Swapped to 528 mech cam slowed down

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joes68340s

joes68340s

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I swapped to a 528 284 Mopar mech cam. I had a Comp 305 525 cam. Car went 107,108 mph with the comp cam. Now with the Mopar cam I am running 102 mph. I set lash at 28/32 like it called for. The valves sound very loose at this setting. I am at a loss for the loss of mph.
 
It seems to me the solid is smaller than the hydraulic,you need to go up 10 degrees as a rule of thumb with a solid just to equal a hydraulic at .050 due to valve lash.Figure the lash in and you lost lift and duartion and I believe the mopar cam has a 112 lobe seperation vs. the comps 110 wich shifts things upstairs slightly so its apples and oranges.
 
That maybe but I find it hard to believe. That I could lose that much mph. I have heard some people run this cam tighter on the lash.
 
I agree, the 528 solid is smaller but we cant say its to small unless we know the rest of the combo?. The 528 should still be able to mph better then that. Have you done any tunning yet ?
 
Yes as far as tuning its good. Engine will rpm in the 1/4mile to 6200 no problem. This engine is a 030 over 340. stock x heads stock 71 TQ setup,3500 stall, 4.56 gears. this setup was a consistant 12.5 car before with the comp cams 305 magnum cam. My 60 foots were only 1.8s But that was with worn 340 springs and stiff shocks. Now I have lost traction. and sixty in the 2.0 and worse. I realize that the rear needs attention for better sixtys. I am probably going to throw
on the ss springs. Didnt want to but dont have a choice.
 
You answered your own question, you lost it all in 60' due to spinning, and your momentum will be down and so will your MPH.
Also I have found the best settings for this cam to be .026 int. and .028 exh.
 
60' times are bad.

I pull a 1.7 on E70-14 bias ply RedLines, Mopar HD stock replacement springs and a 4 speed.

I run a crower solid roller cam with extensive work to the rotating assembly and heads. I shift at 8000.
 
BJR, I though a loss of traction wouldnt show up in MPH only in ET. The loss of MPH shows hes down in power over the old cam.
 
Adam,
I guess that because the fact that he lost .2 tenths in his 60' times means that he's spinning real bad, and every time that I have seen a car spin this bad the mph just wasn't there, as the track becomes shorter and the car cant recover the speed that it would have had, had it not spun. I agree that if the car hadn't spun so badly that in all reality the mph should have gone up and not down. Generally in my cars, if they spin a few hundreths I would see a increase in mph and not a decrease, but because the fact that he's off .2 full tenths due to the loss of traction that the car IMO just doesnt have the momentum going for it to make the speed that he did run. As the length becomes shorter and the way that I see it is when the tires finally do catch up to the race track and the car starts to recover and move the track is shorter and the amount of distance to build speed isnt there.
Just as when a pro stock or fuel car spins the tires and they have to lift the ET is way better than there mph to cover the same distance. They just did this a week or so ago on NHRA Race Day when Mike Dunn was driving Doug Herbert's car and they had a stock car in the other lane, Mike Dunn and the stock vehicle left at the same time on the tree and Mike shut the fuel car off and coasted while the other car stayed under power all the way, both cars ran 88 mph yet the fuel car covered the distance quicker something like 10.50's and the street car went 16 sec., I hope I'm making sense and not confuseing you.
My point being that 88 mph doesn't yeild a 10.50 et as it should be closer to 128 mph.
 
It is more combo related than wheel spin related. Loosing .2 @ 60' wouldn't lower your trap speed by 5 - 6mph, possibly 1 or 2 but not as much as he has lost.

When I loose a tenth or two in 60' I have not really seen any difference in mph. I had an intermitten stumble off the line for awhile and even though I lost 2 or three tenths in ET I ran the same basic mph because my HP was the same. Granted you are lessening the distance to achieve the same speed but not by enough to lower speed 5 - 6 mph, not in this case. She's (the car) is nosing over.

Joe, what was the change in mph at the 1/8th?


