Can anyone give me some ideas for rebuilding my 1970 LT1 motor and get the stock HP and lower the Compression to use pump gass.I would like to use the original heads and as much of the original parts as possable. Thanks Dave

Have the heads extensivly worked over for one.

I'd have to think a while before saying anything else.

Im basicly using those heads and pistons
186 casting with 11.2 domes on pump gas

It will be an easy task. If your bores have little to no wear (doubtful) you can have the domes milled off your existing pistons, hone the block and soforth.
If you need a rebore anyways buy a Pro Tru flat top piston, that will knock your compression down to around 9.75:1, totally pump gas friendly. Have your heads pocket ported and completely port the exhaust runners. Intake runners can remain untouched other that the pockets (bowls under the valves). Your carb and factory intake will be fine. Choose a solid flat tappet cam in the area of 275 to 285 degrees duration (advertised), lobe separation in the area of 110 (108 if you want a tougher idle and a little more midrange power at the expense of lower end torque). You will need the lift to be under .500" net to work with the stock diameter springs and retainers, naturally you would replace the springs. I would suggest going with a roller rocker if you plan to buzz the engine, your originals should be fine for "restoration" operation. Your stock crank and rods are perfectly fine, just recondition as required. You must rebalance your rotating assembly unless your new pistons are similar in weight, but I consider it a "must do" regardless.
That setup should be an easy 400+ horsepower, be trouble free and a dream to drive.
Do NOT mill the decks of your block unless absolutely necessary, the casting numbers on the Pass side will be removed, reducing the value of that block. I would also suggest the minimum allowable overbore possible.
Good luck!
Oh, and headers would be part of that package too!
------------------
Custom Auto, your source for quality machine work, cores and new parts at competetive pricing right here in British Columbia 1-888-563-4050
A Canadian, EH? (with a 10 second street car)

[This message has been edited by rustbucket79 (edited February 23, 2005).]

<font face="Arial,Verdana" size="2">Originally posted by rustbucket79:
duration (advertised), lobe separation in the area of 110 (108 if you want a tougher idle and a little more midrange power at the expense of lower end torque). </font>

I thought the 108 gave more low end torque a broader torque curve at the expense of top end hp?

[This message has been edited by Mwilson (edited February 23, 2005).]

Thanks for the help guys.

A good old CC 282S solid at 9.75 to 10 to 1 CR. will run great, imho!!

No, 108, lower torque on both ends and peaky/higher in the middle, 114, higher torque on both ends, but not as peaky/lower in the middle...

That's why a wide LCA cam produces more Hp above 5250 rpm then a narrow LCA cam will, all things being equal....

It moves the torque up on the high end and the Hp rpm multiplier raises the Hp number!!

pdq67

The book i have here says "Reducing the LSA angle improves low end power and helps broaden the torque curve" "For most street apllications you with want to tighten the LSA and the Lobe centerline to try and build as much torque as possible" page 73

Small Block Chevy Performance
by John Baechtel

John isn't telling the whole story.

Tightening the LSA helps with low end on a cam with short duration, like something with 210 @ 0.050" or so, for example. A big duration, tight LSA solid, however, would exhibit soggy bottom end torque as Rust posted, but come on like a hurricane in the midrange RPM band. At high RPM, as pdq mentioned, the wider LSA comes out ahead. Basically, a tight LSA (108 and tighter as a general example) on a big cam gives the best midrange power but is not the best choice for an all-around street car that sees some strip action on occasion. A track only car will make the best power with the tighter LSA, as there are no other considerations like general driveability, bottom-end throttle response (torque), idle quality and so on that need to be factored in. Street and street strip applications usually work better with a wide LSA to bring back acceptable manners, power brakes, ease of carb tuning, some semblance of bottom end torque, etc due to the inherent compromises required.

Cam designing takes a lot of factors into consideration and takes a considerable period of study before the light bulb turns on.

------------------
'Silver Bullet' 1977 Z-28 413" SB
11.73 @ 115.10 on drag radials
Old Vortec combo:
12.15 @ 110.52

I just read a David Vizard book and it is in agreement with you except it says that the lower the LSA the higher the peak HP at a lower RPM at the expense of Idle quality, fuel efficiancy, and low end torque as well as Top end RPM's.