Not to highjack the tread, but when we are talking standard/tall deck blocks and problems/benifits.

What du you guys see as the smallest compression height to be used in a street car?, will probably maximum see 5-6000 miles a year.

Im looking at dynoflo aswell, interested in either the 420 or the 434 shortblock, but they have very short compression height on both of them.

 

Compression height is a piston dimension. it's from the centerline of the pin to the flat part of the piston deck, not including the dish or the dome. The deck height of the block, the rod length and the stroke dictate the necessary deck height of the piston. If you use a shorter rod, you will need a piston with a greater deck height.

RACE ON!!!

 

Thanks, perhaps i should have been more clear.

Both shortblocks come with standard deck height, 6" rods and either 3.875" or 4" strokes. Thats gives a compression height of either 1.062" or 1.025 if i recall correctly. Thats seem very short to me, wouldent the wristpin have to be in the oilring groove?

Is that something one should do on a streetengine?

 

IMO the benefits of long rod out weigh the pin being so high that the third ring is over it.

I want the lighter piston because I turn my motors 7500 for my past and present 3.750 & 3.875. My present 4.00 stroker has been built with 7000 rpm intended every day of it's life. You just buy the longest rod rotating kit for the deck height you have. I'm not saying over board, but 6 inch bushed rods work fine.

 

Both the 434 and the 454 have 4.00" strokes. The 434 is a 400 cid bore, 4.125", plus .030" over, to make it a 4.155". The 454 requires a special block that can take it's 4.25" bore. With a given block deck height, and rod length, the 434 and the 454, use pistons of the same compression height, because the stroke is the same. I have a standard deck block (9.025") with 5.85" rods. The oil rings do NOT encroach on the pin hole. I don't think there is a piston that will allow a 6" rod, with a 4" stroke, without ring groove encroachment into the pin hole.

RACE ON!!!

 

Depends haw many miles you expect out of that 454. The fact it can't be bored out would have to be taken into consideration;Nitrous would be a little risky with the bore spacing. A 434 would be my choice, followed by a well prepped 406 (2 bolt block w/splayed mains. maybe a little block fill too. Good luck on whatever you decide. Sounds like qa blast

 

A 434 or 406 (both 4.155" bore) in that block, has reached it's bore limit also.

RACE ON!!!

 

RE: Dyo-Flo

I ordered a 580" BBC assembled shortblock from them. I drove all night to Vegas to pick it up and in the morning when I inspected it I discovered it was built with cast iron caps in lieu of the billet caps I ordered. Dyno-Flo built me another quickly and gave me $200 +/- in free parts for my trouble. In fact, they offered to build it that day if I could wait.

The reason I drove to pick it up was to inspect thier facility, its cleanliness and the condition of thier machine tools. They operate out of what appears to be a leased shop in buisness park, about 30,000 sqft. All machine tools appear to be nearly new and are in separate stations. The assembly room is separated and clean. There all pallet loads of Dart blocks in boxes nearly to the ceiling. It's a class act. There was looked like an 1,800 hp pro-mod BBC waiting in the dyno cell for testing that I spent some time drooling over.

Once I received the new motor, I dissasembled it measured everthing I could and inspected for scratches, nicks, clearances. Everything checked out perfect.

I will buy from them again.

Allan

 

I notice Dyno Flo sells on Ebay, quite a bit in fact. Is that what
led you to them???

 

68427: thanks for the info on Dyno-Flo. Sounds like they are not a fly-by-night and stand behind what they sell.

I don’t know if this thread is getting too long but…..I’d like to hear thoughts on the quench issue on the 434 and 454 motors. Because the displacement is so large and the largest chamber SBC heads are around 76cc, you can’t just stuff in a flat-top piston with a .040” quench and keep the compression at 10:1. On 454’s, I’ve noticed full dish pistons being used, that is the dish is over the entire center portion of the piston. There is about a quarter to half inch ring on the outside of the piston top that is flat. Does this outer ring give adequate quench? Are there other piston options people are using? Bigger chamber heads?

 

Use pistons with a "D" shaped dish. This maintains the quench portion of the piston.

RACE ON!!!

 

CFI-EFI:

I'm not sure I'll have much of a choice with a 4.25" bore SBC piston, not a lot of people making that size. (Maybe another reason to stick with a 4.125 or 4.155 bore.) I've only seen the full dish version at 4.25". I'll just have to start calling around.

I was checking an article on Bill Mitchell's 454. They don't really have a quench. .051" head gasket with the piston .025" in the bore. Dish is -20cc.

