So my car wont run right or stay in tune. It smoked pretty good at startup too. I rebuilt the motor my self last year and have only put 350 mile on it so far. So anyways I started her up the other night and I heard an awful chattering from under the hood. I pulled it in the garage and pulled the valve covers. I found that the #7 exhaust valve rocker arm had slipped off the valve spring and bent the push rod. When I remover the rocker arm I found that the stud now has a grove almost halfway though it. So I pulle dthe head off and disassemble it. I found that the machine shop that rebuilt the heads for me in MD didnt do what I paid them for. The valve stem seals are almost non-existent and the valaves themselves are still the original 1978 valves!!!!!. I paid these jerks $400 to rebuild them and replace everything. So now I am stuck with junk heads and a car that doesnt run. GRRRR.. so mad at people.... Here is a picture of the stud. Aslo 7 of the 16 pushrods are slightly bent. WTF?????

 

I think you have the sequence of events wrong, in the chain of failure....

The first thing that happened, was the push rod bent. The push rod guides the rocker; not the other way around.

Push rods don't just up and bend too much. I'd look REAL closely at that particular valve for signs of something binding: coil bind in the spring which would be caused by too much shim under it, or the retainer hitting the guide.

Then once you figure out what bent the push rod, it's just a matter of cleaning up the mess.

I'd avoid spending a dime on those heads, if I was you. If they're 1978 heads, they're garbage. Don't waste any money on them. That includes replacing the one stud. Basically they're trashed; get rid of them, cut your losses, don't throw good money after bad, and get something decent, and be done with it.

 

Looks like I will be saving my pennies for some new heads. I think I will step up to hardend pushrods and some roller rocker while I'm at it. Should have just done it right the first time.....

 

Sounds like you are in financial straits. Get a set of 305 heads from either a wrecker or rebuild shop and then port and polish them yourself. (081, 601 or 416 castings.) Maybe you can reuse some of the parts off the bad heads, like springs or exhaust valves. Then you'll be one happy camper.

Follow the link at the end of my sig.

 

Are those heads pretty much a bolt on? Or do they require machining? I have heard that some 305 heads dont work so well. Thanks for the help guys.

 

Yes, they will bolt right on. Since you are currently using 70's style heads, you should look for 416s or 601s.

Nothing wrong with most 305 heads, just avoid the TBI heads.

 

What kind of compression will I be looking at if I get a set of 601's? Mine is currently at 8.5ish to 1. Thanks.

 

What is your cam's maximum lift and what type of rockers are you using? Stock-ish heads and anything over about .470" lift you can run into problems pretty quick.

Can't estimate a compression ratio change without knowing what heads are on the motor right now (and what size motor it is).

 

Very little the machine shop did or didn't do would cause the failure you experienced.

Either the rocker wasn't adjusted correctly by you, or you used non-self-aligning rockers where you should have either used guideplates or self-aligning rockers, or the pushrod bent and allowed the rocker to slip off.

Sure, they may not have installed seals or replaced valves like you thought they would, but that doesn't cause what happened.

The only imagineable problem related to the shop's parts would be if your cam is lifting the valve beyond or near the springs' coil bind height. This would only be their fault if you gave them specifications for the springs which they didn't meet...and you have either a receipt or a written quote that said otherwise.

 

I wasnt blaming the machine shop for the failure, I am just upset that I didnt get what I paid for which means I have to spend more money on different heads. The motor is a 350 bored .030 over with flat top stock style pistons. The heads that were on it wer 76cc 1.94/1.5 truck heads. The cam is a XE268 which I bought through the machine shop and they matched the springs to the cam. My biggest mistake I know is using stock style rocker arms. Thanks for the info on everything. Also what cc are the 601's and 416's? Is this cam good for those heads? Thanks again.

 

Most 305 heads are 58 cc. Both the 416s and 601s are 58 cc.

It will bump your compression up to 9.x somewhere. That Comp XE268 might be just a tad too big for the stock configuration of these heads but you can have a machine shop work in some greater clearance for you. It is an excellent cam for the heads and compression ratio but right on the border line clearance-wise.

