I just stumbled upon this forum when doing a search for “327 pistons” and was blown away by the info in some of the threads. I don’t have a Corvette, but am building a 327 for a 55 Chevy sedan. Here’s what I have so far.

2-bolt -010 block w/ 1977 casting date – never decked or bored
Cast GM 307/327 crank – freshly ground to 10/10
SCAT 3ICR-5700 5.7” rods with ARP bolts – entry-level I-beam

Here are the plans. Have not yet done any of this work or bought any of the parts below this line.

Bore and hone to 4.030”
Deck to 9.010”
(No align bore/hone because main caps register tightly, and crank spins freely with caps torqued.)
Speed Pro H660CP hypereutectic pistons – 2 valve reliefs, teflon coated skirts, 1.675” compression height
Sealed Power E251K moly rings
Have some ACL main and rod bearings that came with the crank. Are these any good?
Melling std volume / std pressure pump

Above the bottom end:
Cam: Erson custom ground flat tappet solid lifter – 270/270, 220/220, .465/.465, 108 LSA.
Other choices are 280/280, 230/230, .465/.465, 108
OR 270/280, 220/230, .465/.465, 108
OR 106 LSA on any of these combinations. Whew!
I was also looking at a CompCams Magnum 270S solid cam, but the Erson guy really impressed me. He said a 108 or 106 LSA would give me better low-to-mid range torque in a 327, and that the narrower power band would work great with my 4-speed.

Timing set: Cloyes true roller

Heads: 64 cc chambers, 170-180cc intake ports, such as Brodix IK180 or Edelbrock Performer RPM, or modified Vortecs. Would Like AFR 180 if budget permits.

Quench height : 038” with .028” gasket

Compression ratio: around 9.6:1. Can get 10.5 with K-B domed hyper pistons. Haven’t figured DCR yet.

Valve springs: whatever the cam manufacturer recommends

Rocker arms: don’t know yet. Maybe just Comp’s 1.52 roller-tipped Magnum

Intake and carb: Performer RPM with 600-650 Speed Demon, Road Demon, or Edelbrock AVS. Maybe even Edelbrock’s dual quad setup (for nostalgia). Or, I already have a perfectly good Edelbrock 1405 (600 CFM).

Headers: 1-5/8 primaries, 3/4-length (already have on current engine)

Other things you need to know:

55 Chevy sedan, 3.42 axle, M20 Muncie (2.52 low gear).
I want lope at idle and a motor that will rev to above 6000 RPM.
The car occasionally goes on 100-200 mile round trip cruises, but most driving is around town.
Will rarely, if ever, be raced.

I’d appreciate your comments.

Thanks,
Mike

 

My recommendation is to go with the Chevy LT-1 solid lifter cam rather than an aftermarket. That will have way too much overlap for a street engine. Then use the stock chevy valve springs to accompany it.

You can find lots of good reading and results with the LT-1 cam. Sealed Power CS-1145R, or Melling 22415 are equal to the LT-1 OEM 3972178

 

That's the early 70s Z-28 cam right? Seems like that thing would have way too much seat-to-seat duration, and therefore more overlap than a more modern (even 20 year old) design. I'll check out its specs, though.

I know its 30-30 predecessor was used in 327s with at least 11:1 CR and 3.70 gears. I've got 3.42 gears and have to stay under 10:1 CR.

Just found the LT1 cam's specs. I don't see advertised duration, but with 242/254 at .050" tappet lift, it's gotta have more overlap than the cams I listed above, even with a 116 LSA.

 

It is the best cam to use with 10-10.25:1 CR. It is the 1970 350 LT-1 cam and maybe the Z-28 as well. It will provide you with a DCR of around 7.6:1 which is perfect for pump gas. Most guys on the C2 board are using the TRW 2166 forged popups to get 10.25-10.35 SCR with that cam. Mark just finished his motor last month and he is making 270 ft lbs torque and 270 HP at it revs nicely to 7,200 RPM.

Dave McDuffords motor is almost identical and is making similar power on the dyno too.

Just do some searches on the C2 board for ghostrider or LT-1 cam.

Actually it has way less overlap than an aftermarket cam, Duke recently posted all the computed overlaps for the OEM cams. They are all very low, they need to be to idle relatively smooth with an automatic trans and perform with a stock exhaust system.


Why would you listen to this guy who says:
He said a 108 or 106 LSA would give me better low-to-mid range torque in a 327, and that the narrower power band would work great with my 4-speed.

A narrow power band, you're kidding right. Mark's 80 percent bandwidth is like 2,200 to 6,500 RPM with a straight power curve all the way.

This is exactly why you don't want to use a cam like they are selling.

