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  #1  
Old 12-19-2004, 02:33 PM
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Default 308's. Now what?

I recently got a set of 308 heads, plan is to clean them up and install on my 360. I'll have them cleaned up and a valve job cut, hopefully I can take the old springs off of my J heads and have those installed. Anything in particular to look out for? Valve size if the original intakes are iffy? I'm not looking to sink 500 bucks in these, just want a solid cyl head on my motor.

The J heads were cut for 2.08 intakes and after 10 years of use one runner finally sprang a leak where the back-cut to install them ran too close to the water jacket. Little pinhole that leaked coolant into the #1 cylinder, now I've got a pair of J-code paperweights.

These 308's do have narrow ports, I'm choosing to believe what is said here about them being good heads despite appearances. Wish I had a way to compare them to the J's, but the leak hit before i got to the track. Earlier this year I installed a .484/114CL MP shaft that my motor ate, MP was nice enough to replace that with a new one, my motor at it too, so finally I got a Comp Cams Purple Plus 280/.474 cam and that was running well until the leak. I installed new crank and rod bearings after the first cam lunch; it'd been 10 years and I didn't know if any cam material had made it to the bearings.

The rest of the combo: 9.4:1 Badger hypereutectic pistons, M-1 single plane and Thermoquad, 727 and TCI converter that foot brakes in my car to 3000 (Streetfighter, I think), TTI headers, 2.5" exhaust with Dynomax welded mufflers that are really just straight through flow oval shaped with glass packing and VERY loud, the car weighs 3500lbs on the local scale. It'd gone 8.803 and 78.55mph in the 1/8th with the old MP .450/.455 and a Weiand Action Plus dual plane, cams didn't last long enough (15-20 miles) to get the car back to the track for a test of the bigger cam/M1 intake.
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Old 12-19-2004, 05:43 PM
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don't hear about the 308's much & I haven't seen a set yet to comment, getting some in January however, will flow test them stock & ported, until then I'm in the dark
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  #3  
Old 12-19-2004, 06:00 PM
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rumblefish360 rumblefish360 is offline
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Narrower ports? Now I keep confusimg the heads. Are these 318 or 360 heads?
Reguardless, if air flow is a worry, a port matching can help alot.
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Old 12-19-2004, 06:15 PM
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I did 2 sets of '308 heads for my 340. Don't ask why. Anywho, these heads are easily on par with any 340/360 production head. I've ported my share of sb heads, and these have favourable differences from the older stuff.
The exhaust runners are much better, actually emulating the W2's. The intake bowl is higher, offering a better entrance to the valve seat. The narrow intake opening is a consideration, but likely offers good velocity characteristics.
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Old 12-19-2004, 07:37 PM
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RF360, they're from a 360; all the info I've got so far, is from using the search tool on this site. I do see the intake ports being much narrower "looking" than the J head ports, seems the pushrod holes are larger, the result is metal where you'd expect to see port.

I believe that shape has more to do with performance than actual cross section at any given point, the comment on bowl position makes a bunch of sense. I've never shifted this motor at more than 6000rpm, usually go around the 5200-5500rpm mark so if these work to that point I'll be happy.
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Old 12-19-2004, 07:51 PM
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Default What gear and tire size???

I have a 1973 Dart Sport340 with similar type set up. 360 with Magnum heads 9.75 to 1. I have 3.55's G60X15's( sticky DOT tire) 166K Mopar converter in a 727, RB 280/.510(1.6 rockers) cam M1 dual plane (tried M1 single) 650 DP Speed Demon, ignition is FBO's system. SuperStock springs(002/003). Best pass to date in 1/8th 8.11 @ 85.66 still more in tune up. I tried M1 single plane it slowed car up a ton could only get 8.5 at best. M1 single plane needs more converter and gear to make work...


hope this helps
Denny
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Old 12-19-2004, 09:46 PM
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hope these 308's work ok for what I want, going to replace the J's, I've heard that the exhaust port is good on them & I'm counting on it
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Old 12-19-2004, 10:41 PM
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Thanks man. I'm remembering the 302's came of the 318 now.
I think the pushrod holes were opened up for thicker units. (?)
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Old 12-19-2004, 11:57 PM
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LA360, I knew I was forgetting something....gears are 3.91's and tires are 255's on 15X7 rims. For the track I used 8.5" wide 26" tall slicks. Got an electronic distributor and replaced the advance springs, but only ran the car with the factory single point distributor. Lots of room for tuning here, I've got a bunch of TQ stuff to work with as well. S/S springs with front hangers to make them fit.

