So I find a great deal on a 347 locally and I bought it. The engine has never been installed and it's on an engine test stand and it sounded great. Should do 475 hp based on a similar build he says. What he doesn't tell me is that he ground the first cam and lifters into dust. But hey, "the parts that are still good are still worth more than what you paid" he tells me, plus I got the engine test stand. Anyway, after lots of machining, new pistons, rings, bearings, oil pump, heads worked over, new damper & flex plate, the nightmare ends with me doubling my investment. I would have made much different choices for that kind of $$. On to the dyno! After 13 pulls, the best 419.9 torque and 421.1 hp is pretty respectable but not the 450ish i was hoping for. My 750 Holley with annular boosters and an open spacer did the best, but my Demon carb and all other combos was only 4 hp less. The combination: 1987 roller block Eagle crank and rods 58 cc Canfield heads Probe flat tops, Crane gold rockers with a Probe stud girdle 10.5 compression Comp 35-624-5 solid lifter cam (276/280, .584/.592 lift) I would appreciate any comments and if you have any insight on what shift points i should work with based on the attached graph, that would be awesome. cheers, Bert
Oh. I forgot to mention that you shouldn't wait 4 months before actually inspecting something you bought.
Were any of the dynos past 6000? Seems like it stil making decent power up there, wondering why the shut it down at 6 grand. I would think with the cam, valve train, and heads you should still be making power to about 7 grand, I'm not a camshaft guru though so I may be missing something. But a little more power and a little more RPM's your def in danger zone (Key top gun music ROFL) on that stock block.
My 347 was very much like yours except I ran AFR185 heads and a hydraulic roller cam with a little less lift. Our hp and torque numbers are almost exactly the same.
We did do a couple of 6200 rpm pulls. Unfortunately, it was dropping off after 6000. Cam is supposed to be good until 7000 but it all depends on the components. Valve springs are good, but maybe if i had AFR's? The A/F ratio was steady in the low 13's except around the 4000 to 5000 range where it bumped up as high as 13.7
Was that run on dyno headers or did you use your own? The production of almost 1 1/4 hp per cubic inch in an engine that runs at 5800-5900 rpm is about what would be expected but that dip in your torque curve disturbs me. Either the headers are shorties and/or way too big for the engine. Even at that you have decent torque from below 3000 rpm to 5000 rpm. On the strip, with a 4 speed, you should probably shift at 5500 in first, and 6200 - 6500 after that. With an auto set the shift light at 6000 rpm and leave it there.
you deff.,need to check the cam , did you remove the center spring to break it in, sounds like bad springs, bad lobes, the triple springs for that cam require you to remove the center spring and break cam in , ive seen alot of guys not do it and take off lobes, that cam should have ran it up to 7200 easy, and with those heads you was just getting to the hp rpm, that setup should make 475 easy,id check some stuff, make sure you didnt spin the outside ring on the balencer,something isnt right,my motor made 427hp with stock heads with some clean up ,and a 550 lift hyd cam,with 9.5 to 1 comp,at 6250 rpm, it seems to have a nice flat torque curve , it seems like it might have had to much timing , was you at about 35 deg,total ,looking at the hp # you would have to shift at 5700 , you want to be charging hard at the top end of the track not peaking before you get there,it would be perfect to cross the line at 6000 rpm,but i feel you need to explore the problem more theres tons of hp left in that motor ,those heads are super nice i have a friend with a set on his 351w ,it make 605hp with a solid roller 575 lift cam, and victor intake,12.5 to 1 comp,same heads port matched only,at i think 7200 rpm,and the dur. was 260s,i also think theres alittle more torque left in it , but thats great # on that side ,you want it to be flat like that
They weren't my headers but they were still long tube 1-5/8 Hooker. The only apparent difference was how tubes 3,4,7,8 took a slightly different curve to the collector than my 6901's. As for the 25lbs of torque i lose right where I'm launching, I'm wondering if it has something to do with the way my engine reacted on the dyno. When the engine was fully loaded and before the tech hit the button, it would surge somewhat. It could be the last of those surges.
Don't get me wrong it makes great power and is nothing to be upset about, I just feel theres more left in the motor with some tunning. Just trying to help not knock anything (which I hope your not taking it that way). I would through a degree wheel back on it and measure the cam just to make sure its where its suppose to be. Its possible that it could be advanced 2 degrees explaining the drop in peak RPM. Was the cam installed with a degree wheel, or "dot to dot"? What intake is on it? Did you guys try adjusting the AFR down towards 12.5 or 12.0 at all? 13.0 is a little lean for my taste (but each engine likes a little different) , and that 13.7 dip would scare the crap out of me. IMO way to lean under hard load like that. I would be doing a little more tweaking before I had that motor at the track.
I am definitely open to any comments so don't worry about offending me. I am getting lots of good help and ideas which i appreciate. dot to dot I have some time before my converter arrives so i can degree the cam. The Demon carb ran in that range and the numbers were pretty much identical, just differing by 5 to 7 hp less at the top end. I might leave the upsizing of the jets for track tuning since i can't afford another dyno session.
The cam had been broken in previously, but we did a break in run anyway. Triple spring? I'm going to check, but i'm pretty sure i got the standard 2 spring set. I checked the cam specs and they have two numbers. I'm guessing that you're talking about the 26094-16 racing set which seems to have a weird looking spring between the two I'm used to seeing. So possible valve float?? Balancer is a new Professional Products unit. We ran 30 deg toal mostly. 32 didn't make any difference over the 30, but 28 deg lost me about 20 hp. It's all in by 2800 RPM.
Take a look what intake? What fuel? Did the demon carb have that lean spot in afr as well? I'm not sure valve float is it, could be but everytime I seen it it looks choppy on high rpm on the dyno graph UNLESS the dyno operator "smoothed" it out for you to have a pretty graph:16suspect.
i think id try more timing in the future all in by 3000, yes a double spring is going to have trouble handleing those dur. numbers and lift ,id say you may have had valve float ,as the other guy stated im not wanting to say anything bad about your motor ,thats alot of hp you already made, im kinda anal , i worked at a super stock race engine shop for 25 yrs,and every hp was important to us , sometimes 1 or 2 hp was a win or lose for us ,that cam you have is a very large cam , and those heads are super , that motor should have made power up to 7200 easy, should have really started making hp around 5500 and up
