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Results of new combo
Hey guys, most of you know I put a new combo together this winter, I had a post about the engine dyno results. Well we made our first runs today. Air was pretty good, DA around 900 feet.
We had an 11.53 at 114 and an 11.43 at 114.9. 60' of 1.55 and 1.53. Car seems to leave real hard, but mph isn't amazing. I have links to a video of the car just sitting then a few time slips for the day and a few shots of the car. 3800 lbs with driver, 79 transam. 3.42 gear, 10" continental converter, th 350. Holley 750, performer rpm. 280 cfm 87cc e heads. 10.2 to 1 compression. 240/246 hr cam with 109 lsa. 3" xpipe reducing to 2.5" ultrflo, 2.5 tailpipe and splitter. Launched about 2200, shifted off 5300 light, trapped about 5300/5400. Robbmc pickup, filter and fuel pump. http://www.youtube.com/watch?v=9TyQP...e_gdata_player http://s1208.photobucket.com/albums/...er_media_share http://s1208.photobucket.com/albums/...er_media_share http://s1208.photobucket.com/albums/...er_media_share http://s1208.photobucket.com/albums/...er_media_share http://s1208.photobucket.com/albums/...er_media_share |
Garrity-
Car sounds good. Is the cam a custom HR using comp lobes? What lift and lobe sep? Think it might need more fuel? ( I don't know anything about the Robbmc ) |
Sounds good mike!... Maybe u needed to shift it higher? did u try that? May need more than a 750 too. What was total timing at?
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A couple questions...
Are you running power brakes? Are you using the new D port E heads? Double pumper or Vacum secondary? |
Hey guys, I misquoted the cam. I went to hft 240/246 last year. The hr cam is 242/248.
It is comp cam using lobes 3018/3039, on 109 lsa. Lobe lift is .3660/.3630. I think 600 lift with 1.65 rockers. Yes, I do wonder about fuel supply. No noticeable break up, but maybe a little something there? Darby, we didnt raise the shift points any, which could certainly help. Peak hp was around 5500 on engine dyno. But with stock crank and rods, I don't want to shift too high, even of we give up a little performance. I know we still saw 5600 at times between shifts. On the engine dyno the 750 ran step for step with the 950 they tried. But if I knew a 950 would run same ET with more mph and less 60' I would take it :) we were running 37 for timing, but I may try 34 or 35 next time out, just to see what it does. Yes, I run power brakes. I drive the car to the track and drive/race on m&h drag radials. No, these e heads are over 10 years old I believe. Double pumper carb. Actually after the last run, the car died, upon restart we noticed a whistle. There was a vacuum leak on the carb gasket, and we tightened down the carb a little more and the whistle was gone. Not sure if that impacted the run or not. |
Good going for first time out.with a new combo...Hook up a fuel pressure gauge to make sure your pressure isn't dropping.I like your 60fts what is your suspension setup?Your exhaust looks and sounds familiar!
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The stock fuel lines on that car can in no way shape or form feed the amount of fuel that motor is calling for at full throttle and at high revs, you may very well read good pressure, but the needed volume will not be there!
Your high rpm break up is a clue to that, and the next thing to break up at high revs will be motors bottom end!!! Also your carb is a bit on the small side cfm wise and if you are running just one Holley blue type fuel regulator be informed that they are a flow restriction and can just pass enough volume to feed that 750 with that size motor. If it where me I would step up to a better one. |
Good runs Mike. Great 60' times. MPH is WAY down for the power level. I'd look at fuel delivery. I would have thought at 900DA and those kind of 60' times you'd have went low 11's at 119-121mph. How much head wind? ET and MPH at the 1/8th mile?.....Cliff
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Mike I was just looking at something else too, I think u said u were using 28" tire? You look to be slipping almost 700 rpm on top? That could be a player in your lower mph too
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Very nice Garrity. Also think advice given here is very good. I have run a 750dp and 850dp with very similar combo as yours with no change in ET. I think if you had a combo that would run up to 6500rpm, you would need more carb for sure. As far as the fuel system, no two cars seem to react the same with similar set-up. The 7.39 1/8th mile in my signature was run with stock tank, pick up, fuel line and robbmc 550 pump with vapor return. Think I went close to 94mph on that pass. Although I had dialed in the carb using a wide band, I picked up a lot of et at the track that night by going back to the original jetting supplied with the quick fuel 850 carb. Needed a little more squirter as well, and a bump from 38 total to 41 deg. IIRC, jetting went from 74/82 to original 76/84. THis is pretty close to sea level with 93 octane pump fuel. Very nice combo man.
