74 BB Cam
Thread Starter
Intermediate
Joined: May 2007
Posts: 42
Likes: 0
From: Baltimore Maryland
74 BB Cam
All,
I need a new cam, lifters and push rods. What I would like, is a car that has some backside to it, while maintaining the original exterior, ie... intake, exhaust and carb. I know nothing about choosing a cam except, if you don't match certain items the best cam may be useless. I will not be racing, but I do like to be set back in my seat when I hit the gas. 270 hp in 74 is pretty weak for a BB. Mid to high 300, if not more is what I would like.
Thanks
I need a new cam, lifters and push rods. What I would like, is a car that has some backside to it, while maintaining the original exterior, ie... intake, exhaust and carb. I know nothing about choosing a cam except, if you don't match certain items the best cam may be useless. I will not be racing, but I do like to be set back in my seat when I hit the gas. 270 hp in 74 is pretty weak for a BB. Mid to high 300, if not more is what I would like.
Thanks
Pro
Joined: Nov 2004
Posts: 575
Likes: 0
From: Nice Lake Ontario
Lunati 60202 is what you need!
I put a 60203 (1,500-6,000rpm) in mine but sometimes wished I'd have went the next smaller for more of that amazing low end BB grunt
& I never rev her to 6,000 anyway!
Or you could check out the new thumper line, I've seen good reports on them.
Another thing you should check out is heads. Stock your 454 is at 7.8/1 comp. You could look for a set of oval port 1966-70 10.5/1 comp heads that'll give you 9/1 with a .020 head gasket using your stock pistons.
I put a 60203 (1,500-6,000rpm) in mine but sometimes wished I'd have went the next smaller for more of that amazing low end BB grunt
& I never rev her to 6,000 anyway!Or you could check out the new thumper line, I've seen good reports on them.
Another thing you should check out is heads. Stock your 454 is at 7.8/1 comp. You could look for a set of oval port 1966-70 10.5/1 comp heads that'll give you 9/1 with a .020 head gasket using your stock pistons.
Last edited by sxr6; Jul 15, 2008 at 10:14 AM.
Melting Slicks
Joined: Oct 2002
Posts: 2,317
Likes: 111
From: St Louis MO
To recommend a cam, one needs to know the rear end ratio, and the transmission type. If it's an automatic, what diameter torque converter and/or brake stall speed.
When these harmonize, it's smiles - if not, it leaves one wishing for better.
When these harmonize, it's smiles - if not, it leaves one wishing for better.
Le Mans Master
Joined: Apr 2006
Posts: 5,403
Likes: 95
LS4 has pitiful compression won't support much of a cam improvement
regardless of what gearing or trans is. I owned a 73 LS4, 4 speed when
they were new, changed everything in the engine but the two bolt block
In stock form even in the 70s any decent mildly warmed over 350 would just tear it up, you need to bite the bullet spend money on getting the compression up if you ever really want it to start performing.
regardless of what gearing or trans is. I owned a 73 LS4, 4 speed when
they were new, changed everything in the engine but the two bolt block
In stock form even in the 70s any decent mildly warmed over 350 would just tear it up, you need to bite the bullet spend money on getting the compression up if you ever really want it to start performing.
Last edited by Little Mouse; Jul 15, 2008 at 02:09 PM.
Instructor
Joined: Jul 2007
Posts: 108
Likes: 0
Sleeper bb
I hear ya. For our recent rebuild on our L36 427, I wanted to retain an all original look wrapped around a bit of a surprise.
We went with Edelbrock Performer RPM aluminum heads, and a Comp Cams "Thumpr" cam. Pleased with the results. This thing sounds incredible and shoves me back in the seat nicely. (FYI, this car has the close-ratio 4-spd and 370 rear end.)
But this was a thorough rebuild, including new pistons, etc, etc, and for additional grunt we stored the 427 crank and installed a 454 unit. With the +.040 overbore we're at 463ci.
For visual impact (or lack of it), kept the stock L36 intake and exhaust manifolds, carb, air cleaner etc. When laying on the orange engine paint, we painted the aluminum head as well, to hide the Edelbrocks. Exhaust is out the back but is 2-1/2 Flowmaster setup.
If you're just wanting to replace the cam, you'll be much more limited in results. And as others have said, it all needs to be looked at as a complete package. So you'll need to find an expert to spec the best cam to match all your existing components. Good luck!
We went with Edelbrock Performer RPM aluminum heads, and a Comp Cams "Thumpr" cam. Pleased with the results. This thing sounds incredible and shoves me back in the seat nicely. (FYI, this car has the close-ratio 4-spd and 370 rear end.)
