I have heard much about the low and high compression 1.9 what was the ratio's of both and how much difference in hp? any pros and cons of each engine? why did they switch?
For one thing, keep in mind that while one part alone may be worth 6 hp, and another part alone worth 5 hp, combined they might be worth 15 hp as they compliment each other better when used in unison (similar to the way a big valve head might be worth 8-12 hp on a stock engine, but on a racing engine that already has a big cam/big carbs/high compression it can be worth 25-30 hp).Paul said:Bob,
So you are saying, of the ~ 20 HP drop from 69/70 to 71/72, low compression pistons only accounted for ~6 HP and the solid vs hyd cam accounted for the other ~14 HP? Or, were there any other changes to note, jet sizes or spark curve?
What accounts for the drop from 71/72 to 73/74 models?
This has been discussed heavily in the past on these forums. There are tons of tips and 'recipes' in the forums, particularly under the performance headings. The search engine can really help out here, but it's probably better to go into the performance forums and just scroll through the headings, as many of them are self-descriptive. I've probably personally posted 20-30 times on this very subject, not to mention everyone else's input. So there's a lot to absorb admittedly.bozkm said:RallyBob, what might be helpful for us "newbies", is maybe a high level list of what we could do.
The roller rocker will work if you have custom inserts for the lifters that will work with the rocker arms. Spring rates will have to be stock or nearly stock however, if you collapse the lifters there will be problems. Max valve lift should be .430-.435" with stock springs, max duration depends on the lobe separation angle, and how much you can deal with a bad hesitation off-idle. Too much duration (overlap) will reduce idle vacuum and cause fluctuations to the air flow meter. After 220 degrees @ .050", the idle quality suffers enough to adversely affect the EFI.David McCollam said:Bob,
I promise that I'll never ask again, but could you tell me if those roller rockers of Gregg's would work with a hydraulic lift cam, a higher compression (9:1) piston and FI? What would the max cam specs be for a street motor?