 

Forget the dish shape. With a .051" gasket, and a .025" deck clearance, or .076" piston to head clearance, you're already given up the hope of any beneficial quench. The Chevrolet Power book recommends a piston to head clearance of .035-.040" minimum. Some people build their engines with less. Above about .060" piston to head, the benefit of squish is gone. If you aren't going to reduce the piston to head distance, don't sweat the dish shape. If you want to tighten things up a bit, contact J&E and others that will make you what you want.

RACE ON!!!

 

I've seen what Bill Mitchell builds and sells and I don't have any respect for him or his company. Very poorly match components. The .076 quench is just another example of how they are just profit driven.

 

I would like to run 60 or so cc heads with my 20 cc dished wiseco pistons from a sorry Bill Michell kit. It got me wondering why you thought you had so much compression?

I used very common 72 cc heads and you don't have enough compression. You need at least 66 or 64 cc.



You Entered:
Bore 4.25 (inches)
Stroke 4 (inches)
Rod Length 6 (inches)
Cyl. Head Vol. 72 (cc)
Deck Height 0.025 (inches)
Head Gasket Bore 4.25 (inches)
Head Gasket Thickness 0.021 (inches)
Piston to Cyl. Wall Clearance 0.003 (inches)
Top Ring Land Height 0.25 (inches)
Piston Dome Vol. -20 (cc)


Compression Ratio:
10.051 : 1

Zero deck height and .039 gasket 66 cc is about right.

You Entered:
Bore 4.25 (inches)
Stroke 4 (inches)
Rod Length 6 (inches)
Cyl. Head Vol. 66 (cc)
Deck Height 0.000 (inches)
Head Gasket Bore 4.25 (inches)
Head Gasket Thickness 0.039 (inches)
Piston to Cyl. Wall Clearance 0.003 (inches)
Top Ring Land Height 0.25 (inches)
Piston Dome Vol. -20 (cc)


Compression Ratio:
10.776 : 1
Do the Math because Bill Mitchell sure doesn't.

 

Did you possibly typo on the gasket thickness in the first example above? You typed, ".021 (inches)". He stated, .051". If you calculated using .021", his compression ratio, is lower, still. If it is simply a typo...well we ALL do that from time to time.

RACE ON!!!

 

No I said .021, because that's what size copper head gaskets I run from Flatout. It's really about as thin as I have found for performance and aluminum head and iron block.

I was just showing even with normal piston in the hole and small head gasket that the compression was still very little.



You Entered:
Bore 4.25 (inches)
Stroke 4 (inches)
Rod Length 5.85 (inches)
Cyl. Head Vol. 76 (cc)
Deck Height 0.025 (inches)
Head Gasket Bore 4.25 (inches)
Head Gasket Thickness 0.051 (inches)
Piston to Cyl. Wall Clearance 0.003 (inches)
Top Ring Land Height 0.25 (inches)
Piston Dome Vol. -20 (cc)


Compression Ratio:
9.178 : 1


This is with -6 cc flat tops



You Entered:
Bore 4.25 (inches)
Stroke 4 (inches)
Rod Length 5.85 (inches)
Cyl. Head Vol. 76 (cc)
Deck Height 0.025 (inches)
Head Gasket Bore 4.25 (inches)
Head Gasket Thickness 0.051 (inches)
Piston to Cyl. Wall Clearance 0.003 (inches)
Top Ring Land Height 0.25 (inches)
Piston Dome Vol. -6 (cc)


Compression Ratio:
10.325 : 1


This is about the correct static compression for a 240ish duration roller cam.

You Entered:
Bore 4.25 (inches)
Stroke 4 (inches)
Rod Length 5.85 (inches)
Cyl. Head Vol. 76 (cc)
Deck Height 0.025 (inches)
Head Gasket Bore 4.25 (inches)
Head Gasket Thickness 0.021 (inches)
Piston to Cyl. Wall Clearance 0.003 (inches)
Top Ring Land Height 0.25 (inches)
Piston Dome Vol. -6 (cc)


Compression Ratio:
11.026 : 1


I run 11.2 or so and don't have any issues with 91-93 super unleaded

 

I was reading on the Brodix 18 degree heads in sumitt the other day and thought these would be a great head for a 400 + incher sbc. They have 244 cc intake runners, 2.14 valves and take standard 23 deg valve train componets, except i think an offset rocker arm. They flow 320 CFM @ 600 right out of the box. Their $1999 or $2800 with the whole top end.

Do you guys think these would make a good 406-434 head ?

Mike

 

The Dart 18 degree are great also. I really considered them. But that's only the head cost. Start adding in custom headers for spread port ..................

 

As far as i understand the brodix will accept a regular ex. ?