| Author |
Message |
Paul Newman (Newman)
Member
Username: Newman
Post Number: 328
Registered: 12-2001
| | Posted on Tuesday, August 13, 2002 - 10:16 pm: | |
Wont work with the distributor drives and the big hole left over where the air pump used to be driven from. |
Timothy J. Dressel (Tjd)
Junior Member
Username: Tjd
Post Number: 53
Registered: 4-2001
| | Posted on Tuesday, August 13, 2002 - 6:26 pm: | |
I've heard of replacing the exhaust cams with the intakes and just buying performance intake cams as an economical technique. Anyone have confirming experience? --tim d |
Steve Magnusson (91tr)
Member
Username: 91tr
Post Number: 916
Registered: 1-2001
| | Posted on Tuesday, August 13, 2002 - 9:21 am: | |
I think the most trustworthy F cam data is in the OM for any particular year/vesion/model (but they don't include lift) since the cams may have been changed since the WSM was published and/or they vary with version. I thought the 308 2-valve US cams had 2 catagories:
'73-'77 thermal reactor exhaust with air injection (slightly detuned relative to the standard version)
'78-'82 cats with air injection (significantly detuned)
The 150/78 308GTB/S OM shows:
intake opens 16 deg BTDC
intake closes 48 deg ABDC
(intake duration = 244 deg)
exhaust opens 50 deg BBDC
exhaust closes 14 deg ATDC
(exhaust duration = 244 deg)
Anyone have the data shown in other year US 308 OMs for comparison?
The 110/75 308GT4 WSM (showing the thermal reactor muffler) has:
intake opens 34 deg BTDC
intake closes 46 deg ABDC
(intake duration = 260 deg)
intake lift = 8.949 mm
exhaust opens 36 deg BBDC
exhaust closes 38 deg ATDC
(exhaust duration = 254 deg)
exhaust lift = 8.323 mm
|
Paul Newman (Newman)
Member
Username: Newman
Post Number: 323
Registered: 12-2001
| | Posted on Monday, August 12, 2002 - 11:58 pm: | |
I guess anything pre-cat would be good including GT4's. |
Paul Newman (Newman)
Member
Username: Newman
Post Number: 322
Registered: 12-2001
| | Posted on Monday, August 12, 2002 - 11:56 pm: | |
76-78 early, 79-81 sucks |
Philip Airey (Pma1010)
New member
Username: Pma1010
Post Number: 8
Registered: 7-2002
| | Posted on Monday, August 12, 2002 - 10:35 pm: | |
Kermit
Thanks for the info on the cam specs. What defines "early" on the US cars? (Mine was built June 1977).
Philip |
Matthew J. Morgan (Kermit)
New member
Username: Kermit
Post Number: 30
Registered: 8-2001
| | Posted on Monday, August 12, 2002 - 9:23 am: | |
The info that I could find showed that the Exhaust was moved around a bit. The Euro exhaust closes @10 after TDC, while the US closes @ 14, so there is a bit more overlap . The Exhaust opens @54 BBDCon the Euro, with the US waiting until 40degrees BBDC. IMO with free breathing exhaust, this should give slightly more power, due to the ram effect encouraging scavenging. Opening @ 54 degrees unloads a bit of combustion pressure to start the gas to move out of the Cylinder. Interesting that they balanced this out by cutting down the overlap, so that they run smoother at low RPM. As to cost, I couldn't answer that, as I do not get into that end. |
Paul Newman (Newman)
Member
Username: Newman
Post Number: 316
Registered: 12-2001
| | Posted on Sunday, August 11, 2002 - 12:35 pm: | |
Kermit, what are the LCA's of the euro vs the US. Duration only being 10 degrees longer is no big deal. I would be more interested in the open/close timing. Now that you mention it, the early US one was .050" higher in lift than mine. Not .030".I was using a vernier at the time so I ball parked it at .050". What is a typical going price for a set of early US cams? |
Matthew J. Morgan (Kermit)
New member
Username: Kermit
Post Number: 29
Registered: 8-2001
| | Posted on Sunday, August 11, 2002 - 11:03 am: | |
The early US and Euro cams had 9mm lift (.354") This would increase flow, and produce more power. My Flow Bench studies have shown that the 2V flow well up to .430 lift ( it hits the seal there). Tests on 4V show that they run out of flow and flatline slightly above .350. These stats are from stock heads.
And Robert, you are probably very right about the flame. The P6 opens the exhaust at 64 degrees. This is too early for the street. What is occurring is they open the valve early, while there is still a lot of combustion pressure. This forcefully starts the exhaust flow. The down side.....they give up pressure that would have pushed on the piston On a side note: my info has it that the P6 lift is 9.5mm.
As to specs: both Euro and US were 244 degrees duration on the intake. The exhaust is the differance with the Euro @ 244 and the US @ 234. |
Paul Newman (Newman)
Member
Username: Newman
Post Number: 312
Registered: 12-2001
| | Posted on Saturday, August 10, 2002 - 8:19 pm: | |
Philip, the duration, lift and valve open/close times are all different from the US version. I dont have the specs here in front of me and would require some digging but I remember they were different, for the better. I want to regrind mine but dont want to throw away driveability. A cam like a P-6 would cost twice what a custom regrind would. |
Paul Newman (Newman)
Member
Username: Newman
Post Number: 311
Registered: 12-2001
| | Posted on Saturday, August 10, 2002 - 8:16 pm: | |
The stock cams in my 79 308 have .300" lift. An early say 76-77 US cam I measured had .330" lift. Not much but better. The Euro's are better, I havent had the chance to measure one but the valve timing is also different because of the lack of emission requirements in europe. Due to cost though, a US cam reground to your specs will outperform the euros and cost alot less as well as fit the US engine. The euros seem to be faster and I cant see the drysump adding any seat of the pants power and everything internally is the same as the US engine except cams. |
Philip Airey (Pma1010)
New member
Username: Pma1010
Post Number: 7
Registered: 7-2002
| | Posted on Saturday, August 10, 2002 - 7:52 pm: | |
Paul (probably off topic)
What were Euro versus US lift and duration specs?
