ok, the motor in my 72 LT-1 needs rebuilt and the old cam needs replaced. while im in the motor im going to bump the compression ratio up to 10.5-11, and i plan on keeping the solid lifter setup to keep some originality. my question is what kind of cam are you guys running? what do you recommend? specific brands and part numbers would be helpful... thanks!

 

I'm at work right now on a slow remote wireless modem (60K baud rate) and can't do well with downloads. You compression will be too high for pumpo gas if you run iron heads. I would look for a cam in the high 230 degree range or low 240 degree range at 0.050" tappet lift. You need to tell us what you are using your LT-1 for (street driving? no autocross/drag racing intended ever?) What dirfferential ratio in back (my Vette had 4.11's and I switched quickly to 3.70s.) Is your LT-1 an "air car" with factory A/C (I pity you around valve adjustment time if it is.) Do you want or can you afford roller rockers and othe rparts. What cylinder heads will you be running (PLEASE DON'T! tell me you alread bought Dart 200cc heads, they are too BIG for a 355 cu/in motor.) Post some more information, Eric B.

 

have a look at the crower 0321

 

i plan on using the stock heads, and my reason for bumping up the compression ratio is to be more like the 70 lt-1 which had 11-1 compared to the 9-1 of the stock 72. im trying to keep the engine rebuild as cheap as possible and trying to keep it somewhat stock, since its an lt-1 and worth more that way. the car is non a/c, 4spd, and ill check on the rear gearing. i plan on using it mostly for street but its not a daily driver so i want to have as much power as possible , without going crazy of course...

 

I agree, keep the compression ratio friendly to the octane levels available today. Also, find a cam that gives you good mid range power for those short bursts on the street. I am not sure about staying with the solid lifters though in your case. But that would be your preference.

 

I like GM
cam choices
I love my hotcam!!!!

 

The LT-1 cam worked well enough to confer legendary status to those cars. Still a pretty good choice........................

 

I'd say, wait until you get into the engine. Have the block hot-tanked, magnafluxed and then have the cylinders checked for bore taper. If they're ok, and your pistons look ok, then clean 'em up and re-use them... The key, here, is something you said:

"...trying to keep the engine rebuild as cheap as possible and trying to keep it somewhat stock..."

The higher compression ratios will not gain you as much, as spending your money on giving the heads a pocket-porting, and running a roller-camshaft, if funds allow.

Since you're on a budget, I'd do a search on E-Bay, looking for a NEW roller cam still in the box... Basic specs should be ~270-280 degrees of gross duration (~220-230 at .050" lift), lobe separation angle of at least 112 degrees, and lift of ~.450". I'd also look for roller valve-springs online, that'll match your lift... These general numbers will give you a VERY good cam that would idle with a slight lope (depending on ramp profile), give good vacuum to your engine and pull hard up into the mid-range...

Conceivably, you could acquire your entire valve-train well in advance of building your engine, just be being patient and watching for the parts that match your requirements...

Finally, if you can get all that together, I'd recommend an extrude-honing job to your intake manifold, and exhaust manifolds (again, as funds allow). You'll not get the same flows as a high-rise and headers, but it'll look stock, flow pretty well, and nicely support the engine... With 9:1 C.R., DD2000 predicts 370HP, 375 ft.-lbs. of torque. With small-tube headers and a good exhaust system, the same engine (says DD2000) will make 400HP, 400 lbs. of torque...

 

I'm proud that your fixing up your LT1. Higher compression/improved heads/headers/Modern cam is all that's required to make these motors better than when they were new.

Anybody that says 35 year old factory cams are great doesn't build or test motors. Kind of keeps their head in the sand. It's 2005!

I have the 186 casting double hump heads all ported and polished, 2.02/1.6 Manley race flow valves, screw in studs, and guide plates. they are surfaced and cc'ed to 64 cc. With .015 steel head gasket and flat top two valve relief forged pistons. My actual compression figures out to static 10.74 C/R with "Iron heads"

Yes, it runs fine on the local 91 octane super unleaded. Because the Crane 238/248 cam with 114 lc bleed off enough pressure do too overlap that the Dynamic compression is 8.2 or something.

I don't have the part number. The Crane web site has it under mechanical solid lifter Power max or something. I also run it with 1.6 roller tip rockers.

Just a sweet running motor. Any questions just ask.

 

ok, after some reasearch ive got some more specific questions:

ive decided not to do a roller setup, so im gonna stick with a flat tappet cam. i have it narrowed down to 2

1st-crane P/N113841-duration277/288, @.050 238/248, lift-.480/.500, lobe separation 114*

2nd-lunati P/N40134-duration278/288, @.050 239/249, lift .517/.543, lobe separation 106*

my questions: the duration of these cams is about the same, while the lift and lobe separation of the lunati is higher, from what ive read this is supposed to make more power, but im worried that it will not work with my setup as i read that a lift of .500 or higher will not fit due to piston clearances, is this true? i have to get new pistons anyway-what kind would allow this? is it worth the trouble? i also read that the lower lobe separation angle (like the lunati) will lower the engines "total" compression, so is a piston allowing more compression(~10.5-11) necessary so that the "total" engine compression will be less. (lowering it to a level that will allow pump gas??) i read something about that concept, but i want to make sure i get it right. it is important that the car run on pump gas.

my other concern-i looked up the specs of the stock LT-1 cam and found it to be 300/312, @.050 242/254, lift .435/.453, lobe separation 116*. the lift of this is lower and the lobe separation is higher than that of above, but im worried about the duration of the LT-1 being so much higher--basically i want to make sure im not putting a cam in the car thats going to be inferior to stock.

thanks for all the help, choosing a cam is quite confusing

 

I think you have the wrong # on the first cam I think it is 113841.
Im recommending this cam to a friend building up a 383 with old iron heads. Ideally you want compression up around 10-10.5 to 1 with this cam. Set your quench tight and block off the intake manifold exhaust heating. You will need premium fuel.
The other cam witha narrow 106 lobe separation will make more power but have a lousy idle. The wider lobe separation angle (114degrees) bleeds off compression. This 113841 cam is similar to the original LT1 cam, Id try it.

 

yes, it was a typo, real # is 113841, anyone else have any input??

 

If you do not use a GM LT-1 cam, it is not an "LT-1" engine anymore IMHO. I would build it closer to '70 LT-1 specs if you are concerned about originality at all. How bad could it be?

The Crane cam looks to be a pretty good replacement.

The tight lobe centers on the Lunati cam will probably give you a rough idle so while it might make a bit more peak power, it will have less "LT-1" characteristics. The poor idle/low vacuum might give you problems with the power accessories.

Do not try to compare the GM cam specs to aftermarket cam specs. They are not designed the same way so the characteristics are going to be totaly different. GM cams have long, slow lifting ramps so the duration numbers look strange when compared to aftermarket cams.

I like backdating the engine to '70 LT-1 specs with a few minor mods but it is obviously it is your call. If you are running headers you might be better off with an aftermarket cam.

-Mark.