Port and polishing.Is it worth doing?

[67 B-body]

Boy,,,, I dont know what to suggest a person do in this case, only what you could do and how it affects performance.
Changing pistons boils down to a complete rebuild "more or less". I'm not sure what you are calling low compression but I'm guessing it must be something less than 10.0:1?
However, you said "So go from flat top to dome is what your getting at..". Does this mean you currently have flat top pistons in your engine? If so, what's special about them that reduces the compression to a "Low" amount?
According to Cranky, the flat top pistons provide something over 10.0:1 compression ratio. Does your piston set very low in the bore @ TDC? Did you specify a high pin height on the pistons when ordering?
I would think you would at least have a Re-Ring kit, fluids, gasket sealers, oil filter, and pistons for cost conciderations when upgrading the compression ratio.
If you do change pistons to domes, you can specify what type of Dome you want based on combustion chamber shape. The standard dome shape will fit a D type chamber shape, and the Heart shape piston dome will fit the chamber like Victors and some other brands. I'm not sure whata the chamber looks like on the RPM's but you'll need to specify the correct type when ordering, "if you order".

 

[Cranky]

8-1 Compression is pretty low and while 9-1 makes a difference you can feel, 10-1 makes even more of a difference. I build my engines with no less than 10-1 with cast iron heads and shoot for just under 11-1 with aluminum heads. With the right cam and good quench, 10-1 works great with iron heads and have even built 11-1 iron headed engines that worked well on pump gas but the cam is kinda radical on those and bleed off a good deal of cylinder pressure at lower rpms. The last two pics I posted are Eddy RPM 84cc heads.

 

['69Net]

8-1 Compression is pretty low and while 9-1 makes a difference you can feel, 10-1 makes even more of a difference. I build my engines with no less than 10-1 with cast iron heads and shoot for just under 11-1 with aluminum heads. With the right cam and good quench, 10-1 works great with iron heads and have even built 11-1 iron headed engines that worked well on pump gas but the cam is kinda radical on those and bleed off a good deal of cylinder pressure at lower rpms. The last two pics I posted are Eddy RPM 84cc heads.

I can follow most of this thread (not much of an engine builder) but what does quench mean? sorry for My dumbarse.

 

[Meep-Meep]

8-1 Compression is pretty low and while 9-1 makes a difference you can feel, 10-1 makes even more of a difference. I build my engines with no less than 10-1 with cast iron heads and shoot for just under 11-1 with aluminum heads. With the right cam and good quench, 10-1 works great with iron heads and have even built 11-1 iron headed engines that worked well on pump gas but the cam is kinda radical on those and bleed off a good deal of cylinder pressure at lower rpms. The last two pics I posted are Eddy RPM 84cc heads.

Maybe with your gas but not here. My 440 is 10.1:1 with 915's, -.015" deck, steel shim gasket and 190 PSI and I get it to rattle when I lean on it. Driving like an old lady I can get away with a lot, and when it's cool out even better, but for racing I need something like 95 or better. My next experiment is to build basically the same engine but with .5 point less compression.

 

[Meep-Meep]

I can follow most of this thread (not much of an engine builder) but what does quench mean? sorry for My dumbarse.

Not a problem and happy to shed some light. Quench is the area in the combustion chamber that is close to the piston top when the piston is at TDC. It's purpose is to "squish" the gases toward the point of ignition (spark plug) to promote more efficient burn. If you can imagine dropping a book on a flat table and feel the swoosh of air that results from that action that is pretty much what goes on as the piston comes up on TDC compression stroke. If you take two identical engines with 10:1 CR and only alter the piston top and chamber on one so in order to get to that 10:1 a domed piston is required, that engine will most likely require more advance and higher octane to make similar power numbers as the flat top quench head engine.

 

[beezee]

I agree with Cranky,build a 0 deck quench motor,a set of 6 pack pistons such as TRW 3355,s ,cut .020 of the deck should do it. If you want to be "1reallybadgtx" I would build a 500"stroker and be done with it.My 496 with ootb edelbrock,s runs consistant 11:70,s on pump gas.

 

[rumblefish360]

Stock stroke or stroker, IMO, if your going to build or re-build as the case maybe, look at replacement slugs and connecting rods for a lighter rotating assembly to free up power and the abilty to rev up quicker and easier. Skip the OE rods for sure. New after market rods are lighter, stronger (most) and for certainly, much cheaper than correcting the OE rods.

IMO, a zero deck slugs with Edelbrock heads for a quenched area is an excellent street or high performance move. Aftermarket pistons will have more than enuff valve relief to handle high lifting cams, so there is no worry there. Just correctly degree in the cam and check it before firing it up.

The basic idea's of high performance builds coupled with basic good practice rebuilding practices will produce excellent power and longevity in an engine with out issues.

You cam selection should fit into your cruise RPM range and enhanced by the converters stall range and rear axle ratio. This is all part of the combination of the while package which will produce a fun to drive car.

In this way, you will enjoy the car with a newly rebuilt powerful long lasting engine for years to come. IMO, this is the best way to do things instead of band aid aid or simple bolstering / prop up to enhance power on a old engine.

 

[Cranky]

I can follow most of this thread (not much of an engine builder) but what does quench mean? sorry for My dumbarse.

And if you want to get a bit more techy about it....
http://www.forbbodiesonly.com/moparforum/showthread.php?t=12581&highlight=quench

 

[cdr]

yep

Oh I agree that raising compression will be a big benefit but doing other things will help too but a piston swap is a major operation while reworking a set of heads isn't so major....and going with new pistons will probably dictate a rebalance unless you can work them down to what the old ones were if the new ones are heavier....

 

[Cranky]

Back at ya

 

[HEMI-ITIS]

8:1,,,,,,,,perfect,,,,,,,for BOOST:icon_cyclops_ani:

 

[cdr]

oops

Back at ya

hey cranky very sorry i did not mean to say f/u i was trying to agree with you,i will be much more careful picking those icons,i was going to put :iamwithstupid:but thought that i shouldent do that because i dont know you & i dont think your stupid so instead i accedentlly said F U, AM VERY SORRY

 

[cdr]

AND YES TO PORTING ,the more air you fill the cyl with the more running cyl pressure you get, so its in a way increasing the compression because it is now compressing more volume of air & fuel . DO NOT POLISH THE INTAKE PORTS ONLY THE EX

 

[Cranky]

I didn't take it as anything derogative....just internet fun.

 

['69Net]

I didn't take it as anything derogative....just internet fun.

maybe He thought Dirty Harry was gunna come get Him....

 

[cdr]

gun fight

maybe He thought Dirty Harry was gunna come get Him....

down here in texas you just never know ,but would have been a gun fight,problem is dirty harry always wins lol :blob1::blob1:

 

[Cranky]

And I AM Dirty Harry's son

 

[cdr]

Dirty harry

And I AM Dirty Harry's son

I DONT KNOW BUT WHAT I DO KNOW IS WE LIKE GUNS:rev_in_action:

 

[Cranky]

I lost ALL of my guns and ammo on a deep sea fishing trip out in the Gulf!

 

[cdr]

Yep i got rid of all mine