305 Cam Numbers/Ranges
Thread Starter
Registered User
Joined: Jul 2004
Posts: 216
305 Cam Numbers/Ranges
Me and my brother are taking the heads off of his LG4 to get rebuilt and thought what the hell, let's cam it. So tomorrow we are going to drop the heads off at the machine shop. We plan on buying a cam from the shop, but I'd just like to get your guys' suggestions on what kind of numbers to be looking for from the cam. We don't want to have a straight dragster lope, but a little bit wont bother us. I have searched, but didn't get much about the "driveability" of the cams people were putting in. Any info is appreciated!
Registered User
Joined: Feb 1999
Posts: 2,947
From: Springfield,OH. U.S.A.
Re: 305 Cam Numbers/Ranges
Here's something I've been following in my subscription.
Also, the compression on the stock heads sucked until '85, before that it was like 8.5:1.. 
Later models would grow to 9.5:1...and would be a good upgrade for early 3rd gen LG4's.
Camtastic
The next important consideration is the camshaft. While a great-flowing set of heads will pump the power even with a stock cam, adding a little more lift and duration to the mix allows us to take advantage of the better flow by spinning the engine a little higher in the rpm range. The stock LG4 motor tends to run out of steam at about 4,500 to 4,800 rpm. By increasing airflow, and with another 14 degrees of intake duration from the camshaft, our plan is to raise the peak horsepower rpm up closer to 5,000 to 5,500 rpm.
We felt the key to making power with the 305 was not to go overboard with the cam timing. We consulted CHP’s technical guru, Kevin McClelland, and he felt that any cam with more than 200 degrees of intake duration would tend to kill low-end torque—something we don’t have in abundance with a 305ci engine. We decided on a Crane CompuCam grind with a relatively short duration and reasonable lift figures (see Cam Specs chart). For now, we’ll stick with the stock 1.5:1 rocker arms, but we’ll try a set of 1.6:1 rockers to see if that improves the power. Either way, we’ll let you know the results.
The next important consideration is the camshaft. While a great-flowing set of heads will pump the power even with a stock cam, adding a little more lift and duration to the mix allows us to take advantage of the better flow by spinning the engine a little higher in the rpm range. The stock LG4 motor tends to run out of steam at about 4,500 to 4,800 rpm. By increasing airflow, and with another 14 degrees of intake duration from the camshaft, our plan is to raise the peak horsepower rpm up closer to 5,000 to 5,500 rpm.
We felt the key to making power with the 305 was not to go overboard with the cam timing. We consulted CHP’s technical guru, Kevin McClelland, and he felt that any cam with more than 200 degrees of intake duration would tend to kill low-end torque—something we don’t have in abundance with a 305ci engine. We decided on a Crane CompuCam grind with a relatively short duration and reasonable lift figures (see Cam Specs chart). For now, we’ll stick with the stock 1.5:1 rocker arms, but we’ll try a set of 1.6:1 rockers to see if that improves the power. Either way, we’ll let you know the results.
Later models would grow to 9.5:1...and would be a good upgrade for early 3rd gen LG4's.
Last edited by 90rocz; Oct 12, 2005 at 11:50 PM.
Registered User
Joined: Feb 1999
Posts: 2,947
From: Springfield,OH. U.S.A.
Re: 305 Cam Numbers/Ranges
Cam specs for CHP Project:
Stock:
Duration:::INT:178*///EXH:194*///LSA:109*
Lift:::INT:.350///EXH:.385
Crane:
Duration:::INT:194*///EXH:204*///LSA:111*
Lift:::INT:.407///EXH:.429
Stock:
Duration:::INT:178*///EXH:194*///LSA:109*
Lift:::INT:.350///EXH:.385
Crane:
Duration:::INT:194*///EXH:204*///LSA:111*
Lift:::INT:.407///EXH:.429
Thread Starter
Registered User
Joined: Jul 2004
Posts: 216
Re: 305 Cam Numbers/Ranges
Yea, it's an 85 so we're at 8.5:1 compression. We don't plan on rebuilding the shortblock just to get that point of compression back :P
The machine shop was pretty knowledgeable and recommended us a cam with about the numbers that you posted up. After we get it together and broken in I'll repost with the cam card and dyno numbers.
Thanks guys!
The machine shop was pretty knowledgeable and recommended us a cam with about the numbers that you posted up. After we get it together and broken in I'll repost with the cam card and dyno numbers.
Thanks guys!
Registered User
Joined: Feb 2000
Posts: 366
From: Jax, FL
Re: 305 Cam Numbers/Ranges
Since they are at the machine shop, you could get the heads milled and use a thinner head gasket to get the compression higher. Is this a carbed car? Headers? Intake? A lot of info needs to be known for cam selection.
Registered User
Joined: Jan 2002
Posts: 90
From: SANDIEGO, CA,92123
Re: 305 Cam Numbers/Ranges
Originally Posted by 90rocz
Also, the compression on the stock heads sucked until '85, before that it was like 8.5:1.. Later models would grow to 9.5:1...and would be a good upgrade for early 3rd gen LG4's.
Later models would grow to 9.5:1...and would be a good upgrade for early 3rd gen LG4's.
Registered User
Joined: Jan 2002
Posts: 90
From: SANDIEGO, CA,92123
Re: 305 Cam Numbers/Ranges
Originally Posted by 90rocz
Also, the compression on the stock heads sucked until '85, before that it was like 8.5:1.. Later models would grow to 9.5:1...and would be a good upgrade for early 3rd gen LG4's.
Later models would grow to 9.5:1...and would be a good upgrade for early 3rd gen LG4's.
thanks...
Registered User
Joined: Dec 1969
Posts: 1,147
From: Phila., PA
Re: 305 Cam Numbers/Ranges
I beleive 85 was the first year for the higher 9.5:1 compression in the LG-4. Easy to tell- if your piston faces are flattops with 4 valve reliefs it's the higher compression motor. If it's fairly heavily dished faces with 4 valve reliefs it's the lower compression motor.
Regardless, I wouldn't shove in anything big enough to cause a lumpy idle. The rest of the combo won't like it. A cheap Summit house brand cam (#K-1102) would be a good choice- 204/214* on a 112* LSA- all for $80 including lifters. This is the exact same cam as the Edlebrock Performer cam (both made by Crane). It'll work even in the lower compression motor but the higher compression motor would like it even more. Compared to the stock LG-4 cam it's a fire-breather.
Regardless, I wouldn't shove in anything big enough to cause a lumpy idle. The rest of the combo won't like it. A cheap Summit house brand cam (#K-1102) would be a good choice- 204/214* on a 112* LSA- all for $80 including lifters. This is the exact same cam as the Edlebrock Performer cam (both made by Crane). It'll work even in the lower compression motor but the higher compression motor would like it even more. Compared to the stock LG-4 cam it's a fire-breather.
Thread
Thread Starter
Forum
Replies
Last Post
F'n1996Z28SS
Cars For Sale
8
Aug 23, 2023 11:19 PM
oldschool
Parts For Sale
16
Feb 9, 2016 09:21 PM