Bought a big block and discovered a pushrod through a rocker arm!!!

[280zwitha383]

Yes through is right. I just bought a '79 sierra with a 454 in it which didn't run due to the guy that owned it not knowing how to shim the starter... Anyhow, once I got it running it made some typical valvetrain noises so I pulled off the passenger side valve cover and the first thing that I thought was well the pushrod isn't plugged.... then it hit me that I could actually see a pushrod . Has anyone had this happen before? It literally went through the dome part on the rocker arm and is stuck there! Several other rocker arms were loose and it's really not a big deal because I was planning on rebuilding it anyway. It has the peanut 236 heads which I kind of figured but wasn't too thrilled about. Any ideas on some affordable heads for this thing. Is home-porting worth a shot with these? I know there's a ton of meat there but I'm not familiar with big blocks too well and I don't really know what my options are for heads. I do know that they are very expensive when compared to small block heads. Thanks guys

[jbk240z]

Granted I don't have near the experience of grumpyvette or dr hunt. If it were me, I would practice porting these peanut heads, heck you probably can't hurt them. Porting them would increase their performance, altough there are much better heads out there. Think of it as a learning experience. You are lucky to have a big-block to play with at all, even with peanut heads.

I've seen bent or broken pushrods, but never one through the rocker arm. I wouldn't be suprised to find the cam with flat lobes. Anyway, good luck!

[280zwitha383]

Well I've port matched a pair of heads and an intake and I can think of quite a few things I'd rather be doing. I'll try to get a picture up soon of the rocker arm because it is fairly impressive. It's definitely going into my collection of "mechanical failures..."

 

I'm thinking about Pro Topline heads for my rebuild. They seem to be excellent heads for a killer price compared to other big block heads.

[dr_hunt]

Yup, big blocks and valve train are notorious for having problems. If you have a stock big block that has valve train noise, you'd better investigate the cause before you drop a valve and lunch the whole enchilada.

 

Chances are, IMHO, that all the rockers are worn out and need replacing, the guides and springs are in need of replacement and probably most of the valves as well as the cam and lifters. Since about 90% of engine failures are valvetrain related, it's cheap insurance to replace the valve train in it's entirety.

 

I'm sure grumpy can relate to stock high mileage big blocks picked up as a core.

 

When going back consider a hydraulic roller cam and roller rockers, will save you $$$ in the long run IMO.

[grumpyvette]

big blocks can and on occasion do have problems with valve train oil flow when the owners dont adjust the valves correctly or fail to keep the oil filters and oil changed frequently, if ONE rocker had a pushrod wear its way thru the rockers pushrod socket area its a reasonable bet that others are worn also and that you will need to replace at LEAST the rockers and probably the push rods and possibly , (rarely)the cam and lifters.

you did not mention if thats a roller cam engine, (some #236 head bbc engines were?) theres a great deal of potential aftermarket cylinder heads to choose from, youll need to decide on the use youll put the engine too!

Id first point out that mildly ported (236 heads ,"peanut port") with some bowl cleanup can make about 425-450hp while its true they are a huge restriction to making great hp they are not bad for low/mid rpm tq when you use the correct matching compression,cam, and intake.

this is the only PERFORMANCE PEANUT PORT intake, I know of

 

http://www.holley.com/products.asp?product=8017

 

youll need to get the compression up to about 8:1 DYNAMIC which will require about a 9.5:1-10:1 STATIC with cams that match the intake and heads

yeah, to do that requires new pistons,or smaller combustion chamber heads,and the early gen IV won,t work,

 

http://www.worldcastings.com/docs/05_cat_pg23.pdf

 

which again require a new intake

 

you may want to think thru the mods, gen V blocks are four bolt blocks and if your going to replace pistons you may want to add a stroker crank and boost the displacement to 489-496-511 while your swapping pistons

 

http://www.speedomotive.com/489-496-506%20BUDGET%20STROKER%20KIT.htm

 

http://www.speedomotive.com/489-496-506%20LONG%20ROD%20STROKER%20KIT.htm

 

be aware that not all gen IV heads fit MOST GEN V BLOCKS, youll need to carefully research the differances

 

http://www.amazon.com/exec/obidos/tg/detail/-/1557883572/qid=1126017747/sr=1-6/ref=sr_1_6/002-0158106-8265605?v=glance&s=books

[5foot2]

is this a gen V motor or a gen IV? is the motor going back into the truck, and is the truck going to be used as a truck? I'm running a gen IV in a 86 GMC 4x4 ton truck with the peanut port heads. it's true the motor does not make much HP, but it does make a mountain of torque. so if your planning on using the truck as a truck I'd stick with the stock heads and build the motor accordinly.

