[Amc-list] Stroker 304 back from the Dyno

[Greg Taylor <amundaza@xxxxxxxxx>]

Well guys,
The stroker 304 lives, breathes and we did not blow it up on Saturday.  It was a super long day … in all there were about 18 hours of setup and tuning time for the engine, between Friday afternoon/evening and Saturday, when we did the pulls and swapped out parts. We had plenty of issues to deal with, which I guess can help others that would consider getting their engine dynoed.
 
We didn’t start dyno pulls on Saturday, until about 12:30 PM and concluded around 6:00 PM, then packed up everything.  In the 5.5 hours of time, we did a handful of pulls.
 
Baseline pulls were with the points distributor (@ 34-degrees advance) and the 625-cfm Carter Competition AFB 4-bbl.  With the Carter at idle we could get the A/F ratio set, but at 3,000+, it still would run between 15-16:1 A/F.  We did a few pulls from 3,000-4,000 and 3,000-5,200 and monitored the exhaust temps.  That made 260-HP @ 4600 RPM and 315-ft/lb @ 3600 RPM … all with it running lean.   Brian (dyno operator) commented that the engine was running really efficient with that lean A/F ratio, as BSFC for the pull was 0.39x.
 
Switching over to the AMC HEI was interesting.  We got it timed and it was mechanically advancing up to 34-degrees, but when you gassed it, it would continue climbing up to 60-degrees MECHANICALLY.  We ended up swapping out to a lighter spring rate to get it to “stop” climbing, but it would still jump around … not staying consistently around 34-degrees.  It would climb to about 40-degrees and then start dropping back down.  So, we set it at 30-degrees advanced and left the vacuum advance unhooked for the pulls.  I’ll be taking the distributor out and discussing a recurve with the mfg (he lives about 10 minutes from me).  With the HEI, the stroker made about 265-HP and 320-ft/lb torque with the lean AFB 4-bbl.  Concensus was that if we spent some time jetting the AFB, that the engine should make about 300-hp (and ~350 ft/lb).
 
What was really, really interesting, is the torque curve.  At 3,000 RPM it was@ 300-ft/lb. At 4,000 RPM it was @ 300-ft/lb … at 3,600 RPM it was at 320-ft/lb.  Not much of a curve there.  Carry it back on down towards idle and I am going to have PLENTY of low-end torque with this engine …. And it has a single plane intake on it (Offy 360).
 
After doing the pulls with the 4-bbl AFB and “OK” HEI, we swapped out to the big 2.0” bore Fish carburetor.  This took quite a while to get it running on the engine.  First, it wasn’t getting gas, then it took a while to get it tuned, so that it would run.  After we got it running and roughly adjusted, the A/F was pushing around 18:1.  When I got the carb (used), it had some varnish in the float bowl which I cleaned out.  We decided that it was possible that the fuel pickup possibly was partially clogged with varnish, even after enriching the WOT fuel enrichment (a screw which blocks or unblocks the hollow throttle shaft, determining the amount of total fuel flow).  So, we pulled the 2.0” Fish carb off without doing any dyno pulls.  I am going to tear it down and make sure the fuel pick up and throttle shaft are cleaned out.
 
We then switched to the smaller 1.65” bore Fish carb, which took some engineering to hook up the dyno throttle, since it is about 4” inboard from where the Holley linkages hook up.  Once we got that done, the 1.65” was up and running fairly quickly, since it already had been run on the engine break-in stand.  After getting it tuned according to the Fish manual, it was still showing a lean A/F mixture on the dyno controls.  So, we messed with it for a while.  While running “lean” it was not running high EGTs (exh. Temps), so we decided to do a couple quick pulls, while watching the EGTs.  IF they spiked, Brian was going to kill the ignition for the dyno.  The pulls went fine and the EGTs did NOT spike like he thought they would … that had him super-puzzled, since the A/F ratio was 17-18:1 at the time for a 3,000-4,000 RPM pull (400 RPM/sec increase).  So we pulled the hottest cylinder’s plug (#5) and he inspected it.  Upon pulling
 it, the plug immediately looked fine.  He looked at it under a scope and his response was that upon inspection, it appears to be running RICH.  So, the plug went back in and we adjusted the 1.65” Fish LEANER at mid-RPM (no WOT adjustment on this one) and did a 3,000-5,200 RPM pull.  That pull went fine, no crazy EGT’s (1,100-1,400 range for all).  What we did learn is that 1.65” bore Fish carb makes less HP and Torque than the Carter AFB.  Going from memory here, it was about 225-HP and 270-ft/lb of torque.  We still don’t know what the 2.0” Fish will do … which is supposed to be substantially more than the smaller Fish carb we did run.
 
Now that I have had a few days to mentally analyze all that occurred on Saturday, I want to find out what the EGT’s were for the Carter pulls, along with the Fish carbs.  Because the engine incorporates the cylinder head grooves (which run cooler) and Swirl-Port heads, I am wondering if the engine was in reality running highly efficient.  Both the head grooves and swirl-port technology are supposed to generate a much more complete burn.  IF this was occurring inside the stroker, that would account for the lower EGTs in the presence of the lean A/F mixture.  I am wondering if a more complete burn would result in a lean A/F READING, even if the motor was not necessarily “leaned” out.  I am going to contact the guys over at Endyn, who have pioneered the Swirl Port efforts, to see what kind of A/F ratios they are seeing on their dyno engines, as a result.  They have helped build engines ranging from NASCAR to import engines, with the swirl-port
 technology … their website is at www.theoldone.com .
 
Saturday’s events were exciting and disappointing at the same time.  Some questions were answered and some were not.  Were I to do it all over again, I would readjust the Fish carbs, using the vacuum gauge, as recommended in the Fish Carb manual, NOT rely so much on the A/F monitors, and instead watch the EGTs with the Fish running.  Having run the 1.65” Fish last, at a LEAN reading and doing fine, I am wondering if the Big Fish might have been fine to run, also … if the EGTs were monitored and “performed fine”.  I did re-read up on the Fish and found that one guy who had it on his Dodge motor home, ran his at 18:1 A/F ratio … anything richer than that would foul out his plugs.  Since my Thorley headers have AIR injection ports on them, I think that I am going to install EGT sensors at those ports and use that data for tuning the engine with a Fish Carburetor, once I have the Jeep up and running.  I also have an O2 sensor port in the
 Y-pipe collector, which I’ll use as SUPLEMENTAL data for tuning … and I’ll adjust the FISH like the manual says, and not like a typical carb is supposed to be done.
 
So, all in all, I am  a bit sad that the engine did not hit the baseline of 300-hp that I would have liked.  I was pleased to hear Brian say that he thinks it would make 300-hp with the right tuning on the AFB carb.  It would also have made more power with a BIGGER cam, but that would have negated one of the goals of economy.  I am pleased with the torque curve … it will be perfect for a big Jeep.  And finally, it will be real interesting to see how this engine performs in real-world driving.
 
Pics and video will be up later on the build threads at :
http://www.ifsja.org/forums/vb/showthread.php?t=95564 or http://theamcforum.com/forum/forum_posts.asp?TID=8062

Sincerely, 
Greg Taylor :) <>< 
Rochester Hills, MI
1989 Jeep Grand Wagoneer "TRMN8R2"
330-CID AMC Stroker V8

And the testimony is this, that God has given us eternal life, and this life is in His Son. He who has the Son has the life; he who does not have the Son of God does not have the life. - 1 John 5:11-12



      
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