higher compression for a '36 Terraplane
terraplane8
Senior Contributor
Looking at the easiest way to bump up the compression, which is around 6.25:1 standard - don't know what actual ratio my car is though as the head may have been planed sometime in its life. At the moment the cranking compression is 80lbs per square inch maximum which seems very low.
Has anyone here put on a Hudson 112 head? On my calculations using a head that gives 7:1 on a 112 will give 8.5:1 on a 212 standard bore which seems too high. To clarify my motor is the single throat carb small port model.
I'm shooting for around 7.25:1, anyone here have any experience with what is the optimum ratio without overtaxing the bottom end?
Also is there any way to put on a vacuum advance distributor to improve the cruising fuel economy?
I'm also awaiting the feedback from the other member who is putting a split exhaust manifold on his 212 and would also like to do that as it seems the Hudson exhaust manifolds are somewhat restrictive.
It should perk up the performance and enable it to get up hills better before changing down to second and even first on the very worst corners. The hills are very steep, in fact they are mountains. Also a friend has a '38 Ford coupe with a twin exhaust Mercury motor and its a bit embarrassing getting left behind so badly. I want to at least stay in sight!
Has anyone here put on a Hudson 112 head? On my calculations using a head that gives 7:1 on a 112 will give 8.5:1 on a 212 standard bore which seems too high. To clarify my motor is the single throat carb small port model.
I'm shooting for around 7.25:1, anyone here have any experience with what is the optimum ratio without overtaxing the bottom end?
Also is there any way to put on a vacuum advance distributor to improve the cruising fuel economy?
I'm also awaiting the feedback from the other member who is putting a split exhaust manifold on his 212 and would also like to do that as it seems the Hudson exhaust manifolds are somewhat restrictive.
It should perk up the performance and enable it to get up hills better before changing down to second and even first on the very worst corners. The hills are very steep, in fact they are mountains. Also a friend has a '38 Ford coupe with a twin exhaust Mercury motor and its a bit embarrassing getting left behind so badly. I want to at least stay in sight!
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Comments
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You can get a supercharger from a Railton . It will be a Centric vane type . In a Railton I believe the 212 was rated at 140 hp. Now only to locate such a thing. How about the head off a 175 CI motor. Would that give you what you want? I will pose this question to the more aged HET members. Didn't Steve Sessions hop up a 212?0
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I didn't quite want to go that far!
I am interested in any information as to how to significantly improve the performance of a 212. Hopefully some of the more aged members can rack their brains as to how they hosed off those V8 flatheads in the 1950's!!!! Compression seemed an obvious start, the manifold split also makes sense. A 30 degree valve job and some attention to valve head unshrouding and using the thinner valve stems/guides wouldn't hurt either.
I've got an ET8 that does perform very well but I also want to get the T6 humming and working as efficiently as I can.0 -
Some people have put the '112' heads on their 3X5 engines to improve performance. One fellow with a '39 (into which the 3x5 has been installed) put a 112 head on it. However, I can't give you any further particulars. Maybe he'll jump in here, with some info.0
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Walt Mordentti and Geoff Clark I would think would have some answers. Possibly Randy Maas, but he may only be up on the later big six.0
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I've never checked it ... will the '37 and later intakes go on the '36 block "gracefully"? If so, the later 2-barrel intake and the dual exhaust should have a significant effect.0
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Terraplane8
I think you are fighting a loosing battle trying to keep up with a 38 Ford with his dual exhaust flathead. He has a lot of speed options you dont , his are limitless yours are limited as you know. Just by cubic inches your already in trouble. I would like to know the difference in combustion chamber size between a 212 head and a 175 head are, i not thinking at the time put a 212 head on a 175 motor not thinking about a 212 head having a larger comb. chamber and lowering my comp. ratio.0 -
The 112 engine (175 cubic inches) has the same 3" bore as the 212 cubic inch engine.
Therefore, unless the combustion chamber of lthe 112 head has a different shape than the 212 head, there is no increase in compression ratio.
Perhaps you are thinking about how people put a 232" stepdown engine head on a 262 engine to gain an increase in compression. That swap does increase compression because the 232 engine has a smaller bore diameter than the 262, thus there is an area of the combustion chamber part of the 232 head that is flat at block height (minus gasket width), rather than being dished out.
