1970 WS 400 Ram Air 3/4 434 Build
Am having a rebuild of my 1970 WS/9799915 400 block, dated January 6, 1970. (Ram Air III code up front, with the Ram Air IV modified casting number, of which a few were built.)
Engine parts stored indoors continuously, with the WS block which was stored continuously indoors, and is now in machine shop where it checked out ok for an overbore to 0.40. As we now have a multitude of aftermarket internal engine parts, rebuilding with stronger parts is considerably less money than during the 1900s. The best bang for the buck appears to be a SCAT 4" stroke forged standard weight crankshaft with BBC Callies rods, the latter being only about $250 costlier than Eagle or SCAT 4340s, but with apparently better strength qualities for greater sustained higher rpm operation.
I desire keeping this car with a manual transmission, but want greater flexibility, as the original M-21 close ratio with 3.73 differential gives nice torque multiplication (2.20 first gear), but alas 4000 rpm at 80 mph in top (4th) gear.
Ideally I want to switch to a 5 or 6 speed manual transmission. The most prevalent today appears to be the Tremacs, but I am more intrigued by the Richmond, for two main reasons: (1) its far wider selection of gearing options, and (2) what I read years ago when it was known as the Doug Nash, about the greater efficiency of placing the gear multiplication more within the transmission than in the differential, with steeper transmission gearing coupled with a 2 series rear rather than a high 4 series or 4 series differential coupled with an overdrive. But as I would like to reduce expenses where I already have something which could more easily be swapped later, I plan on switching to an M-20 wide ratio for now, (and with the rear having to come part to re-do the powder-coat) with the 3.73 gears replaced with either 3.31 or 3.07s. See and compare the following comparison between these transmissions:
2.20 1.64 1.24 1.0
8.206 6.1172 4.6252 3.73
2.52 1.88 1.46 1.00
8.34 6.22 4.8326 3.31
7.73 5.7716 4.48 3.07
Note, that the M-20/3.07 combo gives not all that much less overall multiplication than the M-21/3.73 combo, and that the M-20/3.31 combo gives a bit more. With regards to the greater torque of the longer stroke and more modern camshafts, never-mind that Pontiacs were generally more torquey than the Chevrolet engines that led the close ratio trend, this appears to give a great bang for the buck, especially with the 3.31.
But what about the things that should and must be set now?
My basic engine recipe consists of (1) factory 1970 1970 WS 4 bolt main 400 block; (2) aftermarket rotating assembly of a SCAT 4340 forged steel 3" journal, 4" stroke crank swinging BBC Callies rods holding either forged or billet pistons with full floating pins; (3) rebuilt 1970 7040270 (1974 service replacement) Quadrajet; (4) 1971 455HO factory aluminum intake; (5) 2.5 outlet coated RARE Ram Air style exhaust manifolds; (6) 1970 614 heads (1973 service replacements) previously milled thus reducing the combustion chambers from 70-72cc to 65-67cc, with the cross-over ports filled with aluminum), with a moderate degree of porting added, perhaps to 270cfm rater than 330 cfm to minimize adversely affecting lower lift flow.
The basic idea is an externally stock appearing engine with significant internal improvements for far greater power while retaining street-road drive ability and longevity.
But what about?
- Pistons? I know they will be flat top design with added D dish somewhat reflecting the combustion chamber shape for better flame propagation to lower the compression ration from the 12 :1 or so that I would have with my already milled 614 heads, or the II+ that I would have with if they were at their factory 70-72cc sizing. But which brand id most preferable? Ross? Icon? CP/Carolo? Diamond? Or? Benefits and drawbacks of each type, including forged and billet? My machinest dislike Icon, citing inferior sizing tolerance, while a thread I have seen shows a preference for CP and Diamond over Icon or Ross as the choice of serious racers.
- rod length- 6.7 or 6.8? What are the benefits and drawbacks of each? I have seen a reference to the 6.8 rod in a 4" stroke Pontiac as ideal. Does it have any drawbacks with providing less space for the rings?
- compression? I would ideally like to run straight 93 octane pump premium, or at least limit the amount of fuel spiking - E85, Race or Octane Boaster - to retain flexibility for lengthier trips. Some considerations: As my machinist recommends a square cutting of the heads, this shall reduce the now at 65-67cc chambers to say 62-64cc. Thus, I want to minimize any decking of the block for the sake of retaining more of a heat sink, and also minimize the size of the piston dish so as to retain flexibility for swapping heads without having to likewise mill any such replacement heads. For instance, setting the compression at 9.5 with 63 cc heads would mean probably high 8s with 72 cc heads. As I intend to always run this engine with iron Ram Air heads that came with 70-72cc from the factory, together with a more aggressive cam, I would like to set the compression of this engine build for 72cc heads to at least 10 to 1, and thus about 10.75 with 63cc heads.
