i,m also going to say that if the op went with eq heads out of the box and a 525 efi cam he would see a decent increase in power for not a lot of money,jmo.in most cases the eq heads would be cheeper than freshening up the stock gm heads and make more power from start to finish,a win win in my book.

could be the cam was retarded 4° from the get go over the spec,and advancing it put it back to straight up.

yup,those heads look really good.

Thats a good point mike. I degreed my cams two ways. Once straight up, with the rollmaster timing set, and once using the -4 on the crank sprocket. Each time it was with 1/2 degree. On the hex adjust, I couldnt say.

Imo, most camshafts, are not 100 percent optimal out of the box. Theres just too many variables that effect what the cam timing the engine will like. Simply doing a nice trick valve job, increasing low lift airflow, can change what the engine wants for cam timing. In other words, just doing the valve job, and no other changes, you might not notice a lot. Change the cam timing to work with the fact the cylinder fill is better within that timeframe of the valve opening and closing, and you might see the benefits of a cam timing change/valve job work. Maybe its 5hp, maybe its 30hp. Nobody can answer that on paper.

Its all time based. You have X amount of time at 2,000RPM, to fill a cylinder the best you can, and you have x amount of time, at 6000RPM to fill a cylinder the best you can. Low rpm, close the valve too late, you lose power. High rpm, close the valve too soon, you lose power. Unfortunately, the BBC , doesn't have variable cam timing like some modern engines, and its a fine line of balancing things out. If you want big power at 6000rpm, you may have to give something up at 2000rpm. Most off the shelf, and even custom cams, have a certain amount of advance built into them, how much usually depends on the LSA. Wider lobe sep's, 4-5 deg of advance is common.

i think generally speaking, if you advance the cam and gain power everywhere, the cam was too big. If you retard the cam, and gain power everywhere, the cam was too small. Then of course theres LSA's, lift values, ramp profiles, and so on.

I think if you really wanna validate your cam choice, to find out if in fact it is the best, it must be compared against other cams, or cam timing changes. Same goes for cylinder heads. But, thats impossible for the average guy, so we pretty much are either happy, or not happy with the power output. I've seen a few builds at the 1000hp mark, pick up close to peak 50hp with just a cam timing change, with a slight loss of torque in the 2500-3000 range. Which can make sense. You are now opening, and closing, the valves later in the combustion cycle. just like going to a longer duration cam may net a little more peak power, and little less low rpm power, and then you get to the point where the cam has too much duration, and simply loses everywhere in the power band.

Well, it's new news to me. I'm still a student, so....I try to learn something new every day. :)

As far as heads go on the same sized cubic inch engines, I was impressed with the 20cc smaller Intake runner size and how well it performed on the Whipple engine at a lower 300rpm range with less boost compared to the larger head sizes of the Roots and the Pro-Charger engines all making the same HP/TQ within 10hp.

Also, I just thought the Pro-Charger was really going to be more dominate....maybe in more of a higher RPM category...like a racing application. Of course, this is my initial observation and opinion. I'm just a weekend warrior, so it's just very interesting for me to learn about it.

Mark, do you know the model of the heads that were used in each setup?

interesting...but over 2k for 70hp give or take.....

If you anticipated re degreeing the cam on the dyno you could use your cloyes hex adjust on the engine stand to advance and retard the cam ahead of time to see where it actually puts it when you change it on the dyno

Speaking of dyno Smitty, do you have any dyno time available?? I have 2 engines that I would like to dyno.

Yes, I have been running them for years. Everything is available, I believe he just sold a set last month.

They are more in the 335-40 range and it made 787 on pump gas.

Give me a call 989 2137434 and we can set it up, dynoing my 502 today after straightening out un balanced injectors, heading to gas station for fuel in 5 minutes. Testing a new protype hp 500 air cleaner from aember next week then pulling motor off dyno. So will be available soon

At what RPM?
Have my doubts over 900hp out of a 320cc head.

I will confirm size and HP with Jim and post. I see rookie post and evidently knows something I don't or I was misinformed by Jim last weekend. If I'm wrong then I will certainly fess up to it.