 

I read lots of those posts today. Very good info.

I also read Vizard's cam article in Popular Hot Rodding. If I choose 55 degrees overlap as a target, and 109 for an LCA, my cam duration should be 273. I got the 109 LCA from one of his tables that shows optimal LCA for specific displacement and intake valve size. It looks to me like this is a CONSTANT, regardless of what kind of performance you're looking for.(???) I know this flies in the face of "wider is better".

From what I can see, the Erson guy's duration (270 or 280) and LCA (108, not 106) recommendations were pretty close, if you use Vizard's article as gospel. Maybe he's learned something from many years of cam grinding.

Mike

 

My combination works extremely well, is easy, very streetable, and now makes about/over 300 hp at the wheels (measured 293 ft-lb, 293 hp on the chassis dyno prior to some flow work and a Lars tune-up). Also, note how consistent my numbers are.



My mild combination:

331 CI, pump-friendly 9.5:1 CR
K&N 14"x4" air filter, Corvette drop base and lid
Holley 600 dp, choke horn milled, polished
1/2" Aluminum open spacer port matched to manifold, exterior polished
Edelbrock Performer RPM, port matched, exterior polished with all extraneous castings and lettering removed
Homemade lifter valley splash shield to keep hot oil off manifold bottom
Camel hump 1.94/1.50 heads hogged out to 2.02/1.60, pocket ported, port matched, pump-friendly hardened seats, 3-angle valve job
Comp Cams 1.52:1 roller-tip rockers
Crane Cam Vintage Muscle 327/350 hp cam, 222 degrees @ 0.05, 0.447" lift (with 1.50 rockers)
Doug Thorley headers, dechromed and ceramic-coated
2.5" mandral-bent exhaust (including tips), 2" cross-over just before rear axle
DynoMax stainless Ultra Flow mufflers
Mallory Hyfire IV CD ignition box triggered off Accel points
Mallory high voltage chrome coil
Mallory spiral-wound coil wire
Mallory solid copper plug wires, ends soldered to wires
Champion plugs
37 degrees total ignition advance (distributor later recurved and reduced to 34 total degrees by Lars)
Carter high volume fuel pump
Melling high volume oil pump
Open breathers
Polished aluminum high flow water pump
Flex fan with polished aluminum spacer
Polished aluminum one-wire 100 amp alternator
Muncie M-20 CR 4-speed (Now a Keisler 5-speed )
Hurst shifter
3.70:1 positraction
225/60/15 Firestone Firehawk SZ50s on 7”-wide Western 30-spoke Turbine Wheels

Prior to Lars, engine had never been professionally tuned up. Car did 293 ft-lb and 293 hp @ 5,500 rpm on the chassis dyno. Engine pulls to 6,200 rpm and does over 200 ft-lb from 1,900 rpm. This was prior to some clean-up work around the junction of the carburetor and base of the air cleaner that smooths the flow through this area and a Lars tune-up that should be good for a few ponies. Car has run 107 mph in the high 13's (old, bad tires) at the quarter. Car is extremely streetable and could probably even run 87 octane if it had to. (I can't get the engine to ping no matter how far I advance the ignition.)

The secret to power is in the attention to details!

 

Toddalin -- That torque curve looks like West Kansas! What does that 293 lb/ft torque equate to at the flywheel -- maybe 330?

That cam was meant to work with around 10.25:1 compression ratio to maintain decent cylinder pressure, but I guess you can't argue with success. Did you advance the cam at all?

 

http://forums.corvetteforum.com/show...&highlight=327

 

Duke -- Thanks. That's one of the threads I read through yesterday. A few questions:

By "LT1 cam", I assume you mean the early 70s Z28 cam? I can't seem to find any event timing specs for it. How does it differ from the 30-30 cam? Either would need a compression ratio of around 11:1 to make acceptable cylinder pressure, right? (Although, I just noticed where Scott said 10.0 - 10.25 yeilds 7.6:1 DCR.)

When GM dropped CRs in 1972 (I think), did they still have a solid lifter engine? If so, what cam did it use?

Am I correct in assuming my large journal cast crank will probably limit RPM to 6000-6500? If that's the case, shouldn't I go smaller on the cam to move my powerband downwards? That powerband may also be more friendly with my 3.42 gears.

Thanks for your help.
Mike

 

The LT-1 cam specs that are comparable to a hydraulic cam are 231/239 110/122/116. The 30-30 is 239/239 110/118/114. Search "LT-1 cam" on the C2 discussion and you should find several explanations I offered on the difference between mechanical and hydraulic lifter cam specs and how to "normalize" mechanical lifter cam specs to compare them with hydraulic cams and indepth discussions of cam performance.

