Motor Options (Need Opinions)

[pat123]

being that the 305 heads are cast will their be a problem with detination?

[5150.4.67]

I agree. Those 305 ho heads are good heads. New aluminum heads are going to break the bank. Edelbrock performer rpm manifold, a good street cam, and headers and you are headed in the right direction. Try to keep the rats out of this build!

[5150.4.67]

Compression ratio is an interesting topic when you talk about detonation. Static compression ratio doesn't take into account your valve closing times. The more appropriate calculation is dynamic CR which takes into account your cam specifications. You shouldn't have a problem with detonantion with the right components. Keep in mind, you want the piston to head clearance 0.040 or less. It's a bit confusing, but get it right and you won't have to worry. You will have to take accurate measurements although. Go to Keith Blacks website and you will find several calculators including DCR.

[5150.4.67]

You will probably run into detonation problems with stock pistons. I'd shoot for 7.5:1 dynamic compression ratio with iron heads to be safe. Use Keith Blacks dynamic compression ratio calculator with the components you would like to use (cam, pistons, head gasket) and see what you end up with. You may not find a piston that will give you the correct dynamic compression ratio AND 0.040 piston to head clearance (quench). In which case a higher cc head would be in order..... vortec in this case.

[Irishpilot]

I just replaced my asthmatic 307 with a 406 (started as a 400 sb). The difference in power and torque is night and day. I built the 406 as a hot-rod engine so the fuel consumption is worse, but just with the increased cubes and better port flow of bigger engines, you are going to get more power without spending money on aluminum heads, etc on the 307.

I personally don't think any carb engine is going to get "good" gas mileage compared to its fuel-injected cousins. So if you don't have too tight of a budget, and want to max power and minimize fuel consumption, pull a stock vortech engine, put some minor upgraded parts, get a good wiring harness and you will have more cubes and better mileage.

Try to find someone else around who has a setup you are interested in and take a ride and see first-hand the differences.

[Bowtie001]

I got 19 mpg out of a full size truck, Qjet th350/350 and a 3.07 gear. Carb can get the same mileage, you just have to tune more carefully.

A 307 will be better, but I would suggest the 200R4. My pops builds them for grand national guys. He thinks they're crazy, but they run in the nines with the transmissions he does. They don't cost anymore than a 350 or a 400 to rebuild, and if you are going to be pepping up the motor, you'll probably want to do some of that anyway, or at least a converter and a shift kit.

Stay small on the cam, a set of vortec heads are perfect, and you'll be golden. I have ridden with some very mean 307s, don't let the naysayers dissuade you.

-Brian

[kcjones]

Originally Posted by Bowtie001

.....

Stay small on the cam, a set of vortec heads are perfect, and you'll be golden. I have ridden with some very mean 307s, don't let the naysayers dissuade you.

-Brian

I agree that a 307 can make power, good power, but let's not forget that building the right engine isn't just about horsepower or torque numbers. It's about what you want, how you drive it, what gears you have, how heavy your vehicle is, etc. Can I attempt a summary?

-With truck weight (3,700+lbs), 3.07 gears, an automatic, 1,800 stall (stock like), you'll be happiest shooting for as much torque as is possible.
-Making real power with any engine is about matching components.
-Matching components starts with heads; meaning, determine the best head for your situation and get the intake, carb, exhaust, cam that best match those heads.
-A vortec head will make the most low rpm torque of any factory iron Chevy head, all components being equal, because of the better flow characteristics at low rpm (where you spend most of your driving time).
-Building a 307 has no particular advantage over building a 327/350/400 other than: a) you already have it, b) you want to be different, c) your first priority is mileage, c) your building a numbers matching rig.
-Valve size is just like any other part of engine building: MATCH it to your engine. No, there is no advantage with 2.02/1.60 valves in building low rpm torque in your 307.
-Most iron heads can be used with roughly 9:1 compression on pump gas, higher in some cases. Aluminum heads provide no advantage to iron, again all things being equal (valve size, runner volume, combustion chamber design), except better heat dissipation, and therefore slightly higher compression without detonation.

-And lastly, you will not beat an 80's/90's 5.0 Mustang in the 1/4 mile with a 307 with Vortec heads, 256 cam, headers/dual exhaust, performer rpm intake, 3.xx gears, and stock stall converter. You can, however, build a nice street engine that will serve you for many years, tow, haul, and accelerate onto the freeway while putting a mild grin on your face.

Sorry for the rambling, and like usual, it's very possibly I'm completely wrong!

[pat123]

Would i get used or new vortec heads?
or aluminum or cast?

[piecesparts]

Originally Posted by pat123

Would i get used or new vortec heads?
or aluminum or cast?

What kind of money are you willing to spend? That would decide the choice on heads.

[pat123]

Depends what their worth?

[tdave00]

Glad to find this post. I too have a 307 in the 68 that I bought last summer and I wanna keep it because it's original to the truck. I have been pondering the same questions and have been doing alot of research over the last couple of months. I am not an authority on this but here are my thoughts.

I am thinking of going with 305/5.0 vortec heads (12552520). Long tube headers.
Small quadrajet carb.
Not sure on the intake (don't know enough to choose one yet).
Hei Distributor.
Mild street cam.

Here's a couple of ebay links to the 305 vortec heads.
http://cgi.ebay.com/ebaymotors/_Car-...3A1|240%3A1318
http://cgi.ebay.com/ebaymotors/ws/eB...m=260344252856

Here's a good writeup on building a 307.
http://www.hotrodders.com/forum/307-...-up-98850.html

[Old Yeller 1970]

Originally Posted by pat123

Would i get used or new vortec heads?
or aluminum or cast?

