Putting a Caprice engine (L05-7) into a 92 g30 van (has L80e trans)

[Danboquist]

If you have the following info I can plug it into my spreadsheet and give you the static and dynamic compression ratio.

How much has the block been decked? If you don't know, how deep in the hole/out of the hole are the pistons at TDC?
Stroke (stock is 3.480)
Connecting rod length (stock is 5.700)
Piston compression height
Piston dish/dome size in cc
Gasket thickness
Head combustion chamber in cc
Cam intake centerline (ICL)
Cam advertised duration
Cam lobe separation angle

Best I can come up with at the moment:

Deck clearance ~ .026
Stroke. 3.480
Rod Len. 5.7
Piston Compression Height. ?
Piston dish/dome size. Try 13cc
Gasket compressed thickness. .039
Head Combustion chamber. 65cc
Cam intake centerline. 204
Cam advertised duration 257/267
Cam lobe separation angle 112 deg.

 

[Danboquist]

Switching from flat tappet to roller camshaft I’m getting that I need to have a melonized distributor gear…. Correct?

 

[PlayingWithTBI]

I’m getting that I need to have a melonized distributor gear…. Correct?

Some people say the original gear is sufficient but, I know Comp Cams require they be Melonized. It's cheap insurance, just measure your shaft (there's 2 different ones) and order one.

Edit: Pay attention to the direction it goes on or you'll be 1/2 tooth off.

 

[Schurkey]

What distributor are you starting with? Genuine GM TBI? Aftermarket TBI? Something else? Is it in good, usable condition? If there's genuine wear--not just "polishing" from use--you need another gear.

Head gaskets are going to be much too thick for proper squish/quench, unless you zero-deck the block instead of merely square-decking.


WHAT DISTRIBUTOR ARE YOU STARTING WITH? If you're using a TBI or Vortec distributor, and the gear isn't worn-out...just re-use it.

Deck clearance ~ .026

Piston Compression Height. ?

Gasket compressed thickness. .039

As said before...unless you zero-deck that block, the head gaskets you're selecting are WAY TOO THICK.

Either get thinner head gaskets, or have the block decks cut ~.026.

Switching from flat tappet to roller camshaft I’m getting that I need to have a melonized distributor gear…. Correct?

You keep asking the same question, and not answering when I ask what gear you have already.

TBI and Vortec distributor gears ARE melonized. If what you have is in good condition, ("polished" not "worn") reuse it.

 

[Danboquist]

As said before...unless you zero-deck that block, the head gaskets you're selecting are WAY TOO THICK.

Either get thinner head gaskets, or have the block decks cut ~.026.


You keep asking the same question, and not answering when I ask what gear you have already.

TBI and Vortec distributor gears ARE melonized. If what you have is in good condition, ("polished" not "worn") reuse it.

I understand where you are going with the bloc being decked. I dont know whether it has been or not. IF I look at the head gaskets that came off and the ones that I have to put on are the same thickness then that will give me a good idea that the deck may have already been done. Ill check the old gaskets.

The distributor that I have, I assume, is a standard stock distributor. As for the gear, I dont know. I cant tell whether it is melonized or not. It appears to be in good shape. See video here

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Measuring the old head gasket I get .03 thickness @ the cylinder, .04 thickness otherwise, and 4.18 or something as the ID at the cylinder.. here..

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The Felpro that I got with the gasket kit is 4.125 in bore, .039 compressed.
I wonder how much difference the .009 will make in the compressed thickness of the head gasket. Ill have to look into the bore size thing as well.

 

[Schurkey]

I dont know whether it has been or not.

Sure you do. The piston-to-deck height you've listed (.026) is exactly what I'd expect from a virgin block.

The distributor that I have, I assume, is a standard stock distributor.

Looks to me like a perfectly-usable TBI distributor.

Measuring the old head gasket I get .03 thickness @ the cylinder,

I have an impression--which may be wrong--that the OEM head gasket would be .028 thick.

The Felpro that I got with the gasket kit is 4.125 in bore, .039 compressed.
I wonder how much difference the .008 will make in the compressed thickness of the head gasket.

.026 piston-to-deck, plus .028 head gasket = .054 quench/squish--which is already on the huge side. Given a choice, I want .035--.040. So .026 + .039 = .065 quench--useless and counterproductive. Prone to detonation.

You want to install a .039-thick head gasket, which means you need to knock .026-ish off the block decks (Zero decking) to create functional squish/quench.