These heads will require you to resize the intake valve out to 1.94" from its stock 1.84". But you don't HAVE to do that if money is too tight. Still, it isn't a really expensive operation, especially if you can reuse all your valves and springs from the 350 heads.

 

Thanks for the info. I will talk to the machine shop here in town and see what I can work with him. Now I just need to find me a set of heads... I found a few sets on Ebay I may check out. Most are ready to run. We shall see though... Do you guys have a rocker arm recommendation? Like I said I want to do it right this time. Thanks.

 

These 305 heads only need regular old non-self alighning rockers.

 

Cool, I called the machine shop and hes got a set of 601's that he will give me for $350. That includes the larger valves and clearancing for the cam plus matching springs. Is that a good price?

 

BTW your compression ratio will go from 8.5:1 to just over 10:1 by using the 58cc 305 heads.

 

Would I need to use 93 octane? Also would I need a high torque starter? Just trying to get my list together. Thanks for all the help.

 

Yeah, that seems fair these days. Once you get them you can port and polish them yourself and have a really nice set of performance heads for a street machine. But you MUST port and polish them, as well as do a bowl blend, if you want decent power. 601s especially have ridges in the bowls.

You can use a thicker head gasket to bring your compression back down to 87 octane levels if you like. Talk to F-Bird'88 about which gasket set to use.

It shouldn't require anything more than your current starter.

 

Correction to my last post. I will be getting 416's not the 601's. The guy said he found a good crack in the 601 he was going to use. The 416's are abou the same right?

 

You have pretty much the identical engine to what I currently have in my S10. Yeah, it's been reliable, I've put 28,000 miles on it, but I can't believe COMP reccomended the 268XE for 8.5:1 CR and those heads.

The cam is supposed to be good 1600-5800 RPM, but as you may have noted the thing falls on it's face at about 5000, as the 882 heads just don't flow beyond that. I should have saved the money and stuck some generic Summit grind with around 218 at .050 and 440" lift or something.

And worse yet, even with the low CR because of the crappy combustion chamber shape, the flat tops being .045" down in the hole (I measured it on assembly) I still have to run at least 89 octane or if hammering on it 93 because it spark knocks if I don't. It has no quench.

With a 750 CFM Q-jet and headers this combo makes a whopping 201 RWHP and 248 Ft/lbs. Adding 20 percent for drivetrain loss that's about 240 flywheel. A FAR cry from the "322 hp and 363 ft/lbs" Desktop dyno predicted!

Consider this a blessing in disguise, your new heads will be a huge improvement. I have a set if 081's to rework for mine.

Eric in Savannah

 

Some say better.

 

It all boils down to...
If you want it done right then do it yourself!

one more smilie

 

Wait, wait, wait. Hold On.

You have a 350 but you want to put 305 heads on it? Why??? If your compression is 8.5:1 right now it'll be up around 10.3:1 with little old 58cc 305 heads. Too high for pump gas and cast iron heads. Also, 305 heads never came with valves any larger than 1.84/1.50 from the factory. Airflow was not their strong suit.

If you have a 350 engine then use some 350 heads on it!!! Somethign with 64cc chambers and 1.94/1.50 valves is going to work much better on that combo than a 305 head. Compression would come it at a more reasonable 9.6:1 for use with pump gas and the 350 heads will flow better than 305 heads will apples-to-apples. There are many 350 heads with 64cc chambers. One example would be a set of stock L-98 cast iron heads off of a 350 TPI engine, or the old tried-and-true "camel hump" heads that are still available rebuilt for cheap from many mail order places and, of course, there are SCILLIONS of aftermarket heads to choose from for a few hundred dollars more that will blow away any stock head in terms of power production.

I'm not sure how this discussion got locked onto 305 cylinder heads but that's not what I would be looking at. You can get 350 style heads that will work better on your engine for the same money.

 

Damon,

I don't understand your reluctance to use 305 heads when I and many others have already shown that they can flow as well as Vortecs. Not to mention they are ideal for someone with very little cash.

Indeed, in my thread you concurred!

What are you thinking of?

 

Why not use them? Once you isntall bigger valves you will increase the CC of the chamber. The comp. ratio will be right back inot a useable range. They will flow just as well, better with some porting in fact. They also will give a little bump in compression ratio. 10.3:1 is no where near to high to run on iron heads. That is just fine. You will need the premium fuel, but it is fine.

