[kyle_blake]

hi

i was thinking of getting my heads removed and sent out for porting etc off my running pontiac 400. it has stock crank, stock rods and the dome pistons.

but prior to doing so I thought what tests can I do on the bottom end?

not many i assume, compression check engine warm of course.

Then is it a valid test to put some fluid , i dunno tranny fluid?, in the cylinder via spark plug hole and re do compression check?

if psi goes up does that mean rings don't seal perfectly?

If it does go up like a ton - i dunno what would a ton be? 20 psi?

Always wanted to ask this question. I suppose a good test is the leak down test too.

thanks for your help. I'd like to try the wet compression test but not sure what fluid to use and how much

[steve25]

What dome Pistons, your not talking about stockers?
How many miles are on the short block?

The best test you can do is a leak down test which will let you prove out the rings and the heads / valves, both dry and wet.

If you pull the heads and find little to no cylinder wall crosshatch left and or a small ridge at the top of the cylinder than its time to rebuild the short block also.

Trying to make more power with ported heads by packing more air and fuel into cylinders in such condition is a full on waste of time and money!

The cheapest sonareo short block wise will be if there is no ridge at the top of the bore and you have a shop hone the bore two both remove taper and get new crosshatch going and then install new fordge pistons that need a .003" to .004" cylinder to wall clearance.

If your current short block turns out to be good, but started out as a 2 bbl motor with its 40 psi oil pump, then in the least you should pull the pan and install the needed 60 psi pump and a new HD oil pump drive Rod .

Also note that in regards to a stock 2 bbl block that the factory used lesser quality rods bearings than the 4 bbl motors and these are not intended for useage over 4800 to 5200 rpm, this goes hand in hand with that fact that the 2 bbl oil pump only has a 5/8" pick up tube and can not supply the needed oil volume to the bearings above that rpm range.

[kyle_blake]

hi steve,

the engine was rebuilt in 1999 and has only been driven like 500 miles a year or something like that so very little use. it made 300 hp and 387 torque on chassis dyno. i do have some history on it just not a full account of everything as i was young back then. they are the speed pro or trw domed piston 160 thou(trw-l2279f30).

there isn't enough miles on it to expect a ridge at cylinder, i do know they most likely sit in the hole some which aren't optimal but for now that isn't my focus.

my main objective is to learn how to do the a wet compression test vs dry and post my results, i just need some help on what fluid to use and how much in the cylinder.

After that to do a leak down i will need to buy compressor and tool for leak and learn how to do that.

[Firebob]

Pretty sure you can use just about any kind of oil for the test. The thing that always comes to my mind when doing this is the placement of the oil. If you just squirt it in the spark plug hole I would think it all would end up on the bottom side of the cylinder and not end up sealing the rings all the way round. So when you do squirt the oil in make sure you aim it toward the highest point of the bore so it will reach all of the rings. Best to have all plugs removed and carb at WOT. 3-4 turns over should do it.

[Skip Fix]

I can tell my first aluminum rod roller motor still running great pulled out to put a pump gas motor in the car so thought I would check it-great leak down. Flipped it over and pulled the pan to check a bearing or two-scuffed pistons and cylinders lost thrust bearing as well as almost had copper showing unevenly on the bearings.

You never know til you look!

[kyle_blake]

Thanks, I'll try some old power steering fluid. And make sure engine is at operating temp of 160F.

Question do all rings expand when they heat up to create more of a seal? Or does it really depend on the rings and the said gap? There is no hard and fast rule on this?

Thanks for teaching me

[kyle_blake]

Found a good link

http://www.freeasestudyguides.com/co...-test-wet.html

[NeighborsComplaint]

Originally Posted by Skip Fix

I can tell my first aluminum rod roller motor still running great pulled out to put a pump gas motor in the car so thought I would check it-great leak down. Flipped it over and pulled the pan to check a bearing or two-scuffed pistons and cylinders lost thrust bearing as well as almost had copper showing unevenly on the bearings.

You never know til you look!

How was your oil pressure at idle?

