Yep...another request for camshaft suggestions.

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ardentindustries

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I've read and read and read. Every time I think I have my mind made up, I read something else that makes me question my decision.

1968 318, stock bore, rebearinged and beringer. Pistons are .070" in the hole.

Factory 675 heads, with extensive porting (dont ask...I know, dumb decision but it was fun...for a bit). Stock valve sizes (maybe bump up to 360 valve sizes of the machine shop says they need to). Will have them decked .020-.025", though that is negligible in compression I'm sure.

Edelbrock Performer and 600cfm 4160.

I've been all over with camshafts. Knowing the low compression, I've looked into LSA and duration for helping the compression issue some..
but again, become confused and second guessing rather quickly.

I'm looking at a hot street build...nothing race only and not totally trying to set the world on fire (it's a 318...). One the other hand, I'd like to see what kind of performance I can get out of the ported factory iron heads.

Am I overthinking this? I do everything else so likely so...

So far, I've considered:

340 Cam grind

Melling 23203 (this seems decent but then there's the "that's 40 yrs old" mentality)

XE256H

Howards 711381-10


Can anyone shed some light on what I should look for based on the factory heads being ported so heavily? Not usually the way people go, yes I should've just bought some aluminum heads.

Thanks in advance.
 
You’re missing the necessary info to pick the correct cam for the application. You pick the cam for the car specs, not build the car around the cam…..

Car and weight
Transmission and gearing
Diff gearing
Tire size
Planned use of the car
 
Scody21 said:
You’re missing the necessary info to pick the correct cam for the application. You pick the cam for the car specs, not build the car around the cam…..

Car and weight
Transmission and gearing
Diff gearing
Tire size
Planned use of
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Will likely go in a D100 pickup to be honest. 4 or 5 speed. Gear and tires to be determined when that time comes.

Maybe I should just set the heads on it and push it back into the corner for now....
 
Scody21 said:
You’re missing the necessary info to pick the correct cam for the application. You pick the cam for the car specs, not build the car around the cam…..

Car and weight
Transmission and gearing
Diff gearing
Tire size
Planned use of the car
Click to expand...
Actually, that's what most people do... but I think is backwards.

Sure if you AREN'T changing anything else, then you need to build it to the car.

The fact that old cars had a massive range in engines sizes/hp is Proof that a car can be built around the engine.

Changing gears and tire sizes, even tq converters are ALOT cheaper than rebuilding/ designing an engine.

It just that most people don't have a clear vision for what they want to plan ahead.

Only real necessity for building an is is, octane of fuel, idle quality, service requirements, vacuum requirement, emissions, etc..



It all comes down to where and what are you willing to compromise.
 
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Sounds like a perfect candidate for a hughes "whiplash" cam. Made just for the low compression 318 with pistons in the hole.
If you ever rebuild, the work on the compression with pistons and deck height, until then, just send it with the whiplash cam ,lifters, and springs kit.
I have used the xe252h cam and liked it very much, but my pistons were only .015 in the hole and made about 9 to 1 compression with the smaller chamber 302 heads.
 
Jersey Devil said:
Actually, that's what most people do... but I think is backwards.

Sure if you AREN'T changing anything else, then you need to build it to the car.

The fact that old cars had a massive range in engines sizes/hp is Proof that a car can be built around the engine.

Changing gears and tire sizes, even tq converters are ALOT cheaper than rebuilding/ designing an engine.

It just that most people don't have a clear vision for what they want to plan ahead.

Only real necessity for building an is is, octane of fuel, idle quality, service requirements, vacuum requirement, emissions, etc..