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Just noticed the 4000+ converter. That is getting you the killer 60ft but likely hurting your MPH. Not sure of the condition or usage on that unit, but for a street car that is regularly driven, I feel you could run just as strong and have much better feel on the street with a tighter 10" unit. Good call Darby
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Hey guys, here is the time slip.
As for fuel supply, two years ago I went to the Robbmc 1/2" pickup, 1/2" braided, and the robbmc fuel pump. I ran his regulator for a little white also, but I blew the diaphram out of it twice, and now have a holley regulator on there again. I actaully have a fuel PSI guauge in the car, so I will check that out next time I run. Too many new things going on. I don't have any high rpm break up, or break up of any kind. The car seemed clean all the way down the track, except for shutting off after the last run, before retightening the carb. There was decent head wind yesterday as well. I will get back out and try some different timing, maybe try 34, or 35 rather than 37. I am going to keep the shift points down, just for peace of mind. I don't have a roll bar anyways. The 10" converter was actually just custom made last year for me. Based on my gearing, tires and weight etc.. although I did have less power then. I will still be driving the car the 300 miles to Norwalk this year at 70 mph :) The suspension is all stock as far as shocks and springs, but I do run the SSM traction bars on the car. Actually my buddy that I got these heads off of, is going to send me his Holley 750 HP to try. I know it is still a 750, but the HP is supposed to be a little better I guess, and he had it tuned pretty well with this heads last year. I will see if that makes any difference. I have to say, my goal for the car was to be able to go 11.3s in great air and so I was pretty happy with the car for the first time out. I certainly think I can hit 11.3s this year. So overall I was pretty happy with it. I will certainly keep you guys up to date if any of my changes make any real difference. Thanks, Mike |
Mike i say its falling off cause of slippage more so then fuel,but yes look at the gauge next time out for sure.Using your 7.19 1/8 th it takes a correction of 1.59 to get to 11.43.. usually u see 1.56 - 1.57 as a better indictator. My car 6.89 1/8th using 1.575, used that in the grandville too it comes to 10.851 It ran a 86 with a zero. I also think those eldey heads like more timing not less. Very nice runs for off the trailer!
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Peak torque was made at what RPM?
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Head wind plays a big role here. I'd make some additional runs where you aren't running into the wind without a lot of changes and see if the MPH improves some?
MPH isn't down that much in the 1/8th mile for the 60' and ET, looks like it's slowing down more on the top end, which could easily be fuel delivery and running into a strong wind on the top side of the track. WAY back when I was trying to run a mechanical pump, and electric pumps feeding mechanicals, etc, my car felt fine for all runs, just didn't MPH that well. Sumping the tank and installing an electric pump behind the tank, and 8an lines/fittings everywhere netted a solid 4mph increase with no other changes. If you want to try a well set-up 850cfm carb, I have one collecting dust above my workbench. I only keep it around here as a dyno "mule", or a "loaner" on occassion.....Cliff |
Hey guys.
The current combo showed peak torque at 4200 and peak hp at 5500 on the engine dyno. I may chassis dyno it as well, just to get a comparison of in car with power steering, stock fan, alternator, mechanical fuel pump, drivetrain etc.. I certainly intend to go out and race it again without changing anything. We actually made 3 runs Sunday. 11.59, 11.53, 11.43, with better 60' and mph on every run. We didnt make a single change during the day. The weather changed, and I guess the vacuum leak got a little worse until we found it after the last run. So it will be interesting to see what we find next time out. I know the edelbrocks always seem to like a lot of timing, but if I find I can run 34 or 35 degrees and not slow down much, I will probably change it. After I get everything all settled with the current parts, I will try Corey's carb next, and then I may take you up on your offer Cliff, thanks for the offer. Maybe I will even try it at Norwalk. As for the converter I will say this. I made that change before Norwalk last year. After a day of running slower than I thought it would, I actually put my old tighter 11" Coan back in the car at Norwalk. I slowed down another tenth then. Came home, raced it once more like that, then put the new 10" continental back in. Next time out picked up the tenth again. So it didn't seem to hurt mph last year. But as I said, I will get some more baseline, then let you guys know the results of any changes I try. And Darby, yes the 1.575 is always pretty close for both my dad and I normally. And that would have my 7.19 to a low 11.3. So I will keep working on that. My dads car went 9.63 this weekend, so he is running well. |
Mike, all of the E-headed engines I've built here ended up making best power in the 37-41 degree range. They were all zero decked with well chosen cams for the compression, etc.
