I am building a 318 stroker (campbells' kit) bored over .060 so it will be a 396. It's a 1970 block so hydraulic tappets. The desired characteristics are broad torque range, performance street, no street/drag racing, peak HP around 5000-5500 RPM (more on this later), road course racing if ever. Will live with a throaty idle (but not completely stupid idle) and crappy start up is OK, it's a fun car, not a daily driver. Must run on pump gas. It has dual headers with isolated left and right 2.5" pipes heading to two flowmaster 50 Deltas. (I had 40s on there but took them off for the neighbors sake).

Specs: (the first group*of parts I have already from the original motor)
MSD ignition with an MSD pro billet (no vacuum advance) and I have the tune up kit for it to swap springs/bushings.
RPM Airgap
Holley 750 DP
Mid 70's J-Heads (aka; not THE J-heads from the T/A) ported to 2.02/1.60 and 68-70 CC.
Valve springs are #150 closed, #340 open @ .500 lift.
Stroker kit from campbell (which is the deep dish kit yielding 9:1 on these heads).

fungible part of the engine spec
The cam is a CompCams 20-224-4 (http://www.compcams.com/Company/CC/c...?csid=628&sb=2).
Lifters are CCA-822-16 High Energy (I would have gotten the 867-16 pro magnum ones but they require adjustable rockers, which I want to avoid).
Rockers are stock (will eventually be replaced by 1.5:1 aftermarket shaft style iron rockers)
Push Rods are 7.500 long with .020 in pre-load. (the high performance option is 7.550 long push rods, presumably with .070 preload)

Now, here is where I really need the sanity check. I want the peak HP to be at 5000-5500 RPM (ie; shift light set at 5000-5500) and the torque to be broadly available in the mid range. The RPM Air gap and carb should go a long way on the broad mid range and the cam is about right too from what CompCams says. The concern I have is the valvetrain. Will this valvetrain support this? The valve float should be around 6600 RPM. I want to use a 6400 RPM MSD redline* which will mean the engine is full power until 5600 RPM. I can also use a lower RPM chip (and just not stand on it) for a while until I save up the duckets to buy a better one. But I REALLY want to avoid adjustable rockers. I don't want to have to check the damned things every few months.

* For those that don't know the MSD setup, a redline of 6400 causes the timing to retard and other techniques to gradually detune the engine as it approaches redline starting 800 RPM prior to the redline.

** For those that care, it's a 4 speed A833 1970 challenger.

 

This build sounds awesome, I've always wanted to do this. What HP do you expect it to make?

 

To be honest, less than I probably could get. I will be happy with 425 frankly. I actually don't want to make too much, because the stroker kit is only good for 500 HP and to make more, I suspect I would need to increase the RPM range it operates in, which I know the valve train won't be able to handle. I am worried about the lifters as it is now at mid to high 5000 RPM.

 

As long as you set it up with the proper length push rods It should be fine

 

Proper length is the issue. Proper (as denoted by the engine's design) is 7.5" for these lifters, rockers and cam. There are oversized rods that CompCams is hocking that are 50/1000 over the proper length. The correct preload is 20-30/1000 but if I use these 7.550 rods, I am at 70-80/1000 preload. Does this configuration of cam, etc have a different definition of proper and require more preload? Or is the extra 50/1000 of those meant to be taken in by the adjustable rockers I am not using?

 

Different heads< surfacing, head gaskets all contribute to the required length push rod. To be correct you need to buy/ borrow an adjustable push rod adjust it on the assembled motor to 0 clearance- add .020 for preload. Compare that to the length of the stock push rods. do Not go over .050 preload .010 as a minimum.
The more pre load the greater chances of valve float due to lifter pump up

 

OK, the key here is that the longer rods are not per se the right length and that .010-.020 is the proper preload, even under this setup. I was worrying that I needed more preload because of the products comp cams are pushing. I can see wanting a slightly longer rod if you have an adjustable setup but I wasn't sure if there was something I didn't know about preload needing to be higher in higher performance engines. Understanding why they were pushing 7.550" rods was one of those proving a negative problems for me. ie; "Was there something I didn't know?"

I feel better now. I have the adjustable rod. I also suspect I will need shorter rods, not longer ones. But we shall see when it's all together. Thanks for help.

 

Sometimes it is the way the cam is made, it needs to fit through the cam bearing. Depending on the valve lift They will use a smaller base circle for the cam SO longer push rods are needed. That is why they should be checked on any non stock cam

 

Couple of things to consider.

With that cam you will make your HP at the RPM you said you needed. Around 5000-5200 IMO. She will not carry any power into 6000+ RPM range. On the usable "RPM" chart on Comps site take off 750 RPM for the stroker combo.

It is a very well thought out build.

Only thing I would double check is your spring pressure. If memory serves me correctly your about 40 lbs heavy on your pressures. Should be 110-115 closed, 310 open.. The numbers you have posted in your first post look like Roller pressures for the retro 274 cam. If I missed something in the post, forgive me.. I tend to skim stuff.

