F15david

Hey guys, if you followed any of my other threads you will see that I recently puchased a Cutlass S with a 455 motor in it. It never ran right so I decided to pull the motor out, go over it and find out what was what. I pulled it out today after work and started the tear down. Im having trouble loading pics but so far I found the block to be .040 over as the PO stated. I dont know if anyone can tell or Identify from the pic what compression or mfg the pistons are. The only markings on the piston are multiple circles with 3 lines in them and 040 stamped on the center of the dish. The heads look like they have been worked on. The machine work looks pretty fresh and there are purple anodized keepers for the valves.( Pretty sure that was not a factory option)

Let me know what you guys think. I want to get it back together and have a real runner.
Thanks

cutlassefi

Low compression pistons, sorry. Check the heads like AH64 suggested and hope for smaller than normal chambers.

You'll need a cam with a smaller intake lobe in order to build cylinder pressure.
In fact there is another member on here (montvaleplace) that might have a new cam for sale that would work well in your build. Otherwise I offer custom grinds if you're interested.

F15david

Yeah I figured they were low comp pistons by the look of them. I was looking into camshafts; one to really wake the 455 up. I want a good sounding street cam that really comes alive and makes decent power. I had goals of 350hp/450tq but Im not sure if thats going to happen with the low compression. What cam specs can you recommend/grind and what kind of numbers can I expect from it?

On another note. Whats the best oil pan gasket you guys have found? The cork one on the car was spewing when I bought it. I just want to get the best one I can find and forget about it. Also do you guys know where I can find the thin steel original style head gaskets? Im looking to help my compression out a bit.
Thanks Guys

ah64pilot

Best pan gasket is an Olds Diesel gasket...it's steel with cork on both sides with a composite / sealer material over it. Ultra Copper on the end seals underneath and on top. Aviation form a gasket on both sides of the pan rail (cork) gasket. Get Mr. Gasket chubby valve cover studs (2 packs) and a short carb stud kit and stud the whole thing. Use the nuts that come in the kits w/ out washer and tq starting in center outwards to 8-10 ft/lbs. Guaranteed no leaks.

If you do get anything it will be from the end seals...spray w/ brakleen and push some extra ultra copper in the leak spot and it'll go away.

I'm no help on the steel shim gaskets, pm joesw31...he uses them on his 350's. I'm sure he knows where to get them.

F15david

Hey guys, I brought my balance puller home today so I could get the cam out. So even though it was rebuilt with 040 pistons, I found a Gm camshaft in it. It had GM L 102 Stamped on the front and 401348 cast along the lobes. Anyone know anything about this cam? So it looks like Im going to slap a new cam in this thing with new lifters and reseal it up.

Techinical question. I have not cc'd the heads yet but I have a spec question. If the heads have been resurfaced and Im using a thin (.21-.27) head gasket, how will that effect the preload on the lifters. I know on a chevy you can adjust the rockers but how do you compensate for this with the torque down rockers? On that note, has anyone used the adjustable rockers for the olds? If so, do you like them? Thanks Guys

Edit: So I just CC'd my setup. The heads are stock 80-82cc however when I cc'd the piston I got +35CC's!!! How can this be? That brings my compression ratio to 7.0:1. Or am I calculating it incorrectly? What do you guys think? This thing has got me scratching my head now

ah64pilot

Mark will have to help you on the cam.

You need to measure your deck height. If you have a depth micrometer you can zero it on the deck, then measure the pistons at their highest point in the cylinder (TDC). Take the measurement on the outer ring of the piston (not in the dish). You can take all of them and then get an average depth. **If you don't have a depth micrometer you can use a straight edge and feeler gauge to get an estimate**

Then use the compression ratio calculator at http://www.summitracing.com/expertad...on-Calculator/ or at http://www.wallaceracing.com/cr_test2.php

*The summit calculator will allow a negative deck height input, I use it...but I don't think you'll need to.

As a guess I plugged some numbers in:
Bore - 4.165
Stroke - 4.250
Head Vol. - 80 CC
Dish Vol. - 35 CC
Gasket - .039"
Cyl. - 8

Compression Ratio = 8.21.1

cutlassefi

That's the dish and deck clearance combined as Steve eluded too. My guess would be you're in the low 8's on compression as well.

A cam with an intake lobe of around 215 and an exhaust lobe in the mid 220's along with some advance should give you what you want/need.

olds 307 and 403

Is that piston picture at tdc? If so Smitty at M&J Proformance sells. 011" shim head gaskets, might get you closer to 8.5 to 1. The Corteco .028" head gaskets are another option. I have used them on a couple of builds, good quality. Rocket Racing carries the Corteco head gaskets.

F15david

Im playing with the idea of installing 9.5:1 pistons and new bearings in with a new cam. However if I can make decent numbers with the 8.5:1 pistons that are currently in it I will keep them. I would just hate to put the engine back together with just a cam and be unhappy with the results. You guys saw my goals and if I can reach somewhere around 350hp and 425-450tq I would be more than happy with that. So Cutlassefi, would one of your grinds get me what Im looking for? I would rather support a member than a retailer