 

I built mine as follows:

 

std bore 454, dished pistons (I'd guess 7.5-8.0 CR)

stock peanut port heads with stainless valves

performer cam and manifold, jet q-jet carb

pertronix HEI dist.

headers into 2.25" pipes into dual inlet sinlge 3" outlet flowmaster muffler.

 

I've never dyno'd the thing of course, but dynosim tells me I'm around 320hp at 4500rpm and 460+ ft lbs of torque at 3500rpm.

 

I still need to tune the carb, it's pretty new to the truck, but as it sits I figure I get 8-9 mpg with it (short runs around town). Plowing snow it must be around 4 mpg.

[American]

When the rocker arms are worn out and the pushrod balls become conical this is what happens.... just punches right on through. I've seen it happen on all kinds of engines.

 

New rockers, pivots and pushrods are always money well spent... in addition to everything else.

 

Rule of thumb... if you can't machine the part then replace it with a new one.

[Michael]

If this is a 1979 then it’s a Mark IV 454 with flat-tappet hydraulic cam. The 236 heads have 225cc intake ports and 119-122cc combustion chambers (depending on which reference source you believe).

 

If your intended application is for the truck, then the peanut-port heads are entirely adequate. Port-work to consider would be partial port-patching (don’t go all the way – see below!) to an Edelbrock Performer intake, clean-up of the inner-radius in the exhaust ports (exhaust ports on 236 heads have a very sharp inner-radius corner!) and bowl-blending on all the ports, as often one finds something like 0.100†“steps†in the port casting.

 

And as the others already mentioned, the pushrod-through-the-rocker situation is probably a symptom of a wiped cam; which means a complete teardown.

 

If this engine is intended for a Z (ambitious, but not impossible) then you’re looking at $2000 for aftermarket heads and >$1000 for a suitable valvetrain (good lifters alone are $500!). Yes, there are cheaper alternatives, but they negate the performance advantages of the BBC.

 

I started with a 454 from a 1978 Suburban – basically, the exact same engine as what you have. I did the above-mentioned port work on my 236 heads. When the machine shop pressed in new valve seats, the heads cracked; evidently, I removed too much material when trying to port-match with my Edelbrock Performer RPM intake. The port work took several months, with 1-2 hours a day, several days a week. This is with a Sears 1/4"-collet electric die grinder (basically a giant Dremel) with a range of grindstones, including a $30 carbide cutter. Even at 25,000 rpm with the carbide cutter, cast iron takes a LOT of time to remove – and the shavings are nasty! With glasses and a mask I still ended up with dust in my eyes and nostrils.

 

So all that port work was for naught. Eventually I mustered the gumption to buy aluminum heads. In a truck the cast-iron Pro Topline heads would be an interesting option, but in a Z I just couldn’t justify not using aluminum heads, whatever the cost. For some time I’ve been waiting for AFR to bring their oval-port heads to market. But 2 years is long enough to wait! Brodix recently came out with their “Race Rite†oval port (271cc) heads – and that’s what I currently have on order.

 

For my build, I used the block, crank, rods and damper. In hindsight, I should have gotten aftermarket crank and rods – or at least the rods. Because the short-block was built with 236 heads originally in mind, I bought 10.5cc-dome pistons, which give around 9:1 SCR with the 236 heads. The original plan was to use a hydraulic roller cam. The current plan is to use a healthy mechanical roller with the Brodix heads. Brodix can mill the combustion chambers down to 110cc, which gives (if I recall correctly) something like 9.6:1 SCR with a 0.039†head gasket. If you follow Grumpy’s posts, you’ll notice that this is quite low for a big block, let alone one with a mechanical roller. But the duration is pretty small and I intend to install the cam with considerable advance, giving a DCR in the 7.8:1 range (or higher).

 

Anyway, my point is: keep it simple if your application is a truck, but if you’re going for a BBC Z, you’re looking at another $4K-5K to build the engine “rightâ€. That should give just shy of 500 hp and around 550 ft-lb torque

[dmyntti]

Michael is right the 79 truck engine is a Mark IV. I am currently building a 79 454 to go into my 1/2 Ton 4x4. I went with a pair of old 781 (large oval ports) head castings that I am going to port match and do a little bowl work to. I put in Hypereutectic popup pistons for a static compression ratio of 9.35 with my head volume and deck height. For the cam I went with a hydraulic roller that has specs of 218/224 @.050 and .540 lift with the 1.6 ratio roller rockers I am using. Desktop Dyno puts this at 450hp and 550 ft/lbs of torque which is extremely optomistic (I think the proper numbers are -50 for both). I built this combination for my truck and with a shift point of 5500 rpm because it is hard to get a hydraulic roller BBC much above that without valve float. If this were to go into a Z I would do as Michael suggested and get good aluminum heads and a bigger cam with coresponding higher compression ratio.

