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Need some 307 advice

8K views 45 replies 14 participants last post by  Bryan59EC 
#1 ·
Hey everyone, first time poster. I just came back from my overseas tour and thought it would be nice to get a project truck. Picked up a '68 chevy C20, hoping it had the 327, i got stuck with the old 307. Im looking for suggestions to get some horsepower out of this thing. I read that a lot of people said to trash it, but i want to see what shes got.
 
#30 ·
Ok, so i found a set of 416's for 25$. Couldnt help myself. Im going to take it in for testing and cleaning and thought of getting all new valves. What is the suggested valvles, and with what cam/lifters. Im planning on getting steel tip roller rockers and replacing the lifters.
 
#31 ·
Roller tips without roller trunnions are a joke. Save your money for some real parts. Have the heads magnafluxed for cracks. If they're cracked, smash 'em with a sledgehammer so that nobody else will get screwed on purchasing them. Competition Products has a "kit" of valves, springs, retainers, keepers and seals to fill a cylinder head. Call 'em up and talk to 'em. You'll need to know the static compression ratio of the motor before you can purchase a cam. You'll need to know what cam you're going to use before you can buy springs.
 
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#33 · (Edited)
The pistons are flat top. How do i measure the deck height? I wrote down what you said about telling the mechanist and will repeat verbatim. I apologize with for the questions, but this is my first rebuild an im having a hard time grasping how all of these parts are working in conjunction with eachother and what the ******* does lift mean? And how do you measure it.
 
#34 ·
a cam opens and closes the valves in the heads,via lifter,push rod,rocker. How far the valve opens is called valve lift. (how far the valve is lifted off the valve seat) duration is how long the valve is lifted from the seat(time wise) counted in degrees of crankshaft rotation. A long duration cam keeps the valves open for a longer time to allow for more air flow,higher lift cams make the opening bigger,to also allow more air flow.
you need a cam that allows the exact correct amount for your engine and application
 
#35 ·
a cam opens and closes the valves in the heads,via lifter,push rod,rocker. How far the valve opens is called valve lift. (how far the valve is lifted off the valve seat) duration is how long the valve is lifted from the seat(time wise) counted in degrees of crankshaft rotation. A long duration cam keeps the valves open for a longer time to allow for more air flow,higher lift cams make the opening bigger,to also allow more air flow.
you need a cam that allows the exact correct amount for your engine and application
Is there a reference for this somewhere so i know which cam to choose?
 
#37 ·
there are dozens of cam grinders/sellers with thousands of choices and 4 kinds of lifters or 2 styles.
decide what you want first and what engine you will use,,,then a combination can be applied.
be specific,how is the engine going to be used,where is it,what you expect from it
 
#39 ·
If you haven't done a couple dozen sets of heads before, then I would advise you not to go grinding on the heads. You might accidentally cut in the right places and add a little flow, but you might just as easily cut in the wrong places and turn them into junk.

I'm gonna tell a story on myself. When my youngest son was in high school, we built a '72 Chevy Luv pickup with a California Stepside conversion. We shoehorned a bone-stock 455 Olds into it, with a TH400 and narrowed 10 1/4" Olds rear diff ('57-'64 Olds/Pontiac). Took it to the dragstrip and turned 101 mph on slicks. Pulled the heads off the motor, spent the next 26 hours sittin' at the bench with a Dumore and carbide burrs, then sanding discs. Bolted the heads back on the motor, went to the dragstrip and turned 103 mph. Picked up a crummy 2 miles per hour in return for 26 hours of labor. Now, someone who knew what they were doing may have been able to pick up some real power with those heads, but I was not that somebody and it is doubtful that you are that somebody either.
 
#40 ·
If you haven't done a couple dozen sets of heads before, then I would advise you not to go grinding on the heads. You might accidentally cut in the right places and add a little flow, but you might just as easily cut in the wrong places and turn them into junk.

I'm gonna tell a story on myself. When my youngest son was in high school, we built a '72 Chevy Luv pickup with a California Stepside conversion. We shoehorned a bone-stock 455 Olds into it, with a TH400 and 10 1/4" Olds rear diff. Took it to the dragstrip and turned 101 mph. Pulled the heads off the motor, spent the next 26 hours sittin' at the bench with a Dumore and carbide burrs, then sanding rolls. Bolted the heads back on the motor, went to the dragstrip and turned 103 mph. Picked up a crummy 2 miles per hour in return for 26 hours of labor. Now, someone who knew what they were doing may have been able to pick up some real power with those heads, but I was not that somebody and it is doubtful that you are that somebody either.
 
#42 ·
Good point. Doing the obvious things like the lip below the seats and removing any casting flash/irregularities should be the extent of it unless you have experience and/or a lot of time and a flow bench- along w/enough heads to find out what is helping and what is hurting. After all, if you remove too much or from the wrong place, the head is now scrap; you cannot add the metal back and welding is in no way cost effective on these commonly available heads.

FWIW, there have been good builds using the L30 305 Vortec heads on the small bore SBC engines. One member here has them on a 283 and likes them just fine. Takes a Vortec intake, self aligning rockers, centerbolt valve covers, and a spring and retainer change.

Some info and photos of the L30 5.0L Vortec head can be seen at NastyZ28.com Vortec Cylinder Heads: The Definitive Guide, post 478.
 
#44 · (Edited)
There are many who say "hog this", "grind that" and that you don't need a flow bench, etc. The guys who want to follow that advice are just setting themselves up for disappointment. And that will happen AFTER they spend untold hours trying to duplicate what they think they see- in a picture!:rolleyes:

I'm not saying that hand porting cannot be done successfully. I was fortunate enough to have made some templates out of brass from a GOOD set of fuelie heads. Using them I can do a pretty good rendition of those heads and they show an improvement at the track.

By eye I can get a little improvement as well- being as how I've done this so many times. But a first timer? Good luck until you've made some goofs- and the goofs will cost you a casting every time unless you have a bench to show you what's happening. And /o a bench you have to port a PAIR of heads, bolt them on and take it to the track, then remove them, port some more, or port another set of heads, repeat until you're happy w/the results or you decide you'd rather spend your time earning some coinage to buy a decent set of aftermarket heads or at least for some time on a flow bench.
 
#45 ·
Im not going to tell you to not port your own heads,,,
I wont do any porting for a few reasons
I want to know the flow numbers so I need a flow bench:\without a flow bench how do I know that I have similar flow in all my ports?:
If it takes 25 hours to port a set of heads? I know that I can make more money doing something else than I can save.
I work with engines that make more than 350 horse power and the castings cost quite a lot more than I want to risk ruining:::
 
#46 ·
This is probably the most civil 307 thread I have ever read.

I opted to use an old, unrebuilt, early 70s 307 in my 66 elky.

All I did was put a q-jet and intake manifold on it.

The car has a 5-speed (TKO 2.87 first) and is plenty peppy even with the 3.08 rear gears.
And gets better than 25mpg on the hiway to boot.
 
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