RISK81

Have a few questions regarding the finalization of my engine build project.

Few items about the build.

Vehicle = 1994 Corvette 6spd (black tag), 3.45 axle ratio, FX3 adjustable suspension.
Engine (Previous) = 1994 350 LT1, spun a rod bearing and took out the crankshaft. Bought the car with a rather loud knock (rod bearing). Car would start and run. 50,000 miles on the car and the original engine.
Engine (Now) = 1994 355 LT1. Had the block bored .030" over, block was zero decked (due to pistions, see below). Balanced rotating assembly. Heads (factory # 374) three angle valve job, new viton seals, Hot cam springs. Flywheel surfaced (AMS single mass).
New Engine parts = MSD 83811 distributor, Taylor Cable 84225 ThunderVolt 8.2mm Ignition Wire Set, Cloyes 9-3651X3 Race Billet Timing Kit, GM Parts 12480002 Hydraulic Roller Camshaft Kit (Hot Cam Kit), Scat Crankshafts 9-10526 Cast Steel Crankshaft (3.48 stroke), Scat Crankshafts 2-ICR5700-7/16 5.700" Forged 4340 I-Beam Connecting Rod, Icon Pistons IC9913.030 Forged piston kit, KB Performance Pistons 4000AM8.030 Piston Ring Set 4.030 Bore, Melling 10553 Oil Pump, Clevite MS-909P Engine Crankshaft Main Bearing Set, Clevite CB-663P(8) Engine Connecting Rod Bearing Set, Cam Bearings & Brass Freeze Plug Set 1968-2003 Chevy sb 350 305 LT1 LT4 (Brass Block Plugs), Sealed Power 260-1931 Gasket Kit, ACDelco 251-554 GM Original Equipment Water Pump with Gasket, Davies Corvette1993-1994 C4 Corvette Engine Cooling System Rubber Hose Set [LT1], ARP 134-3601 1343601 High Performance Series Cylinder Head Hex Bolts. Two QTP Electric motor exhaust cut outs (installed between the resonator and the two mufflers, below the rear axle).

Question #1- Engine Compression. With the pistons that I chose (ICON IC9913 - Flat top four valve releif, 10cc). I had the block zero decked (9.00") thinking I will need to make up for the loss of displacement due to the slighty larger pistons. Since then I have bought two sets of head gaskets. Fel Pro 9966PT (.049" crush) and also the Fel Pro 1074 (.039" crush). With my calculations I am looking at ~10.8:1 with the 9966PT's and 11.03:1 with the 1074's.
- I wanted to up the compression some from factory (~10.5:1) but is 11.03:1 safe to run with 93 octane?
- Also how would I calculate the dynamic compression ratio with the hot cam and the mentioned gaskets (using the Hot Cam springs)?
FYI - Before the first engine start-up, I plan on ordering a mail order engine tune to compensate for the hot cam differences from factory.

Question #2 - Clutch / Shim. After determining that the car came with a single mass flywheel, I had the factory AMS (PN-167426) flywheel resurfaced (figured that I might as well). What clutch options do I have now? The clutch and pressure plate that I removed said (Pressure plate- C70043, Clutch Valeo GM-41/167385). I would like to replace the clutch and pressure plate as the parts removed look a little worn. I would ideally like to replace them with a quality part but I want to retain the "Pull style" clutch. Also what is the shim kit I keep reading about regarding correcting the "rocks in a can" sound? Is it needed? Where can it be purchased from? (ZF Doc?).

Thank you in advance.

cv67

Yes ZF Doc on the shims, doubt you lost any ci eiher remember you bored it.
A port job would go a long way with the hotcam, even if you kept the stock valve sizes.

mtwoolford

In California, 91 octane is the highest available; no problem for my LT4 with a factory spec compression ratio of 10.7. The secret, if there is one, to dealing with high static compression ratios is to increase the cam duration which "bleeds off" some of that static compression.. While its kinda comparing oranges to apples thing, LT1's have EGR; LT4's don't have EGR because the stock LT4 cam has enough duration to make EGR unnecessary; an LT4 "hot cam" has even more duration; with 93 octane you should be fine.

On my 96 I used a SPEC "lite weight" billet steel flywheel, approximately 22lbs and a SPEC stage 3 plus clutch; an excellent combo. I had, but didn't install the ZFdoc spacers....call me lazy, but my ZF trans had no issues, so "if it ain't broke, don't fix it". This clutch disc has a sprung hub. Initially there was some noise but after a few miles the springs loosened up a bit and the "rocks in a can" noise, which was never really anything like "rocks in a can" but more like an old non syncro granny gear truck four speed, basically went away, just like in any "conventional" clutch with a sprung hub. From what I infer from your post, consider getting a "heavy" billet steel flywheel from SPEC which soaks up more transmission noise. What I can't stress enough, get a new clutch fork, pivot and throwout bearing...these ZF specific parts are getting harder to find. Also with the bellhousing bolted up and the clutch installed, but with the pilot tool still inserted into the clutch disc and the transmission out (obviously) bleed the clutch hydraulics and verify that there is enough travel on the clutch fork / throwout bearing to release the clutch disc. Now, not later with the trans and C beam installed, is the time to deal with any issues.

I also had ZFdoc shorten my shifter and rebuild the shifter assembly. I cannot overemphasize how helpful he was.

good luck.

MatthewMiller

You have a few options, almost none of them good. All replacement pressure plates manufactured in the last 6 years or more are made in China from alternate molds, and they are poor in quality. This includes new ones branded "Valeo." The OEM parts were made in the US and then Brazil, and were much better. You can try to find a NOS pressure plate, but that's hard to find and expensive when you do. If the pressure plate just looks "a little worn" and was working fine when you took it out, I'd be tempted to just put it back in with a new disk. At most, try to find a shop that can machine the friction surface and pedestal legs the bare minimum necessary to make the surface uniform again. For disks, if you like to drive this on the street I would go with a good organic disk. Kevlar and metallic disks are aggressive and harder to modulate in traffic and such.

RISK81

Anyone see any reason not to use the LT4 head gaskets? (11.03:1 compression).

Also when I have the ecm reprogrammed, should the timing be advanced some?

Kevova

You need at least .040 between head and piston. Your build is pretty normal. Tuner may already has a solid tune for your combination. Mail order tuners should work with on tweaking it based on what car is doing. Dyno is the better choice, but more expensive.

RISK81

Anyone else safely running 11:1 compression ratio in regards to a similar build?

racerseks

Hey how did those Taylor 84225's work for you? Did they fit in the factory looms without modification?

RISK81

Don't know yet, still assembling the engine. Just installed the Crankshaft last weekend. I'll let you know how they fit (hopefully soon).

racerseks

Thanks...good luck with it. I've been considering those 8.2's, but mostly see people going with the 74225's. I hate all the grinding, chopping, cutting, etc. I always seem to have to do when going aftermarket, so wondering if they fit in the factory looms okay, and looking for opinions. Again...Good luck with it!