I had figured on the larger MP cam and single plane dropping bottom end, but that wasn't the case at all. Like I said, I didn't drive very far with the MP cams before they self-destructed, but taking off from a stop with even part throttle was noticeably peppier than with the .450 cam and dual plane. Something worked out nicely with the combination, could be the converter.
Have you taken your Dart to the scales?
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  #10  
Old 12-20-2004, 02:07 AM
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Default Pushrod Holes

They opened the holes for the roller cam engines. The higher tappets changed the pushrod angle.
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Old 12-20-2004, 04:29 AM
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When the 308's first came out from mopar performance I bought a set and was really happy with them. The intake port is pretty restricted because of the huge pushrod bulge for the forementioned reason. I believe "out of the box" they will not flow better than other 340/360 heads. Despite of that, when I replaced the 2.02/1.60 bowl blended J's with them, the performance gain was noticable. Mayeb the better velocity has something to do with this, but I guess Fast One will provide his opinion when he gets a set. The intakeport pushrod bulge can be ground smaller to achieve at least the same width as in stock earlier heads. In extreme cases, people sleeved the pushrod channels with bronze or copper tubes, epoxied them from the ends and ported all the way to the sleeves.
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Old 12-20-2004, 09:37 AM
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Quote:
Originally Posted by DartGT66
When the 308's first came out from mopar performance I bought a set and was really happy with them. The intake port is pretty restricted because of the huge pushrod bulge for the forementioned reason. I believe "out of the box" they will not flow better than other 340/360 heads. Despite of that, when I replaced the 2.02/1.60 bowl blended J's with them, the performance gain was noticable. Mayeb the better velocity has something to do with this, but I guess Fast One will provide his opinion when he gets a set. The intakeport pushrod bulge can be ground smaller to achieve at least the same width as in stock earlier heads. In extreme cases, people sleeved the pushrod channels with bronze or copper tubes, epoxied them from the ends and ported all the way to the sleeves.

I did just that. Plus relocate the rocker gear with blocks. More an excercise in character building. Now I've gone the the W2's. Seemed like the logical evolution.
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  #13  
Old 12-20-2004, 02:08 PM
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Default lenweiller

would you send me an email - I would like to converse with you on the 308s as I just finished dumping a bunch of money into a set for a 388 stroker.
email:ritwaylg@hotmail.com
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  #14  
Old 12-20-2004, 05:51 PM
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The cars weight is unknown guess ~3400 it's a 1973 will get to a public scale and find out... I tried the single plane but killed to much bottom end even had dams in runners done by DLi in Northridge Ca. Could not get it to work, engine is done by 6200 rpm and manifold probally not even working until 4000 and with 3.55's not the best combo. Wouldn't pull from 2400 converter to 4000 60' was best of 2.2 or worse, now it's 1.8 for 60'. Might try a 2800 (172K) Mopar converter to see if can get engine into powerband sooner. Spanked a few stangs that night even a mean sounding Cobra with a blower. A fun night.
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  #15  
Old 12-27-2004, 12:04 AM
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Default Gasket Matching

I just bolted my intake (M1 SP) to one of the 308 heads, the ports aren't the greatest match and particularly where the pushrod hole bulge is visible through the ports there is a drastic change of direction for the air flow. Gasket matching at that point would probably be pretty difficult, no matter what, there's going to be a harsh change of direction and making that a sharp angle compared to the rounded metal already there doesn't seem like a change in the right direction. Anyone messed with this? The port I can see the mis-match on the most shows this to be on the outside turn of the runner....maybe the inside turn is more important?
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  #16  
Old 12-27-2004, 05:31 AM
DartGT66 DartGT66 is offline
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The inside turn is definitely more important. You can grind some off from the pushrod bulge, but to my surprise it worked really well even without touching the bulge. I later ported the heads and made some other changes, but had ignition problems and never got it working right before going with a BB, so really can't say wether it helped or not.
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  #17  
Old 12-29-2004, 07:14 AM
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308 r suppose to be the best non w or mag head out there!i also head that 308s flow better with the 1.88 than a x or j with 2.02.that came from the head guy at mopar.i think the guy does a write up in Muscle mopar every month.
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  #18  
Old 12-30-2004, 11:15 PM
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Quote:
Originally Posted by BelvedereII
I recently got a set of 308 heads, plan is to clean them up and install on my 360. I'll have them cleaned up and a valve job cut, hopefully I can take the old springs off of my J heads and have those installed. Anything in particular to look out for? Valve size if the original intakes are iffy? I'm not looking to sink 500 bucks in these, just want a solid cyl head on my motor.