See post 50. The engine in question actually made 787hp, with a 340ish cc head. The 900hp number with a 310-320cc head was incorrect.

Refer to post 50.
Haha, Mild is already on it.

I just realized that I havent seen much for discussion on intake manifolds... they are connected and an extension of the port are they not? or does size flow and velocirty only start at the manifold gasket?

I was at the dyno with Jim and might be able to find the dyno sheet I have the pull written down somewhere. Was he referring to our old race boat with highly ported Dart Iron eagles maybe 308's++? I know that was a 509 and made over 800 but that was with ~12.1 compression and race fuel. That engine was wicked!

They did for sure in the 70's and I believe into the early 80's.

My intakes are welded up and matched to my heads. But my ports are not standard oval or rectangle. Also, a single plane outperforms a dual plane on my engines. I didn't believe it until last summer.

Not sure what I was thinking. The math wouldn't work with his top speed anyway. We had to of been talking about a combination of builds with what I've got going on also.

I had the epoxied heads from Jim before he got all into welding. Lol. Regarding manifolds it was really mind blowing at the time however began to make sense with having a torqer 2 dual plane intake REC port on the raised floored darts and made more power. Not so uncommon anymore but in the late 80's people would thought you were right out to lunch.

No, I degreed it ....



That was my last build he's referring to... In was in my little Checkmate... :evilb:

Unfortunately, I didn't get to test the cam timing change back to back on the water...

My goal was RPM..
I had a ton of $$ tied up in my prop and my current engine (Iron head 509) could only spin it to 5200 RPM

When I freshened my engine, I changed to AFR heads and a new cam.

On the dyno it was starting to lay over at 5300 RPM.
It may have been caused by one of the accessories, not sure as we never tested without them.


So we tried retarded the cam timing and it worked out...

Gave up some torque I couldn't use in the first place (stock Bravo outdrive) and got my HP peak where it needed to be.. :)



Doug

As far as intakes go we saw a 10-15 hp change on the dyno with just the intake. Same carb, no other changes. That was just going from the Vic Jr to the 454R, so imagine how much difference there could be between different styles.

What intake ?

I edited, while you were typing Vic Jr to 454R.

I've seen the same on bigger motors. I have heard the Merlin Intakes work well, but have never tried them.

Not sure if the marine version of the Merlin X is still available. I had to use what was available anyways, couldnt afford to buy just to test.

Any of you NA guys ever tried a Sniper intake ?

Someone on the boards has a Sniper Jr. I'll have to do a search.

The description says it has a built in spacer. 7.4 carb mounting height, which would make it most similar to the super victor I believe.

My intakes say "454-R VICTOR JUNIOR" What do you mean when you say you switched from the Victor Jr to the 454-R? Aren't they the same, or are you talking about an older Victor jr?

And you should Know for sure the pile of raw cast iron was sizable even the Boss companied, but you made them right!

Got me too. I know they have a 454-R that has a 4150 flange, and a 454-R with a 4500 flange. I only knew of a "victor jr" or "super Victor", or "super Victor II"

Maybe he will chime in with what he means. My friend has an older 4150 victor junior and it is about an inch taller than my 454-R victor junior.

https://m.youtube.com/watch?v=r-tkaCrRPHU

On a related note here is the very first start of mine. (462 with 308 darts). Just started and brought to temp no adjments made. Wanted to check for leaks or obvious issues but all seemed fine

Then there are the SV 565 and SV 632. Which are the newest and best Edelbrock intakes available. A "ported" intake in cast form.

Sorry for the lack of specificity. The standard Vic Jr to me is the 4150 flange. The 454R is the 4500 flange. There doesn't appear to be a signifigant height difference although I haven't actually looked it up 2902 vs 2907.

I looked it up.
2902 Vic Jr 4150
2907 454 R 4500
5.96(4150) vs 5.90(4500)height. Basically the same manifold but one with a 4150 flange and one with a 4500. Picked up 10-15 hp using the same 4150 carb. One with a plain 2 inch open spacer, the other with a plain 2 inch open adapter.

The confusion is there is a Victor Junior 454R and a Victor 454R.

I believe 454R is the head they fit not any kind of model number...