No need to "grind" up the engine with a high shift point, it will pick up a few hundreths shifting up near 5500-5800rpm's, but why stress the assembly any more than needed? It's doing fine for the first outing, and will slow down a bit anyhow as the hot/humid weather moves in for the summer. There is NOTHING way off the mark with your carb, or the converter, or anything else. You can find a little improvement in just about every component if you want to chase it hard enough? Also consider that making a lot of changes may not improve anything at all, if you are at the limits of the fuel delivery system. How many times have we seen that deal played out on here, folks tuning all over the map, then making BIG gains once they start keeping the carb full on hard runs? I'd try to get some good runs in before things heat up, so you can fine tune and get the full potential from the combo. Once the heat moves in, it's going to slow up a tenth or so for every 10 degree increase. No need to drive yourself nucking-futz trying to chase that deal to death, just drive, race and enjoy it. I pushed my combo pretty hard when the engine was first installed to find it's potential, knew it was EASILY good for low 11's, even in the heat, then just backed off of it, detuned slightly, short shift, and have enjoyed in imensely for 3 seasons now........Cliff |
Mike
I still say its the convertor why your down on mph mostly, I have had a car that is as areo as a bus ,lol and into a wind i only lost maybe 1 -1 1/2 mph? Your converter is showing 12% slippage according to wallace racing. That is a ton! 3.42 Gear is not going to be enough for a 4000 stall convertor, If u have a chance to try some smaller tires it would help put some effective ratio in and tighten that thing up. I say your biggest gain is still there, all one has to do is look at the above number's and see it |
The carb is a tad too small, fuel system most likely maxxed out for the combination, tires a little too tall, and not quite enough gear. A tenth improvement at each point puts him in the high 10's without touching the converter. It's a very similiar combo as I'm running, certainly not "optimized" anyplace, but fun to drive and will easily run under the legal roll bar rule at will.
My own combo pushes right up against the converter at 5000-5100rpm's on the top end of the track. I've ran up near 121mph and down around 116mph and it's always pretty much in that rpm' range pushing against not enough gear for what I'm doing. I swapped in 2 prototype converters two seasons ago and IMMEDIATELY picked up in 60' and the engine revved a couple hundred rpm's harder on top end with about .5-1mph loss over the "tight" 10" converter I normally use. Pretty much a "wash" in ET as the quicker 60' was offset by giving up some top end charge. I really needed more gear/shorter tires to make the converters work like they were intended to. I wouldn't touch the converter, some additional fine tuning, possibly a larger carb and electric pump behind a sumped tank and he'd pick up considerably, IMHO......Cliff |
MiKE
Just to clarify here,I did not say it was the convertor being bad i am saying it was the convertor slipping more than it should cause of not enough gear. |
This is very interesting.
This is the first combo I have seen that uses XFi lobes. Terrific power production. |
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My old 455 used a HR cam with XFI lobes. It was spec's with 230/242 XFI lobes, at .361". It made great power on the dyno, 514hp/587tq with unported KRE heads, and ran great at the track, netting a best of 11.52 @ 118mph. The air wasn't really all that good for that run, but I never checked the DA way back then.
I spec'd out Mike's converter, and yes it was based on the old iron headed 455, not the new set-up.....Cliff |
There's a reason we race cars and not dynos...
