I did mention my concern about the duration on the L-79 just before that as well. In general, is low compression with a high duration cam a bad idea?? thats what I've read...
Depends on the design of the lobes, overlap or the lack there of, lobe separation, lift and the list goes on. In general a lot of duration is not good for a street cam period. The L-79 is not a long duration cam as cams go. There is another way to look at it if cam theory end 4 stroke engine theory is what we want to discuss. If you have a low compression motor that just means that you have a bigger cavity to fill with fuel charge. The more you fill it the more you have to compress and the bigger the explosion in theory. That being the case the longer the valve is open the longer you have to pull fuel mix into the chamber. Granted all that is BS by most peoples standards but it is one school of thought. I have run the L-79 cam shaft with a small intake ( like stock 4bbl intake or the equivalent) on a low compression 283 without any problems at all. Yes it is a little lumpier at idle then it would be in the same engine with a bigger displacement and it starts running at a little higher RPM but not so much as to make it a problem to drive. The RPM difference is in the hundreds and not the thousands of difference. What happens with a lot of guys is that when they order their long duration cam shaft they order a cam shaft that has a lot of overlap and poor lobe design (poor being a nominal term here) the early exhaust opening (overlap) causes the engine to bleed compression at low RPM. Now all at once long duration is a bad thing if they have tried to run said cam in a low compression motor. They normally complicate that with a big intake, one designed by the manufacturers for a bigger displacement motor which is more common these days than the smaller displacement. The smaller displacement engine cannot draw a deep enough breath to keep the plenum full and port velocity goes straight down the tubes. Things can escalate from there if you catch my drift. The L-79 does not have the overlap problem that we have mentioned. The lobe separation is right in line for a street drive small block, probably because it was designed for a street driven small block by the people who were designing and building street driven small blocks. Its original intent was for an 11:1 327 but it works fine in almost any small block ever manufactured. granted you are hearing this from a guy that tossed a long duration .500 lift tight lobe Sig Erson cam in a street driven 265 once just to prove that it could be done. of course if you engine is wore slap out all of this is moot. The elgin cam you chose will be fine. Run it in good health and be happy with it.
I'm running a 097 Duntov copy in my 283 FI '57 Utility Sedan (Black Widow trib car). Nice lope at 900 idle speed, slight tick-tick from the solids (.014-.018"), great bottom and mid-range power. With 9:1 compression, she runs happy on 89 gas...LOVE IT!!! Figure out your CR, then look for a cam... The lower the compression, the EARLIER the intake should close to help build DYNAMIC COMPRESSION. REREAD what 'beaner said, sounds like he's built a couple, and still could!
6bangertim--I also run an 097 (12&18) in a FI 283 with 10/1 compression-3.70 posi and a 3 spd-have run it this way for many years. Runs very well with this combo-again also like the Crane 266/440 lift in a 283 and Sig ErsonTQ30
thanks for the better explanation beaner, main points on this cam choice were getting it running on the cheap as well as possible. just opening the motor up was more than I wanted to do with this one, but i couldn't in good conscience at least look at it before firing it up. glad I did because the cam was completely wiped. next motor will be something that the parts combo fits and works well together. this thing is just a mess. I will be lucky if i'm pushing much over 8.5:1 even with the shim head gaskets on it.
A low compression motor is not a bad thing it is just a different thing. Upside is that it will run on panther piss and if you decide to go out of town that can be a good thing. I got an air cooled engine that won't run on anything by high test, and own a place in the country with one gas station and all they have is diesel and regular. I keep a can of gas there and if I go anyplace I have to use it because it takes one tank from my last gas stop and back to my last gas stop. LOL
it's a bad thing when they use big high flow heads, full roller rockers etc. with cheapo cast pistons... blah.. what kind of air cooled?? VW?? believe it or not I've built a few VW motors that would put this 283 to shame on the dyno
I'm curious WHERE you found steel shim head gaskets for a 283? You said this engine was .030 over, with flat top, 4 valve relief pistons? Most likely, a "rebuilder" type of piston, that come with .020 off the top; they assume a rebuilt engine will have the block decked a comparable amount. But, most guys/shops don't deck a block for routine rebuilds. Are the numbers still readable on the right, front deck on the pad? Your pistons are probably .040+ in-the-hole, then big chamber heads on top. I'm not trying to fault you on your build, I'm doing two 283's myself, and it's hard getting the CR up on these small bore/stroke motors. And you don't want to over-cam one of these little fellas; you're right about the duration at .050 with it being right around 115. I still think you have too much head for a small, street motor; #601, 305 heads would put you in the 9:1/9.5:1 range. If you have a supply of small bore, steel shim, head gaskets, scoop them all up; the Stock/Super Stock racers have exhausted the supply, and GM has't made them for some time. Post more after it's running; inquiring minds want to know. I am Butch/56sedandelivery.
OT V twin. And it puts lots of big inch engines to shame. I only carry 3.5 gallons. Butch @56sedandelivery I can probably capture some steel shim gaskets or copper if you need them. .040 down the hole and you are already screwed. My last 283 was running off the shelf TRW forgings, all we cut the decks was just enough to clean them up. Anyway you can still get or should be able to get good TRW forgings for 283 chevy motors. If that is any help.
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