284/484 swap to summit 6901

-
rigger3006

rigger3006

Well-Known Member
Joined
Aug 6, 2013
Messages
866
Reaction score
249
Location
north america
finally got it done this week, initial test drive i felt like i had castrated my best friend(72 demon), car still didnt start pulling until 3500, same as previous cam,slightly better bottom end, brought it home, lo and behold had a slight vac leak under carb, fixed that and swapped out 3.5 power valve to original 6.5 that came with 670 avenger. vacuum has doubled from 7 to 14 at about 700 rpm idle, right now initial is at 16, not sure about total yet, still working things out, second test drive was better, bog almost disappeared from off idle hard take off, now pulls hard from 3000, but unfortunately this thing starts crapping out at 5600, ive lost 1400 rpm on top end, not too impressed with that. cranking compression did not change whatsoever, still at 120, as was expected. combo is 85 318, ported 302s with 1.60 exhaust valves, ld340,670 avenger, 3000 hughes TC, 355 sure grip, 1 5/8 headers, still cant lay rubber off the line!
 
What did you expect would happen going from a cam that is 241ish at .050 to one that is 218 at .050. It's going to lose a bunch of RPM.

Cranking compression should have gone up as the valve is closing a lot earlier with the new cam. Unless the cam is installed very retarded.

It should have a bunch more low end grunt and idle quality and RPM drop in gear should be minimal. It's lost somewhere in there.
 
Nice Vacuum but that is about where it ends. If you made that much of a change in the Camshaft the compression should have went up..... 120 on each Cylinder?

JW
 
it pulls good, but only too 5500, i was hoping she might hit 6000, oh well i was looking for abit more street manners, be careful what u wish for i guess. T.N.T figured the cranking compression wouldnt change, yes on all cylinders, admittedly though not a bad idle, definitely know theres a cam in there, never happy of course no matter whats under the hood
 
crackedback said:
What did you expect would happen going from a cam that is 241ish at .050 to one that is 218 at .050. It's going to lose a bunch of RPM.

Cranking compression should have gone up as the valve is closing a lot earlier with the new cam. Unless the cam is installed very retarded.

It should have a bunch more low end grunt and idle quality and RPM drop in gear should be minimal. It's lost somewhere in there.
Click to expand...

SLOPAR72 said:
Nice Vacuum but that is about where it ends. If you made that much of a change in the Camshaft the compression should have went up..... 120 on each Cylinder?

JW
Click to expand...

He went from 284 intake with a 108 lsa to a 276 intake with a 114 lsa and .441" lift. The end result is the intake valve closes at basically the same time. A fast lift 268 on 110 would have increased compression, had more duration at .050 and more overall lift.
 
T-N-T said:
He went from 284 intake with a 108 lsa to a 276 intake with a 114 lsa and .441" lift. The end result is the intake valve closes at basically the same time. A fast lift 268 on 110 would have increased compression, had more duration at .050 and more overall lift.
Click to expand...

So he did castrate his best friend then. :D
No tears now it's just a cam and a weekend. LOL
 
ok, i love swappin cams and workin on my car, any suggestions or should i just wait to put the 360 in, frickin318 wont lay rubber off the line just want a bit of low end torque!
 
TrailBeast said:
So he did castrate his best friend then. :D
No tears now it's just a cam and a weekend. LOL
Click to expand...

Castration is such a harsh word. This can be reversed.

rigger3006 said:
ok, i love swappin cams and workin on my car, any suggestions or should i just wait to put the 360 in, frickin318 wont lay rubber off the line just want a bit of low end torque!
Click to expand...

I would go with either Comps XE262 or XE268 max or Lunati Voodoo 10200702 or 703 max.

A Comp 20-310-4 cam might not be too bad either. https://www.summitracing.com/parts/cca-20-310-4/overview/ It should keep more of the sound you like since it has a 108 lsa but you will gain a good amount of compression and power. It kinda falls in between the cams listed above.

To get the low end torque you want you need a shorter duration and LSA like the ones listed above.
 