If you have 80lbs compression pressure, it is low. Sounds like your engine is tired. A rebuild of at least the top end of the engine (rings and a valve job) would give you a good power boost. You could do a 3 angle valve job, and mill the head a small amount (no more than .060") for an increase in power. But ask others for advice on how much to mill the head. Put a Smithy or glasspack muffler on, and that Terraplane will haul right along.0 -
junkcarfann wrote:The 112 engine (175 cubic inches) has the same 3" bore as the 212 cubic inch engine.
Therefore, unless the combustion chamber of lthe 112 head has a different shape than the 212 head, there is no increase in compression ratio.
Perhaps you are thinking about how people put a 232" stepdown engine head on a 262 engine to gain an increase in compression. That swap does increase compression because the 232 engine has a smaller bore diameter than the 262, thus there is an area of the combustion chamber part of the 232 head that is flat at block height (minus gasket width), rather than being dished out.
If you have 80lbs compression pressure, it is low. Sounds like your engine is tired. A rebuild of at least the top end of the engine (rings and a valve job) would give you a good power boost. You could do a 3 angle valve job, and mill the head a small amount (no more than .060") for an increase in power. But ask others for advice on how much to mill the head. Put a Smithy or glasspack muffler on, and that Terraplane will haul right along.
The ratio is calculated on the swept volume of the cylinder versus the unswept volume, so the bore and the stroke are relevant. The 112 has a shorter stroke and a lower swept volume per cylinder. Therefore putting a 112 head on a 212 with its larger swept volume will cause an increase to the CR all other things being equal.0 -
No, I'm pretty sure the "112" cyl head has a higher compression than the standard 3x5 head, because I know of people who have gone this route. Or it may be the early 40's Traveler head. If you could fit your '36 with a '37 dual-through carb as Park suggests, you'd raise your HP to 101 (just like the "Super" model 1937 Terraplanes. If you went with the high-compression head this would take it up to 107, I believe.0
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Chuck G wrote:Terraplane8
I think you are fighting a loosing battle trying to keep up with a 38 Ford with his dual exhaust flathead. He has a lot of speed options you dont , his are limitless yours are limited as you know. Just by cubic inches your already in trouble. I would like to know the difference in combustion chamber size between a 212 head and a 175 head are, i not thinking at the time put a 212 head on a 175 motor not thinking about a 212 head having a larger comb. chamber and lowering my comp. ratio.
Yes, but Hudson quoted the '36 Terraplane at 100hp with the higher compression option and I think this got up to 102-104hp with the twin-throat later models. I don't expect to ever equate to a substantially modified flathead Mercury V8, but a stock one maybe, given that they were also rated at 100hp. The only fly in the ointment is that maybe the Ford horses were stronger than the Hudson ones, ie Hudson was somewhat optimistic as I have heard said about their hp ratings. The Fords were also pretty light so don't think Hudson has much advantage there.0 -
Jon B wrote:No, I'm pretty sure the "112" cyl head has a higher compression than the standard 3x5 head, because I know of people who have gone this route. Or it may be the early 40's Traveler head. If you could fit your '36 with a '37 dual-through carb as Park suggests, you'd raise your HP to 101 (just like the "Super" model 1937 Terraplanes. If you went with the high-compression head this would take it up to 107, I believe.
Jon,
I don't think it is practical to put the later manifolding on the earlier block as the port sizes are quite different, but stand to be corrected if someone has done it and it has worked out OK . Looking at the stock exhaust manifold where the summer-winter valve is it looks incredibly restrictive, quite a convoluted path the gases from the rear 3 cylinders must take to get out the header pipe. Looking forward to seeing how Denverslim's split manifold works once he gets it back and bolted on!
