Lookin good. No issue with rockers clearing valve covers?

 

#4 and #5 both touch at the baffle area. So little I could barely hear it but could feel it when i touched the covers. The push rod end of the rocker is touching the round sheet metal part of the baffle. I thought about denting it in a little since it would not show on the outside but opted to use two gaskets instead.

I used some playdoh when i test fitted. I tested a set of rockers in the center thinking that was the lowest part of the cover and was surprised it hit at the raised parts where the grommets are

 

So far so good, The motor sound great and the cam 570/570 235@.050 sound mild. I am glad I did not go smaller. It idles easily at 800 and in gear. It has 15" of vacuum at idle with 12 degrees of timing. I am keeping the timing low until a few hundred miles and then I will experiment a little.

I will post a video when i get the truck back,, It is at the transmission shop now because it will not shift after a "professional" rebuild. I would still rather have used a custom piston that matched the heads better but had to take what was available.

Chris

 

Thank you for the update.

No doubt the thicker head gasket assisted with preventing detonation.

Is your vacuum advance timing connected to ported ? If yes then 15'' vacuum is healthy, allowing for your elevation.

Your truck sounds great.

 

My timing is connected to manifold vac. The pertronix distributor is set for 24 max mechanical advance. I think I will change it and limit the mechanical advance to 16 and set the initial at 16 giving a max of 32. I allows use manifold vac so when pulling a load or hill it will take some timing out.

 

I'm a big fan of the Pertronix distributors because they offer a useful variety of limiters which one can mix 'n match.

I had a tiny mechanical curve of only 10 or 12 degrees at one point.

Your total of 32* sounds like a good starting point as the OE of 34-36* is reduced by the closed chamber heads efficiency, and increased by the altitude.

Before you start changing limiters and/or springs, verify that your curve, as it stands now, read at 500 rpm intervals, is linear between 12* and 36*, and does what it is supposed to.

My first ever Pertronix was faulty, determined by checking the curve, but the one they replaced it with was 152% perfect, and I could definitely feel the difference while driving.

When you are driving up a steep hill, or pulling a load, it doesn't matter if the vacuum advance is ported or manifold, as the drop in vacuum in those driving conditions has the same effect on both setups, I.E. reduces the vacuum advance timing.

That said, manifold vacuum at idle should advance your timing by 15 - 20*, whereas ported would advance by 0*.

Your vacuum at idle (800rpms?) of 15'' does strike me as being at least 2'' lower than it should be (but I could of course be wrong), after allowing for the semi bad boy cam and altitude. (I assume the needle was solid.)

It wouldn't hurt to check your timing, with the vacuum advance connected, to verify that you are in fact getting say 27 - 32* timing.

I hadn't realized earlier that you changed the cam.

In theory your new cam intake valve closes 6* later than your first one, which is a huge influence on detonation avoidance.

But ! I see that Comp Cams website shows 67* at 0.015 lift. (WTF is 0.015 lift ?? LOL Your initial cam timings are stated at the widely used 0.006 lift.)

Did you degree the cam to check the actual cam timing ?

If not, no worries, if your cylinder pressure is at +/- 170 on a warm engine, then chances are that the 0.015 was a typing error.

I noticed on my first engine build that the vacuum dropped by a few degrees when I applied too much preload on the lifters. (Adjustable valve train)

So thinking out loud, if the timing turns out to be correct, could the lash on the solid lifters be out ?

Hmm, are there any vacuum leaks and is the carb dialed in ?

Now, back to the subject of me being given the keys to the Camaro............................................ ................................... LOL

 

Here is a short clip, using full length headers with a Jones Exhaust MAX Flow Mufflers
https://www.summitracing.com/parts/jex-mf2468

 

Update again,
This combination is a beast. I finally got on it the other night. Nothing crazy but, this thing pulls, I run the comp magnums in three other motors and have always been happy. I have two AMC 360s, one, iron heads, 11-1 and a magnum cam and it pulls harder than #2 360 with edlebrock heads and a voodoo. all other component exactly the same, (intake, gears, ignition, etc)

When i get a gopro i will post an in-cab video letting it rip.