Throw my X on fuel delivery. One fast way to check would be to toss the 950 on there and see if there is any incremental corrected or repeatable improvement. What kind of alterntator are you using, and is it giving a full charge to the system, including the fuel pump? I've heard of electrics being fine in the pits at high idle, but then as system demands increase, bogging down at mid-track when the volts fall to 6 to 9V at full accel (belt slippage, high demand) and the pump output drops (this can also eff up your ignition box/coil too.) What sort of filter and base are you using? Is there any disruption to the air that could cause underhood buffeting that could mess with the mixture as the car gets down to the top end? Any way to get some data feed from an O2 sensor? Wonder if mebbe it might want a little boost in the secondaries to richen slightly, will need it if you put more timing in the Eddys. As a friend used to say, "they sound perfect just before they explode." Still, even if you bolted the hood shut, you have a hellastrong combination to be proud of! |
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My ignorance I thought most of the cams mentioned were XE or magnum lobes. |
Hey guys, no need for any heavy debate.
We built the combo with one goal in mind, to be able to race it in an 11.6 index class in the summer air, and I think we will get that. Although ironically the series we built this for folded this spring. Many people told me ( including Pontiac vendors) that with my 3.42 gear, 3800 lbs, shifting at 5300, and 750 carb that I wouldnt get there with these heads and cam. I am really glad to have 11.43 already and figure with more tuning I will get 11.3s and 11.6 in the heat. I was shocked by the 1.53 60' and a little curious about the mph. But with no intention of a roll bar I am not Going to try to get the car into the 10s or anything. For the record my fuel pump is mechanical with no electric. I know the eheads love timing and my dads combo showed max power at 38, but found he runs the same ET with 35, so he leaves it there. I may do the same if I get the same result. I am sure curiosity will eventually get the best of me and I will try some more parts, but no hurry. I will max out this tune first. And as always I will share the results. One last thought. After our last pass we tightened down the carb to fix a vacuum leak that was whistling, but we never ran again. Maybe that will have a little impact too? Although our last pass was also our best one, so who knows. |
Hey guys, went and made 4 passes yesterday. Temp was mid 60s, 90% humidity, but very little wind.
It was time trials, so I tried experiments. Run 1 was just as we ran it last week. 5300 shift light( results in about 5500 or 5600 shift). Left the air filter off. And the carb was retightened after the vacuum leak last week. ( carb spray at the bottom of the carb, still seems to show impact on idle), would that impact performance? Not sure. Run 1 1.57 60', 11.66 at 113.6 Run 2 with air filter on 1.57, 11.64 at 114 Run 3 air filter on, in drive 1.59, 11.62, 113.9 (shifted I think around 4500 and then 5000) Run 4 air filter on, in drive, timing retard of 3 degrees on. (spun the tires). 1.74, 11.88, 113.4 So wanted to give an update. Mike |
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Both days have been at route 66 in joliet il.
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We were out with the car yesterday. I have my buddies Holley 750 hp carb on there now.
With temp in the upper 80s, car went 11.64 at 114 with 1.57 60'. So 60' and ET slowed up but mph didn't drop off. I have an electric pump mounted and wired in, but didn't plumb in the fuel lines yet. The bad thing is 3 of the last 4 runs, we had tire spin. This is the third season on the m&h drag radials, so I will get a new set. So June 2nd at Pontiac door spammer nationals I should have new tires and the fuel pump wired in and we will see what she does. Mike |
Mike, sure you don't want to step up to my 4781-2 850 DP carb?
I need an excuse to clean it up and put a kit in it anyhow.....Cliff |
Cliff, if you don't mind lending it out, I would be happy to try it.
I could even go to a test and tune and try 2 hits each on the 850 vs 750 hp vs my old 750. I have heard that the 850s use a bigger body. Could be worth trying. |
I'll get it cleaned taken apart, cleaned up and sent your way. May take a week or so, as I'm alone in the shop this week, Marie is on vacation, and Deb is busy at the bar......Cliff
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Ok, sounds cool. I should be able to have it all dialed in for Norwalk :)
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I'll use non stick gaskets, feel free to jet it wherever you need to. It's got .093/.097" jets in it right now, that is the actual orifice diameter. Flawless on the dyno on several engines I've ran it on, and worked perfectly on my old 455 at the track.....Cliff
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We need to make some passes together at Norwalk. Call it the super heavy shootout! |
Cliff, Ok cool, that sounds good.