Vortec heads only come in cast iron. Regarding new or used, I would only run used if they are rebuilt. Regarding price, new Vortec heads are not that expensive so if you buy used price out the cost of the used head plus the cost of the rebuild to compare the difference.

[kcjones]

Originally Posted by Old Yeller 1970

Vortec heads only come in cast iron. Regarding new or used, I would only run used if they are rebuilt. Regarding price, new Vortec heads are not that expensive so if you buy used price out the cost of the used head plus the cost of the rebuild to compare the difference.

And if you go used, there is a great car craft article ( http://www.chevyhiperformance.com/ho...458/index.html ) that will help you know what to look for and how to have the machine shop work the heads for best results. It's invaluable in getting the right used head and reworking it to best meet your needs. Heads are truly the place where the power is decided, so read the article, arm yourself with knowledge, and get it right the first time!

[pat123]

Glad to find this post. I too have a 307 in the 68 that I bought last summer and I wanna keep it because it's original to the truck. I have been pondering the same questions and have been doing alot of research over the last couple of months. I am not an authority on this but here are my thoughts.

I am thinking of going with 305/5.0 vortec heads (12552520). Long tube headers.
Small quadrajet carb.
Not sure on the intake (don't know enough to choose one yet).
Hei Distributor.
Mild street cam.

Here's a couple of ebay links to the 305 vortec heads.
http://cgi.ebay.com/ebaymotors/_Car-...3A1|240%3A1318
http://cgi.ebay.com/ebaymotors/ws/eB...m=260344252856

Here's a good writeup on building a 307.
http://www.hotrodders.com/forum/307-...-up-98850.html

Are you sure the heads in this link (http://cgi.ebay.com/ebaymotors/_Car-...3A1|240%3A1318) are Vortec heads? They dont look it to me, correct me if im wrong.

[Slik69]

Just a question on why you would use a smaller somewhat inferior motor when you can build a nice stock 350/vortec headed motor with more torque, thus better mpg? Just curious. I'm buildiong a motor for my truck and 350 bone stock is the minimum. What are the advantages to having a smaller motor. Help me understand this.

[pat123]

I guess the big thing is to be different. I think you can make some nice power with a 307

[tdave00]

Check the part # (12552520) on the third picture down. It's the correct part number for 305/5.0 vortec heads.

[pat123]

Just a few question about vortec heads. Can you get them with the old style valve covers? Should i be getting aluminum? What are some specs?? (etc. valve sizes, runners, chambers)
THanks Pat

[67_C-30]

Originally Posted by pat123

Just a few question about vortec heads. Can you get them with the old style valve covers? Should i be getting aluminum? What are some specs?? (etc. valve sizes, runners, chambers)
THanks Pat

You have to use centerbolt valve covers unless you buy a billet adapter to use centerbolt valve covers. The Vortecs have 170cc intake runners 70cc exhaust runners, 64cc chambers, 1.94/1.50 valves. As the chart shows, the Vortecs flow better than older heads like 461, 462, 492, 186 double humps, 041's, 441's, 882's, and flows better than aluminum Edelbrock Performers, aluminum LT1, and aluminum L98 Corvette heads, as well as the World products S/R Torquer heads. In fact, Vortecs only flow 4 cfm less than 200cc World Products Sportsman II's with 2.02/1.60 valves at .500 lift. They are BY FAR the best bang for the buck as far as SBC heads go. You can spend $1100 a set of Edelbrock Performers or around $750 for a set of World Products Torquers, and the stock Vortecs out perform them both.

[5150.4.67]

Good chart c-30! Aluminum allows for greater compression ratio although. Just another factor to throw into the equation. Agreed, Vortec's are very hard to beat for their relative cost!

[pat123]

so should i be looking for some aluminum ones?
and would it be cheaper to get used ones and have them worked?

[67_C-30]

Originally Posted by pat123

so should i be looking for some aluminum ones?
and would it be cheaper to get used ones and have them worked?

Aluminum is not a necessity. There were no factory aluminum ones, so any aluminum heads you buy will have big valves (2.02/1.06 mininum) and big springs that are probably way overkill for a what you going for anyway. Buying set of used Vortecs (or even new) will be the cheaper and they will perform very well for you. Remember though, that you have a Vortec style intake because the bolt pattern is different. You can pick up one of those on ebay for less than $100, so that's no big deal.

[67_C-30]

Originally Posted by 5150.4.67

Aluminum allows for greater compression ratio although. Just another factor to throw into the equation.

That is true, but like you said, the Vortecs are hard to beat for the money and very sufficient for a strong street engine. I am in the process of building a new engine for my red '69, and I'm using Vortecs. I am using a '92 factory roller block and and I'm going to run the GMPP Ram Jet 350 hydraulic roller camshaft (GM P/N 14097395). The Ram Jet 350 has Vortec heads, 9.4: 1 CR and this cam, and produces 350HP at 5200RPM and 400 ft lbs TQ at 3500 RPM and has a nice smooth idle. My engine will basically be a .030" over Ram Jet 350 with a carb.

[697498chevy]

My '69 307 has 256,00 miles on it . Never been out of the truck . I did take the heads off and had them re-built . May have added a new cam and lifters also . I'd be happy with a good rebuild . No need for high performance . My truck's been original for 40 years and I see no reason to change it . Just my two cents worth . Hope I didn't step on any toes .

[tdave00]

Originally Posted by 697498chevy

My '69 307 has 256,00 miles on it . Never been out of the truck . I did take the heads off and had them re-built . May have added a new cam and lifters also . I'd be happy with a good rebuild . No need for high performance . My truck's been original for 40 years and I see no reason to change it . Just my two cents worth . Hope I didn't step on any toes .

This is not my thread, but no toes stepped on. We all have different ideas. It just happens that my idea is better than yours . Kidding!