Im planning on basically freshening up the motor and doing a little work while Im at it. Im going either 20 or 30 over on the block with forged speed pros, a CC306, and a little polishing on the heads.

Qs are, first, I need a DEFINATE answer from someone on the stock CR of a 96 LT1. One guy told me 8.0-8.5:1, and brian from PCM4less said like 10.5:1. I thought both of those seemed a little off. For some reason I was thinking they were more like 9.4-9.5:1 stock. But before I buy higher comp. pistons, Id like to know what Im starting with.

Second, when I get the cam, what exactly on the valvetrain would I have to get. Id like to know if ANY of the stock parts could be reused. Tell me whats best, ok, and acceptable.


I appreciate any and all replies and info...



Thanks Jon

 

LT1 motors are pretty close to 10.5 to 1 CR each motor might show a little more little less if you get real picky with it. As far as parts you can reuse you can keep the crank and rods they are pretty strong. will handle over 500RWHP. You can bump up the compression if you want to make more power I think alot of guys go 12.0 to 1 CR and still run pump gas. but you will have to have it tuned right on the money. Do you plan on spraying the motor? If not you can get by with a hyper piston. And save some more money. Let us know alittle more about what you plan to do with the motor.

Good luck Sean

 

You might get by with reusing the stock push rods and lifters but that is it.. I replaced my liffters with the comp "R's" and reused the stock push rods. You will need new springs matched to the cam you pick out. You will have to check the push rods when the motor is put together to make sure the Rocker tip stays on center of the vavle. If you reuse the stock vavles this shouldn't be a problem.

 

Id replace the lifters while your at it. Both me and my friend had a lifter collapse right after 100k miles.

 

Ive been spraying the motor and will continue to (150wet). Im reusing the stock crank/rods and buying the forged pistons for the juice. I wanted to raise the CR since Im replacing them anyways, but I would like to know for sure though what the stock CR is.

As for the cam, I thought most cams come with new lifters?? Most Ive bought have... Do the CC LT1 cams not come with anything? I planned on trying to use the stock pushrods but figured I would prolly need new springs. Could someone help out with the cam Q though- does the Comp Cams LT1 cam not come with new lifters??



Thanks, Jon

 

Nope they run about 250ish for new ones I think C motor sports has the best deal on the comp R's

 

COMNBYU - Most older flat tappet cam kits did come with lifters, but roller lifters are a good bit more money. Heck even the roller cams are more expensive. Compression is 10.5:1 for LT1, 10.8:1 for LT4. You might be ok on 12:1, but I'd say no more than 11.5:1 just to make sure it doesn't ping if you get a bit of bad gas. MOst of the 12:1 and higher guys have strokers, which let you get away with more CR and more cam. I apologize for missing it if you posted, but are you going to spray it? If so, I would recommend getting some decent rods. While the stock ones SHOULD handle it, alot of people recommend putting good hardware on them. Why spend almost $100 on rod bolts when you can get a stronger set of rods for about $300 - $400. I'll be the first to admit that most LT1 guys WAY overbuild their combos, but somethings are just cheap insurance. Since you are taking it apart, why not make it a stroker? The torque will help immensly, and make the car easier to drive around town. You can get a SCAT cast crank thats good to 800 hp for about $300 if I remember right. Unless you plan on 700 hp or more, especially with forced induction, I don't think a forged crank is warranted. A stroker would make it a good bit easier to crack 400 rwhp too. Heck, GMHTP had 420 with a 305 cam and heads. (GTP or Lingenfelter, can't remember). You'll be cutting it close to get 400 rwhp from a 306 unless your heads are top notch. Anywho, good luck with it which ever route you go.

 

Like brain said, I would also replace the rods. You are going to have to rebalance it too. I ended up getting some H-beam rods for around 400 bucks, but you can get some pretty good I-beam rods for around 250 if you look around. For most part, the I-beam rod is not as durable as a H-beam. Of course the over $1K Oliver billet rods are a different story.
So far, the stock crank has held up in my motor. A 4-bolt block would be a good idea if you can afford it.
Later & merry x-mas,
Ed

 

WRONG lt1 is 10.25:1 lt4 is 11:1

 

Lt1 10.4:1
Lt4 10.8:1

Thats what I always thought.

Jeff D.

 

nope its definately listed 10.4 LT1 10.8 LT4 like others have mentioned



and what exactly do you have planned for the heads? if its just cleaning up some stockers and giving it a cc306 cam you wont see anywhere near 400rwhp that i thought i saw someone write. assuming even 350rwhp and a 150 shot of sqeeze though you are looking at getting near 500rw and higher 5xx motor hp, which would be a nice time to look into some stronger rods, but i would probably still trust the crank if it is in good shape. 4 bolt main conversion would be a 'nice to have' but not neccessary unless you just want to do it while you are there

as for stock valvetrain, kiss it goodbye, it is pretty bad. Its probably best to just get new springs, lifters, pushrods, roller rockers etc while you are there and doing any head/cam work. (lifters and pushrods might be ok, but stock springs, rockers, et )

 

See this is what Im talking about with the CR. Everyone seems to say something a little different. Anyone know where I could go to get a positive answer on this? Hell, I work at a GM dealer and I couldnt even find it in any of the old service books.

AS for the rest, Im planning on doing a little porting/polishing on the heads myself. I used to work at a machine shop and did headwork on a daily basis, among other things. Id love to do a stroker, but funds are just not there right now. Only thing I can afford to change on the bottom end right now are the pistons, which, as I said are going to be Speed Pro forged. Ill clean the stock rods up and have the stock crank turned and maybe balanced.

Im not looking to have the badest ride out there, but judging by what the car ran with a all stock motor (in sig), if I could get low 12s/ high 11s NA with headwork, cam, and higher CR, then spray my way into the 10s, Id be happy as a clam for right now.

I dont know about HP #s and how much of it it would take go run the #s I want, all I can go by is what the car has already run and the work I plan on doing to it. I think that my ET goals are fairly attainable with the plans I have for the car.



Merry Christmas, Jon

 

Give http://www.cmotorsports.com/ a call they work on LT1 cars all the time and can give you the exact compression ration on most LT1 cars each car will differ a little. good luck with it.

 

the only argument ive ever heard about the compression of an LT1 is if it was 10.4 or 10.5. There is actually more argument about whether the heads are 54cc or 58cc than about the compression they give.

it is not 10.25 and DEFINATELY not anywhere in the 8s or 9s. The whole point of the reverse flow cooling was so that you could have mid 10 compression more easily. But if you are buying pistons, you should be able to find out what that piston with that CC head will make for compression and go by that