New Cam Same Power

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archerandethansdad

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I recently purchased a 68 barracuda with a 318 with Indy heads and slightly larger valves. It was also converted to 4bbl carb. My issue is i used have no issues with power braking and breaking the back tires loose. It's not something i do often but just curious to see if it would. I tried again a few weeks ago and it wouldn't spin but once i lifted my foot off the brake it would chirp. I just installed a new cam 285 duration and 480 lift. I broke it in and took it out for a ride it seems to have the same performance. My timing is set around 14-18 degrees. Curious as to what i might be missing. It's HEI not points. Any tips would be appreciated.
 
archerandethansdad said:
I recently purchased a 68 barracuda with a 318 with Indy heads and slightly larger valves. It was also converted to 4bbl carb. My issue is i used have no issues with power braking and breaking the back tires loose. It's not something i do often but just curious to see if it would. I tried again a few weeks ago and it wouldn't spin but once i lifted my foot off the brake it would chirp. I just installed a new cam 285 duration and 480 lift. I broke it in and took it out for a ride it seems to have the same performance. My timing is set around 14-18 degrees. Curious as to what i might be missing. It's HEI not points. Any tips would be appreciated.
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"Around 14-18 degrees". That's a lot of uncertainty and a wide range. I know exactly where my timing is, as should you if you expect performance, which it sounds like you do. Can you give us some more details like static compression ratio? A measured pressure from a compression gauge would be good, too.
 
archerandethansdad said:
I recently purchased a 68 barracuda with a 318 with Indy heads and slightly larger valves. It was also converted to 4bbl carb. My issue is i used have no issues with power braking and breaking the back tires loose. It's not something i do often but just curious to see if it would. I tried again a few weeks ago and it wouldn't spin but once i lifted my foot off the brake it would chirp. I just installed a new cam 285 duration and 480 lift. I broke it in and took it out for a ride it seems to have the same performance. My timing is set around 14-18 degrees. Curious as to what i might be missing. It's HEI not points. Any tips would be appreciated.
Click to expand...
Welcome to the forum! A few more details would be needed to provide any meaningful help. What rear gear ratio do you have? What size rear tires? What are the exact cam specs that came on the card with the cam?
 
archerandethansdad said:
The compression is 100 on the nose every cylinder.
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Well there you go.
With alloy heads, that is about 70 to 80psi short of a good time below 3300. Yur gonna need a very hi-stall TC and lotsa rear gear to get past that.
Or, a better idea is to back up the bus and bring the Scr up to speed.

But that very low pressure is pointing at other factors besides a very low Scr; and since Wiki says MD is at about 350 ft, I'll guess part of it is in the cam timing.

Even if your flat-top 318 pistons are .057 in the hole, the total chamber volume is likely to be about (11.2 +8.8+63) =83cc, and therefore, at stock 3.91 bore, the Scr comes to 8.8 . And if the Ica comes in at 70* for that big cam, the pressure should be around 128 still in the basement very low, but a long ways from 100.
So IDK, it looks like maybe the gauge is reading low. or your test procedure was lacking.
But it don't much matter cuz the Wallace-predicted 128psi is still calling for gears and a TC; 3.23s and a 2000 will not cut it..
 
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Ricks70Duster340 said:
Welcome to the forum! A few more details would be needed to provide any meaningful help. What rear gear ratio do you have? What size rear tires? What are the exact cam specs that came on the card with the cam?
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Cam specs are 285/285 480/480. The Indy heads springs were rated up to .509 lift the intake and exhaust valves are 1.88/1.60 bowl ported and 63cc chambers.
The rear is factory 3.23 sure grip.
 
archerandethansdad said:
I recently purchased a 68 barracuda with a 318 with Indy heads and slightly larger valves. It was also converted to 4bbl carb. My issue is i used have no issues with power braking and breaking the back tires loose. It's not something i do often but just curious to see if it would. I tried again a few weeks ago and it wouldn't spin but once i lifted my foot off the brake it would chirp. I just installed a new cam 285 duration and 480 lift. I broke it in and took it out for a ride it seems to have the same performance. My timing is set around 14-18 degrees. Curious as to what i might be missing. It's HEI not points. Any tips would be appreciated.
Click to expand...