Or

Get thinner head gaskets, and take somewhat less off the block deck. Even the steel-shim gaskets at .020 thick still get you to the high-side of effective squish/quench. They need a smooth, flat surface to seal against, so you'd be doing a clean-up cut of the decks at minimum (square-decking.) And likely the same on the head surfaces.

Ill have to look into the bore size thing as well.

Don't bother. 4.12x is plenty big enough for a .040-over 4" bore--4.040--and stock heads.

 

[Danboquist]

Sure you do. The piston-to-deck height you've listed (.026) is exactly what I'd expect from a virgin block.


Standard, stock distributor FROM WHAT ENGINE?

If this is a TBI or Vortec distributor, it's got a melonized gear. If it's pre-TBI, then no, and you'll have a 0.491 distributor shaft.


I have an impression--which may be wrong--that the OEM head gasket would be .028 thick.


.026 piston-to-deck, plus .028 head gasket = .054 quench/squish--which is already on the huge side. Given a choice, I want .035--.040.

You want to install a .039-thick head gasket, which means you need to knock .026-ish off the block decks to create functional squish/quench.

Or

Get thinner head gaskets, and take somewhat less off the block deck.


Don't bother. 4.12x is plenty big enough for a .040-over 4" bore--4.040--and stock heads.

TBI. Then the gear that is on the distributor on the video should be good.
Thinner gaskets down to .035-.040. Thanks!

 

[Schurkey]

TBI. Then the gear that is on the distributor on the video should be good.

Yes.

Thinner gaskets down to .035-.040. Thanks!

Remember, its the squish/quench that needs to be kept thin enough to be functional. It's gonna be difficult to do that without shaving material off of the decks...which is fine because it allows the decks to be cut parallel to the crankshaft; and 90 degrees apart (square-decking)--which the OEM machining is not that great at getting correct.

How MUCH you plane from the decks will depend on the head gaskets you select.

 

[L31MaxExpress]

Sure you do. The piston-to-deck height you've listed (.026) is exactly what I'd expect from a virgin block.


Looks to me like a perfectly-usable TBI distributor.


I have an impression--which may be wrong--that the OEM head gasket would be .028 thick.


.026 piston-to-deck, plus .028 head gasket = .054 quench/squish--which is already on the huge side. Given a choice, I want .035--.040. So .026 + .039 = .065 quench--useless and counterproductive. Prone to detonation.

You want to install a .039-thick head gasket, which means you need to knock .026-ish off the block decks (Zero decking) to create functional squish/quench.

Or

Get thinner head gaskets, and take somewhat less off the block deck. Even the steel-shim gaskets at .020 thick still get you to the high-side of effective squish/quench. They need a smooth, flat surface to seal against, so you'd be doing a clean-up cut of the decks at minimum (square-decking.) And likely the same on the head surfaces.


Don't bother. 4.12x is plenty big enough for a .040-over 4" bore--4.040--and stock heads.

I have learned through using them, that the stock GM dished piston design does not offer anything benificial in quench even if you zero decked the block and ran a 0.038" thick gasket. The pistons dish is still ~0.120" down the bore. I will never run a GM dished piston in a fresh build again myself. A flat top piston with good quench is much more detonation resistant even with the added nearly full point of compression. If I had to run a dished piston it would be a D shaped dish to closely match the chamber shape yet offer good quench on the flat surfaces of the cylinder head. At 10.25:1 with a flat top piston and 195 psi cranking compression the L31 in the 1987 G20 will run 30-32* of timing advance on 87 octane all in at 3,400 rpm without spark knock. I had it pinned on the floor for a couple of miles the other day climbing a grade in hot weather and took it as high as 5,300 rpm without encountering knock retard. When I let it upshift to 3rd, climbing said grade at WOT it stayed around 30* advance and did not spark knock at full load after shifting into 3rd either. The engine was turning ~3,700 rpm after the shift were VE and cylinder pressue is very high as well.

 

[Danboquist]

Yes.


Remember, its the squish/quench that needs to be kept thin enough to be functional. It's gonna be difficult to do that without shaving material off of the decks...which is fine because it allows the decks to be cut parallel to the crankshaft; and 90 degrees apart (square-decking)--which the OEM machining is not that great at getting correct.

How MUCH you plane from the decks will depend on the head gaskets you select.

These look like they may do the trick. The 4.1 bore gives me .06 over the cylinder bore and the compressed thickness is .015. Any red flags with this?
This would give .026+.015= .041 and looks like I would gain .06 on the reduced bore size.

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