Anyway, If you are going down the 400 rebuild road and I can answer a question, feel free to ask,

Chris

 

Out of curiosity, what is the gearing/tire setup? At this point, would you rather have a lower compression ratio, or keep it higher? How does it being 11:1 effect your fuel mileage vs a lower compression ratio?

 

I have 38 BFG KM2s (measure ~37") Before the rebuild a few years back i went to 4.88s, the truck was still painfully slow but just spun more rpm. We have a grade north of me that is a few thousand feet (~6% grade) and it couldn't do in high gear. I went back to 4.11s

Today it is 38 KM2s , 4.11s with a C6. It has more power than it needs, I might run 39 Irocs, they measure a full 39. I might try the 88s then if needed.


As for the compression, I would not want less. I do wish i had a better designed piston, If I were to do it again not sure if I would use a TM piston on a CC head. I run 11.7 in my CJ7 and 11.4 in my 67 camaro. Compression makes power. In the truck I am at 12 degree base and want to limit it at ~32. I started at 12 for the break in and might increase it a little when i have time to fiddle with it. At 12 the motor is crisp, cruises at 65 mph just barely touching the gas. I haven't checked mileage yet but I think I increased it by 50%. My old motor was a turd, all stock with only 75k miles but it could not get out of its own way.

For the compression, on the net there are thousands of people repeating the same thing. Not sure if any of them have first hand experience or not?

That said. In five years I have only restored four projects. All but one have higher compression ratios than the internet pros suggest. My engine shop, trans shop and other local builders feel 11-1 is fine.

At 2800' elevation I knock a 1/2 point off
Quality aluminum heads subtract ~1 point.
Proper quench combustion design subtract another point.
That is the max I would try to run on pump 91.

Cams and compression go hand in hand. If you want more duration, you will need more compression or it will be a dog. This 400 is a comp magnum .570/282s. 235 @.050. sound so mild at idle I am a little disappointed but any more duration will push the rpms up and it is still a cast crank and rods.

I love the sound of a motor with compression and solid flat tappets, it revs different/faster and all around more crisp. Solid flat tappets will out run hdy rollers al day long at a fraction of the cost and spring pressures. the Internet pros all say hyd rollers. Hydraulic anything is blahhh in performance. Rollers better than hyd flat but still blahhh. When i upgrade my square body suburban I will go hyd roller. that truck sees a lot of hyw miles and is not a hot rod so Rollers are a good choice for that.

Sorry for the ramble

 

Dig the build. Think you may have got more action in the engine forum. Still collectin parts for mine. Aiming for lower compression though, like to be able to run on Mexican pump gas 87 in rural areas. Haven’t selected a cam yet either, definitely don’t want to sacrifice any bottom end, like crawling around in the desert hills as well as roarin down the highway.

 

go to the link,
Dynamic CR

and scroll to the bottom and download
DCR Calculator with VB6 Runtime files 1.55 MB

It is a complete and easy to use calculator for static and dynamic ratios.


If you have the coin, by a set of aluminum heads. The cost add up with new bolts, rockers, pushrods, etc but I think they are worth it. I sold my old iron heads on CL.
There were a few companies i found that made a true flat top. I would have bought a set but i was stuck with the 62cc heads and 72s were not in stock.

Chris

 

yessir thanks already have the trickflow 72s. Have most of my pre tear down stuff, aside from the cam/lifters. There are some outfits that have d dish’s for them, gonna go that route, may have to get a custom dish but the shelf ones look real close, see how the deck comes out.

 

I had a thread at Hotrodders when i was figuring out the rocker arm problems. Maybe I can save you hours of headaches. I needed longer studs than what cam in the head. honestly, can see the installed short stud working with any combination.

Take a look, hope it helps
https://www.hotrodders.com/threads/t.../#post-4802843

Also, can you post a few pictures of the 72cc chamber? I was going to modify mine to lower the compression but TF had no CAD drawings or information. Doubt I will do it now that the motor is assembled but have a pic may help someone in the future.

Chris

 

Trick flow 72cc

I didn’t buy assembled heads, unfortunately I did buy 1.90 studs.