 

Premium gas and a perfect tune. 10:1 is pushing streetable on iron heads.

 

What I'm saying is..... given the choice to use 305 heads or 350 heads for basically same same money why would you choose 305 heads? Installing bigger valves in 305 heads costs money. Porting out heads costs money. Money is the enemy here, right? Find a set of 350 heads with 64cc chambers, 1.94/1.50 valves (or larger) and bolt them on. 305 heads can make power on a 350, sure, but I'm talking about stock-for-stock bolt them on and go here. Get an old set of L-98 350 heads, bolt them on a be done with it.

305 heads and 350 heads aren't going to be much different in price. Certainly, if he's willing to lay down $350 for a set of 305 heads he could find some L-98 heads done up equivalently for about the same $350, no? I sold a set of good condition original 1987-vintage L-98 heads recently for $100 complete. That's pretty cheap, but not outrageously so.

I'll stand by my assertion that 10.3:1 compression with cast iron heads is too much for pump gas. Yes, you can get it to run without detonation if you keep the spark advance dialed back, but it''ll run better and make more power if you keep it under 10:1 and run full spark advance for best power.

 

Why not use a thicker gasket and get it down to 87 octane levels?

I have seldom seen L98 heads go for cheap.

Doing your own porting and polishing is how you save money and that's what we were talking about all through the thread.

 

Read up on quench height and its effect on detonation, it'll surprise ya.

Given two engines with same compression ratio, the engine with the more quench area volume (thicker head gasket) will be more prone to detonation.

 

Essentially we are NOT concerned with quench on what we desire to be a low compression engine like this. It may, however, be his desire to get that last 5 or 10 hp that high compression would give him on a 305. Personally, 5 or 10 hp is meaningless to me when the price difference between 87 and 92 octane is what it is.

And it is easy enough to set the timing properly and not worry about detonation.

 

If it is a comp 268 XE cam they reccomend 8.5-9.5:1 maximun compression with that cam. It would be better to run a lower compression setup that works with low grade pump gas and all the initial timing you need. Like I said in a few other posts theres no reason to have a high comp setup just to run 5* timing to keep it from detonation. Your loosing more power by having the timing retarded then you would make with the higher compression.

 

Well, the boss is letting me spend more than I thought so I will be getting a set of World Products Sportsman II's. What type of rockers should I use with these? 1.5 or 1.6? Self aligning or non? Thanks for all the help you guys. Hopefully she will be running by the end of turkey day.

 

I have ran 10.5:1 on many engines, and didnt have detonation problems. Keep the advance right, and its all good. I have seen higher ran on pump gas with iron heads too.

 

Perfect tune.

 

Or just coat the bloody combustion chamber, that'll help more than a thicker head gasket. Ok, not price conscience, just had to mentoin it.

 

to those of you who think people should save their money for 350 heads...



That's fine and well, and I'd even agree with you, except that that statement implies there is money to be spent. my 82 T/A becomes my only vehicle.... both the ground-pounder and the grocery getter for the next year or so, until i can fix my finances. I got stiffed 3 weeks of pay by my former employer, and am scraping by... but only because i have really good friends and roommates. I can't afford to replace my heads, but i have no choice, because i didn't make sure the casting matched when i bought the engine..... everything else checked out... the tranny, the stall, the forged bottom end..... but not the heads. but since i have 2 sets of SBC heads in my basement, a set of 416 305 heads and a set of 193 TBI 350 heads, I have a choice. port and polish my 416's, slap on the 193's, or risk engine damage by doing nothing. I have a set of gaskets for the top end on my spare parts shelf, and a good set of 305 heads. desparate times, my brother, call for deliberate, logical measures. but believe me.... when i can afford $1200 on my ideal set of heads, I WILL spend it, i guarantee. thanks for listening.

 

Groundrat's original problem brings up a question from me.

A few years ago my LB9 broke a pushrod on the #6 (can't remember if it was the intake or exhaust) valve. I replaced the push rod and the engine ran perfectly for a few more years until I sold the car. What could have caused the push rod to break?

 

Probably just a flaw in the metal it was made from.