The DCR for the L-46/82 cam on Dave's engine is only 6.93:1 according to EA, which is less than the LT-1 cam.

This is not a good cam for a 327 unless you advance it four degrees, which effectively makes it the same as the L-79 cam. Otherwise, with massaged heads, peak power will be beyond the 6000 rev generally accepted valvetrain limiting speed for hydraulic lifters.

That's why I like mechanical lifter cams and stout bottom ends on 327s and 302s. Everything else equal except stroke, "similar engines" will make peak power at about the same mean pistons speed, which means higher revs on shorter stroke engines. You need to build high rev reliability into a short stroke engine if want you make use of the entire power curve sweet spot, which extends to about 7200 with SHP cams on a 327 with massaged heads - more on a 302

The points of maximum lift of the L-46/82 cam are 114/114 versus 110/118 for the L-79 cam. This is because of the 350's longer stroke. It also has three degrees more .050" duration - 224 versue 221, but this is not signficant.

Duke

 

With correct springs and valve train I've never worried about low 7000 rpm with H-flat cams and lifters. You don't used wimpy 100-110# seat pressure 1.26 springs. You use 125-130# 1.46 dia with other good parts. Lifters like the Crane Hi-intensity. Run fine in motors that have 65 psi hot over 5000 rpm

 

Duke: Two questions. The first is What is the source and actual name of the Engine Analyzer program you use. I have found a lot of EA things from gadgets to programs. The closest is from Smiths, but they quote $149.00 and 178 pages of instructions.

Second question. Do you know, off hand, the cc dome on the stock 1964 365/375 horsepower 327. I probably knew 40 years ago, but it is lost in space now. Thanks, Jim/Arnolt57

 

Some months ago I googled on "Engine Analyzer" and found a vendor who had the basic version 3.0 for about $110.

The net dome volume for the OE 327 forged, domed pistons that are now supplied by Federal Mogul Speed Pro is 5.3 cc.

Duke

 

Duke: Thanks. I have the original pistons in my short block and they probably have less than 35K miles on them. I will "assume" (hate that word) they are the same as the new aftermarket pistons when plotting compression ratio.
Jim/Arnolt

 

The GM part number for the 327 SHP pistons for a given size (std. or overbore) changed over the years, but it's never been clear to my why.

AFAIK the dome volume is the same. The 5.3 cc spec is from my mid-nineties vintage Speed Pro catalog. Federal Mogul bought the TRW Automotive group some years ago and the high performance OE replacement parts (pistons, valves, cams) are listed in their Speed Pro catalog, and AFAIK they all conform to the original GM drawings.

Duke

 

Thanks, Duke. You have to be the "Guru" of old Corvette specs. My Dad was an A and E engineer and spent 45 years at Pacific Airmotive. As you say, he would have probably given a nut for the current AE programs. He used a slide rule and a lot of big books. I have a few of them, like the "Machinists Handbook", etc. I find some of them usefull. I wish he were still around to interpret some of the info.

I inherited some of his skills, but not enough. There is so much knowledge on this board that I might be better off searching old entries and asking new questions.

I have a 327/375 shortblock that I bought new from Chevy in around 1965. I have the 461X 202 heads and the correct year fuel injection. I also have a 1969 Z28 Camaro 4bbl manifold and correct 780 Holley carb that I tricked out way back then. It was certainly a nasty combination in a 2400 pound Arnolt Bristol.

I took it off the road when they started taking the lead out of gas and it has been a "life time project" since. I am now retired and starting to work on it. I am looking at aluminum heads for the better weight distrubution and am looking at Brodix Race Rite 200's. I really like the 30/30 cam and will keep it if the lobes are in good shape. I was limited to 6800 rpm with the old motor due to either valve float or point bounce. The point bounce will not be a problem (unless I put the F.I. back on). I have an MSI distributer and 6AL box.

I looked up the Sportsman rods you like and so far, all I can find is rods listed for big journals. If my old brain serves me, my 327 probably has the small journals. I won't know untill I pull the engine and measure them, which will be later in the year.

Thanks, Again, Jim/Arnolt.

 

The big journals did not show up on 327s until '68. They were exclusive to 350s in '67 and were used across the board on all SBs beginning in '68. The primary reason for going to larger journals was to restore lost journal overlap when the SB stroke was increased to 3.48", and standarizing on a common journal size for all strokes meant the same bearings could be used on all production SBs. Small journals are actually an advantage on short stroke SBs because they offer less friction with more than adequate strength. Back in the seventies a lot of F5000 engine builders preferred small journals because of the lower friction, and those engines were revved to 8000.

I've heard the small journal Sportsmans are on back order from Crower.

Beginning '66 or '67 all SBs got new valvesprings. 3911068, with slightly higher rate and about the same seat pressure as the previous spring. A single point distributor will rev to at least 7000, but it has to be "right" - no wobbly breaker plate, tight endplay, and the 28-32 oz. points.

With a 30-30 or LT-1 cam, PROPERLY adjusted valve cleanance (which is tighter than OE spec), a 327 with massaged heads should rev useably to 7000 and good rods will keep the bottom end together.

The 30-30 cam doesn't make materially more top end power than the LT-1 cam, but the LT-1 cam has better torque bandwidth. I recommend the LT-1 cam for street engines. For vintage racing I recommend the 30-30 cam as a well designed and fabricated header/exhaust system cam exploit the additional overlap. With manifolds and mufflers the additional overlap doesn't do any good at the top end and hurts the bottom end.

As long as you build a SHP/FI SB with a compression no higher than 10.5:1, which is easily achievable with production machined decks and a typical composition head gasket, they appear to operate detonation free on premium unleaded pump gasoline, and "hardened seats" are not necessary.

If you e-mail me I will send a write-up on how to properly adjust the valves on all OE mechanical lifter cams. This information is based on my review and dynamic analysis of the lobe date on the GM drawings. The lobe data on the drawings is specified to five decimal places every cam degree. This data along with my dynamic analysis and measurement of rocker ratio behavior allowed me to establish precise valve clearance recommendations.

Duke