It all comes down to where and what are you willing to compromise.
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Yes and no. As a have first hand experience on this. 72 duster, 340 4 speed. I picked a Comp XE285HL. I set my car up for Auto-X. Well this cam sucks for the application. The cam I have on the shelf that has to go in is better suited for my application as we took all of the engine specs and car specs for the selection. Call a cam company and that’s what they are going to ask for…
 
Scody21 said:
Yes and no. As a have first hand experience on this. 72 duster, 340 4 speed. I picked a Comp XE285HL. I set my car up for Auto-X. Well this cam sucks for the application. The cam I have on the shelf that has to go in is better suited for my application as we took all of the engine specs and car specs for the selection. Call a cam company and that’s what they are going to ask for…
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I still don't agree, if you are building an new engine. ALOT of cams in a wide range of specs. will work with a given engine...but they will all make compromises in one way or another. There are so many cam possibilities (I didn't say off the shelf) that something will be right for one person but Not for another. If it only depended on weight, gearing, tire size and engine... everyone with that combo would be using the SAME cam.

I've emailed the manufacturers and the "SALESMAN" only push what the off the shelf cams or don't reply at all.

If you are never going over 5500rpm, then you obviously don't want a 265 @ 0.050 lift soldi roller cam in a 318 in a 1985 W150 with stock heads 8.5:1 cr. You are also not going to use the same cam for a 273 as a 408 with W2 heads and a tunnel ram.

Sure you will want a different cam for a 3spd automatic vs. a 6 spd manual. For the most part it comes down to Fuel you are running, rpm range, displacement, transmission, heads, (P/S P/B) and emissions if applicable. The intake, carb, even compression ratio depends on the cam and the factors I stated in the previous line.

If you are building an engine with the cam as the Last item...you are Definitely Not going to get the max potential. Obviously if you have a wide ratio 4spd manual with highway gears you are going to be way out of the powerband with a high rpm (peaky) engine.
 
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i would call ken up at oregon cams and ask him for a rec and to grind something to suit your needs.

but if you want something off the shelf the melling spd-20 and spd-25 are good economical choices and would likely work well with what you've got combination wise.

if you can find it the P4452755 purple shaft is my number one with a bullet for that set up. it's .405/.410 240/248 and you can use stock springs.

you have a performer and a 600, that's your limiting factor. when you couple that with the low compression the 340 cam, the melling 23203 and comp stick are gonna be dog water in a heavy truck. the howards *might* be okay.

different intake and carb and you're okay wringing its neck, then it's a different conversation.
 
To me the problem is a lot of people don't want to run a lot of gear and stall, so if that's the case the combo should be built around that decision.

Being a small cid and low cr can make the problem worse but in this case the OP has picked fairly mild cams any of them should work I'd go with the Howard or Comp.

I wouldn't overly worry about your heads, even ported they still have relatively small ports not like you got to run a crazy cam to match them. If they came out well your just gonna make a little more overall power then stock heads.
 
junkyardhero said:
i would call ken up at oregon cams and ask him for a rec and to grind something to suit your needs.

but if you want something off the shelf the melling spd-20 and spd-25 are good economical choices and would likely work well with what you've got combination wise.

if you can find it the P4452755 purple shaft is my number one with a bullet for that set up. it's .405/.410 240/248 and you can use stock springs.

you have a performer and a 600, that's your limiting factor. when you couple that with the low compression the 340 cam, the melling 23203 and comp stick are gonna be dog water in a heavy truck. the howards *might* be okay.

different intake and carb and you're okay wringing its neck, then it's a different conversation.
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Thanks for the great info! What intake and carb would allow more "power"...or utilize the ported heads more?
Maybe I'm thinking wrong but just curious. Those components are easy changes.
 
ardentindustries said:
Thanks for the great info! What intake and carb would allow more "power"...or utilize the ported heads more?
Maybe I'm thinking wrong but just curious. Those components are easy changes.
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I would just think your heads are now probably more on par with stock 360 heads and treat them as such.
 
ardentindustries said:
Thanks for the great info! What intake and carb would allow more "power"...or utilize the ported heads more?
Maybe I'm thinking wrong but just curious. Those components are easy changes.
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performer rpm, LD4B LD340 or air gap or one of the weiands, even a holley strip dominator. lots of choices.

a performer is a good manifold for what it is and a good match for small port 318 that is going to see low to mid range RPM.

this is going in a truck, which to me says: more cruiser than bruiser. keep it mellow and enjoy driving it. "upgrading" the intake and carb isn't some magic that's gonna fix low compression and small cubes of that 318.

would any of those be "better" than the performer and 600? probably only above 4000rpm. maybe. possibly.

and when are you driving a d100 4000~5500 rpm?
 