The J heads were cut for 2.08 intakes and after 10 years of use one runner finally sprang a leak where the back-cut to install them ran too close to the water jacket. Little pinhole that leaked coolant into the #1 cylinder, now I've got a pair of J-code paperweights.

These 308's do have narrow ports, I'm choosing to believe what is said here about them being good heads despite appearances. Wish I had a way to compare them to the J's, but the leak hit before i got to the track. Earlier this year I installed a .484/114CL MP shaft that my motor ate, MP was nice enough to replace that with a new one, my motor at it too, so finally I got a Comp Cams Purple Plus 280/.474 cam and that was running well until the leak. I installed new crank and rod bearings after the first cam lunch; it'd been 10 years and I didn't know if any cam material had made it to the bearings.

The rest of the combo: 9.4:1 Badger hypereutectic pistons, M-1 single plane and Thermoquad, 727 and TCI converter that foot brakes in my car to 3000 (Streetfighter, I think), TTI headers, 2.5" exhaust with Dynomax welded mufflers that are really just straight through flow oval shaped with glass packing and VERY loud, the car weighs 3500lbs on the local scale. It'd gone 8.803 and 78.55mph in the 1/8th with the old MP .450/.455 and a Weiand Action Plus dual plane, cams didn't last long enough (15-20 miles) to get the car back to the track for a test of the bigger cam/M1 intake.
Belvedere11....A question about you badger hyper pistons. I was not aware that badger made anything other than cast. I have them in my 340 and they are two valve relief and sit out of the hole. Thanks
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Old 01-01-2005, 12:21 AM
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LittleCampbell,
The motor was assembled in 1992, when I recently spoke with the guy who built it he told me if something else went wrong with the motor, no matter what to hold on to the pistons as they're no longer available. Maybe they were only made for a few years, I really don't know. They have 4 reliefs and sit down in the bore, I'm guessing about .030"-.040" since I only checked them with some shim material and not properly with a dial indicator.
As it ran, with J heads and 2.08 intakes, that motor using the .450/.455 MP cam would knock when I used 2.94 gears in my A-body barracuda but never had a problem with audible knock when I used 3.91's. Later I ran that motor in an A-100 108" WB van and could go full throttle with the 3.91's but the 2.94's could never allow full throttle without nasty pinging. I figure it was right around the 9.4 range as assembled.
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Old 01-01-2005, 12:45 AM
littlecampbell littlecampbell is offline
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Interesting Belvadere.......but i dont think they are hypers...I freaked when i found out mine were badgers...a lot of negativatey at first. But after some interesting research came up with they are well made cast pistons. The four relief and in the hole are the low compression slugs. Not hypers...keep me posted with your findings...The way to tell is to take a piston out out and check the # under the skirt....Happy New Year!
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Old 01-02-2005, 12:27 PM
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lil' c, you are likely correct. I've asked the builder again about specifics on the pistons but he doesn't have a record available to tell for sure. This was built in 1992 or 93, guess it doesn't really matter but I'll refrain from identifying these pistons as anything other than "360 pistons" until I know for sure. I didn't look for any numbers when I had the bottom end apart to replace bearings, but here's a picture of them as I go about getting new heads ready. The #1 hole is cleaned out a bit from the coolant! Four reliefs and a notch cut into the forward edge, for what I do not know.

http://www.imagestation.com/picture/...5/f5a7adb5.jpg

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Old 01-17-2005, 12:18 AM
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Well, they're off for porting and assembly. Gotta clean up the block and figured to scrape off the old residue/grit. What do you use to scrape a block surface clean for cyl head bolt-on?
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Old 02-18-2005, 10:34 PM
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Default They're back

Got the 308's back from Muscle Motors. They re-used the stock 1.88 intakes as well as the 1.60 exhausts from my J-headed motor, figured it wasn't worth messing with the 2.08" intakes and I'm not surprised. They installed new springs, new guides, did the stage one porting and painted them orange. All I've gotta do is paint over that in the red of the rest of the motor and they'll be ready for install. Now if only the weather would cooperate!

