So, after a less than stellar build, I'm planning to tear my engine down and build her up the right way. I've spent the last month or so reading and studying and calculating and I think I've finally gotten educated enough to build a strong running truck. However, I'm hoping to get some opinions on that because I'd rather not be tearing it down again.

The plan is for a solid daily driver with a nice strong bottom end. 5,000 rpm would be a rare occasion. Engine is a 302 utilizing stock crank and bored 30 over. Upgrades include Edelbrock E-street heads (Still trying to figure out how I could get flow numbers on them), 4 Barrel 500 cfm Edelbrock Carb, Edelbrock Performer Manifold.

I will be running a 1500-1700 stall torque converter w/ stock geared C4. Thinking after I get the engine going that I will also upgrade to a 3.25ish rearend putting me around 2200 RPM at 65. Most driving for me is around town 50ish mph.

Exhaust will include shorty headers with dual super 44 flowmasters out the back

So with all of that in mind, I'm looking to use the Cam and specs pictured below.

Are there any critical items that I'm not thinking about here? Any "did you consider" type items?

Thanks in advance

 

Did you consider going to a bigger carburetor, say a 600 cfm?

 

Carb selection is something I factored in. To be fair I originally bought the carb and put it on the bone stock engine. However, with what I am building, I don't see how anything bigger would be necessary.

(306 CI x 0.85 efficiency x 5000 rpm)/3456 = 380

By that calc I could go even smaller couldn't I. This is the one calc I haven't sat down and proven out to myself.

During my reading, it seems the two biggest mistakes people will make is over-carbing and over-camming the engine.

Feel free to set me straight though.

 

I would stay away from the tight 110 Lobe separation angle and go at a minimum of 112 for better idle quality. You are going to have a tough time with "low end" in a 302 merely because of the short stroke. Since you posted the picture of the xe250h I'm assuming you wish to stay flat tappet lifter or I would recommend the factory 5.0 roller camshaft. But, good news is melling still makes the factory spec 93-95 Lightning cam that is flat tappet. For a daily that would have great idle characteristics and plenty of across the board pull its about as big as I'd go in a 302. I believe its part number syb-35.

​​​​​​​https://m.summitracing.com/parts/mel-syb-35

 

Thanks Mudsport - I looked at the Cam you listed here. By my calcs, the overlap is almost 64 degrees with the intake valve not closing until 79 ABDC. All that would add up to a running engine with no compression unless I build it to >10:1 static compression, correct? I'll dig a little further to see if I can find a dyno curve.

Noted on the idle quality though. Comp advertises the cam as good idle. I need to confirm this... I think their dyno sheet for a chevy 350 showed 21 in-hg @ 1000 rpm.

As for LSA, doesn't a wider LSA reduce low end power because it moves the power curve of the cam to a higher rpm range? 110-112 seems to be the middle of the road LSA.

I am looking to stay hydraulic flat tappet.

 

​​​​​​​Also if the cam caused compression issues the fuel injection would not have like it and the trucks would never have passed emissions testing in various States

 

I have been running the Comp XE250H (31-230-3) cam in my truck for almost 10 years now. I am very satisfied with it.

My idle is set at 750 RPM in Park, and I can pull 21 in-hg of vacuum. Idle drops to 500 RPM in gear. Idle is always smooth with no fuel mixture issues at all.

 

Excellent. Thanks for the info. I also placed another call to Comp yesterday and got a rep that seemed to be pretty knowledgeable. His reasoning was - smaller LCA is okay because this cam also has short duration. That agrees with the reading I've done and essentially says the same thing Motosport was saying above.

Last thing on the LCA... I read (How to Build HorsePower by David Vizard) that a Ford 302 dyno'd at peak horsepower using a 110 LCA. I try not to believe everything I read, but since this is only my second build it's hard to rely only on experience. And when it's accompanied with dyno charts, it's hard to argue against.

I've got another week or so before placing my order, but I think I'm going to stick with the XC250H.

Lariat 85 - I will be running a somewhat similar setup to yours. Makes me feel re-assured.

Mudsport96 - I'm not convinced that Melling camshaft was the right camshaft. I looked at some specs yesterday that indicated it might be more mild than that Melling. If I can get some time today, I'll look a little more to confirm. I'm curious about it now... Have you run one of these in a 302?

 

Got my acronyms mixed up - I was talking LSA (Lobe Separation Angle) not LCA (Lobe Centerline Angle).

 

I have not run the lightning cam in a 302. But, I should have started by asking the more important question of what is the static compression ratio you are shooting for? This will have a significant impact on what cam you should choose.

 

Static CR will be about 9.1:1. That said, the Intake Valve Closing Angle becomes pretty important to keep from falling too low with the Dynamic CR.

To go back to the beginning it all started at the link below... But it's a bit of a long thread and after it was all said and done, turned out I needed to do some studying to right my wrongs.
https://www.ford-trucks.com/forums/1...elling-me.html

The plan for now is to tear down the engine (completed this past weekend) and have the deck shaved down to set the piston about .005 in the hole and end up with a squish/quench height of .044. This combined with my 60 cc heads (measured volume today), and my +8 cc pistons, will put me in the low 9's static compression and right around 8:1 for the dynamic compression.