I think the spec most overlooked for this type of decision is cam overlap based off advertised specs.

To me you probably want to be in the 30-50 range.

1745097627566.png


1745097719136.png
 

273 said:
I think the spec most overlooked for this type of decision is cam overlap based off advertised specs.

To me you probably want to be in the 30-50 range.

View attachment 1716394791

View attachment 1716394795
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That top graph is so vague that it's useless...atleast to me. The ranges are way to wide.

Also I have read that was for a 10.5cr 350. 35 degrees difference iin overlap is Massive especially when you categories them in the same class.
 
you're slipping, no links to dyno results and not near enough DV quotes or content.

we'll wait for AJ to get on the maths train
 
junkyardhero said:
you're slipping, no links to dyno results
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Here ya go, stock low cr 2bbl 318 and headers vs 4bbl xe262h and headers, dyno results below
https://www.hotrod.com/articles/mopp-0312-318-long-block-bolt-ons/

junkyardhero said:
and not near enough DV quotes or content.
Click to expand...
I'm not a DV disciple, I've question a lot of his conclusions but not a hater either.
The pictures are from DV books though :)
junkyardhero said:
we'll wait for AJ to get on the maths train
Click to expand...
Tag in AJ, wait, scratch that will just confuse the OP more :)

TORQUE SUPERFLOW 901 DYNO-TESTED AT WESTECH
RPMBASEMOD 1MOD 2
2,000292
2,500287
3,000287338336
3,500272335340
4,000248326330
4500218309319
5,000188285296
5,500250258
HORSEPOWER SUPERFLOW 901 DYNO-TESTED AT WESTECH
RPMBASEMOD 1MOD 2
2,000112
2,500137
3,000164193192
3,500182224227
4,000189248252
4,500186265274
5,000179271282
5,500262270
https://www.hotrod.com/how-to/mopp-0312-318-long-block-bolt-ons/photos/
 
One reason why I like the MP 3.51 inch'ish truck series 2-1/2 inch main journal cranks so much. I wish that someone made a quality discount variant of them (even cast steel be nice!) just to give us the option of using 1.72 inch sealed power pistons and early bushed 318 rods. 318s are so much better with zero deck. Of course, having the deck milled .070 to .090 when it's all apart will accomplish the same thing.
 
Jersey Devil said:
That top graph is so vague that it's useless...atleast to me. The ranges are way to wide.

Also I have read that was for a 10.5cr 350. 35 degrees difference iin overlap is Massive especially when you categories them in the same class.
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Yes if you looking for you need X overlap it ain't gonna tell you.

It only a guide to help you narrow it down.

There’s a lot of overlap between types of engines you can use that to help narrow it down even further.

Tow 10-40 street 30-60 street performance 50-75.

So street goes from in tow range into street performance range since OP has a truck he probably wants street but probably more towards the tow side of things.

Especially with his cam choices.
 
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That Melling 23203 214/224 is one of my favorite cams for a drive around SB engine. A little bigger than a stock 340 cam and really has good low end manners.

Get the tune up right and it a great all around easy on parts, quiet valve train running camshaft.

If the heads are ported well, show the engine some valve lift. Fill it, compress and bang! You won't likely lose low end with the better cylinder filling.

Since you touched up the heads, open the window on your performer intake. They actually work great with a 1" open spacer on them.
 
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