hensen1954

Just started stripping and cleaning my engine and what do I find............- the block has *** writing stamped into the surface where the sump pan goes on. Will take a photo and post later - anyone speak the lingo.

Then No 7 piston has a broken upper ring.

Pistins are not numbered as far as I can see. Should they be.?? They are the type with 4 valve relief sockets and are a shouldered design - is this right for an 81 ?

jotto

why does this forum not allow j a p to be spelt as one word. Japanese....is it offensive or does it mean something else stateside?

tracdogg2

Please post a pic. I'm curious what you are seeing.
Pistons are not numbered. It sounds like you have stock design pistons which all 8 are identical. If you had 2 reliefs then you would have 2 sets of 4 matching.
If you are torn down to this point you should replace the pistons. You are describing the low comp pistons with the beveled top land. This piston was designed for emissions only and terrible for performance. The actual quench surface area is almost non existent causing a very poor flame travel. Go back together with a 4 relief or a 3.4cc trough relief flat-top piston and you will be amazed of the performance increase. This will also get you heading in the right direction for any additional mods down the road.

Mike

Jerky_san

Hey I had a question about when you replace the kind of pistons that are in a 75' 350. Does anyone know how much gas millage is decreased if you were to put flat tops like described above in the engine?

exdrag77

Pretty much everything offends someone in the US. We just have to live with it!

tracdogg2

You don't have a decrease in gas milage, you should have an increase. You are increasing the efficency(sp) of the engine. It allows a smooth flame travel across the top of the piston creating expansion. Anytime you disrupt this smooth burn you loose power. In worst cases the burn stops and explodes. Everyone has heard it, called pinging or spark knock. Actually it's the cylinder wall ringing. As a band-aid to prevent pinging you have to reduce initial timing, slow down the mechanical timing advance and run EGR valves. But retarding the timing raises cylinder temps which induce pinging. This is a very primitive way of describing it. But a good set of pistons is the basis for performance and efficency.
Mike

hensen1954

All sorts of things going through my brain now.....

First off, the piston with the broken ring - don't like the look of the con rod. Either suffered damage or not a good casting in the first place.

Looking at the pistons, they are also not of the best quality castings.

Rings are a little worn, but end gap is still OK. Look standard to me. Bores are OK for 100k miles.

If the pisons, conrods, end caps are not numbered, are they all interchangable - place to place and with each other ??

Regarding flat top pistons as sugested, I am gonna use the 58cc alloy heads - will this make a difference to either type of piston choice ??

tracdogg2

The caps on the rods need to stay matched. Normally everything gets numbered during a proper overhaul. If you are using the same rods on the same crank you need to mark their location. If you have the rods fully machined then it doesn't matter. Same with the pistons. But even new pistons need to be miked along with the bores to try to keep clearances equal among the cylinders. The more parts you reuse the more you need to mark their location.
Normally a flat top piston, .025 down in the cylinder at tdc, using a composite head gasket .039 compressed, and a 64cc head puts you around 9.5-9.6 comp ratio. This is getting a little tight for pump gas. If you run an aluminum head you will need the higher ratio due to heat loss. A 58cc alu head with 4 relief pistons and a composition head gasket will get you in the 10's for comp ratio. The quality of gas available to you may be an issue. Check with piston manufacturers for what ratio their pistons will have with those heads. Head shim gaskets are avaible in .010 if you need to drop the ratio. Camshaft centerline and overlap will also have an effect on ratio.
Mike

hensen1954

Actually starting to think that I should bite the bullit and go 383 ............. would my standard box and diff take it ??????

JPhil

Perhaps it is an old J. A. Prestwich engine from Britain. I didn't know they made V-8s, but they made a lot of high performance V-twins & singles in the pre-war days for motorcycles. Morgan 3-wheel sports cars used *** engines, and *** ruled the speedway cycle tracks for decades. I'm not positive, but they may even have made some aeroplane engines.....



John

Well whaddya know. It won't print the name of a well known famous engine manufacturer in Britain. Capital "J", capital "A", capital "P", with no space between the letters. Oh well.

rastadr

i wish my small block was made in japan. it would get twice the mileage, rev 25%higher and run on regular.

turtlevette

and have 150 cubic inches wrapped in some guady sheetmetal.

Bob Onit

My 73 L-48 gets better mileage than my 86 Toyota Pickup and it was alwayas well tuned
Its just a fact

AGVI

guady?

DZRick

***.

***.

Just checking

Damn we are way to PC

jackson

While they were trying their damnedest to kill my dad & uncles during WWII ... Yellow devils ... yellow hun. Now we give the farm away & tax breaks to them if they'll locate a plant nearby. Nearly sixty-five years passed ... and NO, they've yet to officially apologize for that infamous attack.

Wrencher

Those pistons have had it. 100K on those things is a miracle. I know, I know, someone's got some that went 500K without an oil change, but your broken ring is the clue. These pistons are so soft that the ring groove wears at the outer edges (think ring banging up and down in the groove) 'till they are tapered, then the ring flexes and breaks. Low grade fuel doesn't help.

I use forged pistons exclusively. It's probably overkill, but my engines take a beating and I've never had a piston failure in 34 years of engine assembly. A few connecting rods , but not pistons. Venolia or Jahns are my favorites.

Hans

turtlevette

Your motors must suck more oil. Forged pistons just aint gonna seal as well.

you're gonna tell me your forged motors don't use a drop of oil

yada yada yada

hensen1954

Well, pistons, rings, and a rod that I don't like the look of - more than half way to the price of a 383 kit - so should I make the jump to " light speed " ????

jotto

Hensen,
Push the button and engage warp speed!

If your block has *** writing on it...why not go for a crate such as yearone? Not bad for £1580

http://yearone.com/serverfiles/part....13VF73496&trk=

CT350PC1 Year One Power Crate 400hp 350 crate engine assembly.

Engine Specifications:
·Horsepower- 400+
·Torque- 400+ ft/lbs
·Compression ratio- 9.5:1
·Dyno-tested: Yes, includes harmonic balancer and flexplate
·Dyno sheet: Included with engine's output
·Vacuum produced: 12hg @ 800RPM
·Recommended fuel- 92 octane
·Max recommended RPM- 6000
·Block- Seasoned 4-bolt iron
·Crankshaft- Nodular iron
·Pistons- Hypereutectic
·Connecting rods- Powdered metal
·Camshaft- Hydraulic roller
·Valve lift:.520"
·Duration @ .050" (int/exh): 218deg/228deg
·Rocker arms- 1.6:1 ratio
·Cylinder heads- Ported Vortec
·Valves- Stainless steel 2.02 int/1.60 exh
·Valve springs: Heavy duty
·Bore x Stroke- 4.030" x 3.48"
·Intake manifold- Dual-plane aluminum
·Oil pan, timing cover, valve covers included
·Engine fasteners: High tensile strength
·Warranty- 12 month/12,000 mi