Would love to hear from someone who has put a 112 head on their 212 before I go down this path.0 -
junkcarfann wrote:Perhaps you are thinking about how people put a 232" stepdown engine head on a 262 engine to gain an increase in compression. That swap does increase compression because the 232 engine has a smaller bore diameter than the 262, thus there is an area of the combustion chamber part of the 232 head that is flat at block height (minus gasket width), rather than being dished out.
junkcarfan
What you are describing is the compression jump from using a 262 head on a 308, the 262 and 232 are the same bore but the 232 head has a smaller chamber to get an equivalent compression ratio so when put onto a 262 raises to ratio.0 -
I would like to measure combustion chamber volume on a 212 head and a head off a 112 smaller engine. Any race shop does this on cylinder head work by measuring a liquid and filling a chamber and comparing the two I know its not to complicated i just dont have a tube to put the liquid in thats graduated measurements. Maybe a hobby store or performance shop?0
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According to the Master Chassis Group Parts Book, Hi comp heads were available back to '32. Those heads were rated at 7:1. Wonder how engines left the factory with that option?
The 112 head was rated at 6.5:1 but this was on the 3X4.25 engine. With a standard head sitting next to a 112 head the difference in the combution chambers is VERY noticeable! I believe the 40 & 41 Travelers came with the 7:1 head and the 42's had the 7.25:1 head. Perhaps someone with a parts book for the 40's can verify this.
Once upon a time, I had taken a photo of a standard head, the 112 head and a 7.25 head sitting side by side. Alas, I don't know what became of that picture but once again the difference in the combution chambers from first to last was significant.
We put the 7.25 head on the 3X5 in our 39 112 coupe along with a dual-throat carb (501S) when we had a valve job done about 5 years ago. The mechanic that did the work estimated the comp. ratio at approx. 9:1. (He checked the main bearings for wear before he installed the head) He test drove the car and said he did not notice any detonation. (the rods would have to be trying to beat their way out of the block before I would hear it! LOL)
Comparing the difference in performance before/after is like comparing apples to oranges! A 1 barrel carb on an engine in dire need of a valve job versus a 2 barrel carb with hi comp head and new valves! The only thing that did not change was the timing.
One other change to enhance performance that I did not try was switching to an electronic ignition. If I was to reuse that 3X5 engine, I would certainly go that route if for nothing more than to eliminate the points in the distributor.
Kevin0 -
nick s wrote:junkcarfan
What you are describing is the compression jump from using a 262 head on a 308, the 262 and 232 are the same bore but the 232 head has a smaller chamber to get an equivalent compression ratio so when put onto a 262 raises to ratio.
Thank you (and Terraplane8) for the clarification.0 -
OK I've now found myself from EBay a 112 head off a '39 model. Once it arrives I will c.c. it and see what the head volume is and go from there.
Proposed plan of attack:
1. Ensure the thinner stem later model valves are installed if not already.
2. Port match the intake manifold, with a small anti-reversion step.
3. Do a 3-angle valve job and undercut the back of the valve head.
4. Do what it takes to get the compression around 7.5-7.8:1 with the 112 head, the exact final amount depending on what compression the 112 head is, ie 6.5 or 7.25:1 on the 175 motor.
5. Relieve slightly the side of the head's combustion chamber around the inlet valve to unshroud it.
6. Install a split exhaust manifold if denverslim gives a positive report on his one.
7. Look at a better single throat carb if more airflow is indicated with the improvements than it can deliver. Any ideas from anyone?
All the above will still be with the small-port single carb 212 motor, but as Hudson advertised 100hp for this model just with the 7.0:1 HC option alone I may be able to get a little more than that with the extra detailing, say 108hp? That will make a 23% increase from the stock LC 88hp. It would give a power to weight ratio better than a stock 94hp ET8.............25.7lbs/hp cf. 28lbs/hp for the 4-door sedan models....and we know that the ET8 did 0-60 in 14.4 secs according to The Motor road test.
The Terraplane chassis is so good that it will easily handle more power. The stock hydraulic brakes are fantastic. In fact the handling and steering of my one is very competent with 6-ply bias tyres; cornering is very good indeed and it doesn't wander or track either.0 -
Maybe this is silly but I will toss it out there. could you send the carb out to one of those places that put the carb on a flow bench and they grind and polish it out to a greater CFM based on your application? My brother had a BB Olds carb sent out for this procedure and they did amazing things with it. I believe they actually cut some of out ect ect.0
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here is the link. http://www.customcarbs.com/carbshopcatalog.htm0
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Hello,
Skimmed all the responses and feel you received very good advice. I suggest adding a 2bbl intake if at all possible to your final List then install a later 4 bolt carb from Chevy or Mopar V8. May need to taper openings below carb with die grinder for smooth flow and modify linkage. (If all fails use a gas pedal cable).