I asked about cleaning up the intake ports to match gaskets, but was told that with a smaller cam (.474"), that wouldn't be worth messing with. Helpful guys, I think I was lucky to get my heads in when I did as they and Hughes seem to be ramping up for the new racing seasons!
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Old 01-19-2006, 11:56 PM
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To wrap this up, long overdue, this past year I ran the car at the same 1/8th mile track I've used since the start. Best previously was 8.803 at 78.52mph. Best with the new combination was 8.801 at 78.59mph.

Earlier combination was MP .450/.455 cam, Weiand Action Plus, "J" heads with 2.08" intakes and no porting, just relief of the bowls to clear the path with the bigger valves. That work was done by a professional.

New combo was with a Comp .474 "Purple Plus" with split duration, an M1 single plane, "308" heads given stage one porting by Muscle Motors using 1.88 valves on the intake and 1.60 on exhaust.

Only thing I did different beyond that was add an MSD 6AL and electronic distributor before making final trips in late October.
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Old 01-20-2006, 10:51 AM
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Default BelvedereII

What are you shifting at?
In my opinion you are running out of camshaft long before the M1 starts to work. The RPM Performer would be my recommendation for your combo and believe you would pick up considerable <5000rpm performance over the M1 - M2CsW.
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Old 01-20-2006, 02:38 PM
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Default What did it cost?

Quote:
Originally Posted by BelvedereII
To wrap this up, long overdue, this past year I ran the car at the same 1/8th mile track I've used since the start. Best previously was 8.803 at 78.52mph. Best with the new combination was 8.801 at 78.59mph.

Earlier combination was MP .450/.455 cam, Weiand Action Plus, "J" heads with 2.08" intakes and no porting, just relief of the bowls to clear the path with the bigger valves. That work was done by a professional.

New combo was with a Comp .474 "Purple Plus" with split duration, an M1 single plane, "308" heads given stage one porting by Muscle Motors using 1.88 valves on the intake and 1.60 on exhaust.

Only thing I did different beyond that was add an MSD 6AL and electronic distributor before making final trips in late October.
If you don't mind, what did the head work cost at Muscle motors?
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Old 01-22-2006, 12:25 AM
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Shifting is a bit under 6k. Tranny's got a high RPM governor that lets 1-2 happen at around 5900. This is only 1/8th mile so I leave the column-mounted shifter in second and cross the line in second gear. Soon, will have a Quarterstick or similar shifter and manually shift for consistency. A couple of runs, the MSD was cutting in with the 6000 rpm rev limiter as I came to the finish line, so some of the runs beforehand likely saw a couple hundred rpm more. I'm contemplating going from 3.91's to 4.30's. The 3.91's are in a 741 case and I've got a 742 3.23 case I'm going to have set up.

Since I'm leaving the line at about 2500rpm and the converter will take revs to 3000rpm against the brakes, I figured the M1 single plane would work between there and 6k just fine. I know single planes are supposed to feel weaker at the bottom end, but it sure doesn't feel like it. In fact, as the motor was eating the first MP 284/.484 cam with the M1 on, the car was turning the tires from stoplights and I wasn't leaning on it yet. Not exactly scientific analysis by me, but it's what I observed.

The MM heads were the Street Killer "package" except I didn't have them provide new valves. Their listed cost for heads set up like that is $999, they pretty much deducted the cost of valves. Shipping was something like 50 more. I pulled the heads from a junkyard van and sent them in, after the cost of them and shipping them in, it might be best just to buy outright, all set up. I figured the 308's would be a curious route to go. I had asked about just getting the port work done since I don't know of any Mopar shops around me, but MM, like many others, I'd guess, prefers to do the valve job at the same time as the porting to make sure it's all correct. So, I just had them do it all.

They did install larger diameter valve springs; when I called about them they told me they were GM-design springs (Crane, I think) and that the heads didn't care what diameter springs were used, ratings and heights are more important. I found out my sockets sure DO care about spring diameter as I had to remove one spring adjacent to the center head bolt so the socket could fit down over the bolt. Not much room there with two springs side-by-side for extra crowding. Once that was done, they've worked just fine. Glad I had a spring compressor handy.
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