Chuck
 
I probably should clear up a mistake here that I have made. My 107-108 mph was done at another track. Sacramento CA. Last night I ran at Infineon. The winds are terrible there and in previous cars I have lost 2 mph average at Infineon vs SAC. I may only be done 3mph now, I have to do something for the suspension for next week. And I do need to adjust the lash tighter. Thanks for the responses It woke me up.
 
The difference in cam specs was just the first thing that stood out to me but 3-7 mph is a bit extreme,hopefully some more fine tuning is the ticket.
 
Yes I am pulling the SS springs and shocks from an old SS340 Dart I have and I will tighten the valve lash on the cam and see what happens on the next trip to the strip.
 
I would not have bothered with that swap. I would have called that a lateral move really. If you arent sticking anymore, the power band went down in the RPM range. Typical for the .528 really. That Comp hydraulic isnt a bad grind either. I would have suggested something bigger.
 
The problem with the comp 305/525 was it was to radical. At the time I was trying to detune the car for more of a daily driver. I had the mopar cam and I new it would Idle better. I have a 410 stroker Im building,but I wanted to get to the track this summer and my Dart wont be ready for quite sometime. Now Im faced with tearing the suspension apart to go to acouple of races. Im trying to find a good compromise, I know that means extra work.
 
Mopar 284/.528 mechanical. I like that cam. My low compression .030, 340 went over 114mph with that cam regularly. I also found .026 and .028 as best lash settings. It made the most power (mph) at .026/.028. The previous cam was the Mopar 292/509 hyd. I HATED that one. I didn't have enough compression for it. Engine made only 4" of vacuum and with auto trans. the low end was terrible but @3800 it would explode..I actually had people asking if I was using nitrious..I wasn't. Changed to the '653' cam (284/.528) and vacuum went up to 10.5" and it was a whole different car. Wonderful on the street and it flew at the strip. 11.60's were normal, and most runs were over 114 mph. I shifted at 6800 and it went thru in high at 7100. I special ordered a set of Harlin Sharp roller rockers with 1.65 ratio that gave me as installed at the valve with lash .538 lift. Joe there's nothing wrong with the cam you are using, it will work you will just have to tune it 'in'. Your 60 ft. is off because now you are blowing your tires off...get the suspension dialed in and it will run the numbers. Good luck, Terry.
 
That was also one of my questions. How much can I rev this cam, Ive only reved to 6200 and it felt like it was still pulling. Im not used to engines that run much higher than 6000 rpm. Thanks Joe
 
Talked to my machinist today and he said lash is considered in cam profile and the looser you can run it the better it will perform. said most cams (mech) have about 0.020 extra to compensate with 1.5 rockers
 
Daredevil, I must strongly disagree with your machinist. You want to use the lash that maked the most power. Tighter lash makes the engine think the cam is bigger and more clearance does the opposite. Why do you think that the newer grinds are 'tight lash' cams....I wonder....
 
Well, the lash is "fogured in", but they dont add lift for it. It's just part of the design phase. The tight lash have a different ramp shape to deal with the less lash. I run my big block .528 solid at .018 int and .022 exh, because I hate the sound the recommended lash gives too. A tight lash cam runs about .004-.006 tighter than that in the cases I've seen. To me, if tightening the lash makes the car faster (assuming the 60'/traction deal wasnt occuring, I'd say you chose the wrong cam. Lash is not a power maker, it's a maintenance thing. Getting the right size cam is where the power is made. My .528s give up lower in the rpm range, but a lot of that is the heads. Truthfully, a small block .528 will lose more thru pushrod angles than a big block anyway. So really, minus lash and loss from angles, you're looking at a .490ish cam. That might rev real well in worked heads, but may not go as high on stock castings in some packages. The Comp 305 is soft on the low end, and limited by lifter type on the high end. The MP will be much stronger down low and mid range, and may not have the pulling power. So it's just a "rethink the package" deal. Honestly, if you can't stick the tires with a torquey cam in it now, you have extra time until the 418 is done to figure out how to stick it.
 
loose lash increases time during bleed off making more power not good for high compression street engine but good for race engine.Street engine needs to bleed to avoid detonation.
 
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