Keep this in mind. Some State Police Agencys began using Terraplanes in 1937 because of their great power to weight Ratio. Additionally we successfully raced a 212" motor two Seasons against stock flathead Ford & Mercs until switching to Hornet Power.... We only milled the head, ground the valves, installed a large Carb (from a White Mustang Truck), opened the exhaust (no headers) and never blew the motor!
Lastly,perhaps your friends flathead is not stock and maybe a later 259. Newer Merc Motors have the Dist up front of motor. Also maybe he has a 2 spd giving an advantage.0 -
Thanks everyone for all the suggestions. Nash and Ol racer good points, after looking at the inlet manifold it's pretty basic just two rectangular openings to the block so the later twin-throat manifold must be able to be retrofitted to the '36 block with a bit of grinding and playing around.
I can see how horribly restrictive the exhaust heating routing of the inlet manifold is, as the exhaust gases from the rear three cylinders must make a complete circle around the back of the inlet manifold in the winter setting, and it's not a very wide passage either. It may be possible to modify the inlet manifold in some way to allow some water heating when required rather than exhaust heating.
Quite keen to keep it to "original" or period mods as the car is so original down to the faded paint. I wonder if an H8 twin-throat carb would work, or are they the same carb as the later 212's anyway? Failing that there must be a '30's-'40's twin-throat around off some sort of big straight six or eight that will do the job.
Ol racer, what sort of racing were you doing? Tell us more.................0 -
Denzil, the compression ratio with the head off a 179c.i. motor (as used on the H112) will be around 7.9:1. (Calculated as a 21.2% increase over the 6.5:1 when used on the 179 motor, which is the increase in swept volume with the 212 motor). The optional head supplied for the Hudson Jet was alloy, with a c.r. of 8:1, so you are within the parameters, but you may need to decrease the advance curve, or fit perhaps a Holden or similar distributor with vacuum advance, to elimnate pinking and detonation. The later cars (41 onwards, had a vacuum controlled distributor advance. It will also necessitate the use of high octane petrol. My Jet has been shaved on both the head and block, and I have trouble with it pinking at high revs, even with 96 octane. So you may need to be careful that the bottom end is in perfect condition before modifying too much. Good luck,
Geoff.0 -
Hello,
I went out in my garage to look at a '37 notor & trans along the wall to jog my memory how we put the White Trk Carb on and found someone had put a Merc 3 bolt Stromberg 97 carb on the intake over the yrs by removing one stud then drilling a 3rd hole in-between the two rear studs. Either for necessity or performance?? Either way Carbs have been retro-fitted a long time.
I think back in the day we opened the inlet holes below carb with a regular grinding stone, then enlarged the carb base holes or counter sunk bolts into the stud holes then bolted the Trk carb to the plate.
Swap meets usually have 2bbl aluminum adapters that will accept couple different size carbs with tapered holes.
I would really stick to the 'basics' by getting your compression up to par, Comp valve job, 30deg Int seat, mill head safe amt, go with larger carb using adapter, split exhaust. If really want to wake up the motor send the Cam to Isky to have a street/strip Grind put on it. (about $ 105 in 2wks)
I wouldnt mess with the heat passages. Just open up ports enough for smooth flow and do not thin the valve stems or guides.
Additionally, Check your gear ratio. You may have a 4.10 which wont scoot away as quick as the optional 4.55 gear., 4.10 Best Highway gear.
I raced dirt Tracks a long time & yesterdays news0 -
I just accept my 36 the way she is, drive it and have fun.0
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The 1937 Model 72 Terraplane with the twin-throat 2x1" carb was quoted at 107hp @ 4,000 rpm with the 7.0:1 Super Powerdome head and 101hp @ 4,000 rpm with the standard 6.25:1 head.
This compares to the Model 71 Terraplane with the single-throat 1 1/4" carb that was quoted at 96hp @3,900 rpm with the standard 6.25:1 head and 102hp @3,900 rpm with the same 7.0:1 Super Powerdome head.