Philip |
Matthew J. Morgan (Kermit)
New member
Username: Kermit
Post Number: 28
Registered: 8-2001
| | Posted on Saturday, August 10, 2002 - 7:42 pm: | |
I would definately not recommened the P6 for the street. It was designed to be a track cam.
Low RPM performance will suck, and so will driveability. Sure, it will help make gobs of power at high RPM, but realistically, how often does the motor see that kind of speed?
Bear in mind that ALL of the motor Must work in harmony. The P6 is designed to work with radical intake, open exhaust, radically ported heads etc. Remove any one of these factors and it will not work well
The P6 cam events are: Intake open@ 48, and closes @ 62. The late Intake closing late works well at high RPM where the "ram" effect is stuffing more into the chamber. However at low RPM it will invariably cause reversion in the intake. What occurs is without the intake charge ramming into the cylender, the rise of the piston stuffs the mixture back into the intake. Bear in mind that it was mixed with feul the first time, as it is sucked back in on the next stroke, more fuel is added. Mixture content, as well as power go down radically. |
Robert Moore (Nail_it)
New member
Username: Nail_it
Post Number: 5
Registered: 6-2002
| | Posted on Saturday, August 10, 2002 - 1:06 pm: | |
The only way to find "REAL" power from a 308 is to install a set of P-6 cam.There were some cars sent out in the world in the 70's with whese cam installed. They are easy to find, if you walk by one idleing and it set's your pants legs on fire,you found it. |
Paul Newman (Newman)
Member
Username: Newman
Post Number: 308
Registered: 12-2001
| | Posted on Friday, August 09, 2002 - 9:23 pm: | |
Changing the timing to euro spec is ok but the lift of the euro cams even the early carb US cams are different and dont have the same potential. The euro cams are ok, and the US ones suck to put it bluntly. Regrinds of course would be best but now we are off topic. Sorry. |
Philip Airey (Pma1010)
New member
Username: Pma1010
Post Number: 5
Registered: 7-2002
| | Posted on Friday, August 09, 2002 - 2:31 pm: | |
One point to add. In Bishop's tuning manual on the 308, he identifies that one difference between the early US 308s and their Euro counterparts was the timing on the intake cam (4 degrees different). He reset his US spec'd car to Euro specs using the pulley markings and holes. |
Richelson (Richelson)
Member
Username: Richelson
Post Number: 803
Registered: 12-2001
| | Posted on Friday, August 09, 2002 - 1:01 pm: | |
Thanks for the info. Mine are fairly close but not spot on. Maybe I should leave them alone. It may not be off too much since they are not very accurate. I have a 3 hole system too. |
Mitchell Minh Le (Yelcab1)
Member
Username: Yelcab1
Post Number: 256
Registered: 11-2001
| | Posted on Friday, August 09, 2002 - 12:56 pm: | |
I just did this with my engine out for a rebuild. I did have to mess with 2 of the pulleys on the one bank to get the registration to line up well. Now everything is lined up except one cam shaft is just half a hair out. I will call that good enough because I have a 3 hole cam and 3 hole pulley and the adjustment is not that fine. |
Verell Boaen (Verell)
Junior Member
Username: Verell
Post Number: 244
Registered: 5-2001
| | Posted on Thursday, August 08, 2002 - 2:25 pm: | |
IF CAM ALIGNMENT AIN'T BROKE,DON'T MESS WITH IT.
Normally if you're just changing belts, & the cams were properly timed, you'll find that original pulley-cam alignment will still be good with the new belts.
Otherwise, you're in for 2-4 hours of iteratively trying holes, rotating the engine 2-4 turns to check out each new hole combination, until you do have the alignment you want.
|
Paul Newman (Newman)
Member
Username: Newman
Post Number: 306
Registered: 12-2001
| | Posted on Thursday, August 08, 2002 - 1:14 pm: | |
You only mess with those holes to dial in your cam timing if you are playing with cam phasing like advancing or retarding the cams to the crank. You want to make sure the marks on the cam caps line up with the marks on the shafts at TDCC when the belts are installed. If one or more cams didnt line up with the marks, then mess with the pulleys to get them lined up. Mine were ok so I didnt have the pulleys off the cams at any time. If you want to use a degree wheel and dial indicator, you can verify the cam timing or opening and closing times of the valves against the specs in relation to crank position and play around for more power. Its time consuming but you can extract more power by doing this. That is one of the advantages of having multi-keyed cam gears. Its a big thing in the aftermarket for the ricers and our cars come from the factory that way. |
Richelson (Richelson)
Member
Username: Richelson
Post Number: 801
Registered: 12-2001
| | Posted on Thursday, August 08, 2002 - 6:35 am: | |
Paul had brought up a good point in another post. I was wondering about cam timing on a 308. My car has 5 hole pulleys and I believe 3 hole cam shafts. I was under the impression to set the cam timing was to line up the appropriate cam pulley holes with the holes on the end of the cam shaft. Is this correct? Are there other items that need to be address? |