AFR 165 or 185's for a 289?

I had the same experience as iwantmore with the AFR165's and had to flycut my pistons to get the necessary piston-to-valve clearance. I'm running a cam with 230 duration @ 0.050 and 0.512 lift, so you might be okay with your smaller cam. However, if you step up to a slightly bigger cam in the future you might then have clearance issues.

Unless the Tw heads are professionally ported, they are NOT as good as the AFR heads. The 468 HP 302 was a 12 to one motor, with a solid flat tappet cam ( like 248 at 050 ) RPM performer with a reworked 650 Demon carb. It peaked at 7000 RPM and he could rev it up tp 75-7600 whenever he wanted to.He alway ran on race gas ( 110 octane ) I did another 302 hotty that made 504 or 506 with a roller cam and AFR heads too.

JOE SHERMAN RACING ENGINES

Originally Posted by BIGJOE

The 468 HP 302 was a 12 to one motor, with a solid flat tappet cam ( like 248 at 050 ) RPM performer with a reworked 650 Demon carb. It peaked at 7000 RPM and he could rev it up tp 75-7600 whenever he wanted to.
JOE SHERMAN RACING ENGINES

Hello Mr. Sherman,

The 302 in my car is very similar to the 468hp 302 listed above.
248/254 @ 0.050" Solid flat tappet cam w/110 lobe seperation
10.8 cr
750 Speed Demon
Victor Jr
Twisted Wedge heads

It's a pump gas engine that runs race gas when a 200hp plate is used.
Only been to the track once, and ran 7.46 @ 93 n/a and 6.68 @ 105.4 w/200hp nitrous. Seems to want to be shifted around 6800 rpm.

The car is a 3300lb w/driver 4-speed 1966 mustang with a 4.33 gear and 28/" tires.

Anyway, I can't really seem to get the 750 speed demon carb just right. It starts to go rich around 6800 rpm. I was thinking a 650 Mighty Demon, or something similar would be a better fit for the engine... and I saw where you mentioned your 468hp engine used a modified 650 demon. Can you point me in the direction I might need to go with a 650 Mighty Demon, or offer any of your wisdom towards my combination?

I'm thinking a slightly smaller camshaft... around 242 @ 0.050" with around 6 more degrees on the exhaust, along with the 650 would work better with my compression ratio...

Thanks!

Mike

165's

Originally Posted by 65FalconLover

Would I be better off swapping the cam for something bigger or going with the 1.7 rockers? Obviously that's the easier route.

I just want to do this right.

Thanks again for all your help!

I went to 1.7 rockers, actually Probe shaft rockers at a great price, knowing that the HP gain would be small. I had to rebuild my motor and I decided long ago that if I did I would switch to beehive springs and 1.7 rockers. I also decided I would set up the rockers for the best possible geometry (mid-lift rule appears to be the way to go). It all adds up in the end.

Going to 1.7 rockers generally does not provide very much gain if any. I know i'm contradicting myself since I did switch to 1.7s, but like I said...hopefully it all adds up in the end. I probably get more gain by optimizing the geometry of the new rockers and tightening the lash by .005. Going to 1.7s from 1.6s increases the duration by a very small amount and lift is increased by about .030 at max lift and less everywhere else.

You would be better served by getting a larger cam. You have a 289...make it rev!! You should be able to make it rev to 7000 and stay together without breaking the bank. Your cam won't support this though. I nice solid lifter cam would do ya well.

JOE: So are you saying that you think the 185s would have made less power? What do you mean by "There is a BIG misconception about what the bigger heads will do. MOST people have it all wrong. "? What's the big misconception? I think that the smaller ports help with inertial tuning, but at higher revs above the inertial tune sweet spot, less restriction/higher flow is more beneficial. Is there something I'm missing?

Mike: Does your Demon have replaceable high speed air bleeds? Have you tried larger bleeds to lean out the top-end? What are you using to determine that it's going rich above 6800rpm?

Tracy,

The only reason I was looking at going from a 1.6 to a 1.7 rocker ratio is that is what the tech at AFR recommended over going bigger on the cam. It sounds like they believe in shorter duration and larger lift for my application.

I was considering a cam swap, and still would if that's what works but I figured AFR's advice was pretty solid. Of course what he was given was that my car was a daily driver and now that I'm turning it into a weekend cruiser that advice may change.

I'm really just looking to get the most out of what I have without going deep into the bottom end. It's tight and I'm not going to raise the compression anyways but if a cam swap is in the cards so be it.

As it stands right now it'll spin up to 6200 without missing a beat but I usually shift at a much lower 5500 RPM with this set up.

I believe your idea of going to from 1.6's to 1.7's might be a waste of money. The way I understood it was a 1.7 roller rocker arm you might gain 5-10hp more.... but only in the upper 6500rpms and up higher. If your only spinning to 5500rpms, your not even taking advantage of what the 1.7's can even start to contribute. My advice, stay with the 1.6's. You'll have more dead on/accurate valve geometry going on for ya. You probably won't even feel a hp improvement either with the 1.7's.

Originally Posted by Motorhead

Mike: Does your Demon have replaceable high speed air bleeds? Have you tried larger bleeds to lean out the top-end? What are you using to determine that it's going rich above 6800rpm?

No replacable air bleeds in the Speed Demon. LM1 wide band was used to determine the air/fuel ratio.

I was curious what BIGJOE did to the 650 Mighty Demon that went on an engine similar to mine... as he said it was 'reworked'.

I thought a 650 Mighty Demon would be about right for my engine, but wondered what else it might need.

I'm also game for a possible cam change, even though it seems to work really well with the bottle.

Here is an area thats is confusing to many people. When you use something like an O2 sensor for tuning (Jetting) you DO NOT tune to a certain number (12.8 to 0ne) you tune to where the engine makes the most horsepower, THEN you look at the meter to see what it says. On my dyno, most engines make the best HP when I see an air to fuel ratio around 13.3 to 13.5 to one. On very high output engines( 2.0 HP per cubic inch, this ration even becomes greater ( 14 to one or higher)It is true, you can look at an O2 sensor to get you close, but remember, this is just a better starting point. On another subject, almost all Demon carbs are very lean ( jetting ) out of the box. I usually jet up 5 sizes before I even try it on the dyno. Now I know that most of the engines I am working with make more horsepower than normal, but unless you try bigger jets in any Demon carb, it will probably be too lean.

JOE SHERMAN RACING ENGINES