Hey man, welcome to FABO!!

Post up a Pic or 2 of your car when you get a chance.

If you don't have a compression gauge, the parts stores will let you "borrow " one. You basically pay for it and they refund you when you return it.

It's a fairly simple process and the answer will tell a lot.
 
Ricks70Duster340 said:
Welcome to the forum! A few more details would be needed to provide any meaningful help. What rear gear ratio do you have? What size rear tires? What are the exact cam specs that came on the card with the cam?
Click to expand...
Rear is 3.23 suregrip with 225/60/15. The cam specs are 285/285 duration and 480/480 lift.
 
AJ/FormS said:
Well there you go.
With alloy heads, that is about 70 to 80psi short of a good time below 3300. Yur gonna need a very hi-stall TC and lotsa rear gear to get past that.
Or, a better idea is to back up the bus and bring the Scr up to speed.
Click to expand...
 
AJ/FormS said:
Well there you go.
With alloy heads, that is about 70 to 80psi short of a good time below 3300. Yur gonna need a very hi-stall TC and lotsa rear gear to get past that.
Or, a better idea is to back up the bus and bring the Scr up to speed.

But that very low pressure is pointing at other factors besides a very low Scr; and since Wiki says MD is at about 350 ft, I'll guess part of it is in the cam timing.
Click to expand...
 
It has over 200k on it anyway so new pistons were on the list of upgrades just didn't want to do it this summer. Either way. Any good recommendations as far as pistons go?

Also i'll do another compression test with the new cam. Haven't done that yet.
 
a new car showed up at cruz night a couple of years ago with a very nasty idle. An old timer who has a lifetime of racing and a well deserved reputation looked up and said "another Dud"
Maybe that cam is too big for a lo compression 318?
I might suggest a stock 360 2 brl cam for your engine as a street driver?
 
archerandethansdad said:
Cam specs are 285/285 480/480. The Indy heads springs were rated up to .509 lift the intake and exhaust valves are 1.88/1.60 bowl ported and 63cc chambers.
The rear is factory 3.23 sure grip.
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What's the duration @.050 and the LSA?
 
Pretty much like the lunati bracket master 2 i have in my 413 and in my old 9.5.1 360.
 
Yeah its the summit cam. I wasn't looking for a strip car. Just something with a nice sound and decent response. Otherwise i'd have dropped 4-5 hundred on a hughes cam.

I ran the compression test again and 1,3,7 were all 120 (factory manual says 125-155 so not disappointed at 200k miles) 5 was 135. 2,4,8 were about 125 and 6 was 130. So not as low as originally quoted. I'm happy with the sound and it does seem to pull harder then it did before. New pistons and rings are on the list but doesn't seem to be as pressing as originally thought. It doesn't smoke when started and oil pressure stays right around 50 at idle and 75 when driving. I think my expectations were higher then they should have been.
 
archerandethansdad said:
Yeah its the summit cam. I wasn't looking for a strip car. Just something with a nice sound and decent response. Otherwise i'd have dropped 4-5 hundred on a hughes cam.

I ran the compression test again and 1,3,7 were all 120 (factory manual says 125-155 so not disappointed at 200k miles) 5 was 135. 2,4,8 were about 125 and 6 was 130. So not as low as originally quoted. I'm happy with the sound and it does seem to pull harder then it did before. New pistons and rings are on the list but doesn't seem to be as pressing as originally thought. It doesn't smoke when started and oil pressure stays right around 50 at idle and 75 when driving. I think my expectations were higher then they should have been.
Click to expand...

You can probably increase the cylinder pressure and performance by advancing the camshaft timing some.
 
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