- Camshaft. My initial idea was a hydraulic roller for the potential for more area under the curve and the reduced rotational friction. But I am told of problems such as of use above 6000 rpm (I would like the capacity for sustained 6500-7000 capability), e.g. pump up, or worse a catastrophic lifter failure. Also, would not much of the friction reduction benefits from the roller be negated by the required greater valve spring pressure. I have had suggested to me the option of a solid roller. Asides from the added maintenance, what is the deal with its friction issues- e.g. are its friction reduction negated by the value springs? What's the issue of the distributes gear with either a hydraulic or solid roller setup? And given how flat tappet camshaft technology evolved by the mid 1980s with lobes considerably more aggressive than those of the 1960s, how much of a bang for the buck would either a hydraulic or solid roller give over the more proven technology of the hydraulic flat tappet cams from the mid 1980s and later, which open and close the valves significantly quicker then the 1960s era cams?
A quick comparison:
1969-1970 Ram Air III automatic
9779068 288/302 212/225 LSA 116.0
1969-1970 Ram Air III manual
9785744 301/313 224/236 LSA 115.5
1969-1970 Ram Air IV
9794041 308/320 231/240 LSA 113.5
Butler recommended hydraulic roller with 9.5cr
CCA-3315 / 3316 282/288 230/236 .340/.347 .510/ .521 .544/.555
Jim Lehert recommended SR
CCA-3315/3316 282/288 230/236 0.510"/0.521"@1.5 0.544/[email protected]
CCA-3316/3317 288/294 236/242 0 .521"/0.540"@1.5 0.555/[email protected]
Butler recommended hydraulic flat tappet with 10.5 cr
XE284H 284/296, 240/246, .507/.510, 110 Hyd. (112 lsa optional)
Other HYDRAULIC FLAT Tappet Cams
CCA-51-224-4 274/286 230/236 .488 I - .491 110 1800-6000
CCA-51-225-4 284 /296 240/ 246 .507 I - .510 110 2300-6500
CCA-51-226-4 294/306 250/256 .519 I - .524 110 2800-6500
10510703 268/276 227/233 .489/.504 LSA/ICL: 110/106 1600-5800
10510704LK 276/284 233/241 504/.527 LSA/ICL 110/106 2000-6000
10510705LK 284/292 241/249 .527/.548 LSA/ICL 110/106 2400-6200
I had to review these figures myself to see that somewhat surprisingly, that the more recent roller cams offer not so much more in opening tand closing he valves then I expected. Sure they do so way more so than the 1960s cams, but not so much with the 1980s+ hydraulic cams. For instance a 1960s [email protected]
cam being well over 300advertsied duration (a spread of 70-80degrees), yet both the rollers and the later flat tappets such cams being high 270s/low280s advertised duration (a spread of 40-50 degrees). As I was already aware of this with my circa 1984 Comp Cams 280 flat tappet, I was hoping to see this spread between advertised and 0.50 duration reduced a bit further, perhaps at least down to 30 degrees.
Give that the roller cams are apparently not much more aggressive then the more recent flat tappet cams, I still see a potential benefit in a roller for reduced friction. But again, what is the consensus regarding how much any such friction reduction is negated by the increased valve spring pressure, as well as the reliability issues?
Perhaps a solid roller is better than a hydraulic roller due to it having greater simplicity.
But given the relative spreads between advertised and 0.50 duration lift, is the benefit worth the significantly greater cost of the parts?
And as well, what about the surrender of the added benefits of the long proven technology of having lifters that are variable duration? AKA Rhodes lifters?
Jim Hand apparently got good results with Rhodes lifters, allowing a larger cam allowing greater upper rpm power with the Rhoads variable lifter reducing the duration at lower rpms thus improving power there and thus providing greater power over a broader rpm range.
In now reviewing the Rhoads lifter line, I see that in addition to their "Original Rhoads Lifters" that they now offer two extra lines, "V-Pro Street" and "V-Max Race", each of which is adjustable. The V-Pro Street lifters can be adjusted to vary the bleed-down to reduce the lower rpm lift .010" to .025", and the likewise duration between 5 and 15 degrees at .050" cam lift, with full lift and duration coming on by about 3500 rpm. The V-Max Race are likewise adjustable to reduce lower rpm lift by as much as 0.40, and duration between 5 and 20 degrees @0.50, with full lift and duration coming on by about 4000rpm. Each of these newer adjustable lines of lifters offer greater flexibility than the original Rhodes lifters which are non adjustable and which reduce lower speed lift by about 0.10" to .020" and duration about 10-15 degrees, with full lift and duration arriving at about 3500rpm. Since the bleed-down is going to likely increase the engine's dynamic compression at lower rpms, this added adjustable feature could be quite useful in tailoring the duration and lift curves to work better with the higher static compression permitted by the cam's intrinsic duration profile, as well as further fine tuning with the flow of the cylinder head's porting.
Interestingly, Rhoads offers an additional sub variant of these adjustable variable duration lifters- rollers, yet alas not for Pontiac. Ideally I would like to see such developed for Pontiac engines and refined to ensure greater reliability, but alas that has not happened, at least not yet.