Originally, I was trying to buy new pistons for the engine instead of changing cams (original cam edelbrock 2122), but once I started digging in, it seemed to me that I could get what I wanted with a new cam rated for a lower rpm range (i.e. less duration, overlap, etc) which just so happened to have an earlier IVC than the edelbrock. I understand that peak HP won't be as high since it is a function of torque and RPM (less RPM=less HP keeping torque constant), but I think my combination works for that (considering the heads and carb I'm starting with).

One thing that I keep coming back to is head to cam comparison. Everyone talks about good flowing heads, but it's proving a bit difficult to define "good". The Edelbrock advertised flow #'s are below. That's with 170cc runners. I'm very interested for a source that discusses cylinder head to cam matching using actual numbers as opposed to "good flow and big cams".

 

Glad I got that link. That fills in sooooo many gaps. Yeah, with a quench of over .070 I can understand your problem with vacuum.
One thing you need to check before anything else, is if the valves are sealing. I know you had new springs put on the Edelbrock heads but unless the shop checked to make sure the seats and valves were mated right that can also cause erratic vacuum behavior.
If you have the heads handy put them on their sides with the intake ports facing up. Now, fill the ports with carb cleaner and watch for it to run out around the valves into the chamber. I have seen this on brand new heads and that is a problem. Repeat on the exhaust sides.
Now as for shooting for 8:1 DCR, after closing up your quench and boosting your compression, the can you have will probably be fairly snappy. Your issue was the horrible burn rate and flame travel you were getting due to the stacking of tolerances against you.
​​​​​​​Another issue you are going to run into is that its a 302 in a truck. Over in the OBS part of the forum the biggest reply to how do I get my 302 truck to perform better is , put a 351 in it. Now I know you have invested money in this already so I won't give that answer. But, what I will say is I would use the Edelbrock camshaft and advance it four degrees to move the I take closing point up and that will help bring up the dcr. The duration at .050 is good at 204° if I remember the picture right. And the intake center line being 107 four degrees would net you 103 ICL close to the preferred 102 ICL that Vizard seems to like.
​​​​​​​Id post more but lunch break is over lol

 

OK, so after so digging through old boxes, I found my Sealed Power piston specs book....

​​​​​​​


With the 73-76 vintage 302 with the 8.229 deck height block the H273 pistons .030 overbore size and a 60cc head with the standard. 047 head gasket from felpro final static compression is 8.41:1and 8.97:1 with a 54.4 head
With the 68-72 and 77 and later deck height block of 8.206 the h273 .030 overbore pistons are 8.46:1 with a 60 cc head and 9.02:1 with a 54.5 head.

So even decking your block to the shorter factory deck height you are barely in the 9s SCR with the smallest available chamber. Honestly I'd be looking at new pistons.

 

Yeah, you hit the nail on the head. New pistons is where I started, but there aren't that many options for pistons available (not hypereutectic and from speed pro) and I'm not really interested in a domed piston.

As I said, originally the pistons were the plan for change but I wanted to look at all combinations. What if I change pistons, what if I change cams, rods, etc.?
After running through all of the options, it seems that I could switch out the cam and pretty much keep all of the other stuff I've already bought. Second, if I were doing it again, I don't think I would've chosen the edelbrock cam anyway so why not use a cam I would've wanted to run (now that I've done the due diligence of reading)?
Last, as it turns out this is probably the least expensive way to fix the engine too. Although, that was the last consideration I made.

Advancing the Edelbrock cam that I have is an interesting idea and I hadn't thought about doing that... I'll be looking into this a little more as that also has the effect of changing all of the valve timing points. Better in my case for IVC, but I don't know about IVO, EVO, EVC.

That is a good idea for the heads - I have them sitting on my bench right now so I can easily perform that check this evening. Was also going show them to the machine shop and see if there was anything needing done before I reinstall them.

So my setup as of last night looks like the calc below. With all numbers and dimensions verified - no guesses. I also added the cylinder head flows. Realized I forgot to attach them to my last post.

BTW, I appreciate the time/help. I wasn't necessarily looking for anyone to tell me how to do it, but I did want to ask if there was anything about my proposed setup that I was missing.

 

I'm a 3rd shifter so it will be mid morning before I get back to my book, but I have something for you to check if you have the tools.

Actual deck clearance of the pistons. You need something fairly sturdy and totally flat. Small piece of flat stock or even a bubble level. Lay it across the deck and get a piston to tdc. Now using a feeler gauge set find the distance from the edge of the level or flat stock to the highest point of the pistons which will probably be around the outside edge. This is your true deck clearance.
​​​​​​​I bring this up because I see in your chart you calculated deck height at 8.2. Perhaps it was decked for this build and that's what the machinist cut it to. Well there is 8.206 and 8.220, and .014 is a big deal. If the engine had ever been machined before it could be different or if it wasn't machined properly from the factory you could be at 8.23 for example. This will affect quench so actually deck clearance is a MUST KNOW.