what would happen if i put l98 heads on my 305??

 

You will lose compression and flow on the exhaust side. Leave your stock heads alone. They can support nearly 300hp. Your car has other bottnecks that need to be addressed first (exhaust, cam, fuel, tuning).

 

cast L-98 heads have 64cc combustion chambers. So if you're replacing 58cc 305 heads with 64cc heads your compression ratio will be lower.

L98 aluminum heads have 58cc chambers so your cr will remain the same.

if you're using cast L98 heads and want to maintain the compression ratio, mill the heads to get 58cc chambers (about .030 to.040")

if the head gasket is thicker than the old stock one this will also lower the compression on your 305. Many replacement gaskets are thicker than the stock gasket.

You can use Felpro thin shim #1094 350 gaskets on your 305 with cast heads.
its .015" thick. Your cr will be about 1/2 a ratio higher then a typical .040" composite gasket.

Other than that they will work just fine. Which heads do you have?
Which (305) heads are you replacing?

 

...but isn't the chamber shrouded by the small 305 bore ??

 

Any head you bolt onto a small bore motor will be more shrouded than on a bigger bore. It will work fine.

 

They WILL shroud. The chambers are wider than the bore diameter

 

thus makeing them a bad choice ...no?

 

a 350 cylinder head is not 4" accross the chamber. the cahmber is much smalle r than a 350's bore. if it did hang over the 305's bore it would be minor.

Wether its the best choice all depends. thats why I asked the poster what he was replaceing. If he has a good L98 head ready to bolt on his 305 it may be a good deal. reguardless it will bolt on a work fine as far as the chamber/bore is concerned.

 

swirl port heads cant handle anywere near 300hp also im going to do heads,cam,carb ect.. at the same time.

if i get them milled .030 to.040" would it be about the same compressoin i have now??

im not set on l98 heads or anything im just seeing what my options are

 

What proof do you have?

187 (305) swirl port heads flow 165 on the intake which by using David Vizzard's hp calculator these heads can reach 288fwhp. When ported much higher numbers are seen.

2.0*165*305/350 = 288 fwhp

Using Vizard's estimate for power potential based on head flow, and equated to a v8 305.


TBI and TPI head flow data


As an example to back Vizard,

Dwewey316 made almost 300hp on stock untouched heads. His back to back dyno runs of stock 187 heads vs ported 416's dissproved a lot of hearsay on TGO. Refer to this thread to see how "worthless" these heads really are. Note how the SP heads embarrased the claimed "better" (and ported no less) 416 heads under 4500 rpm. Had the SP heads been ported like the 416 test subjects the power difference above that rpm point would have been reduced greatly.

We like these heads now

Fast355 also has many 300+ hp motors that run swirl port heads. A few searches will teach you a lot.

Garage Ported 193's

TGO needs to stop the hand waving claims that TBI heads are terrible. Hearsay is the plague on this site. Facts, dyno data, and track times tell all.

Have you flowed a set of swirl port heads? I have and the math doesn't lie.

 

shifty you just have to know every thing about l03s

if my heads where ported and all that do you think i could make as much power is i would with just stock l98/601 ect.. and are casting #'s on l98 heads 083?

 

Casting numbers for L98's are indeed 083's. Fast355 has made 350hp on ported 305 SP heads and has run a best of 15.5 in a TBI 5500lb van. If that motor were to be placed in a 3rd gen he would have no doubt been deep into the 13's.

We have to remember that no Gen I head was considered a performance head. That didn't appear until the Gen II two heads arrived.

TPI and TBI heads are basically in the same league as far as "potential power" is concerned.

Chip tuning is the weak link of TBI vehicles. The heads are not. We are only seeing this now that competent tuners truly expose the weak links of these cars. Stay tuned to my SP head project.

 

if you want to go fast with your 305, please click on the link in my sig. the 416 casting heads are pretty much the cats meow when it comes to stock 305 heads that do well. 3angle valve job and a back cut on the stock valves will prove to be worth a TON of flow.

 

If you can find some 305 heads with casting number 14022601 USED IN CARS AND TRUCKS FROM 1980 TO 1986 you can bump your compression even more on your 305 to up to 10.2. One catch though. These heads come with 1.84intake 1.5 exhaust. I've recently recieved my heads from the machine shop, now they have 1.94 int 1.50 ex stainless steel valves

I'm taking them to get ported by another shop that's going to charge me $250 dollars to port and polish them to 195cc intake runner includes flow benching them as well


Eric...