| Slant Six Forum https://slantsix.org/forum/ |
|
| quick motor HP question https://slantsix.org/forum/viewtopic.php?t=15658 |
Page 1 of 1 |
| Author: | terryx [ Fri Jan 06, 2006 7:40 am ] |
| Post subject: | quick motor HP question |
Hey , what did they do to the motors as they got into the 1970s that dropped the HP such as a 1967 slant is rated at about 145 hp while a 1974 slant is rated at about 110 hp Did they just put a smaller carb on it ? Or was it smaller valves in the head? What I'm getting at is .... does a 74 motor block have the same hp potential as say a 67 block. after rebuilding my head my bottom end has gone out and I'm looking at just swapping it out for another motor, but all I can find so far are 70s blocks. I'm thinking that theres no differance....? right , wrong ? ? answers please |
|
| Author: | DusterIdiot [ Fri Jan 06, 2006 10:11 am ] |
| Post subject: | Several factors... |
In 1972 the 'system' went to SAE net measurements over 'Brake' measurements... The old system was like your slant, not accessories or belts on an engine dyno (figures at the crank), net was supposed to be more accurate with a full load of accessories (A/C on, load on alternator), and supposedly they took the measurements from measurement on a chassis dyno. The 1967 block is all the same as the 1974 block...but a few things happened: The 1967 motor will have a baby Holley 1920 on it, not the bigger mouth gaping Holley 1945. The 1967 stock cam is a bit 'smaller' than the 1974 stock cam. The 1974 head would have hardened seats for unleaded gas, and better combustion chambers (you won't notice much driving an automatic to the grocery store...) For rebuilding, you can grab any forged crank 225 up to 1976 and swap your 1967 crank into it... -D.Idiot |
|
| Author: | slantvaliant [ Fri Jan 06, 2006 11:13 am ] |
| Post subject: | |
The later Net Horsepower ratings were not made using chassis dynamometers, but they do include factors for parasitic losses - water pumps, etc. - that were not addressed under the Gross Horsepower rating. Not that there has recently been another change in the rating systems, one that cost several advertised horsepower for several cars - but added a few to some! |
|
| Author: | SlantSixDan [ Fri Jan 06, 2006 11:26 am ] |
| Post subject: | Re: Several factors... |
Quote: In 1972 the 'system' went to SAE net measurements over 'Brake' measurements
Yep, and the SAE Net numbers, for any given level of engine power, are lower than the old SAE Gross ("BHP") numbers. That accounts for most of the difference between the '71 and '72 ratings.Quote: The 1967 motor will have a baby Holley 1920 on it, not the bigger mouth gaping Holley 1945.
There were multiple venturi sizes and two throttle bore sizes for the Holley 1920 and Carter BBS carbs used in '67. Multiple venturi sizes and only one throttle bore size for the Holley 1945. In no case is the Holley 1945 bigger than the 1920 or BBS.Quote: The 1974 head would have better combustion chambers
The combustion chamber improvement was introduced for the 1967 model year and was the same as in 1974. The primary main effect of this change was not on horsepower, but on emissions.Aside from the rating system change giving lower numbers, the rest of the differences in pre-'72 and post-'72 engine ratings are due to the progressive introduction of stricter and stricter emission standards in North America, and the half-baked measures taken to comply with them with the slant-6. EGR, then more EGR, then even more EGR. Lower compression, then even lower compression. Smaller and leaner carburetors. Shorter and slower advance curves. Hotter running. More restrictive multiple-catalyst exhaust systems. Still with the same old stone-age combustion chamber! Had they not dropped the late-'70s program to produce an aluminum fast-burn cylinder head for the slant, the poor old 225 might not have been down to 80 pathetic, gasping, wheezing horsepower in its last few years. Back to the question of ratings: I have a hard time placing much stock in the factory ratings year to year. Consider: The 225's published rating remained at 145bhp, 215 lb-ft of torque, at the same RPMs, from 1960 through 1971. That's across three different camshafts, multiple different ignition advance curves, and a lot of markedly different carburetors. The only change in ratings during this whole time was in '67 when the 170's published rating was changed from 101bhp to 115bhp, correlating with the installation of the larger 225-sized carburetor (1-11/16" throttle bore) and the 240°-236°-16°-0.395" cam that had been installed in the 225 for '65. Other ratings of interest: 160bhp for the export 2bbl setup of '67-'76, and 180bhp for the Argentine twin 1bbl setup. |
|
| Author: | terryx [ Fri Jan 06, 2006 12:18 pm ] |
| Post subject: | ....very interesting |
wow you really know your stuff You said that they began to progressively drop the compression as went thought the seventies. HOw was this achieved? Did they fatten up the head or the block? And what would it take to get a 74 electronic distributator to perform like say a 67 one. Change the springs? thanks |
|
| Author: | slantvaliant [ Fri Jan 06, 2006 1:15 pm ] |
| Post subject: | |
You don't want the '74 distributor to perform line a '67 - points vs. electronic - but you could benefit from giving it a better advance curve. Springs are part of it, but so are the weights and slots, as well as the vacuum canister. A search of the forum will give you several hits, including these: http://www.dutra.org/doug/draft-webpage ... ibutor.htm http://www.slantsix.org/forum/viewtopic ... ht=recurve |
|
| Author: | emsvitil [ Fri Jan 06, 2006 1:17 pm ] |
| Post subject: | |
Quote: You don't want the '74 distributor to perform line a '67 - points vs. electronic - but you could benefit from giving it a better advance curve. Springs are part of it, but so are the weights and slots, as well as the vacuum canister. A search of the forum will give you several hits, including these:
http://www.dutra.org/doug/draft-webpage ... ht=recurve linky no worky.... 
