FE Power Forums
FE Power Forums => FE Technical Forum => Topic started by: Aussie Rob on October 09, 2014, 07:23:54 PM
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Hi everyone, been really ill and haven't been involved for a while but good now apart from results of engine build.
It's a .060 block 10.5 compression with the oiling mods that are recommended, Edelbrock heads and perfomer rpm intake cleaned up faced and portmatched, Harland Sharp rollers ,FPA longtube headers, Comp hydraulic roller 232 and 237 @50 , 524 and 535 lift, 106
degree centre line and 110 separation, 780 vac sec holley. Have been on a chassis dyno and can't produce any horse power over 4500 rpm. Torque starts at 1800 and peaks at 3400 then holds through to 4200 before starting to slide off. HP is a pretty flat curve from 3300 and peaks at 300 rwhp at 4250 then starts to die off and it's all over by 4900. The ignition is Msd distributor 6al box ,18 initial - 37 total all in by 2800. Have played with curve and initial combinations and this works best, have also double checked degreeing of cam
Exhaust is twin 2.5'' from headers to x pipe high flow mufflers over diff to rear. I really expected this combo to produce to at least high 5's or 6000. Comp states this cam should be good till then I'm a little frustrated .Where have I gone wrong.
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You may just need some carb tuning, its possible that your secondaries aren't opening enough, or at all. Try tying a small tie wrap around the secondary actuator rod, coming out of the vacuum diaphram housing. Slide it all the way up to the top against the housing, then go out and get on it a little, and come back and check it. If the secondaries are opening it will have slid down on the rod quite a bit.
On your chassis dyno session did you get air/fuel numbers? If so, what did they look like?
I think your peak horsepower RPM ought to be around 5500 with that combination.
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Thanks for the reply Jay, Ihave checked the secondary opening and it's fine, af ratio 12.2 beginning at 2000rpm with it being 12.9 at peak power @4200, I thought this is probably ok. MY tach and dyno are within 50 rpm and a seat of the pants drive gives the same result, no point going past 4900. Is it possible that it just needs more cfm in as I'm sure that exhaust is big enough for that combo.
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i have pretty much the same combo except I have a 750 DP. It starts out at around 12.7 and at WOT is around 14.7. It pulls about 375 @ 5K and still is pulling although it is over at 5500. I will ask about the springs. are they correct and shimmed to the right height?
GT
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Fuel system details?
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Springs are the comps supplied with the cam kit .I believe they are 135 seat and around 300 on the nose, they replaced the edelbrocks
According to the machine shop they are correct installed height, The fuel system is standard lines with high volume holley pump
Thanks Rob.
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What do you have the Rev Limiter set to ? , also try it without a limit or change it to a higher setting
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The fuel system is standard lines with high volume holley pump
That was the same reason my 428 wouldn't run over 4500rpm at the drag strip...could be your problem. What diameter are those standard lines? 3/8"? 5/16"? Simple test would be to bypass the tank on the dyno, go to an external tank with larger line. Bring a fire extinguisher...
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Hey...you say its a 780 Holley so I am going to guess its a 3310.The first generation of 3310's have secondary metering blocks and after that they just have metering plates and are sold as 750's...Do you have a secondary metering block or plate..
That being said if it doesn't rev past 4900 in any gear I would suspect something else.....Cory
The rev limiter crossed my mind as well and I see two people suggested it while I was two finger typing
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Sorry ,I probably didn't explain that properly it will continue to rev past 4900, It's just that the power drops off dramatically and you are going nowhere. The rev limiter is set at 6200( won't need that the way I'm going). Pretty sure fuel lines are 5/16. The carb is a 770 street avenger and did experiment with p/valves and jets on the dyno ,also used a 750dp and ended up with slightly lower readings all in the same rpm range. I have also made sure that msd supply is actual battery voltage and not ballasted.
thanks rob
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My money is on the fuel system. 5/16 is marginal at best. Which holley pump? It needs a holley black minimum. Also check the fuel line pickup for clogs. What fuel filter? I put my fairlane on a chassis roll two years ago. It had 486 tq at 3000 rpm and 276 HP at 3600. It fell steadily from there. After two pulls with the same result I watched the fuel pressure gauge bounce all over hell at 3500 rpm. Took the car home and found the filter was so plugged you could hardly blow through it. Oops! I upgraded to 1/2" line and black pump, but have not had it back to the dyno yet.
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That sure looks like something I'll have to seriously investigate. That pump is supposed to 110 gph but I don't have a pressure gauge, I just assumed that if the sight bowls showed fuel during the run then there was adequate supply.
Thanks Rob.
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I'd look at installing a pressure gage to help troubleshoot the problem and it's a bonus down the road any time you hunt trouble or just need the info.