But this was a thorough rebuild, including new pistons, etc, etc, and for additional grunt we stored the 427 crank and installed a 454 unit. With the +.040 overbore we're at 463ci.
For visual impact (or lack of it), kept the stock L36 intake and exhaust manifolds, carb, air cleaner etc. When laying on the orange engine paint, we painted the aluminum head as well, to hide the Edelbrocks. Exhaust is out the back but is 2-1/2 Flowmaster setup.
If you're just wanting to replace the cam, you'll be much more limited in results. And as others have said, it all needs to be looked at as a complete package. So you'll need to find an expert to spec the best cam to match all your existing components. Good luck!
Thread Starter
Intermediate
Joined: May 2007
Posts: 42
Likes: 0
From: Baltimore Maryland
Thanks all,
I recently purchased the car and really do not know what has been done to the motor. I know I want to put in the above mentioned items and I was going to have the heads pulled and looked at. Any ideas as to what I should have done to the heads? How do I check the rear end gear ratio? Getting lots of good info here. Once I decide on a couple choices, I'll ask first before purchasing.
Todd
I recently purchased the car and really do not know what has been done to the motor. I know I want to put in the above mentioned items and I was going to have the heads pulled and looked at. Any ideas as to what I should have done to the heads? How do I check the rear end gear ratio? Getting lots of good info here. Once I decide on a couple choices, I'll ask first before purchasing.
Todd
Drifting
Joined: Aug 2005
Posts: 1,682
Likes: 3
From: League City TX
The heads are not a bottleneck on the performance of your engine at this point.
While you would probably gain a small amout of power from some port work in the bowls,
the big ovals as cast can be used on some pretty potent engines.
The low compression and tiny little cam are your biggest issues.
If you are planning to pull the heads anyway, you could have them milled to reduce the chamber volume some.
Of course you cant mill enough to make huge differences in your compression ratio, but you could get a little.
If you were to find a set of closed chamber heads to switch to, you could bump the compression a pretty decent amount.
While you would probably gain a small amout of power from some port work in the bowls,
the big ovals as cast can be used on some pretty potent engines.
The low compression and tiny little cam are your biggest issues.
If you are planning to pull the heads anyway, you could have them milled to reduce the chamber volume some.
Of course you cant mill enough to make huge differences in your compression ratio, but you could get a little.
If you were to find a set of closed chamber heads to switch to, you could bump the compression a pretty decent amount.
Le Mans Master
Joined: Apr 2006
Posts: 5,403
Likes: 95
Open chamber heads from chevy seem to range in the 118cc to 122cc
range makes it little hard to get compression, the layed over angled wall of the chamber does help unshroud the valves better then the old bathtub style closed chamber. www.wiseco.com. has a couple piston/ring kits that will give you 9.6 compression has the right size dome 21cc
Kit # PT-010H3, .030 over 2.80 bore 454= heavy duty street
Kit # PT-081H3 has the same 21cc dome, but is listed as a race piston.
You could cut you head say .010 anymore might cause intake manifold problems. .010 cut would barely help you any, if you really want some
compression using the factory head you need to consider the thought
of changing pistons.
range makes it little hard to get compression, the layed over angled wall of the chamber does help unshroud the valves better then the old bathtub style closed chamber. www.wiseco.com. has a couple piston/ring kits that will give you 9.6 compression has the right size dome 21cc
Kit # PT-010H3, .030 over 2.80 bore 454= heavy duty street
Kit # PT-081H3 has the same 21cc dome, but is listed as a race piston.
You could cut you head say .010 anymore might cause intake manifold problems. .010 cut would barely help you any, if you really want some
compression using the factory head you need to consider the thought
of changing pistons.
Last edited by Little Mouse; Jul 16, 2008 at 08:00 PM.
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Thread Starter
Intermediate
Joined: May 2007
Posts: 42
Likes: 0
From: Baltimore Maryland
Enjoying all the info, I do appreciate the help. What I am gleaning is that I need more compression to make a difference. Is this correct? I can do this with a cam and piston swap? If I bore the motor, is it the rings that are replaced or does the whole piston get replaced?
Thanks
Todd
Thanks
Todd
Drifting
Joined: Aug 2005
Posts: 1,682
Likes: 3
From: League City TX
Enjoying all the info, I do appreciate the help. What I am gleaning is that I need more compression to make a difference. Is this correct? I can do this with a cam and piston swap? If I bore the motor, is it the rings that are replaced or does the whole piston get replaced?
