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Discussion Starter #1
Ok, Last season, 3300 DA my car runs 11.40 to 11.43 at 117-118 mph and the 60's all 1.55 or 1.56 and this is with a cheap $100 pair of 1 5/8 headers that were beat up and had tubes pounded down to clear spark plugs, just very restrictive.

Over the winter I do two things, put external tranny cooler on, and put hooker supercomp 1 3/4 headers on it and in the exact same air the car slows down to 11.51 to 11.54 and mph stays the same, but the 60's all are 1.59 to 1.60??? confusing. Now this is honestly the only change I made to the car. The engine was dyno'd with 1 3/4 headers and made 550 hp and 460 ft lbs, so obviosly it wasn't making that with the 1 5/8 headers. I have not done a leak down but I did run a compression test and all cylinders are exactly the same. The converter has only last season on it so I doubt that is the problem espcecially since on sat. all of my times were within .03 hund. and all 60's with in .01 hund. so the car is very consistent, just slower.

Now I can see if I lost torque somehow thru headers but it should have picked up mph on top end. Now almost everything I see runs 1 3/4 hdrs with my hp and C.I. which is 357. I just figured I would give you all a chance to throw your 2 cents in and maybe it strikes a chord and I figure something out.
 

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If your 60 ft times are worse I'll bet money that the track wasn't as good for various reasons or your tires are old. I tested my car last Thursday evening and it runs 5.96 back to back with 1.32 sixty ft times. I go race it Sat at another track in the same weather and it runs a 6.09 out of the trailer with 1.37 sixty ft time. Humidity, air temp and altitude almost the same as Thursday but the track is 130 degrees under full sun at 2:00 PM so while the car is doing the same thing there is no grip to the track. Sun gets over the hill and bingo the tracks cools off and the problem is gone, cars back to running 1.32 sixty ft times again. If your tires were brand new last year and you let them set out all winter they will not work like they did last year also. Slicks can look brand new and be junk due to time. JMHO, RM
 

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Discussion Starter #3
This is what I am after, just keep giving me opinions and I will keep pondering each one.
 

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There may be something to the tires thing, but I would think tires would also make it inconsistent, not just slower...then again, since I am running your older old slicks, maybe you are trying to set me up so I don't consistently run in the 10's :D Just kiddin ya.
 

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Discussion Starter #5
No I don't believe it is the slicks because of the drop in all 3 phases, not just 60'. I did talk to my dyno guy and he said that I could bring it out and put it on the dyno again and see if it is still making the hp or not and then for sure we would know if we have an internal problem, but he is perplexed since the car is still so consistent, just slower........and so the thought process continues.
 

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maybe the track got a new timing system, that is either more or less accurate than last year....

just thought i'd throw something out there;) ;)
 

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Discussion Starter #7
good thought but no, it is the same timing system. I don't know maybe I am just overthinking things and should leave well enough alone and not complain, the car is working great, just slower.

Keep the thoughts coming if you have em.
 

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Have you thought about the smaller headers making more low end torque and that making the sixty foot times better. If the car is 60 footing better that means its got more mph at the sixty foot clocks and at the 330 and 660 etc. Have you tried leaving at a higher rpm and even changing shift points. My buddy has a 57 four door he runs in footbrake. He took off an old gm aluminum intake and replaced it with a edelbrock rpm. On his first pass he overturned (6000)the motor in first gear and the car ran a 8.16. He goes back and runs it like he had before (shifting at 5500) and it runs a 8.26. I suggested the motor likes to be turned a little more now with this intake. He goes back and shifts at 6000 and it runs a 8.159. Little changes do make a difference. Hope this helps. I know the thought of bigger tubes make better airflow but maybe the motor likes the smaller headers.
 

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It seems to me that you made a change that improved the efficiency of your engine, but you did not re-tune to take advantage of the change. You also may want to search the drivetrain forum, and the best of tech sub-forum in the drivetrain forum for threads on headers. I believe Mike Goble has shared some very good information on header tube size, collector length, and overall header length.

Randy (NPHNP):)
 

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Discussion Starter #11
This is a good point that I have not thought about, but if the smaller headers did make more torque due to back pressure I understand, but it made the power on the dyno with 1 3/4 headers. I should have seen an increase in mph if nothing else since 60' will change et but hp changes affect mph, so what is confusing is that it should have improved in some area, not gone backwards in all three. The shift point could be an issue, I currently shift at 6.9k and trap at 7.1k....something else to ponder, I like it.
 

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Stan D. said:
This is a good point that I have not thought about, but if the smaller headers did make more torque due to back pressure I understand, but it made the power on the dyno with 1 3/4 headers. I should have seen an increase in mph if nothing else since 60' will change et but hp changes affect mph, so what is confusing is that it should have improved in some area, not gone backwards in all three. The shift point could be an issue, I currently shift at 6.9k and trap at 7.1k....something else to ponder, I like it.
Did you dyno the engine with the old headers on it? If not, you don't really know if the numbers with the 1 3/4 tubes were better or worse than with the 1 5/8 tubes.

Randy (more to ponder!);)
 

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Discussion Starter #13
No I didn't but if it would have made more than 550 hp with the smaller headers then by al means it definitly should run quicker than 11.40's. Even if it had held true to the 550 hp and 460 ft lbs with the 1 3/4 headers it doesn't equate to 11.50's. I do know that 118 mph is actually very good mph for 11.50's.
 

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Its the headers, although that much difference does seem excessive. Might be a ''perferct storm'' type deal. It also could be productive to completely tape off the cooler and make some back to back passes. Operational efficency of the trans might be reduced with heavier, cooler fluid.
 

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Discussion Starter #15
It's hard to argue with you fatcat, since it is the only change, but it doesn't make a bit of sense to me at all.
 

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The primary size isn't as important as Collector, seems like ya lost some power with the 1.75s. Try adjusting the collector length to get the power back.
 

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My 2 cents.... 1 If the track just opened as it did here the track may still be "green"...and 2 You may have lost more down low than the increase in top end horsepower can make up for. I would say try leaving harder,you could try a bit more air pressure to try to get a bit more tire slip on the initial movement,try an HVH Super sucker carb spacer to help low end.Or just see what happens in a week or two after the track gets some laps.Have any other friends cars experienced the same drop in perf.? Ok so its 2 1/2 cents sorry
 

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I just recently toasted my first gear and forward clutch in my trans. It seemed to happen over a short period and had me guessing too. It just went 1-2 tenths slower for like 10 passes or so then just let go. Now having a car that runs close to the same as yours I run a th350 with pretty much stock stuff inside, so if yours is close to the same setup and/or gettin old maybe it's doing the same thing? Just a little more food for thought.
 

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Discussion Starter #19
Well I do run a t-350 but it built to the hilt and the converter only has one season and tranny shifts imediately and hard. We are pretty much of the opinion that the porting on the heads and intake were not done properly and so the new headers are not working with this set up. I am going to put a 2" spacer on next race, see what it does and then look to change intakes. We are positive it is not a mechanical issue in the short block just a tuning issue that has changed with the header change. I will do this one change at a time but I will fing the missing hp and kee you posted.
 
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