Extrapolating from this, the twin-throat carb gave an extra 5hp, and the bump in compression from 6.25:1 to 7.0:1 gave an extra 6hp. Total 11hp extra over the base Model 71.
Interesting that the carb throat cross-sectional area of the twin-throat was 60% greater than the single throat yet the peak horsepower was only up 5hp. Indicates that the carb size was not a seriously limiting factor here.
Raising the compression to a max. of say 7.5:1 and doing the other little mods mentioned earlier and including a 2bbl carb may well result in 112-114hp. Compared to my '36 Terraplane's 88hp that is a 27% increase and well worth chasing for.0 -
You might consider having the camshaft profiled for higher lift and duration and still keeping good idle by not going over 254 duration. No overlap. Weld up the head and machine. Make sure head is bolted down on corners to another head to keep warpage to a min.
Randy0 -
I've now got the new 112 head and pulled the head off my 212 motor. What I have found is that the valves are all looking very worn, plus the exhaust valve guides are totally slogged out causing the valve heads to have lots of sideways movement. No wonder the compression was so low.
By calculating everything including the fact that the deckheight is -18thou and the bore is +20thou, the compression ratio will end up around 7.4:1 which should be ideal. The info was from here, a useful link: http://www.circletrack.com/techarticles/ctrp_0505_calculating_engine_compression/index.html
I have noticed that the 112 head is not as cut away around the inlet valve as much as the '36 212 head (ie it is relieved a lot less on the manifold side); can anyone comment on whether the 112 head gasket is the same or different from the '73-'38-on Terraplane/Hudson 6's? I am concerned that using the 112 head on the 212 will cause shrouding of the inlet valve on the manifold side of the valve due to there being less cutaway compared to the original head. This is shown also by the fact that the '36 head gasket reflects this difference in this same spot compared to the 112 head gasket. But if the later Hudson 212's have the same detail as the 112 head then obviously I don't have anything to worry about. I hope someone can understand exactly what I am on about here!
One further question what are the best quality valves and guides to get for modern unleaded fuel and from who?
Finally, has anyone successfully grafted a later twin-throat manifold set onto the earlier block? If so, does anyone have a spare set they would sell me, hopefully with the carb too? Failing that a couple of good images of the later manifolding would be very helpful.0 -
Head gasket is the same0
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Chuck G wrote:Head gasket is the same
I beg to differ. As noted, the cylinder head is cut away slightly more around one valve on '34-5-6 models, so the head gaskets are different from '37 onwards. You can get away with using the earlier gasket on the later engines, but there is a danger of the edge of the gasket burning away if you use the later gasket on the earlier engines, as the crimped edge of the gasket protrudes into the combustion chamber.
Geoff.0 -
Updating progress, the 112 head is now on as well as a new set of later thin-stem valves and 3-angle valve job. I cc'd the original 1936 6.0:1 compression 212 head at 104cc, and the later model 1938 112 head at 78.5cc. The 112 head may have been milled at some time in its life though as it is 1.4mm less than the full 2" thick which I understand is the factory head thickness.
The actual compression ratio is now calculated at 7.34:1, allowing all factors such as cylinder bore 20thou over, deck height -18thou, valve head volume 0.5cc each, top ring volume 0.5cc, head gasket crushed volume 13cc, head volume 78.5cc etc.
Valve to head clearance is just under 3mm with the standard cam 11/32" lift. This is to the spark plug boss which is raised 2mm higher than the surrounding chamber over the valve area. Plugs are 1/2" reach NGK B6HS which are a perfect light tan colour.
I have posted on another specific thread recently the performance difference which is very significant. The hill climbing ability is now practically as good as my T8, except not as silky smooth under load at lower revs.
The next steps are a set of 1 1/2" headers over the top, a bit of cam optimisation probably more lift, a better carb, and look into even more compression by fill-welding the chambers a little at the high point over the piston (plenty of space to do that). I'd like to see compression of near 7.8-8.0:1 as the engine seems totally fine on 7.34:1 even on low octane 91. Compression is the easiest way to increase efficiency and thus power.
Remember Brough supercharged the old 3x5 to get 140hp presumably without blowing it to bits!0
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