[tom s]

Im just trying to wrap my head around why you want to pull the heads to be ported?Do you plan on making any other changes like cam,intake carb etc?If your planning on making some motor changes then you will be looking for a complete rebuild and would not worry about a leak down or compression test?

[455rebel]

Port matching the heads to the intake and exhaust,should show some gain in power.

[tom s]

You will NEVER feel it is a street car IMO.Tom

[steve25]

Do not port match the exh side!
The stock size D-port exh flange area can flow 35 cfm over stock when ported and completely matching it to your header or exh manifold will allow reversion to take place .
This will reduce bottom end torque and make the motor need a higher rpm to come on the Cam which is what you do not want.

[72blackbird]

My 406 with ported no. 48's was built in 1998- it still pulls very hard through the midrange. It also has TRWs, cast rods, but was balanced, blueprinted- probably why it still runs strong. It would stay where it is, but about 4 years ago I started a 455 build, and that engine will be completed soon, so the 406 will get pulled and installed in my 76 TA or 75 Formula. I'm curious to see how the bearings fared through the years, because this engine gets nice oil pressure on the throttle (55-60 psi) and idle (25-30 psi). I may pull the oil pan, pop the main caps, but I doubt I'm going to even overhaul it because it runs so well.

Geno

[steve25]

Well as far as ćost go these days you do not have much sunk into the short block of your 406 cid!
I know that in my 45 plus years of experience that if the motor is out then the ćost of a new pan gasket and a tube of sealer plus one hour of time helps me to sleep very well at night and let s me drive home and not have to be hanging on a hook to get home!

[kyle_blake]

Oil pressure is great at start up 65+ and after a long day of driving it's about 18psi at idle. It doesn't blow blue out of pipes at all.

I just want to learn to try the test and post the results. Just curious if it will show anything, same for leak down.

I'm not at that stage in the hobby to pull the engine and flip it over and start pulling it apart. One day!!

I am at a stage of removing the heads and sending them to sd for the full meal deal on them and an intake.

slap it back on and see what happens?

I have no idea what max lift could be in the engine as I never built it. putting it back together I would do the test and see if I could go bigger but the ram air 4 knock off cam is ok.

After that the engine is essentially maxed out, time for a new engine 455 build all together since I can't run aluminum.(insurance)

[NeighborsComplaint]

Oil pressure is fine, focus on the top end.

[77 TRASHCAN]

Those pistons have an unusual 1/8" oil ring w/ 1/16" top rings. The Sealed Power/Speed Pro book lists the only set of rings they make for that particular as "light or low" tension rings. I'm guessing essentially for racing, and the alloy is the 2618 alloy that is low or no silicon content which makes them stronger, but they need more piston/wall clearance for assembly because they expand more after warm up.

I do not know the pro's and con's of running these low tension rings on the street. I guess I should ask what brand of rings you have???

I started a thread here 2-3 years ago, asking about these particular pistons, and what other brands of rings are available. Total Seal was mentioned as making rings for these pistons. Sorry I do not know how to post a link

I got a good deal on a set of these pistons, .060 over. Hope to try them out some day.

I'd send your heads to SD Performance!!!

[Skip Fix]

My motor had great oil pressure still felt good as new-had about 50 passes.

[kyle_blake]

hey 77,

yah i was told that about my pistons rings and to always let the engine warm up before heading out. unfortunately i don't know what brand of rings they used.

it's interested the heads look like someone ported them way way way back, it would be neat to get them flow benched to see what the flow (#64) then get them cnc'd.

I don't know a lot about it but i wonder if anyone has ever flow tested someone's hand work and then got it cnc'd and found out it didn't flow much better?

I wonder if SD gets heads in that have already been worked over and don't require the cnc?

another thing people have told me is these pistons sit in the hole quite, i guess most people like the flat top pistons and flat decking the block so there is no gap.

i'm still learning though

[JSPONT]

Pull the motor,check the bottom end for insurance, if you are doing port work to the heads and intake why not put a cam in to match? SD can tell you what would work well with your set up.
You will feel better if the bottom end is perfect, and even better if there was wear and you caught it now. JMO