[Blued and Painted]

I dont recall any recommendations for small domes with the large chamber heads. Milling old iron too max, then cut the intake side till the manifold sits on the valley pan seems to be the norm.
Who wrote the rule and why?
Are any members running small domes in street or street/strip applications?

[PAUL K]

Domes work good with the large chamber round ports. However I'm not the guy that made the rules.

[J GLASGO]

I prefer domes to raise compression verses over milling rare heads. Most people that bash dome pistons have never used them.

[Old Man Taylor]

Originally Posted by J GLASGO

I prefer domes to raise compression verses over milling rare heads. Most people that bash dome pistons have never used them.

Ditto.

[tom s]

FYI,virtually all HiPo N/A guys running 15-1 CR have some kind of dome.Maybe not 530 plus CI but the guys in the 400-440 range are.The 63 421 SD 12-1 engines used a small dome from the factory.Tom

[tempest1964]

Originally Posted by tom s

The 63 421 SD 12-1 engines used a small dome from the factory.Tom

Interesting. I did not know that. Which doesn't mean a lot. The older I get, the dumber I realize I am. Lol

[77 TRASHCAN]

Originally Posted by J GLASGO

I prefer domes to raise compression verses over milling rare heads. Most people that bash dome pistons have never used them.

Every engine design is different. All the times I went to my engine builders shop, in the olden days, any engine he had on a stand with domed pistons, the pistons had been massaged, and quite a bit, never seen an engine with domed pistons left alone.
It's likely that most domed pistons need some work on them BEFORE they can be installed to run properly!!!

I have some L2279 Sealed Power pistons that I plan to use in a 400 build, soon, they have a very short dome, but I will check clearances before final assembly.

[promptcritical]

Didn't the old high compression Chevy motors use domed Pistons? I have small domes (JE custom pistons) in my 72 HO motor with 7F6 heads for about 10:1 CR. I didn't build the motor so I don't know if it was a hassle setting them up. It runs really strong with no issues.

[NeighborsComplaint]

My car's basket case motor originally came with Venolia popup pistons (that's what we used the call domed pistons) on SD rods. I slapped on a set of 6H "bathtub chamber" (114cc) heads in order to reuse the like new pistons but still had to run 50/50 premium /race gas.

There was some thought that the domes blocked the "flame front" during combustion and did not give an efficient burn. I thought the car ran well until I destroyed the rings and ring lands on 4 pistons from detonation while running straight pump gas.

[Skip Fix]

I do know some of my friends that tried the TRW domes in 455s had detonation issues.

[Old Man Taylor]

It was important to machine a "fire slot" into the dome of my domed pistons so the flame front could propagate better. Total timing before wanted to be greater than 40 degrees. It made peak power at 30 degrees after the fire slot.

[steve25]

All Pontiac iron heads have the spark plug hole high enough up in the chamber to run a dome atleast equal in height to the depth of the chamber lip on a shallow side with no need for a fire slot.

It's not hard to pick up a easy 6 CCs this way on a open chamber head, or 4 CCs on a early closed chamber head.
On the darn 6H heads you could run a .360" tall dome without blinking a eye!

I look at things this way, if I am not doing battle to get the lightest piston in the motor then the added cost of a dome piston is pretty much offset by not having to spend big bucks getting the deck and Intake flange milled a ton even when only .040" has been shaved off.

This also saves you from going thru the gyrations of cutting back the valley pan , and or grinding the bottom of the manifold.

[Schurkey]

Crappy, large combustion chambers need domed pistons to get the compression back.

Domes (and dishes) add more surface area to the piston top.

More surface area means more heat transferred into the piston. If your piston isn't overheating and causing seizure or detonation, maybe the compression gain is worth more than the heat loss into the piston. If the piston is showing signs of excess heat; or detonation, or seizure...

But in the end, the REAL solution is to get a proper-sized chamber and ditch the dome or dish.

[steve25]

Yes, that's true also ,if your after every last Pony and your just running Gas or pure Alky with a dome piston then you should get it heat barrier coated .
If your boosting with big loads of NOS or a Turbo or Blower you had better know what your doing with piston top coatings!

[Cliff R]

I've worked on a few Pontiac engine builds that used domed pistons in them, most were HO or later Super Duty 455's. It's something that I don't recommend, unless one were doing a flat out race application and really needed high compression.

The ill-fated 455 Super Duty we rebuilt last Spring didn't even make it 200 street miles with domed pistons in it, and tons of other "high performance" parts on a fresh engine build.

We removed the domed pistons, went to Icon flat tops instead, zero decked, tight squish and custom ground HR cam. It made 1hp/cid and over 500 ft lbs torque across most of the loaded rpm range on the dyno even with relatively "low" compression.......Cliff

[bkmont]

Originally Posted by promptcritical

Didn't the old high compression Chevy motors use domed Pistons? I have small domes (JE custom pistons) in my 72 HO motor with 7F6 heads for about 10:1 CR. I didn't build the motor so I don't know if it was a hassle setting them up. It runs really strong with no issues.

Yep, my 70Z28 has the dome for a factory advertised 11:1 for the Z28 Special Performance Package known as the LT-1 engine in Corvettes.