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Hey guys, I am new here and have a question regarding my motor configuration and performance. I am not looking for a race car but would like to have better performance than what I am getting. I have '71 with a 350 SBC everything is stock and not numbers matching.
That's where it gets interesting. I had the motor rebuilt with these mismatched parts mostly because I did not know any better. Now I am researching what I have and wonder what needs to be changed. I am guessing the heads will bring these pieces together but not sure and need some advice.
Stock 350 4 bolt main block
Stock quadrajet and intake manifold
Stock 2.5" exhaust and manifolds
Stock 3932441 76cc truck heads 1.94/1.50
Aftermarket mild Comp Cam - 12-234-2, 256/268, 447/454.
I plan on getting aftermarket headers since my exhaust manifolds are mismatched. Passenger side off a 327 and drivers correct for a 350 Vette.
What would be the best setup for me? Should I trim my existing heads down 10-15mm to get a smaller combustion chamber, around 70cc?
Should I get the 64cc camel hump heads? If so which ones, 186, 461, 462 or LT1 041s? Do I need 2.02/1.60?
Are aftermarket the best for my configuration or do I need a bigger cam to really see benefits?
I would like to not change the cam. I am hoping heads and headers will get me to the correct performance that this Vette should have, if not a little better. Let me know what you think and where I should go from here.
I should have done this research when I first got the car and had the motor freshened 12 years ago but looking for the correc mix now, better late than never.
Almost any current performance head will be an improvement. It all comes down to what you want to spend. Edelbrock E series heads seem to be the go to for stock replacement. Maybe a set of 1.6 ratio rocker arms and you may see a good 40+ horse power.
The pickle is that you can get good castings and well built aluminum heads for only a few shuckles more than what rebuilding a set of steel heads costs.
I would have been $750 in to refurbishing my 64cc Camel Humps.
I was just over $1,000 into getting a new set of aluminum heads custom built with 0.10 over-long valves, 160# seat pressure, undercut and swirl-ground valves, and 7/16 rocker studs.
The change allowed me to go from a max cam of somewhere in the 0.480 lift range to the 0.600 lift range.
Just something to consider.
Last edited by keithinspace; 12-09-2015 at 09:34 PM.
Even if you go with a set of stock vortec heads, you will be able to increase lift on the cam. If staying stock looking is something you want you could get aftermarket iron heads also that will be way better than what you have.
Almost any current performance head will be an improvement. It all comes down to what you want to spend. Edelbrock E series heads seem to be the go to for stock replacement. Maybe a set of 1.6 ratio rocker arms and you may see a good 40+ horse power.
How do I tell what ratio my current rockers are? Changing just these could add 40+ or this plus the E series heads?
Even if you go with a set of stock vortec heads, you will be able to increase lift on the cam. If staying stock looking is something you want you could get aftermarket iron heads also that will be way better than what you have.
Will I have to change my intake manifold for a set of Vortec heads? I looked at a set of 906 heads but was not sure my stock intake and quadrajet would still work.
How do I tell what ratio my current rockers are? Changing just these could add 40+ or this plus the E series heads?
If you have stock looking forged or cast rocker arms (and typical pressed in studs), it is more than likely that you have 1.5:1 ratio rockers.
A set of 1.6:1 rockers will add additional lift to your current cam and provide a boost in power. With your current heads however not a lot. Also depending on the pistons you have, you may or may not have enough clearance to run them.
One thing you haven't mentioned is what pistons you have in your engine. Are they flat-top as would have come on a typical 270 or 300 hp engine, or are they domed pistons that would have come on the 330 or 350 hp engine? Or are they dished pistons which came on later 350 c.i. engines? Your pistons will play a significant role in deciding what heads you will want to use.
Will I have to change my intake manifold for a set of Vortec heads? I looked at a set of 906 heads but was not sure my stock intake and quadrajet would still work.
If you use stock heads you will, I thought I read somewhere about a set of aftermarket vortec heads that use a regular bolt pattern.
