Thanks. I’m considering a mild porting on my OE heads. Nothing big. Just a valve job and bowl work for a 100% daily driven street car. Dragging my feet on a cam. I have the Hughes spring kit for added lift on the valves.
360 Magnum building on an existing bottom end
- Thread starter 65TTCuda
- Start date
-
Thanks. I’m considering a mild porting on my OE heads. Nothing big. Just a valve job and bowl work for a 100% daily driven street car. Dragging my feet on a cam. I have the Hughes spring kit for added lift on the valves.
65TTCuda
Well-Known Member
Finally pulled the heads off my 360 magnum and the cylinders don't look to bad. No ridge and no scores on the walls. Need to clean the piston heads a little. The cam doesn't look terrible either, although it is going to be replaced. The roller lifters look really clean and in good shape also, but I'm wondering if they will hold up under a high lift cam. (.530+) Like I said before I would like to use the short block as is and put a new cam and heads on it. what do you guru's think?
You are going to want to put new roller lifters on your new roller cam.
Not a Guru. I just did a similar 5.9 magnum build. Looking at your mill I would check rod and crank bearings (mine were good) send the cam to Oregon cam grinders for regrind (I used the cam listed below .528/.536) and Hughes 1110 spring set and cam eccentric assuming mechanical fuel pump. Clean and reuse your lifters. Measure for pushrod length. My stock pushrods were perfect with my cam. Carefully go over your heads. I used Aussie EQ's which are no longer available. Runs great.
Dan the man
Well-Known Member
I would replace the rings, rod and main, cam bearings. It's cheap insurance and a piece of mind. 100,000 miles and thing's can go south real easy, especially when you "tighten" up the top end and start spinning it in a higher rpm's then it was before. Oil pump drive and oil pump should be changed as well.
I can still see the factory hone marks in the cyl walls. 100k is nothing IF it's had any type of care at all. The roller lifters (providing they are good to start with) will be fine at .530 lift. I will bet you'll find a bad cam bearing or two. Easy to replace. Then I'd just spin the oil pump over with a drill and primer and see what pressure it has. If the pressure is good, I'd leave the bottom end alone. Throw your new cam and timing chain in it. Make sure your valve spring match the cam
I did that with my 5.9. The engine I bought had 80K mikes and looked much better than the OP's. Still wanted new rings and bearings.
I dropped off the short block to a machine shop for hot tank, crank polish, hone, rings, and main, rod, and cam bearings. But that ran $900 three years ago.
I used stock pistons and Rods, but replaced oil pump. Then spent $$ buying a new top end. Sent my cam to Oregon Cam Grinding for a regrind. I reused stock lifters. Runs like a raped ape!!
Good advice here. I forgot to mention ring replacement and timing chain. Also....I had issues with my reground cam and had to use an offset keyway and 3 way timing set to degree it. I should have just used a 9 way adjustable timing set. I went with a melling standard flow oil pump and my original intermediate shaft with the reground cam. 60lbs cold oil pressure but I have fresh bores and .030 over.
Same here...Melling standard flow and intermediate shaft. Went with a double roller chain.
I'm wishing I would have gone .030 --- never satisfied, lol.
Oh, and I rebuilt the 904 myself and went with a PTC 9.5" converter.
65TTCuda
Well-Known Member
65TTCuda
Well-Known Member
What kind of HP do you estimate you are getting from this engine.
I honestly don't know but from other builds here that I based the build on and 9.3 CR thinking about 370. The torque is what I was after. Figuring around 420+.
65TTCuda
Well-Known Member
So I theoretically am basing my build from a web page call Dyno Proven 360 packages, package # 9. Comp Cams 305AH-8 camshaft with .525"/.540" lift and 305/312 degree advertised duration, 253/260 degrees @ .050", 110 lsa, installed at 108 intake centerline. 495 h.p. @ 6,000 rpm 500 lbs. of torque @ 4,500 rpm). There is a lot more to it but basically with the right flowing heads (260+ cfm) and 10:1+ compression you could achieve 495+ HP. I'm not sure if the lift is based on a 1.5 or a 1.6 ratio rocker arm.
This is the only Comp I see close to what you mention
PLYMOUTH COMP Cams 20-244-4 COMP Cams Magnum Hydraulic Camshafts | Summit Racing
IIRC, this is the cam listed on that page. Regardless….
Some of the other newer cam options have higher lifts which I would look at with fully ported heads. If the cam doesn’t lift the valves well into the heads best and highest flow area, look at 1.6 rockers, which the Magnum head has but I’d look at better than stock for this.
Personally I’d take a peek at this and do some math on the valve lift w/1.6 rockers and see if it fits.
