pages/photos for 235 engines.

Ok - I'm just reading along. Looks like you guys pretty well have this figured out.
Joe

OK, we might be going in circles, but maybe we are also learning something. Look at this article by Bob Adler - he is an expert. He shows the head casting date on the top of the head (under/inside the valve cover) as shown in the link I gave above.

It would be nice to see photos of 40s, 50s, and 60s head and block date codes.

The spark plug side date code is the one used by anybody I talked to so far.

I have owned four 235 heads and one 216 head where that outside date code matched the history of the head in all cases.
Two heads where still on the original block and both block and head date codes were from the same year.

If I ever find out what the code inside the valve cover means I shall post it here.

How do you decode the casting codes on the plug side (for example, on the head in my link above)?

Here is the photo at that link.

B 61 = February 6th, 1961

One interesting thing is that all codes on the spark plug side, I have seen in person and online, always started with B.

I also noticed that the last two digits often simply show the year.
Heads I owned were B 62, B 58 and B 54.
However I also have a 'B 47' and remember seeing a 'B 26' head...

The numbers inside the valve cover do look exactly like the block date codes, don't they ? Who really knows...?
One thing is certain - if the last digit would be a '3' on a 848 head, we know it isn't the casting year.

In any case, the last digit on the spark plug side of my heads always showed the correct year, if the history was known.
And the casting number is what really makes the difference in compression ratio and nickel content, regardless of the year it was cast.

Two people on the VCCA site (and Bob Adler) confirm that the head date code for high-pressure 235/261 engines is under the valve cover, as shown here.

All the codes between spark plugs 2 & 3 on my 235/261 heads start with a "B". I doubt if that is a month code.

Tim

I have an 848 head on my 1956 235". The engine was rebuilt before I got it so it may have been added later.

Thanks for the update.
Makes sense from a visual aspect.
The 'stamped plaque & screws' date code under the valve cover looks exactly like the one on the block.

The date codes between the spark plugs is info I got from the inliners and chevytalk forums.
The sellers of all three 848 heads I have also used that code.