Thanks
Todd
Thanks
Todd
If you want to keep the stock short block together, the only way to make a significant change in compression
ratio will be with closed chambered heads, unless you go with aftermarket aluminum heads.
Le Mans Master
Joined: Apr 2006
Posts: 5,403
Likes: 95
Enjoying all the info, I do appreciate the help. What I am gleaning is that I need more compression to make a difference. Is this correct? I can do this with a cam and piston swap? If I bore the motor, is it the rings that are replaced or does the whole piston get replaced?
Thanks
Todd
Thanks
Todd
the open chamber heads that were on LS4s. But the only way you can really get any decent compression with your open chamber heads is to find pistons with a modest dome like the example I gave you. bore the engine use new pistons rings. There is no cheap solution to the problem. If you can get your compression up to a decent level then you can make use of a good cam. You have plenty of cubes to work with just very poor compression. Most of the pistons for open chamber heads have 36cc domes or bigger for very high compression used at the race track where high octain fuel is available.
Edelbrock has an aluminum head with 100cc chambers but with your stock pistons
even if you spent $1800/$2000 for the heads you still would only be at 9.2 compression.if you hunted up a set of old closed chamber oval port heads they are 101cc/106cc that would get you to maybe 8.8/9.1 compression depending on the chamber size you can find.
Last edited by Little Mouse; Jul 16, 2008 at 10:44 PM.
Pro
Joined: Nov 2004
Posts: 575
Likes: 0
From: Nice Lake Ontario
I used an old set of closed chamber 290s from a 1970 454 + a .020 head gasket to bump comp to about 9/1. Not a race engine but huge improvement from the stock 7.8/1 & pump gas has never been an issue. There are a couple other older GM heads that are fairly readily available thru swap & such but I don't have a number book on me at the moment.
Thread Starter
Intermediate
Joined: May 2007
Posts: 42
Likes: 0
From: Baltimore Maryland
If I were to change the pistons to the domed to get a higher compression down the road would it hurt me to put the cam in now just to get the thing running, or should it all be done at once?
Todd
Todd
Le Mans Master
Joined: Apr 2006
Posts: 5,403
Likes: 95
You can change the cam do anything you want. But will the compression raise ever get done ?? if its not going to happen better go with just a slight increase in cam.
Last edited by Little Mouse; Jul 17, 2008 at 09:41 PM.
Drifting
Joined: Aug 2005
Posts: 1,682
Likes: 3
From: League City TX
SXR6 made a good recomendation, the Lunati 60202. Despite it having a larger duration at .050", it has
shorter seat timing than stock so you will actually have more cylinder pressure than you have now.
If you ever tear the engine down to change the pistons to bump up compression, then you can benefit from a larger cam.
Racer
Joined: Jul 2006
Posts: 478
Likes: 56
From: Woodstock Georgia
If you just want to do the cam now, then check out the first response that you got.
SXR6 made a good recomendation, the Lunati 60202. Despite it having a larger duration at .050", it has
shorter seat timing than stock so you will actually have more cylinder pressure than you have now.
If you ever tear the engine down to change the pistons to bump up compression, then you can benefit from a larger cam.
SXR6 made a good recomendation, the Lunati 60202. Despite it having a larger duration at .050", it has
shorter seat timing than stock so you will actually have more cylinder pressure than you have now.
If you ever tear the engine down to change the pistons to bump up compression, then you can benefit from a larger cam.
Advanced
Joined: Aug 2006
Posts: 54
Likes: 0
Lunati 60202 with 9.1:1 L2399 and -049 with 2.19/1.88 through stock cast iron exhaust manifold 
http://www.garaget.org/video/fs5vbtgev3re
>Mr. Beam
http://www.garaget.org/video/fs5vbtgev3re
>Mr. Beam
Instructor
Joined: Feb 2008
Posts: 140
Likes: 0
From: Tulsa OK
Lunati 60202 with 9.1:1 L2399 and -049 with 2.19/1.88 through stock cast iron exhaust manifold
http://www.garaget.org/video/fs5vbtgev3re
>Mr. Beam
http://www.garaget.org/video/fs5vbtgev3re
>Mr. Beam
How many seconds to get to 100 ????
Advanced
Joined: Aug 2006
Posts: 54
Likes: 0
Actually more like just under 11 
but ok...call this one as well then.
Before and after mod from using a -215 head with oem flattop and some unknown cam.
http://i84.photobucket.com/albums/k2...006/result.jpg
/Mr Beam
but ok...call this one as well then. Before and after mod from using a -215 head with oem flattop and some unknown cam.
http://i84.photobucket.com/albums/k2...006/result.jpg
/Mr Beam