262 versus 308 head

[Deleted User]

Here's one for the engine guru's among us.



My '54 coupe (ex race car), had a 262 head on a 308 block. I realize this was to "up" the compression a bit, for performance purposes, but when you look under the hood now, those not in the know would deduce that the engine displacement is 262 cubic inches, not the 308 that it really is, because of the big 262 in raised numbers on the head.



So here's the question. Can a milled 308 head, produce the same compression advantage as a 262 head? Thusly, can I have the correct head on the engine, and still get the performance boost from it (equivalent to a 262 head)?



While we're at it, I have an aluminum head too. Would this head, planed down a few thou, give similar compression to a 262 ? Is this the better choice of the three options ? ( the engine is using a clifford 4bbl manifold and carb, headers, petronix, etc. )



silverone

super651

When we were drag racing the Hornet-Jet we took a grinder and removed the 262 on the head then,we bought 308 letters from a Hobby store.( they were the same size as the 262) They were raised and chrome plated,we then painted them the same color as the head and, Presto a 308.

Also a local was racing a hornet Jet on the Dirt track and he just had to grind the 6 a little and JB Welded the 6 into an 0 to make it look like a 202 head but after outrunning most of them they found out it was a 308 ,

Hope this helps Rudy

Nevada Hudson

silverone wrote:

Here's one for the engine guru's among us.



My '54 coupe (ex race car), had a 262 head on a 308 block. I realize this was to "up" the compression a bit, for performance purposes, but when you look under the hood now, those not in the know would deduce that the engine displacement is 262 cubic inches, not the 308 that it really is, because of the big 262 in raised numbers on the head.



So here's the question. Can a milled 308 head, produce the same compression advantage as a 262 head? Thusly, can I have the correct head on the engine, and still get the performance boost from it (equivalent to a 262 head)?



While we're at it, I have an aluminum head too. Would this head, planed down a few thou, give similar compression to a 262 ? Is this the better choice of the three options ? ( the engine is using a clifford 4bbl manifold and carb, headers, petronix, etc. )



silverone

I had a 232 Head on my Hornet engine when in High School, and it was very quick. Didn't look to impressive to my friends, so I traded it for a 308 head. Boy, what a mistake! The difference in power was very noticeable, (less !) Now, I don't care what anybody thinks about a 232, I'll just take the extra power and fool them all.

[Deleted User]

Nevada Hudson wrote:

I had a 232 Head on my Hornet engine when in High School, and it was very quick. Didn't look to impressive to my friends, so I traded it for a 308 head. Boy, what a mistake! The difference in power was very noticeable, (less !) Now, I don't care what anybody thinks about a 232, I'll just take the extra power and fool them all.

Ok - but can I have my cake and eat it too"? By that I mean can I plane down a 308 head and wind up with the same compression ratio, and subsequent performance improvement, as changing the head to a smaller displacement one?

Nevada Hudson

Haven't done that to a 308 head, but some of my Hudson mechanic friends told me that it will cause more blown head gaskets. If you can find an old Clifford parts folder, it tells you the maximum you can mill a 308 head until it turns into junk.

[Deleted User]

You can safely go .060 if you go over .100 you have an ornament. And no you cannot get the same compression using a milled 308 head. It would probably be close enough you wouldn't care. But to most in the know 262 head was the racing accessory of choice so that makes it historically correct. And therefore more enjoyable in my book.



If you want the compression and 308 on the head get a Clifford head that will get you the look and the compression and with a good gasket the sealing. The old Hudson aluminum head shaved will be nothing but a pain in the butt.

Geoff

The difference is not in the depth of the combustion chamber, but in the area of "flatness" of the head above the piston top. The limit for milling the head is when the valves start hitting the spark plugs. If you really wanted to lift the compression ratio of the original head you would have to fill in the area of the head above the piston top and get it re-machined.

Geoff.

RL Chilton

Silverone-



This is certainly not my area of expertise and you have the guru's attention on this thread, but I've asked some of these same questions before to many Hudnuts.



The 262 head on a 308 is certainly an old racer's trick, and yes, it is to get the comp. ratio up where it's respectable. I know how you are gearing towards originality, but the 262 head on a Hornet was a common thing to do. Nothing wrong with people thinking it's smaller, when in actuality, you'll have much more power. People in the "know" can spot the 308 block anyway, even with a different head on it.



If it really bothers you, best advice has already been given: either grind off the numerals "262" (leave it blank or put other #'s on it) or put on a clifford head. For a regular or semi-regular driver, I wouldn't use an aluminum head, but to each his own. If it gets even a little hot and the head warps, you have a real cool paper weight (expensive one at that).



