289 head swap

I knew where you were going, cough cough proform etc... Mine was in response to Larry more or less, not a dig at you Larry, just random babble from a bald guy!

 

my thought was...how did we get from his 289 head swap to China...

 

289 (as well as 302) heads don't flow worth a crap unless they are ported, after which expense you could get aftermarket heads for only slightly more. The bump in compression is nice but offset by the poor flow in stock form.

 

The jump in compression is outstanding! The car is actually worthy of competition now. "Runs like a scalded dog"
Alot more pop in the exhaust. The compression went from under 8:1 to almost 10.5:1. The heads were shaved, making the new pushrods .075 shorter. This made my valve lift go from .444 to .498. So, as another post ranted about my advertised duration @ 50 which ended up being .249@ 50.
1965 289 heads have normally small valves, but also small combustion chambers. If the valves are changed to a larger diameter and you take out the radius under them, they will completely change flow characteristics. Some have been flow bench tested to be over 220cc of flow, with only minor porting. The exhaust ports are particularly small. I would suggest at least a .500 lift cam to push the air out better with this setup. I may go that direction in the spring, if I decide to race it.

 

The bump in compression will add a noticeable change in power through the entire rpm range. The larger valves and bowl work also help. A gasket match on the ports would aid flow as well. The lift of the cam does not change due to shaving the heads or shorter pushrods. It is based solely on the cam lobe itself and the ratio of the rocker arm. Duration is measured in degrees, not inches. There are two common measurements, advertised and @ .050. Advertised is very subjective and not a reliable number for actual duration. The@ .050 method is a more accurate way of comparing duration profiles. I doubt that your cam has 249* of duration @ .050. With a lift of .444 I’d bet it’s around 210*-218* @ .050.
Flow numbers are measured in inches, not cc’s.

 

Assuming you are still using 1.6 rocker arms, you could swap out the exhaust for 1.73. If you have the clearance, it would be a cheap/easy way to change .444 to around .475 - .480.

 

I guess I should let the knowledgeable people help you on your head info quest.
My numbers are so jacked up, if I try to help I'm just going to get bashed more by other "car genius" members.
I obviously don't know how to explain myself properly, therefore the "smart ones" can finish the thread.
Bullies come in all forms.

 

I am relatively new to this stuff and have little experience. I have an iron head 302 with 1968 2v heads. I have read this thread with interest in what you have done with iron. I know for sure that my motor has too much overlap (irritating exhaust fumes and 10mpg ) and not enough compression for whatever cam is in there.....and although aluminum would be the optimum replacement head since I probably will not experiment with porting, I am always curious about what folks can still do with iron.

 

Have 289 C6ae heads without the thermactor bump on my 302. I like them also. My son has GT40 heads on his 302. We both are running the same camshaft. I believe the extra bump in compression makes up for the flow difference.

 

Bob's response was far from bullying and his correction was accurate. As far as turning the responses over, no one else can speak for your opinion on how it runs. Iron heads have merit, if not the cars running FATS wouldn't be running the times they do. I believe there is genuine interest in your combo, tells us what you like or dislike about it, inquiring minds want to know!

 

Some people just try to help sort out the confusion over spec's and power output potential. No need to be so sensitive when mistakes are made and corrections are offered in a matter of fact attempt to help another forum member out.

I've had and ported several of these small chambered heads and they run decent for the intended purpose. This is what thousands of others were forced to do before the aftermarket came to our rescue. The other hot setup was to mill down a set of 351W c9oe or dooe heads with 1.94" valves to get compression up for the littler 302's.

My last set were true hi-po's ported to within an inch of their lives(VERY thin and right near water at the short turn) running 1.90/1.6 undercut stem valves. You can put bigger valves in but there's not near enough metal to get the short turn right to take full advantage of higher lift flow potential. Also angle milled about .090" to reduce chamber size to around 48cc's but than after the prerequisite chamber work to unshroud the larger valves ended up similar to stock 53cc's. 0 decked with 2 valve relief pistons gave 10.5:1 static compression. Intake, exhaust ports, valves(undersides with exposed stem and faces) were fully thermal barriar along with chambers and piston crowns. That .060" over 310" motor made around 330-340 horsepower with a 224/229 @.050 custom hydraulic stick bumping rhoads variable rate lifters pushing 1.7 roller rockers to open the valves around .530" lift.

A lot of work and very cash involved for very little gain compared to even a cheap set of offshore out of box castings. A really good set with some extra port work would be up nearly 100 horsepower over my old iron headed combo. Nostalgia is great but horsepower is what keeps people interested over the long term after the shiny new has long worn off.

 

This is exactly what I have today. Would I prefer some AFR aluminum heads, sure. However, I already had a set of mildly ported d0oe heads with the larger valves and screw in studs laying about. Had the chambers all cc'd to 58 and bolted them onto a mildly worked over late 80's roller 5.0 h.o. with some 1.7 rockers. I calculated the compression to be around 10:1, it is a great daily driver with a bit of a boost in performance. If I was starting with nothing, it would definitely be aftermarket aluminum, but with some work the old casts can be made quite decent.