DAVECS1

iTrader: (2)

I did a great deal of searching on the net and did not find much on the subject of doing a high lift cam and using OEM roller lifters. I did find many wives tales of not using a reduced base circle cam of cam with over .535 lift, unlest you go with Crane's 600 dollar lifters or the aftermarket link bar type lifters that broke and destructed my last engine.

I purchased a Dart SHP block (I am not sure how different it is from a stock roller block), Comp Cams Big nitrous, roller cam with reduced intake duration and a 112 center line on reduced base circle, and LS7 lifters. I am happy to report, it all mocked up excellent with no problems of losing the oil groove out the bottom or falling below the dog bone. I am extremely happy as I am going to have the performance I want with the proven reliabilty of the OEM setup and I do not have to fear link bars coming apart.

Here is the Comp base part number I started with.


Here is cam on the base circle and the dog bones.


Here is a picture of the bottom of the lifters.


You can't see it well but there is almost exactly .25 inches above the lifter bore, when the lifter is on base circle of the cam.


The bore is about 1.7" long as shown here.


So if you add 1.7 to .25 you get 1.95 and that will give you the liength down the lifter that is in the bore, to make sure the oil groove is not falling out, which I am glad to report there is quite a safety margin as shown here.


So it is not a .6 inch lift cam but decent size, but after looking at these pics and measuring I don't think I would be scared to go considerably larger, and if using Ls7 lifters supposedly these if setup right can rev to at least 7000 RPM. Sounds like a win win to me.

Damon

Sounds like a good plan. You wouldn't happen to ahve a side-by side pic of the LS7 lifter and a "standard" 80s-vintage stock rolelr lifter, would you? Just trying to gague the difference up top and on the oil channel.

1989GTATransAm

iTrader: (3)

I am running at .594" lift also using the factory setup with the LS7 lifters and the Dart SHP block. I am also using the AFR hydra-rev kit which did require some machining to fit into the Dart block. I have had mine up to 6800 rpm with no sign of valve float.

There are some minor differences between the Dart SHP Block and the GM L98 block. One of them is the oil port above the oil filter boss that I used for the oil pressure sensor. For me it required some doing to fit in the oil pressure sensor in order to clear my headers. I had to use a 90 degree brass fitting.

Orr89RocZ

iTrader: (20)

Didnt see this thread til now.

I have run .603/.613 to 7K on my 383 no problems and thats using 5/16" pushrods which generally would be considered alittle small for the build.
Comp magnum lobes, 286/306 230/245. Base circle I think was near 1" from what I could measure. Cleared fine.

What I'm worried about now is my new cam. Its .640" and will also go to near 6800 I think but with much larger/heavier valves, larger 3/8" pushrods, and abit more spring pressure than before along with boost acting on valves. Also comp mag lobes, but 246 duration intake 252 exhaust.

So far, cam clears rods fine and lifters fit the bores well. No worries from dipping too low from what I can tell so far. Will double check when the time comes but some lifter experts told me to run Morels since they have a tool steel body instead of casting and wont flex under operation. They say oil pressures in the lifter bores/lifters at high rpm is in the thousands of PSI range, so strong materials are nice to have. But since I didnt have a problem before with these lifters on my 383 using comp mag lobes, I dont expect problems on the new setup