 

Thanks for the compliment. This was a very unexpected event to need to rebuild a motor that someone just rebuilt so I have been diving in head first trying to figure out all of the relevant info to fix what they screwed up and make something similar to what I wanted long term*.

Sorry, there was a typo up there on the the force numbers. I wrote the wrong closed force. The closed forces are 125# @ 1.75, not 150#. I just double checked the measurements I posted with what I wrote down. The closed measurements were pretty consistent at 125#, but the open measurements ranged a bit more from 325# to 340# @ 1.25. The numbers on the springs that compcams recommends are 115 @ 1.700 and 336# @ 1.150. This closes at 1.75 and opens at 1.30ish with this cam. These looked pretty close to me to me but one thing Comp Cam doesn't do that crane does is provide a max open force. On an "equivalent" crane cam, they claim 400# as the max open force. Since I am using 1.5 ratio arms, this seemed right enough. This not the case?

*Irrelevant back story beyond here...
In case any one cares, the issue is I just bought the car and I did so because the engine was rebuilt. I did not want to deal with the engine for a long time and was happy to focus on brakes, suspension, etc; which has a lot of issues, all surmountable. I don't do engines. Well, it turns out bubba hand his beer to his buddy and said "Watch this, I can build an engine". I open it up after a few months to swap the torker II manifold (which was causing very low manifold pressure at idle) and low and behold, I find two lifters with the spring retainers popped and the corresponding lobes ripped to hell with some significant wear on the ramps and a third valve had a bent pushrod. It turns out bubba replaced bad lifters while leaving a bad cam in. One cylinder probably saw a handful of actual firings before the intake push rod was bent. It got bent because the guy who sold me the car said his cousin (bubba, who was a mechanic by trade) did donuts with the car right after getting the engine back together. He told the seller it was a great break in routine... So he likely overreved it because the rev limiter was set to 7000 and with donuts, the tires have no torque applied and can spin up faster than the red line.

Anyhow, I pull the engine out hoping the bottom half was OK. I feel the bores and they are smooth as a baby's bottom, even up in the top 2/10ths of an inch area where there is no piston or ring contact. He had the bores bored out but never honed the engine. They were 3/1000ths undersized waiting for their honing. The rings were obviously crap at this point, the rods looked like they were mismatched and so I pull the crank and the rear bearing which was brand new and it was trashed. I measure and the rear of the crank was out of round. I expected to put in $1000 but $4000 later and climbing, here I am, "doing engines"... It's not the first one I have done but it's the first dodge and the first one I am doing totally on my own (with your all's help now).

 

Make sure to use a good zinc additive with your new cam and do a proper break in..
That means getting every thing set before start up Then start and run it at 2200-2500
RPM for a minimum of 15 minutes

 

Got it. If someone already cut on that block / heads I would advise you to port / gasket match that intake to the heads. And check its alignment dry using the bolt holes as guide. Ive had to use double intake gaskets before but the motor didnt mind. Turbulence in there will drop your numbers and have you looking for gremlins.

The 995 comp spring they spec'd you are a triple spring. Pull the inner and dampener for break in. Extra work but worth the piece of mind.

Let us know how she runs the cones when you get her moving.

Good Luck!

 

Well, it's running but I shut it down after 1 minute. The inner headers (3-6) started to glow while the outer ones (1-2,7-8) didnt. It's an rpm air gap so it blocks off the exhaust feeds to the intake manifold. That may be the reason. Anyhow, I didn't want to push it. It was getting dark so I packed it in for the night.

 

It's Alive!!!

Thanks for everyone's help. A little advance and a little choke kept the headers from glowing and I got through the breakin period. I only have one issues to deal with outside of the mechanical advance on the distributor and drilling the holes for the PCV and breather on the mopar performance valve covers I bought to match the air cleaner.

That issue is, there is a bolt leaking water on the block. Right side of timing cover mid way down. I don't know if I put the wrong bolt in there or what. It's definitely coming from around the bolt itself (see pic, the black bolt and the rust spot is where the water is pooling). Likely in between the washer and the bolt head. It's not coming from the gasket, that is for sure. Is this common? Does this bolt end up in the water cavity, which is why this is happening?

 

A little fine tuning and you will be set..... Congrats....
As for the bolt... Pull it and use some liquid Teflon to seal it.

http://www.permatex.com/products/pro...sealant-detail

Works for me....

 

Just an update. I had the engine chassis dyno'd and it came out to 340 HP @4500 rpm and 450 ft lbs @ 3000 rpm. The heads are restricting flow and keeping the HP down. That said, it's still impressive numbers if you add 80 to the 340 it's 420 HP to account for the transmission parasitic loss. When I get more money to spend, I will invest in better heads, which should raise this some.

 

Now enjoy it a little bit....

 

450 ft lbs. at the wheels... That's gonna be a fun ride!! I cant tell from your pic but it looks like a low profile tire? With 450 ft lbs, any extra money you have will have to go towards tires! youll be lucky if they last an oil change..