Done all that. I’m just putting the intake back together after fixing a small vacuum leak. I also verified cam timing (intake valve opening) but it was degreed during assembly
Yep
Anybody running the '68 4 speed 340 cam?
- Thread starter 1MeanA
- Start date
-
jimjimjimmy
lobsterman
How do you identify a factory 68 4spd cam is there a number on it ? . I hope this is not a thread hyjack .
Cam retarded?
Swinger340 had his set at Zero as per spec. I suggested at least 10°
Mean,
If other folks are getting higher vacuum than you are in the same engine, then you need to look at what can cause loss of vacuum:
- low CR
- cam installed retarded
- problem with the grinding or wrong cam.
If other folks are getting higher vacuum than you are in the same engine, then you need to look at what can cause loss of vacuum:
- low CR
- cam installed retarded
- problem with the grinding or wrong cam.
He said he had a small manifold vacuum leak. Maybe fixing that will help.
Well the whole point of the thread was to gather a bit of data but unfortunately no other 340 4 speed cam users have responded.
I should get it fired up today although its a little cold to drive it...maybe this afternoon. Its below freezing this morning.
stroker402
1968 dart GTS convertible
hope this video comes thru ....... not sure what cam it has but it sure sounds good and runs strong !
Swinger 340
Well-Known Member
If I can read the numbers correct, it is a 4286630 DC cam, with sealed Power 288 lifters
Its still 10-11 in at idle. I'm not sure its broke
...just wondering what others are getting.middleagecrisis
Well-Known Member
I'll look in my old Chilton repair manual tonight. You can look online, but I couldn't access a free pdf. I seem to remember vacuum at idle specs for specific motors in the tune-up section. It will be for stock specs, but a 1968 340 will be listed, probably differentiate between auto and manual trans.
I've done a bit of work on the engine. I'm getting about 12 1/2" at 20 degrees initial advance at 750 rpm. I sent an email to Ken at Oregon Cam and told him what I was getting and asked him what he thought I should expect with this cam. He said he wasn't surprised with the numbers.
I believe your hg reading is close. I ran a .462" lift 226/226 @ .050 hydraulic with 111 lsa in my 2.02 valve 340 with 2 v relief Sealed Power oem replacement forged pistons. Equipped with Carter Comp 750, the best I could get at Idle, running a mechanical Mallory Unilite Distributor was 13hg. The set up ran far stronger with a spreadbore.
What's the overlap on that cam?
Advertised duration was 310/310 4* at .050 and 88* on the seat timing.
Any progress on this? I know in one post you say you have it timed at 0 (TDC) then another you say 18.
I never said 0 unless its a typo. I have an update at post #65
Gotchya. Lemmie ask you.....have you gotten compression test numbers? Forgive me if I or someone has asked and you've answered.
No. Its a newly rebuilt engine. It was 0.040" over with pretty good looking bores and the engine shop honed the cylinders for new rings. I did test one cylinder cold at 150 psig (2200 ft elevation). The calculated compression is 9.75:1. The engine runs fine so I don't think there is anything wrong with it....just curious about the low vacuum.
I wasn't talking about for diagnostic purposes to see if it's hurt. I'm talking about for diagnostic purposes FOR TUNING. You need to do it. This might be a big key to the whole thing. I'd get the engine warm, hell......do one side if you're lazy. That'll tell us something. If the cylinder pressure is on the lower side, this thing could need 25 degrees or more initial timing. I run my truck with the vacuum advance on manifold vacuum. It has 36 degrees timing at idle. It's a low compression engine with a moderately sized old school Crane Fireball. That's how it runs best. You need to run the compression test. It's perhaps the best tuning tool we have.
That's not low vacuum for that cam/tune up IMO
It may well not be! But without the compression numbers, we have a lot missing.
-
Similar threads