Wow, does the 850 really run jet size that different than the 750? Mine came to me from Corey with 80/80 Holley, which is about 87/87 orifice. I switched it to 78/88 with power valve. But the 850 might be up to 93/97 huh? Is that with our without power valve? And quickta, yes, that would be cool to run in Norwalk. My brother always tries to get me to take the trailor hitch off of the back that came on the car when I bought it. But I leave it on there because I think it is funny and holds my gas cap when I get gas :) |
PV in the front only. Last time we had it on the dyno the fuel curve was right on the money. They told me to leave it alone!.....Cliff
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http://promaxcarbs.bizland.com/HolleyJetSize.pdf |
THanks for the info guys.
I do see the 850 came with jet sizes almost 10 larger than the 750 stock. 70/80 with power valve in front only. 4779-2 80/80 with power valve in both. 4781-2 ( 10 larger in front, added PV in rear). I actually use maxjet jets, which are supposedly more Precise. They size their numbering goes along with orifice or Holley flow equivalent or something like that. According to maxjet it 93/97 would be about 83/87 in Holley size. But who knows if it works, it works. I will try it. |
Ok guys, got back out to the track tonight. Last time out I had mounted and wired the holley black fuel pump, but did't have it plumbed in. Last night, I plumbed it in, inline with the Robbmc 1000HP mechanical. Also put the new drag radials on. Same size as before.
Last time out it was in the 80s and the car went 11.64 at 114.0 Today was 70s, first two passes, the car went 112.8. But we ran an 11.64 at 112.8, which is kind of impressive in a twisted way. We then found the fitting at the inlet to the mechanical pump was leaking. And with electric force feeding it, it was leaking. So we replaced the fitting. Next run was 11.52 at 114.2 (so basically back where we started). Now for the first three runs we had the air filter off and were shifting around 5400 to 5500. For the last run we put our 10x3 air filter back on and left the car in drive, where it shifts about 4900. The car ran 11.56 at 114.1 So the pump didn't make any difference it doesn't appear. the car will run the same et shifting under 5K with a tiny air filter as it does with no filter and higher shift point. The car went back to back 1.54 60's on the last two runs. Next trick will be to try Cliffs 850 DP and see what that does for the car. Here are some pics of the times lips and air filter. http://s1208.photobucket.com/albums/...er_media_share My brother was driving tonight, so I didn't get to watch the fuel psi. I don't know if it still drops. If it does, we could try bypassing the mechanical. I could also run the lines a little better, they have some un needed curves right now. Overall, pretty happy with the car. Love what it idoes in drive with the airfilter. Just a little surprised it doesn't pick up without it. Will keep working on it. Mike |
Nice passes. Keep at it.
Jim |
The mechanical pump is just a stumbling block for the Holley black pump, I'd bypass it.
The big Holley is on it's way. Ray took it completely apart and replaced all the gaskets, two new needle/seat assemblies and cleaned it out. We both spent about an hour scraping all the stuck gaskets (they were the blue no-stick variety) from all the parts. The float adjustment gaskets were stuck in place as well, and of course the gaskets on the bowl screws had to be removed with a pocket knife. Reminded of the good old days when I had my 1970 Roadrunner. I wore the bowl screws out on several big Holley carbs racing that car! We hooked it up to my electric pump and set the floats, pumps worked fine, but didn't run it on my engine. Have fun with it!.......Cliff |
Agreed...bypass mechanical.
Nice runs. |
Do you have any way to check voltage to the electric pump when you are on the way down the track?
I have a savant recollection of a guy who had the whole system totally sorted, but the car would just not deliver. Turns out the alternator belt was slipping and not delivering full voltage to the pump, resulting in inadequate fuel volume. Dunno if this applies or not but you might check it if you can. Awesome that you ran within a tick after 25 years! |
Heavy race weight, not enough rear gear, and converter has too high a stall speed.
That's the issue. It 60 foots great, but there is way too much slip to get the mph up. Some 3.73 gears will really wake the car up. |
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Yes, I am sure I will hold the car back from ever reaching full potential. I upped the gear fr 3.23 to 3.42 but that is the most I will go, as I drive the car 5 hours on the interstate to Norwalk each year. As for the weight, probably won't get much better there either as I want to stay stock appearing for the most part. For the same reason, I won't run a sump for the tank. But I will try the electric pump, and I can even try bypassing the mechanical. I will also try a bigger carb and see what that does.
Will keep posting results for you guys :) |
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