Don't laugh, but I'm about to ask a question that is going to show my ignorance when it comes to GM engines.

I need to replace the valve guide seals in my '84 Z 28. It's been sitting for a very long time and burns a little oil when you start it and if you set at idle for a while. It doesn't increase when warm and doesn't do it when you're driving. The mechanic told me that's what he believed it to be, and that's what I thought as well.

Anyhow, I was thinking of adding some aftermarket heads, or some that have been ported and polished. I can picked them up several places no problem.....


My engine work experience is very limited, only on high-performance VW's. The displacement of one engine and the next is either changed by crank stroke of bore of the cylinders, usually the bore of the cylinders, it's cheaper.

With this v8, is mine a 305 instead of a 350 because of bore, or stroke or both. If it's because of bore, how can they sell heads that are for all "Small Block Chevy's" of certain years?

I know the answer has to be simple, but before I go drop a load of dough somewhere, I want to be sure.

Thanks for you help, and hope you've enjoyed a good laugh.

 

The don't sell heads "for all small block chevys" If you look at World Products they sell regular heads and 305 heads. A 305 isn't a performance engine with it's small bore. You need 305 specific heads or 4" bore heads with small valves. Most aftermarket SBC heads are designed for 4" and larger bores since a large bore engine builds HP better than a small bore.

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Follow my racing progress on Stephen's racing page
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87 IROC-Z Pro ET Bracket Race Car
383 stroker (carbed) with double hump cast iron heads and pump gas
454 Big Block almost ready for the 2001 racing season

Best results before the 383 blew up
Best ET on a time slip: 11.857 altitude corrected to 11.163
Best MPH on a time slip: 117.87 altitude corrected to 126.10
Altitude corrected rear wheel HP based on power to weight ratio: 476.5
Best 60 foot: 1.662

Racing at 3500 feet elevation but most race days it's over 5000 feet density altitude!
Member of the Calgary Drag Racing Association

87 IROC bracket car, 91 454SS daily driver, 95 Homebuilt Harley

 

To elaborate on Stephen's answer, any heads will fit. That is, they all have the same bolt pattern and stuff like that. But just becasue they fit doesn't mean that they're all the same. Like he said, the 305 was not originally designed as a performance motor; it was a hurry-up retrofit that GM did in the late 70s to meet the CAFE requirements that they couldn't get close to with the pig 350s of the day. Unfortunately it stuck around way too long. Just because it wasn't originally intended for performance doesn't mean that it can't be made to run pretty good though; with the proper choice of heads and cam and intake, it can produce close to the same torque per cubic inch as a 350. IMHO since you will spend more geting a 305 to approach that condition that condition than a 350 core will cost, and the 350 will already out-power the 305, anything beyond external bolt-ons for a 305 is economically inefficient. I hate being economically inefficient, especially when it's my own money.

Thin about what I just said: same torque per cubic inch. Hmmmm... that means I can spend $1000 to get 1 ft-lb per inch out of the 305, or 305 ft-lbs; or I can spend $1000 to get 1 ft-lb per cubic inch out of the 350, or 350 ft-lbs. Hmmmmm..... I'm struggling here, I need to consult my financial adviser I think...

Don't waste your money on trying to upgrade the 305 to that extent. Change the valve guide seals, which costs about $25 and 3 hours, that's definitely worthwhile. Your mechanic's diagnosis is probably correct, as it is a very typical thing that these engines need. Then if you really want more motor, look around for a 350, and sink your money there; each buck gives you alot more results when spent on a 350 than on a 305.

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"So many Mustangs, so little time..."

 

If you keep your 305 you don't need new heads, only bigger intake valves and a new cam. If you look at the buildups
http://www.hioutput.com/tech.html
http://members.nbci.com/_XMCM/scauff...ne_buildup.htm

you will see that you can get up to three or four hundred horsepower naturally aspirated. When you have the mechanic replace you seals, have him put in bigger intake valves while he's at it. Then later you can put in that cam and you'll be set.

 

Not worth it! either put the vortecs on like in the article with the new intake and cam or screw it all and get a 350......Do not waste time modifying dogsh*t 305 heads when for 430 bucks you can get a set of vortecs that only need to be milled and dropped right on. As a side note, you can keep the vortecs and the intake if you decide to put it on your 305 and put them on a 350 later down the road when you feel like it.

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91 RS W/carbed 350, Vortec heads, performer rpm, Comp cams Xtreme energy 226/230 duration and .477/.480 lift. BFG Drag radials. 3.42 posi,Corvette servoed 700r4, ****ty stock converter. Edelbrock TES, 3inch cat, flowmaster with single 2.5 inch exit.
13.24@104

 

Thanks alot for the input. I am going to buy a couple of books and educate myself a little further. I may just do like the last reply and pick up a set of vortec heads, slap them on and run the 305 until it dies. Then I'll up-grade.

Thanks again.

 

Just to be clear, you do not have to remove the heads to do these seals (but you do have to remove them to change the valves). If that is your only problem, then changing to Vortec heads is bound to bring you a bunch of problems - starting with the need to buy a different intake manifold, then going to having them shaved to keep your compression up, needing to shave the intake to make it seal properly, needing self-aligning rockers, etc., etc., etc. Not that the problems aren't insurmountable, but changing the heads to Vortecs just for a little smoke at startup doesn't make sense.

The seal replacement job may take a little more than the 3 hrs it takes RB, but if you're better at VW's than SBC's, the seal replacement would be a better way to get your hands dirty than a 305 Vortec conversion would be. In my opinion, anyway.

If you're going to replace the heads, then go with the World Products S/R 305's - cheaper than the ultimate cost of Vortecs.

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R. 2.93 limited slip. Cat-back from '91 GTA, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LB9 w/ZZ3 cam, TBD heads, exhaust, paint, etc.).
57 Bel Air, my 1st car. 0.030 over 396, Weiand Action+, Edelbrock 1901 Q-Jet, Jacobs Omnipack, 1-3/4" headers, TH400 w/TCI Sat Night Special conv & shift kit, 3.08 10-bolt, AMSOIL syn lubes bumper-to-bumper. Best 15.1 @ 5800' Bandimere. Daily driver while Camaro was being put together.

 

Yep, figure about 450-475 for the vortecs to your door, $200 for an intake(they use a decicated intake with taller / narrow runners), $125 or so to have them milled, $50 in new gaskets and another $200-400 for custom calibration for the computer because you just totaly changed the airflow characteristics of your motor... that is if you want to see any improvement from the extra airflow. To do it right, its a bunch more than $435 to "just slap a pair of vortecs on"