Story of a swinger 340
- Thread starter Dart Frog
- Start date
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When picking my camshaft I kept my six pack in mind. I have never ran a solid before but wanted to give it a try because if I'm tuning three carburetors I might as well be setting lash too LOL. My camshaft choice was a Mopar circle track cam once again. New Old stock p4529970. This cam comes in at 284 advertised duration, 525 lift and 241 @ 50 . I feel this cam has about 232 of effective duration after lash on a 106 centerline and right around 500 lift after lash.
This cam became surprisingly in need of a lot of valve spring to control float. 90 lb on the seat and two 260 ish on the nose were only good for about 4000 RPMs where severe valve float began. I really couldn't believe it and thought I was possibly having a fuel problem or ignition problems and dinked around with it for too long trying determine the problem.
I even shimmed the springs up and noticed a slight improvement. So I remove the springs one more time.
I even shimmed the springs up and noticed a slight improvement. So I remove the springs one more time.
Thanks Garrett I'm glad someone's reading this post LOL.
I’m sure the light springs were great for breaking the cam in, though. For anyone wishing to look further into the spring specs, here’s the tfs link. They’re one of PAC’s “hot rod” springs.
Trick Flow Specialties TFS-16315-16 Trick Flow® by PAC Racing Dual Valve Springs | Trick Flow Specialties
But that’s definitely a great small block performance cam!
Trick Flow Specialties TFS-16315-16 Trick Flow® by PAC Racing Dual Valve Springs | Trick Flow Specialties
But that’s definitely a great small block performance cam!
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I scope the cylinders and determined they were within spec so I honed them to establish a new cross hatch.magnafluxine and inspecting all the rotating assembly I reinstalled them to the new eagle 4340 340 crankshaft. All specs on the crankshaft were spot on from eagle. The motor was assembled with ARP studs. High volume oil pump, New summit racing timing assembly which fit beautifully without slack.
After a new clutch and surfaced flywheel I reinstalled my new solid lift camshaft 340 back into my swinger. I decided to put my m1 single plane back on for now till I get my tuning in order. It also gives me a chance to try something new in the form of some gas anesthesia or nitrous oxide.
Yeah note the 90° oil adapter is backwards I won't admit how long it took me to figure that out when trying to put the motor back in yikes
Yeah note the 90° oil adapter is backwards I won't admit how long it took me to figure that out when trying to put the motor back in yikes
I initially grabbed a couple of my old TQ carbs but found out that both of them had dried up and were dripping fuel into the manifold after opening them up a couple of times to correct the problem I did not have the proper seals to repair them I just moved on to a new quick fuel 750 VS the price was right and a new carburetor is always nice. And steady and proper fuel distribution with the nitrous I felt was essential.
After installation and the routine loose ends I began the tuning process. And quickly found that I would not be able to get RPMs past about 4,000 and if I pushed it it would backfire hard through the carburetor after searching for vacuum leaks and replacing the fuel pump I was unable to make any progress. I even purchased a new distributor thinking that it was contributing to the problem but to backfire and lack of RPMs continued.
Thinking that my problem was valve float I installed a new set of pack valve springs basically a hydraulic roller upgrade for LS heads which is the same spring that Edelbrock and speedmaster heads use with a spring rate of about 425 I finally cured the problem. The mechanical lift 285 advertised with a 106 centerline makes a beautiful exhaust note. And pulls right off the get-go. And will light up my 275 drag radials fairly easy till they get hot LOL.
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