- Joined
- Aug 14, 2014
- Messages
- 4,516
- Reaction score
- 1,563
- Location
- Madison, WI
- My Car
- 1971 Mach 1 w/408C stroker
At the end of last year I got the bug of more horsepower. Who doesn't! I did a lot of research on cylinder heads and although I had mildly ported 4V heads I figure I can squeeze more power out of aluminum aftermarket heads plus the 50 lbs lighter weight was very appealing (https://www.chiheads.com.au/shop/heads/4v-ford-cleveland/). There was not much data out there about the CHI's 4V heads, but their 3Vs are top of the line. The advantage with the 4Vs is that I could use any manifold and/or headers since the port location is the same. So back in September I took the jump and bought me a pair. They finally arrived in November and had Billy Ray Morgan in California install the valves and springs. Based on CHI's recommendations I went with REV valves 2.19" and 1.65". Yes, the CHI 4Vs have a slightly smaller exhaust valves. I paired the valves with beehive springs. Maybe not needed for my application but it won't hurt. I got the PAC 1219X springs with a seat pressure of 145 lbs and a rate of 340 lbs/in.
The heads are obviously beautiful. Installation was as expected. Spent a good time measuring push rod length and settled with Trend 3/8" push rod with the 210 tip. The car immediately felt more responsive and with more power. Did the dyno at the HRPT with the same vendor that I did it two years ago with the worked 4V heads. I was blown away with the results, 472 HP and 507 torque. So that's an increase of about 68 horses and 80 lbs of torque with the new heads. I had mildly ported by Bluethunder at home which may have given me a little but I believe most of it is from the heads. Super happy with I estimate that my engine is making close to 550 at the crank.
You can see the attached dyno sheets. The different runs are with the exhaust cutoffs close and open. Obviously there is more power with the cutoff open but also notice there is a bump in torque. That's about 13 extra horses with the cutoffs open. My cutoffs as right after the extended 3" collector. I have a 8" collector extension. After that it goes down to 2.5" and then down to 2" after the muffler.
The heads are obviously beautiful. Installation was as expected. Spent a good time measuring push rod length and settled with Trend 3/8" push rod with the 210 tip. The car immediately felt more responsive and with more power. Did the dyno at the HRPT with the same vendor that I did it two years ago with the worked 4V heads. I was blown away with the results, 472 HP and 507 torque. So that's an increase of about 68 horses and 80 lbs of torque with the new heads. I had mildly ported by Bluethunder at home which may have given me a little but I believe most of it is from the heads. Super happy with I estimate that my engine is making close to 550 at the crank.
You can see the attached dyno sheets. The different runs are with the exhaust cutoffs close and open. Obviously there is more power with the cutoff open but also notice there is a bump in torque. That's about 13 extra horses with the cutoffs open. My cutoffs as right after the extended 3" collector. I have a 8" collector extension. After that it goes down to 2.5" and then down to 2" after the muffler.