The LT-1 cam was used on LT-1 Corvette and Z-28 engines from 70-72, both high and low compression, then emissions and noise standards killed it.

I don't see any problem running a large journal cast 327 crank to 6500 or even 7000 as long as the crank is qualified via Magnaflux inspection. With the LT-1 cam yielding 90 percent of peak torque at less than 2500 you don't need to lower the torque or power bandwidths.

If you build your engine like ghostrider20's you'll have a high rev screamer that's almost a stump puller on the bottom end - a very flat torque curve with OE reliabililty. It doesn't get any better than that.

Duke

 

GMPP sells this LT1 cam:

P/N 3972178
Advertised: 300/312
@ .050": 242/252
Valve lift: .435/.455
LCA: 116
Lash: .024/.030

Looks like their .050" duration numbers are not normalized, but this must be the cam you're recommending, right?

I couldn't find where ghostrider20 listed his compression ratio. Do you know what it is? I plan to order pistons this week.

Mike

 

The cam was installed "straight up." It's probably flatter at the bottom of the curve now as Lars distributor recurve was focused in this area. The old vacuum advance can was creating way too much advance way too soon.

 

Yes, that is the LT-1 cam P/N, the same Sealed Power CS-1145R or the Melling 22415. You can find the Sealed Power for around $110 online. The last time I tried to buy the GMPP cam made by Crane it was discontinued but Crane still sells it under P/N 969551.

Mark's SCR is 10.35:1 with a .026" Victor Reinz Head Gasket.

Dave's engine is at 10.25:1 with a thicker head gasket.

BTW, If you can't afford the TRW 2166s, KB makes a Hyper clone P/N KB157.

 

Scott -- Thanks for the alternate cam P/Ns.

We think alike re the KB157 piston! It fits my budget and has retainers for floating pins. (My SCAT rods are bushed.)

The only gotcha with K-B hypers is having to file the top ring to a .026" gap.

Todd -- vacuum advance should have zero effect on WOT dyno runs.

Happy revs!
Mike

 

Mark's engine came in at 10.5 with the Victor gasket and IIRC he said it's .028" compressed.

Dave's was 10.35 +/- 0.1 across the board with a .038" Felpro.

Both use the OE replacement Speed Pro forged, domed pistons. I think the KB dome volume is about half as much, so they won't make quite as much compression, and since they are designed for a tight fit, they probably generate a little more friction.

Duke

 

OK Duke, how did I screw that one up??

Scott

 

I have my shift light set at 6000 RPM so i am hiting 6500 -6600 RPM all the time on my 327 LG cast crank. Haven't had a problem yet.

 

I dunno. Mark called me just before installing the heads and said the computed CR with a .028" Victor was 10.5 and something near 10.25 (I don't recall the exact number) with the .038" Felpro. I recommended he go with 10.5 since Dave's engine was okay on unleaded premium at 10.35.

The KB 157s have a .100" dome with a net dome volume of +0.5 cc and a compression height of 1.678". The OE replacement Speed Pro 2166s are .125", +5.3cc, 1.675.

If the head and block deck are dead level you also have the option of using the OE type steel shim gasket. The OE thickness I have is .018", but I don't think GM offers them anymore, and I've heard that aftermarket replacements are .015".

Each .010" of gasket thickness is about 0.3 compression change, so there appear to be enough options to get the CR within any reasonable 0.25 target range spread .

http://www.csgnetwork.com/compcalc.html

Duke

 

My 9.010 deck height will make up for the smaller dome. Also, the K-B 157 has a .003" taller compression height than nominal.

My spreadsheet shows prox 10.5:1 with a .028" gasket. I can play with deck height and gasket thickness to get whatever I want, but plan to keep the quench height around .040". Just noticed the above combo would give me only .035", which is way too tight for me.

Re steel shim head gaskets, I see where Fel Pro makes a .015" and .016". Mr. Gasket makes one they list as .018" - .020". It's their P/N 1130. I bought an .018" set from a Chevy dealer about 8 years ago.

Mike

 

Chevrolet specs minimum quench clearance at .035-.040, which I think is a little conservative. I know guys who have run near zero quench clearance, but strictly drag racing engines. I don't think .035" is pushing it on a street or road racing engine.

When you disassemble an engine you rarely find any deposit buildup in the quench zone. That's because the tremendous turbulence as the engine approaches TDC keeps it scrubbed clean.

You can run even tighter quench clearance on an aluminum block engine because the the quench clearance grows around ten thou between room and operating temperature.

With minimum quench, 10.5 CR and the LT-1 cam detonation won't be a problem - probably even with a real aggressive advance curve.

Duke