Incidentally, my 7X will have the 262 head on her. Niels has one similar on his coupe. Those in the know will appreciate what she's got and I'll educate the rest.

oldhudsons

I believe a 262 was std. equip. on the factory 7X block so a "262" IS a correct head. If you've got a parts book handy look in the "Z" section & see if the 262 wasn't offered.

As the 7X also used bigger valves I assume they also "cleaned up" the head.

oldhudsons

I was wrong in last post. 309390 was the parts # of the 7X head & from my interpretation of the parts book it would have "308" on it. No other head was offered for the 7X but 4 different cams were - probably the best was the 311040.

oldhudsons

Just remembered the nomenclature for working on heads, it was "port and polish" & I'm sure that would have been done on those 7X heads. Of course, as you probably know, the 7X came with 1/2" studs so those heads drilled out bigger than a std. one.

[Deleted User]

It is my understanding, the 7X came with a 232 head not a 262 head. The 7X 232 head has the severe usage part number 309291 stamped on it.

The flat top cam SU number was 309742.

[Deleted User]

nhp1127 wrote:

It is my understanding, the 7X came with a 232 head not a 262 head. The 7X 232 head has the severe usage part number 309291 stamped on it.

The flat top cam SU number was 309742.

Did it also have "232" on it in raised letters as well as 309291 ?

[Deleted User]

Yes had 232 on it.



The 309742 flat top cam came out in 54 and was only out briefly it was replaced with 306344A in April of 54. The 311040 came out late 53 and was severe usage its lift was .390 and was considered the Super 7X cam by guys like Jack Clifford. It actually had a better HP rating than using the 309742 cam which ran pretty rough.

oldhudsons

I just don't remember anymore but the parts book has "308" associated with the parts #. I don't recall if there was a parts # stamped on either.

I think nph is correct, the 7X used a 232 head rather than a 262.

I have a whole bunch of papers on all this, copies of original factory parts sheets, etc., that Jack Miller sent me many moons ago.

If Neil got an all original engine from John Soneff he should be able to enlighten us, or Bill A. if he looks at the head on that '51 HH he's restoring for a customer.

[Deleted User]

Be hard to tell lots of customers swapped out the heads. I have a 7X engine sitting on a stand waiting to go into my 54 HH (It will wait a while LOL) I am using it as the guide to rebuild two other 308's mine had the Aluminum 232 head I am going with a Clifford head for fun & giggles.

RL Chilton

oldhudsons wrote:

I just don't remember anymore but the parts book has "308" associated with the parts #. I don't recall if there was a parts # stamped on either.

I think nph is correct, the 7X used a 232 head rather than a 262.

I have a whole bunch of papers on all this, copies of original factory parts sheets, etc., that Jack Miller sent me many moons ago.

If Neil got an all original engine from John Soneff he should be able to enlighten us, or Bill A. if he looks at the head on that '51 HH he's restoring for a customer.

It is my understanding the 7X used the 232 as well, or so I've been told. The 262 was a "racer trick" incorporated by many. Don't know the exact differences between the two heads, but wish I did.



oldhudsons-



If you come across those papers, I would certainly be interested in copies, as I'm sure would many others. I've got some literature on the 7X's but all I can get would be helpful, as my engine is soon to be going to the machine shop.

Nevada Hudson

My 7x had a 232 head.

[Deleted User]

Difference between the heads is compression. With the Aluminum 232 head compression ratio is 9.2-to-1 or 8.7 to 1 with iron head. With the 262 head its 8.25 to 1 with iron head. I will send you an email Russ with a decoder ring and you will know.



Of course if you want to get technical its the profile of the combustion chamber of the head. The 232 has more meat in there which raises the compression. 262 less meat and the 308 less than the 262. So its all a matter of volume. 308 has more volume 232 has least volume and 262 is just right. Somewhat like porridge.

[Deleted User]

51hornetA wrote:

Difference between the heads is compression. With the Aluminum 232 head compression ratio is 9.2-to-1 or 8.7 to 1 with iron head. With the 262 head its 8.25 to 1 with iron head. I will send you an email Russ with a decoder ring and you will know.



Of course if you want to get technical its the profile of the combustion chamber of the head. The 232 has more meat in there which raises the compression. 262 less meat and the 308 less than the 262. So its all a matter of volume. 308 has more volume 232 has least volume and 262 is just right. Somewhat like porridge.

All this is giving me a "head-ache" !



Think I'll go with the 262 that the previous owner was using.



silverone

RL Chilton

silverone wrote:

All this is giving me a "head-ache" !



Think I'll go with the 262 that the previous owner was using.



silverone

Well, it all comes down to your application. In my case, I just want a little more power than stock, but not too radical. The car is going to be a driver, albeit a fair-weather, dry road lurker. I have no plans to take it to the track and race Danny Spring or anyone else for that matter.