[280zwitha383]

This engine will be put into my '85 daily driver. Currently it has a 3.73 rearend and I have a 350 turbo, 400 turbo, and 700-r4 all of which would need to be built up. I'm not too comfortable with putting the 350th or the 700 behind a built 454. I could be wrong about the 700-r4 and if I am please tell me because that's the ideal tranny I would like to use. Also, would the 400th still need to be rebuilt? I have heard that they are bulletproof but I can't imagine anything being bulletproof after close to 30 years and who knows how many miles on it. It does shift well from what little I've driven it however.

 

What I want from the truck is something that is fun to drive normally (part throttle response), reliable, and can whoop more than a little tail at the stoplight. In numbers, I would think a flat 450ft-lb torque curve and 350-400hp would be essential to even call the thing a big block or justify throwing money into it. I'm not familiar with big blocks in particular and I don't really know what's mild and what's not. If someone could give me some good build suggestion including compression ratios and cam for both the heads I have as well as maybe the Merlin or Pro Topline heads with predicted numbers I would really appreciate it. What I don't know much about in specific is the compression for big block engines. I definitely want to keep this thing running 87 octane and I don't know exactly how to calculate dynamic compression. Is there a little program for this somewhere? I have DD2000 but no flow charts for the heads and I've been too lazy thus far to put any in from CHP's website so I will do that and definitely put a lot of research into this thing before I try and throw it together. Again, thanks for any suggestions.

[dmyntti]

The numbers I quoted for my engine were from Desktop Dyno 2000. A web search will often turn up flow DD2000 flow files for the heads. As far as the tranny goes, I would probably go with the 400. As far as a rebuild, it is a toss up in my mind, rebuilds can tend to be a crapshoot. If it shifts well then I would probably run it as is. Remember the driveshaft is different for the 400. Also you will want to fix the shift points on that 400 as it should currently shift at 4500 rpm. I think it is the govenor that needs modified but automatics are not my bag. For the HP/Torque goals you are looking for I think you will need to get better heads then the peanut ports. What you are describing I would call a relatively mild big block but that is an opinion. As far as running on 87 octane, I think that will be tough. Big blocks are detonation prone and you don't want a huge camshaft for the torque you are looking for. A big cam would allow more compression at a given octane rating but kills bottom end torque. With my cam as specified above I think I will be looking at midgrade gas if not premium. I do intend to polish my compression chambers and run a 160 degree thermostat (I have coated skirts on the pistons to help with scuffing).

 

Keith Blacks website has compression ratio and dynamic compression ratio calculators.

[5foot2]

If I was building a daily driver truck I build or have built the 700r4 so that it'll stand up to the max torque I expect out of the engine. If I was going to work the truck hard I'd go with the 400. The 400 is a stout trans, but it also takes a lot of power to run it when compared to the 350 or 700r4. I don't remember the numbers but I saw a chart once that listed the spread between the GM transmissions and the 400 was say 50-60 hp where the 350 was 30-40 hp.

 

If your set on going with after market heads, 450hp is a pretty simple goal to hit. Note: when you get into this hp/torque range the work needed to keep the 700r4 alive will cost a bit, not crazy numbers, but not cheap.

[Michael]

If you’re comfortable with 350 hp I’d stick with the 236 heads; they should be adequate at this level. 400 hp should be possible with a little portwork. With no valve job (at all), my home-ported 236 heads reached something like 260 cfm at 0.500†at the local flow bench; this is about 25 cfm above stock. If one believes the rules of thumb, even the stock 235 cfm is enough to support 350 hp, easily.

 

For the 236 heads I would recommend straight-milling them a bit to increase static compression – if you don’t plan to rebuild the short-block. If you do rebuild the short-block, get mild-dome hypereutectic pistons, such as what I bought (“Sealed Powerâ€). BTW most aftermarket BBC pistons already have their skirts coated. For the 236 heads, 0.007†of straight-milling gives approximately 1cc of combustion chamber volume reduction. For your application you only need to remove about 5 cc – but check piston to valve clearance.

 

Chevy High Performance magazine has a web page with a database of most SBC and BBC head flow numbers. And if you search in this forum under “DCRâ€, several of Grumpy’s posts on dynamic compression ratio calculation should pop out. There are various sites where you can download a DCR calculation program – not to say that it’s difficult to write one yourself. What’s more difficult is reaching a consensus on what DCR value is OK for what octane value, and various other variables. It depends on combustion chamber shape, piston dome shape, quench, cylinder head material, alignment of the planets and color of the pavement. Well, not entirely, but sometimes it feels that way.