PLYMOUTH COMP Cams 20-229-4 COMP Cams Xtreme Energy Hi-Lift Camshafts | Summit Racing
Lift (.564) divided by stock rocker ratio (1.5, which the advertised lift is based on) then multiply by new rocker ratio (1.6) will equal the new lift of .6016
The new ratio (or stock ratio in the Magnums case) will add a minor intensity to the cam and really help open the valves up quicker and higher into the cylinder heads best flow area of its curve. It’s worth a little power, for sure.
PLYMOUTH COMP Cams 20-244-4 COMP Cams Magnum Hydraulic Camshafts | Summit Racing
IIRC, this is the cam listed on that page. Regardless….
Some of the other newer cam options have higher lifts which I would look at with fully ported heads. If the cam doesn’t lift the valves well into the heads best and highest flow area, look at 1.6 rockers, which the Magnum head has but I’d look at better than stock for this.
Personally I’d take a peek at this and do some math on the valve lift w/1.6 rockers and see if it fits.
PLYMOUTH COMP Cams 20-229-4 COMP Cams Xtreme Energy Hi-Lift Camshafts | Summit Racing
Lift (.564) divided by stock rocker ratio (1.5, which the advertised lift is based on) then multiply by new rocker ratio (1.6) will equal the new lift of .6016
The new ratio (or stock ratio in the Magnums case) will add a minor intensity to the cam and really help open the valves up quicker and higher into the cylinder heads best flow area of its curve. It’s worth a little power, for sure.
65TTCuda
Well-Known Member
Since it is a magnum engine I want to keep it roller, so this is the cam I was thinking of COMP Cams 20-814-9 - COMP Cams Xtreme Energy Retrofit Camshafts Advertised Duration 292/300, Lift .549/.544. Its a little bit bigger, but go big or go home LOL. It will probably get me in the 500+ HP range where I want to be. I was thinking of trick flow 190 heads, but they don't make them with the pedestal for the magnum rockers. In which case I would have to switch to shaft rockers. But I like the new magnum style pedestal rockers and the reason I chose a magnum engine for my build. So if you have any suggestions for high performance heads for my build please let me know, I would appreciate and will investigate all suggestions.
If you must, Edelbrock RPM magnum heads use pedestal mount rockers, although I think it uses chevy rockers.
Dan the man
Well-Known Member
They are Chevy rockers.
I went with the Edelbrock 2.02 RPM Magnum heads. Just installed them OOTB. I used Comp Cam 1.6 rockers.
Some day I'll run it on a chassis dyno.
Some day I'll run it on a chassis dyno.
65TTCuda
Well-Known Member
Do they perform well OOTB ? What kind of HP do you estimate your engine is producing ? Do you think these heads can support 500+ HP ? Did you buy them bear and build them to your cams needs or buy them all assemble ? What cam are you using? Thanks in advance for the info.
I’m not going to answer the question to him but instead give you an in general answer to a question you asked.
The head OOTB is a good performer. (As long as it checks out OK with hood valve sealing) Achieving 500 hp is possible but you may not like the way it has to be done since the head flow and capacity is limited being a street/performance head. It would require a good bit of compression to support a relatively large camshaft pushing the heads intended use. It’s usable range would be narrow and at a very high rpm. This is why people port the head. It offers a greater amount of flow and volume of air and fuel for more power.
500 HP is a good bit of power for a small block. It’s really not a throw together engine.
I'm still kind of a rookie when it comes to performance engines so I don't have a lot to compare them to. It's 15-16 vacuum at idle, 160ish Cranking Pressure. Runs very strong, I hope it's putting out at least 350 hp, maybe a little more? Be great if it was close to 400. Bought the heads from Mancini 3 years ago during Black Friday sale fully assembled. Sent my Magnum cam to Oregon Cam Grinding for his #1280 grind. .216/.224 @ .050 and .517 with 1.6 rockers. Doug's headers and a 9.5" PTC converter. 650 AVS Edelbrock.
First time I went that deep into an engine and transmission all by myself. Well, I did get online tech support from Roy @SGBARRACUDA (RIP) and @RustyRatRod. Probably wouldn't run so well without their help.
350hp sounds reasonable.
65TTCuda
Well-Known Member
I finally cleaned up the pistons and removed the # 3 and # 8 rod cap to look at the bearings. Then removed the first and last crankshaft caps to look at the crank bearings. Also pulled the camshaft out to look at the cam bearings. This is what they looked like. The rod bearing may look like they could be replaced as it looks like there is some grooving. There for the crank may need to be polished. What do you all think? new bearings or use as is.
65TTCuda
Well-Known Member
Here are the main bearings.
Those bearings are toast. Hopefully crank will polish. Looks to be turned .010 under on both rods and mains. Keep that in mind when ordering parts. If the other four cam bearings look like the front, you'll be ok on those. Clean the oil passages really well.
-