Have you physically checked,you are actually getting ACTUAL FULL THROTTLE? Need a partner,for this.... Someone hits the gas pedal,to the floor,second person actually uses a light,& makes sure the secondary blades ,are wide open .Never seen this mentioned,threw it out there...
 
rigger3006 said:
frickin318 wont lay rubber off the line just want a bit of low end torque!
Click to expand...
I love this quote...... it's the 318's fault she won't lay rubber. Unless it has Drag radial tires and a sure grip.... never mind.
Yes, the 360 will give ya more low end for sure......
 
You have a good head for the 318" engine but exhaust valve size size is not a restriction to flow,its the port that is to small and ported with the 1.5" valve is as goods as its going to flow.
The intake on the other hand with a 1.88" 360 intake valve and then ported to match is worth while. They make good low lift flow. Done by .450" lift but will flow well up to there.

Your low cylinder pressure is killing your bottom end torque,check the specs and make sure you have it installed correctly.
You didn't specify which intake you have but it needs to be a small port intake like a standard performer not a performerer rpm.
I would turn the timing up until it performs best and not rattle. Check with the light then and see if your in a known exceptable range.
How do your plugs look,may need to go step hotter with the low cylinder pressure.
 
If the cam wasnt degreed in you can pull the intake , put the engine at tdc lay a straight edge across both int and exh lifters on no 1 cyl the int lifter should be around .020 higher than exh lifter. If not the cam is definetiy in wrong. Also are you using manifold or ported vacuum ti dist.? I would try manifold vac + the 16 initial to see if any improvment.
 
The 284/484 cam is awesome! In a 318 however lack of cubes & torque(short stroke) kill the 284 cams potential! A 360 is better suited to this cam as are minimum 3.91 gears @ the rear!! Also converter efficiency is also an important key factor.
 
full throttle, cam was not degreed, i know, ld340, heads have been ported at a reputable mopar shop, new 901 springs, will play with timing
 
Dont get me wrong but a 318 can be made to run just as nice as any 340 or 360. If you like the 284 cam maybe degreeing it like to 4 degrees advance from specified cam card will help a good bit. A custom curved distributor will help a bunch also. I got one from FBO ignition. The pro street version it gained me torque & power everywhere!
 
Few things.

Cam not degreed = bad... you have no idea where it's installed and having it retarded is going to KILL the bottom end power. I put the 284/484 cam in low compression SB's at 100 ICL. Advance the crap out of it and it will boost low end and not kill the top end much at all. Too late now.

Hughes 3000 converter. No chance it stalls/flashes 3K behind that engine if it's consistent with other hughes converters I've used.
 
ya it flashes around 1900, maybe i should clarify not being able to lay rubber, if i foot brake it it will fry the tires with ease and leave about 2 80 ft strips, tires brake loose around 1800 with foot brake applied.now have initial at 20, hooked up to manifold vac and changed to a stiffer secondary spring, bog is gone and and she takes off pretty good, could be im expecting too much out of an old 318
 
Crackback is correct a quality converter will also influence quickness. I replaced a cheap dacco 10 or 12 " converter with a FTI 9.5 converter boy take offs are awesome!
 
rigger3006 said:
think im going to order fbo limiter plate, 20 initial, 46 all in, vacuum plugged
Click to expand...

46!? Hopefully you mean 36 all in? Even that is a lot for an SBM...

Also the 670 Avenger carb you have is actually closer to a 750 cfm going by "dry-flow" ratings like most other carbs are rated; that bog might be from primary bores that are too big for that little 318 with 302 heads.
 
Definitely 46, car never bogged with 284/484 in it, i never did check total with that cam cause it ran so strong
 
MOPEkidD-3 said:
Also the 670 Avenger carb you have is actually closer to a 750 cfm going by "dry-flow" ratings like most other carbs are rated; that bog might be from primary bores that are too big for that little 318 with 302 heads.
Click to expand...

You sure about that? According to this spreadsheet, the 80670 670 street avengers have the same venturi diameters and throttle bore diameters as a regular 1850 600 holley (1-1/4, 1-5/16 1-9/16, 1-9/16).

http://documents.holley.com/techlibrary_carb_numerical_listing.pdf
 
You must log in or register to reply here.
-

Back
Top