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why are high rpm motors such pigs on the street??? i have a buddy with a 7000+rpm sbc which is daily driver. Big cam, idles at like 1100rpm. not the nicest but it works
Simply explained..... b/c they are not combined correctly. You could have a perfectly potent street cruiser, providing great fuel economy by comparison with OEM stock setups, and still enjoy (or have others complain about) the best average performance when required. The following is a quote from one experience following tech concepts, that even the OEM's have been using for some years now. The engine setup was not a stroked 302 block, it was a .030" over block with stock rotating assembly (306 CID) and carburetor in a 1983 convertible:
Quote:
Next I had to decide on a what I wanted for the top end. The route I chose is the same as many others have done. I did not want a lopey race car nor did I want to spend the money for aftermarket heads I sourced a set of GT-40 heads, a TFS1 cam, Stealth intake and rebuilt the factory carb. This provided a major seat of the pants improvement but the car was not fast by any means.
I played with the car for a while doing some small modifications and working on the body. The car was lowered slightly and received many suspension modifications to make it better suited for the Auto Cross. This worked well for all the street driving I was doing but eventually I got tired of the lack of real performance.
Through exhaustive research I came to realize that there was more to making power than the traditional bigger cam is better technique. This was a throw back to the days when hotrodders were modifying factory heads because there was not much else available. I saw that the OEM's were using big heads in the GM LSx and Ford Mod motors and these were ending up in everyday cars. I knew if Ford could use a 175cc head on a 4.6L motor that a typical 165cc head was too small for a 306. I looked for a cylinder head that was larger than normal and a cam that would compliment the heads. In the end I settled on a Canfield 195 and a custom cam from Camshaft Innovations. The cam had a tiny 214/228 @.050 duration with .600 lift (1.6 rockers). The lobe was very aggressive so a billet steel cam core was necessary. (5.0 HO engines are said to have a steel cam. The reality is they are a SADI core.) Valve train stability is always a concern so a double spring with 175#s on the seat and 460# on the nose was chosen along with Comp Cams 851-16 hydraulic roller lifters and roller rockers. I finished off the induction with a Vic Jr intake and a Holley 750HP carb.
I was told by many that this combination would be a dog on the street. It would have no low-end and would not rev past 5500 with that little cam. This turned out to be partly true but not for obvious reasons. The motor idled well and reved freely but made far less power than it should. I found that the shortblock had a problem as a leak down test showed 25% leakage that improved when oil was squirted into the cylinder. This was a tell tale sign that rings were not sealing. The motor cam out and was torn down and I found chrome rings had been installed, they never sealed. A quick bottle brush hone and a set of moly rings and the motor was back in the car.
Once the car was back on the road I was able to get a pretty decent street tune. The throttle response was instant and the car idled with 17" of vacuum. In normal driving the car was tame but when I opened it up the RPM's would rocket to 7000 and it felt like I hit it with a 200 shot.
Knowing that chassis dyno's are not always reliable in thier horsepower ratings I had little interest in having it dyno'd. The proof is in the time slip but there was one problem. No cage. In a convertible anything faster than 13.99 requires a cage and, at the time, I still had not installed one. On a road trip to see friends some 200 miles away I was talked into taking the car to the track using a buddies drag radials and skinnies. After some playing around I was prodded into making an all out pass. I was rewarded with an 11.40 at 117 but told I could not run the car any more.
__________________ ACRONYMS:
LUK=Let Us Know, GL=Good Luck, LMK=Let Me Know, JIC=Just In Case, BTSTDTRT=Been There Seen That Done That Repaired That, YCYDYP=Your Car Your Dough Your Prerogative and the classic... DILLIGAS=Do I Look Like I Give A S***
1986 GT-X303-289 heads-1.72 rockers-RG 4+1 Trans.
Quote:
Originally Posted by Joel5.0
Great thoughts will overwhelm a feeble mind.
There is never money to do it right, but there's always money to do it over.
The proof of understanding is the ability to explain it. (H. Torruella)
so then head wise from what ive learnt, AFR's are always a safe choice and Trick flows are also working good for people?? if that article posted above on the 306 with the 195's then im assuming a 205 or 210 cc would be good for the stroker?
for a cam either a custom or im thinking the comp Xe274.
80 or 90mm maf with a 75mm tb bolted to a ported gt40 intake?
im also thinking of going with the 331 so i dont have to notch the pistons as i would on the 347, any thoughts?
thanks guys, im doin lots of research and doing this build once right the first time
__________________
1989 Mustang coupe, 5.0 5spd swap, Centerforce DF, 3.73's, BBk's, Flowmaster cat-back. BLACK
1988 Mustang GT 5.0 5spd.-- 1962 Ford Falcon 302 5 spd
__________________ ACRONYMS:
LUK=Let Us Know, GL=Good Luck, LMK=Let Me Know, JIC=Just In Case, BTSTDTRT=Been There Seen That Done That Repaired That, YCYDYP=Your Car Your Dough Your Prerogative and the classic... DILLIGAS=Do I Look Like I Give A S***
1986 GT-X303-289 heads-1.72 rockers-RG 4+1 Trans.
Quote:
Originally Posted by Joel5.0
Great thoughts will overwhelm a feeble mind.
There is never money to do it right, but there's always money to do it over.
The proof of understanding is the ability to explain it. (H. Torruella)
__________________ ACRONYMS:
LUK=Let Us Know, GL=Good Luck, LMK=Let Me Know, JIC=Just In Case, BTSTDTRT=Been There Seen That Done That Repaired That, YCYDYP=Your Car Your Dough Your Prerogative and the classic... DILLIGAS=Do I Look Like I Give A S***
1986 GT-X303-289 heads-1.72 rockers-RG 4+1 Trans.
Quote:
Originally Posted by Joel5.0
Great thoughts will overwhelm a feeble mind.
There is never money to do it right, but there's always money to do it over.
The proof of understanding is the ability to explain it. (H. Torruella)
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ported e7's and an e303 cam 