A quick inspection of the fuel system for restrictions, dents or bad hoses seems in order also. Since you're on a chassis dyno I'll assume the gas cap is on and locked down during your pulls, might want to make sure it's venting properly.
I'll follow up with a +1 on the lines, 5/16" can be even less at the bends or where couplers may have been installed over the years and likely isn't enough to get you where you want to be.
All the previous info you've got above is good stuff, so you have plenty to look at. Bet these guys don't quit 'till you get it sorted out.
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If those fuel lines are original look for a pinhole on the suction side of the system - between the tank and the pump. It'll KILL flow...
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Replace all the rubber between the fuel lines too....although if you do have 5/16ths steel lines I agree they should be a least 3/8ths...and the requisite new rubber of course to the new lines. Be sure too that the tank is properly vented, a vented cap or on some old Fords a separate steel vent that exits under the car. Do not assume a replacement vented cap is actually venting since I've seen the gasket totally block the cap's vent hole, essentially making it non-vented!
Cheap and easy test: remove the cap and duct tape the filler tube closed. Poke a 1/8th" hole near the top of the tape. Make a run and see what happens.
On edit: If you do replace the lines, inspect the OEM Ford sender assm. as the line that goes thought the disc is also a 5/16ths steel tube. Get a OEM sender with a 3/8ths tube or break out the old one and braze/weld in in a new 3/8ths tube. Dump as well the metal mesh OEM Ford filter sock at the end of the tube and let the engine bay side and/or carb filters handle any crud.
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If the A/F ratio logged on the dyno still looks good at the higher engine speeds, its not going to be the fuel system. Fuel starvation will show up as a lean condition on an A/F log. Did the A/F numbers lean out above 4200 RPM? If they leaned out significantly, say to 14:1 or higher, then I'd agree that the fuel system could be an issue.
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Hey Barry, how would one look for a pin hole leak? What about a leak at a flared fitting? I redid mine years ago and used solid line. Problem was I had to make sections and used flared fittings. While they don't weep how could I really check them?
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at 4250 then starts to die off and it's all over by 4900
To echo and agree with Jay above, what is the AFR doing in this range? Still at 12-13? If it's falling off the chart above 14 or so, I'd say you're running out of fuel. If not, there is something else going on.
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Thanks for the replies,the a/f ratio stays in the mid to high 12's so I don't think it's running out of fuel either, I just had a look at the plugs and not as clean as I would like to see a bit dark and this car runs perfectly ,great start up ,crisp idle, no flat spots , plenty torque and acceleration. Just hits the wall when you really want to push to the next level so I'm wondering about the rotor phasing etc. There's no scope on this dyno , so I may have to go to another.
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Did you check for WOT? Engine off, have a pal mat the loud pedal and check that those butterflies are straight up....at least the primary side on a vac. secondary carb.
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Yes mate I checked wot before the first run.
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Assuming your build is as per spec, I'd try changing carb, preferably to a Double pumper. I' Ve never had good luck with the street avengers.
Where are you at Rob? I'm in Perth and can help out if you need.
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Hi Todd, I'm at the Sunshine Coast QLD mate. I tried a750 dp on one run and made 5 hp less , I bet this something so simple that I can't see the forest for the trees. A/F ratio's were simlar , no apparent leaning off. When I get a chance I will install original distributor and see if there are any variations. Thanks Rob.
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If everything checks out with the fuel system, you might look at the valve springs. Maybe something is wacky there. Did you check installed height? Hydraulic rollers are pretty heavy. Combined with the FE's high rocker ratio, it could cause some float if the installed valve spring pressure is off.
Just a thought,
paulie
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Air Filter?
Did you do the test with the filter on and off.
Some air cleaners and filters act as rev limiters.
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Two good thoughts above. FYI I have purchased the springs recommended by Comp for at least one FE build where they turned out to be completely inadequate for the Comp cam in the engine. On the dyno, I can usually tell if there is a spring problem because the graph of the horsepower curve gets unstable. I assume that this would also be visible on the chassis dyno plot. Rob, do you have a picture of the horsepower curve from the chassis dyno that you can post? That would answer a lot of questions, I think.
One other thing to think about is with the chassis dyno, you have the transmission and rear end involved. Could be a problem there too...
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Given that the A/F ratio seems good, I would suspect valve springs as well. The spark advance curve would be the second place to look.
Best of luck! You should be pulling hard and clean to 6K with no fuss, given your setup.
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Your posted spring pressures appear to be light to me. I would be 150/350 on the mildest of hydraulic rollers. There is more weight to control......harder to keep that heavy lifter on the cam. Also, be sure that there was not an error during assembly of the springs......a mistake in the math could have put you a whole bunch lighter than "too light already" just by an honest mistake.
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Springs are the comps supplied with the cam kit .I believe they are 135 seat and around 300 on the nose, they replaced the edelbrocks
According to the machine shop they are correct installed height, The fuel system is standard lines with high volume holley pump
Thanks Rob.
