Not to someone who knows his early1980's 383 67 Fastback would walk all over your 340 N/A and on spray. lol
Street car mid 11's at 115
We won't talk about the 451 it has now.
1 5/8 headers
- Thread starter moparstud440
- Start date
-
Street car mid 11's at 115
We won't talk about the 451 it has now.
Dan the man
Well-Known Member
Mo
I don't believe so. Power improved, et times went down.
Dan the man
Well-Known Member
How big of tube headers? You talking about a small block or a big block
Dan the man
Well-Known Member
I didn't think that they made 1 1/8" headers, that's awful small
B3422w5
Well-Known Member
from what I have read, stock 68 383 roadrunners ran anywhere from 15 flat to 15.30’s
i had a 69 Dart GTS 340 in 1972. Came with 3.55 gear.
I added cheapie headers. My first drag strip pass in my life was in that car
went 14.23@99 mph
quite a bit faster than the BBody 383 cars, even allowing I had headers and glass packs
Rat Bastid
Dunamis Metron
How do you know? Post up the before and after MPH and that will give a clue as to what happened.
Rat Bastid
Dunamis Metron
I‘m talking about small blocks. I have 1.625, 1.750 and 1.875 to test. On pretty much a stock 360 and then on my 340.
I say the 1.875 header will make the most power on both engines and it won’t kill any bottom end.
I have tested this before so I already know the outcome.
The time slip can lie to you just like a dyno or a flow bench.
justinp61
Well-Known Member
- Joined
- May 15, 2009
- Messages
- 3,146
- Reaction score
- 4,148
Over the years I’ve seen several 340 A bodies soundly thrash 383 B bodies. It seemed they always got them off the line and the big block couldn’t run them down.
Dan the man
Well-Known Member
Question, if the dyno can lie then how you going to know for sure what headers make the most power? Isn't true that a to big of a header tube hurt cylinder scavenging?
Dan the man
Well-Known Member
Ill
I'll check to see if he still has them. I know that he had them for a while
Dan the man
Well-Known Member
Well, for one thing I'm sure that the B body out weight the A body. And what gear ratio did the B body have? I know that the 340's were strong runner but I think that everyone thinks that they were unbeatable and that's not true
If it picks up 25hp, it should run in the 10.50-10.55 range.
Stock 340 A cars with the same gear as a 383 B body would eat that B body. 440 and Hemi cars, not so much.
Rat Bastid
Dunamis Metron
Because you dont just look at the power numbers and you don’t let the dyno lie to you.
And no, too big a header won’t necessarily over scavenge the chamber. Look at valve overlap because that has far more affect on combustion chamber scavenging than a header does, BUT you can kill header function with incorrect cam timing.
Just for sake of discussion, do you have 1-5/8 headers and are simply wondering? Or contemplating those or bigger and trying to determine how much you might give up if going with 1-5/8? I know some might spec their cams with a touch more exhaust duration at the least to try and possibly minimize the difference if they have to use a smaller diameter than what might be optimum. That’s in the build stage of course, sometimes you gotta work with what you have, or can fit, afford or find.
B3422w5
Well-Known Member
my goal has been to get a 10.4x slip.
that would approach respectability with the cam and weight of the car, IMO.
hoping the vert adjustment does something to help too.
B3422w5
Well-Known Member
Per request( what a pain to get these out of the box)they packaged these things like sardines with mustard sauce in a tin
Last edited:
B3422w5
Well-Known Member
One more
lol The first engine I put in my 67 fastback was a 68 383 magnum with hp manifolds, with matching convertor and torqueflite. that combo and a 4.57 sure grip was unbeatable by any stock a-body 340. lol
a couple years later the 383 got 12.1 comp , ported 906, 557 purple, street dominator / Carter AVS and hooker fenderwell 2" primary. lol I forget what convertor we put in, but that combo was beast. lol
Dan the man
Well-Known Member
What would be a good valve overlap for the most scavenging? I'm looking forward to seeing your results, sounds interesting.
Curious, are those the flange port openings you get (for LA heads) period? All they offer. I’m wondering if they offer openings sized for a head like Trick Flow ports, assuming there would be any benefit.
B3422w5
Well-Known Member
yes, they only make them this way. Looking at them, they appear generous, size wise.
my Bloomer heads were fine even with the smaller ( it would appear to me) Doug’s headers openings
I can’t imagine these wouldn’t work.
I know the Bloomers have a bigger intake port than Trickflows, but I didn’t/ haven’t measured my exhaust ports
I ment 1 5/8 typo
Same flanges as the Dougs and others. I’m just curious since TF (for example) made the exhaust ports a particular size and shape whether having the flanges of any headers shaped similar, without the shape of the typical LA exhaust ports. A topic for another thread, don’t want to sidetrack here.
B3422w5
Well-Known Member
not sidetracking at all my friend. My thought is plenty of guys are running trick flows with existing headers that have been around forever with these flanges. Can’t say as I have heard of anyone with any issues??
Some headers have the tubes through the flanges and a weld on the head surface . Some are welded to the out side of the flange and have a smooth head surface. I have used both with no complaints.
-
