Thread: Welding up combustion chambers?

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Is there such an art? If heads are matched to intake manifolds for the form of fuel induction, wouldn't that be a workable method to increase compression?

We do that in the Corvair world, but not to increase compression. We do it to make a better squish area in the head. Better squish = less pinging.

Now days, builders make compression with piston design. The heads can be left more open. Small chambers have a bad habit of shrouding the valves. You get more compression, but less flow.

If you want to build a strong street engine, stick with a 10:1 compression ratio or less. If you have good airflow and precise fuel metering, 10:1 will not ping.

The wedge-shaped chambers with the small squish area have good airflow. If you fill between the valves (to get the heart-shaped chamber) you have to step way-up on the cam to compensate for bad flow.

Build compression with the pistons (it's their job), and let the heads flow (it's their job, too)

.....Sun is finally out this morning. I'm going out to pull a valve cover off of my motor to get the head number for sure. I will then see if there is a factory head with a smaller combustion chamber. At least that would be engineered. I'm trying for some improvement without the time and expense of pulling the motor out of that behemouth. Earlier inquiries showed that I would spend as much to pull and reinstall as I would replacing pistons.

I earlier posted that the stock compression was 7.8:1 but charts in my Chilton manual show it to be 8:1. My local engine shop thinks that I can get a point with about a 18 cc's reduction in combustion chamber size. 9:1 with a cam would probably give me the extra poop I'm hopping for with moderate effort and expense.

My local shop says that you can use smaller port TBI intake with larger port heads. you just can't go the other way around.

I will also talk to Edelbrock because they show a TBI intake for 454's up to 1990. That intake might should be an improvement and might match earlier larger port heads.

Techinspector: I am re-looking at that option. Earlier inquiries elicited negative opinions on the subject. I just went, amonst others, to Whipple's sight. Theirs seems pretty impressive, with controllable boost and electronic management. They also claim the best low end boost in the business with the twin screw compressor. Unlike other units, the whipple provides very modest boost when the engine is unloaded then comes up quick when the demand is made. Boost is not rpm dependant.

Questions I would ask them would be:
What is the effective compression ratio
What is the longevity? of the compressor
Is it rebuildable if nec.

I've found a wide variety of prices. This link is for the best price I've found.

http://www.superchargers4less.com/whipple/gm454.htm

To properly weld the heads, you'll need to heat the entire head to 1500 degrees during the weld. Then, maintain 1300-1500 for 15-30 mintes, and finally, allow the heads to cool slowly for 24 hours This will eliminate the cracking problems associated welding cast iron. Sounds complicated don't it? You'll be better off not welding the heads and doing something else instead.

If I'm not mistaken, any aftermarket or pre-smog head will bolt onto your applicataion. 9.0-1 to 9.5-1 compression should be streetable. The new smallblocks all run 9.5-1 on unleaded, but they have aluminum heads and a reverse coolant flow design. You won't be able to run 87 octane. With a good camshaft, this should put you into the 400 fwhp range.

Dang, you must have some serious dish on them pistons. Edelbrock casts a smog legal head specifically for the TBI setup. It has 100 cc combustion chambers and still yields only 8.8-1 compression. Edelbrock advertizes it will put you up to 357hp and 475 lbft. That should definatly get you moving, and with a camshaft, you may be able to push it near 400hp. These heads are aluminum and, therefore, expensive. Aluminum is useless at that low of a compression ratio and I would look for a good set of irons with a 100 cc or smaller chamber.

Since I first posted 76GMC, I've been picking up a bit of info. I pulled a valve cover to get my head #. It is 10114156 w/ 118 cc combustion chamber. You could hold a party in there. Also, best that I can determine, the piston does have a 'dish' in it, probably in about 1/2 the surface area of the top of the piston. I'm not into pulling that motor out to remedy that, however.

Chilton lists the HP of that motor at a whopping 230. That's hardly enough to pull the motor around by itself, let alone that 3/4 ton body. I will say that the Banks Power Pack I installed made a huge difference in driveability, but newer 350 mpi's can easily keep up with me, with a boat in tow and blow my doors off unloaded.

Did anybody mention a steel shim head gasket, that should up your compression, Cheap, and easy way to up your compression. You could also have your heads decked a little bit to increase compression. Or buy a different set of heads with a smaller combustion chamber, that would make the most sense.

....to see if there are any factory steel heads, with 100 cc combustion chambers, that will work with my motor. My local machine shop has a computer program that computed a compression ratio of 9.04:1 using 100 cc heads on my motor.
I reallly don't want to go any higher than that. I'd have to use premium fuel.

Heads have to be able to accept anti knock sensors that are screwed into heads.

I think an anti-knock sensor works much like a stethoscope and should be able to be placed anywhere on the head fairly easily. 9:1 compression should be about perfect for your application. It should run 87 or 89 all day, but you will want to run 89 or even premium under tow.