I purchased a pair of Promaxx aluminum heads and they are drilled out for both Vortec and Gen 1 intakes. Even the valve covers are interchangeable and you can go with either the center fastened style or the older, perimeter bolted style. They were made on order for me, as I called them directly and they were very helpful. They came ported and polished, and cleaned up by hand. Stainless valves and heavy duty valve springs. All of this, for less than $1K.
You would ruin the heads taking off 10-15mm. The deck isn't thick enough.
I would never advise anybody to put a dime in double hump heads. The chamber design and low cfm ports make them undesirable compared to modern heads.
Dart iron eagle heads are cheaper than aluminum, But your desire to keep the stock intake would defeat going to better heads
What intake do you suggest that would not require any modifications to the stock hood? I don't care for the aluminum look since it would look less stock.
What setup would work best with my existing cam? Is there a specific package configuration that can be purchased of matched parts? Would it be possible to get close to 400hp with new heads and headers?
Wow, you're worried about a 'stock look', yet you're going to be running headers? That's not going to look very stock at all. As far as aluminum, there's a reason they're more expensive (despite their 'non-stock' look). First, you'll lose an easy 40 pounds, right off the bat (and I'm just guestimating), they are far lighter than iron heads. They also transfer heat, a whole lot better and a whole lot faster than iron, meaning your car can run cooler and because of that, you can up the compression ratio, just a little bit. Next, if you're going to have 400 horsepower, nothing says 'cool', like a set of aluminum heads on a Small Block Chevy.
And finally, no way are you going anywhere, with a stock manifold. You might as well, give in and get an Edelbrock Performer or something similar. You might as well get the whole package, in fact. Then get yourself a nice aluminum radiator, for even better results. I got mine for under $150 and it works fine. And if you really want to have a trouble free, run hard, SBC, with no squealing, pick up a single belt, Serpentine Belt drive off've a '87 to '91 Chevy Caprice, put it on, paint it and never worry about adjusting a belt again or hearing belt squeal.
What intake do you suggest that would not require any modifications to the stock hood? I don't care for the aluminum look since it would look less stock.
What setup would work best with my existing cam? Is there a specific package configuration that can be purchased of matched parts? Would it be possible to get close to 400hp with new heads and headers?
The better question is what do you want the car to do, budget, and what torque convertor/gears/transmission do you have?
I've never understood keeping the stock look, but you can paint aluminum.
When it comes to HP you have to think about how hard it is to make 400 hp. Chevy never produced a 400 hp 350 ci two valve until the famed C-5 Z0-6 It had about 10.5 c/r, roller cam, big flowing head, and the ability to spin to 7000 rpm.
Wieand Stealth is one of the better intakes, but you have to have a quadrajet adapter spacer.
This might work, but I would find out what the port size is as to what heads it can use.
It has been a while since the motor was open but I don't remember having anything but the stock pistons. I don't know the compression ratio. Also, I have a stock TH400 tranny, may have a shift kit in it but stock converter.
Definitely a lot of options. I want it to be a nice cruiser that is fun to drive and has decent power that can push you back in the seat. Right now all it does is chirp the tires shifting into second and bogs down when you get on the throttle after cruising around. Most driving will be around town so I think low end power would be the best.
It has been a while since the motor was open but I don't remember having anything but the stock pistons. I don't know the compression ratio. Also, I have a stock TH400 tranny, may have a shift kit in it but stock converter.
Definitely a lot of options. I want it to be a nice cruiser that is fun to drive and has decent power that can push you back in the seat. Right now all it does is chirp the tires shifting into second and bogs down when you get on the throttle after cruising around. Most driving will be around town so I think low end power would be the best.
Through your thought process, just toss a $400 converter into the mix.
Decide what you want the engine to be...how it should sound at idle, what power you want, how temperamental you'd like it to be, what type of gas you'd like to run...then choose your cam.
Once you choose your cam, choose a converter that matches the cam. Where it makes power and how much power it makes, I mean.
12-09-2015, 09:03 PM
Replace Heads for performance