|
|
| Author: | slantvaliant [ Fri Jan 06, 2006 1:41 pm ] |
| Post subject: | |
I edited it. Two links got stuck together. Had to spray them with the garden hose to get them apart. Try again. |
|
| Author: | emsvitil [ Fri Jan 06, 2006 2:01 pm ] |
| Post subject: | |
Here's a thread I did on recurving my 64 http://www.slantsix.org/forum/viewtopic ... ight=curve |
|
| Author: | NewLancerMan [ Fri Jan 06, 2006 2:20 pm ] |
| Post subject: | |
Hey Ed, that's some SWEEEEET steering you got on the valiant there...is that like 15 turns lock-lock?  btw where in s.cal are you? I'm heading down in a few weeks to Claremont/Pomona area
|
|
| Author: | SlantSixDan [ Fri Jan 06, 2006 2:29 pm ] |
| Post subject: | Re: ....very interesting |
Quote: You said that they began to progressively drop the compression as went thought the seventies. HOw was this achieved?
Mostly with the head. It's possible/likely the block deck height might've been increased in the late-'70s/early-mid-'80s blocks, but I don't have specifics.Quote: And what would it take to get a 74 electronic distributator to perform like say a 67 one. Change the springs?
See other responses—yes, you'd change the advance mechanisms. Be advised that if your '67 advance curve is set up and working well for you, it can without too much difficulty be transferred to the '74 distributor (both early and late vacuum advances fit late distributors, springs also interchange). Then the only thing you'd have to match up would be the centrifugal advance slots.
|
|
| Author: | emsvitil [ Fri Jan 06, 2006 2:30 pm ] |
| Post subject: | |
Quote: Hey Ed, that's some SWEEEEET steering you got on the valiant there...is that like 15 turns lock-lock?
btw where in s.cal are you? I'm heading down in a few weeks to Claremont/Pomona areaNo, only 10 turns. I'm right next to LAX, but I'll be out of town for the next couple of weeks....... |
|
| Author: | mpgFanatic [ Sat Jan 07, 2006 6:11 pm ] |
| Post subject: | no point in counting the number of revolutions... |
Quote: 42:1 manual steering
Yea, I've been chuckling at that, too. Quote: Hey Ed, that's some SWEEEEET steering you got on the valiant there...  It does hit pretty close to home. My arms feel like a windmill when I'm parking the little '64. Gotta keep it rolling slightly, to avoid the futility of trying to swivel a tire on dry pavement.- Erik |
|
| Author: | emsvitil [ Sat Jan 07, 2006 8:05 pm ] |
| Post subject: | Re: no point in counting the number of revolutions... |
Quote: Quote: 42:1 manual steering
Yea, I've been chuckling at that, too. Quote: Hey Ed, that's some SWEEEEET steering you got on the valiant there... It does hit pretty close to home. My arms feel like a windmill when I'm parking the little '64. Gotta keep it rolling slightly, to avoid the futility of trying to swivel a tire on dry pavement.- Erik I just make sure I keep my thumbs out of the way when I release the steering wheel to let it unwind............. 
|
|
| Page 1 of 1 | All times are UTC-08:00 |
| Powered by phpBB® Forum Software © phpBB Limited https://www.phpbb.com/ |
|