I didn't even notice the spring pressures on my first read through of this thread. That sounds very low if it is correct. i would say 300 lbs open pressure is not enough. I run over 400 lbs open pressure on my solid flat tappet cam. Mine is not the usual flat tappet deal, but you get the idea. I'm leaning towards valve springs even more now.
JMO,
paulie
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Might even want to put the Ed springs back on.
They show a bit more K factor.
#5792 Edelbrock #60069,#60079 Non-Rotator 145 lbs. 1.885" 355 lbs. @ .580" 1.460" 1.060" 1.130" #9734 #9612 All Performer
& RPM Cams
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Found the box my cam kit came in and the spring pressures are different to what my machine shop told me. They are comp part # 924-16, Seat Load= 112lbs @ 1.90 installed, Open Load= 355lbs @ 1.20. Alternative upgrade (which I know about now) part# 26120
Seat Load= 155 , Open Load=355 , just a little better than the E/brocks, there is every chance that this where the problem is.
Why do manufacturers and suppliers not tell you these things up front so you can make the best choice without having to go the long way round to get the right outcome. I work away so I have to shelve things now until I get back in about 2 weeks or so.
I have a tool to change springs with the heads on, do you recommend doing it that way or pull them off for accuracy?
Should I use the Edels or spend more money on the comps? :)
thankyou all for your help and advise I'll let you know when I've changed them over.
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The Comp 26120 is a beehive spring that would work very well on your package. But you will need the matching retainers and locators as well. Its a fairly expensive combination - but a good one. We alternately use a PAC racing 1924 here, a double spring which catalogs at a seat pressure of 144 lbs @ 1.900, and open pressure of 403 lbs @ 1.300
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That 924 is a very common flat tappet street build spring, not enough for heavy hyd roller stuff
If it were mine, I wouldn't spend a penny until I saw what my actual installed height and spring pressures were, you are likely to be even lower than what the paperwork says
Then I would go with something like Barry said, or if the budget is less forgiving, a high quality standard spring with damper that that matches your installed height and lift.
The factory Edelbrocks may be good for this application too, but you have to measure installed height, calculated or measured lift, and the resulting pressures.
Sounds like a lot of work, but less than an hour of work for the machine shop if you showed up on his door with one head. Even less time if you measured installed height on the car and calculated the rest, then he just measured spring pressures for you
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What sort of X-Pipe is used? Is it a name brand, or something an exhaust shop fabbed up? Sometimes, exhaust shops will TRY to build them, and either use crush bent pipe or simply run one pipe through the other. If they do this, the merge area is often the same as, or less than the diameter of ONE pipe. These might sound "cool" but create a horrible restriction in the exhaust that will keep the engine from making power.
What size exhaust is on the car? What sort of bends? If it is crush bent pipe that's 2.5" or less, and has some tight bends... that can keep it from making power when revved up as well.
As a test, I would uncork the exhaust, and take it for a drive. If it runs significantly better, you've found a bottleneck.
Good Luck!
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Thanks for the replies, I won't be taking anything for granted in the future, I'll be assessing the individual parts supplied in any kit I use.
As this was delivered directly to the machine shop I'm pretty disappointed in him as well(spent plenty there over the years-as well as recommendations). After several emails to comp they tell me I need better springs ,go figure, so I let them know my thoughts. They are telling me the same as you guys, the supplied springs are even less than advertised. I'll probably have to save a bit and go with the beehives. The x pipe is a Summit product and the pipes are coming off for a dyno run next time I'm off shift, he's not charging me for this one. Thankyou all for your tech expertise, it would be easy to dig a bigger hole without it.
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Standard issue at my place is the Comp 26120 beehive for anything up to .600 lift in a hydraulic roller, as long as 6000-6200 is the max rpm. Past that lift, or rpm range, I have seen that the conical springs are better. The beehive is head and shoulders above "regular" springs, and the conicals are even better. Less resonance=more rpm, less weight=more rpm, and also more control of the valvetrain with significantly less required open pressure. A typical dual spring and retainer usually weighs double what the conical weighs, and almost double what the beehive weighs.
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Hi everyone, I've decided to replace the 924-16 springs with the 26120's as suggested and need some help to ensure I order the correct locators to fit the edelbrock heads. The vehicle is 400 miles from where I'm working so I can't carry out any measurements . I am unsure of the inner ID to fit over the guide. Part # are 4696, 4697 and 4698. Also would the installed height of 1.880 giving 155 seat and 355 open be appropriate pressure wise, this still leaves .110 before coil bind with my lift. If I order the parts online now they will be there when I get off shift. Thanks Rob.
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The 4696 is the best bet with a .570 ID.
Helpful if they have a lathe nearby - sometimes you'll get heads with a larger guide in them
Easier to open the ID hole up than it is to shrink it...