9 to1 CR on a straight 6 is race-engine territory and street-engines have no business in that range, IMO. Last thing I want to do is re-build my engine every 5,000 miles. I'd rather do a comprehensive maintenace schedule and get 150K out of it. If I was building a vintage race car, it would be different (I'll wait for that basket-case coupe in my future that no one else wants and hot-rod it).



Every individual's application should dictate your own route. Just ask yourself the questions:



1) What is the purpose of this build?

2) What do I want out of the restoration?

3) For whom am I going to this expense and trouble?



And so on . . .

Answers to the questions you ask yourself always determine the best course of action.



Food for thought . . .

[Deleted User]

silverone wrote:

All this is giving me a "head-ache" !



Think I'll go with the 262 that the previous owner was using.



silverone

I probably should have mentioned this engine is for my '54 coupe, not the '53 convertible.

The '54 coupe is gonna be my "performance" ride, the convertible --- my "cruiser" ride.



silverone

[Deleted User]

9-to-1 would be fine on the engine. Biggest problem with that compression in the old days was keeping a head gasket from blowing. With the new head gaskets and 7X head bolts you are fine. Another consideration is octane and the gas so if you can get the good gas and no ping you are golden. You will still get high miles out of that well maintained high compression engine.



My 70 Buick Riviera had a 455 Stage One engine my Dad and I rebuilt that engine with new pistons and redid the heads it had 12-to-1 compression. I got over 100,000 miles of kick in the butt driving in that car. Oh those were the days.

[Deleted User]

Ok, ok, I can't resist -- one more niggly little question regarding these heads, and their respective compression ratios, etc.



We all know that if we're going to 7X an engine you should "relieve" the area between the valves and the cylinder to provide better fuel/air mixture flow from valve to cylinder, and this is done by milling away some of the block between the two components to make a deeper "trough" (so to speak).



So if milling a few thou off the head will up the compression a bit, will opening up the area by deepening this passage not then lower the compression ratio a bit ?



Seems quite a bit of metal is carved away in this process, and surely this must affect compression, since we're talking about the small area inside the combustion chamber being reduced by lowering the "ceiling" inside a few thousandth of an inch certainly does.



Has anybody ever done any research on this?



silverone

[Deleted User]

Exactly right Ryan relief will lower the compression and once you have decked the block and head surfaces it all comes out around the same compression ratio. As Jack Clifford said its around 8.25-to-1 and 9-to-1 and the relief will increase the breathing so that any slight loss in compression is unnoticeable.



You would be splitting hairs discussing compression ratio effects over relief effect. Combined they increase the performance considerably.

[Deleted User]

Actually there is a sales slide show where Hudson explains the Super Induction engine for the 54 model year. They go into quite a bit of detail discussing the benefits of the relief on the breathing of the engine. Its informative and entertaining.

ivanz62

Well here's my two cents worth. The 7X 232 head (stamped with its additional seperate part number) was modified in the combustion chamber area to go with the amount of valve relief in the block. The valve pocket area was opened up to match the head gasket and allow for the big 7X valves. I don't know what compression ratio they ended up with but I do know that they had some monster deep relieving of the block. The area between the valve seats and the cylinder bore sloped down toward the bore to be only 1/16" above the top piston ring.



I do believe that with current 91 octane fuel, it would be unwise to run much over 8.7:1 based on my own experience. Detonation is the source of most head gasket roubles and care to avoid too much ignition advance--especially at low RPMs is what is called for.



And any old Hudson man will tell you that the 308s did have head gasket troubles where the smaller bore 262s were bullet proof in that area.

Ivan

464Saloon

I did quite a bit of research on this when I built my motor. I did a lot of reading and talking with Randy Maas and Danny Spring, among others. I was shooting for between 8 and 8.5 to 1. The car already had the 262 head but I was doing the 7X reliefs so I needed to mill the head to get the ratio I wanted. I hit the number of 8.4 to one BUT the motor only ran 20 miles before I blew a hole in the head. I was so focused on compression that I didn't take into account the integrity of the head and apparently got it too thin. I really wanted an aluminum head so I replaced it with a milled one from a 51 308 I got from Lance Walker. I didn't want to mill it too far so I now have 7.7 to 1. Higher than stock but not much. It will creep up as carbon builds up so you have to keep that in mind too.There is a fine line between flow and compression. Remember with a flathead if you mill the head to get compression you also cut the flow down over the valves. Relieving helps this but then your compression goes again. One of the reasons the OHV was invented. Ultimately, filling in the dome will increase the compression without milling the head thus weakening it and cutting the flow over the valves. It is costly and labor intensive though. The Clifford head is already made this way but at 800 a piece it is something you have to think about. Hope this helps.