My friend ODB did this conversion to a set of 305 heads for me to use on my engine. He said it was okay to share this information. He got the stock LS1 valves for free (take offs) and paid $40 for the 1.7 ratio roller rockers. It cost approx $200 to get new 8mm guides pressed in and the seats re-cut for the bigger valves. He says my cam will give me .570"+ lift with LS1 rockers and the valve-train will be very much lighter.
I put up some pictures of the conversion on my site.
I can't wait to see how these run!

My SITE

 

Thats a cool idea that I've never seen before. What it lacks though is the technology in the Gen 3 Vortec/LS1 heads. It will probably run just like 305 heads with aftermarket rockers and valve springs, it was probably a bit cheaper though. As for being light, that will make your engine rev smoother but the small bore of a 305 and TPI is going to keep you from taking advantage of this light valvetrain at high rpm's. It's hard to build a good valvetrain for that price, I'd say it's a good call. Aren't the stock LS1 valves too big for the 305 combustion chamber?2.00 Intake,1.55 Exhuast?

 

Interesting.... Are you going to do some porting on the heads as well?

 

These heads have been ported twice already and are in process of getting ported a 3rd time to match the bigger valves. Yes the valves fit just fine with no problem at all.

 

I would think the 1.7 ratio would require larger valve covers, and the 1.7 rr's are a tad expensive arent they? Very good idea, but it might be cheaper just to go with 1.6 ratio for regular gen I small blocks, but 10 thumbs up for the enginuity of it!

 

thats the beauty of take offs.

some guy swapps valves or rockers in his LS1, and his old ones are cheap...


or the part new from GM may be cheaper then a aftermarket one.... in this case i donno if thats true, but its possible.

 

That looks like a awesome conversion, I didn't think anything from an ls1 would swap over to a gen 1 smallblock. One question though, on your site it says you have a 5.7, wouldn't those 305 heads put your compression ratio through the roof? Or is that what you're going for?

 

Not really.... the corvette uses aluminum heads that have the same 58cc chamber as teh LB9 heads have. It would be a cheap way of making more power.

 

True but vette heads are aluminum aren't they? I don't think you could run that much compression with cast iron.

 

The aluminum will disapate heat better, and will alow for a higher compresion ratio... but I dont think the CR is high enuff to worry about knock.

 

I'm told that my compression will be around 10.5 and some minor modifications to the engine cooling system will be needed to run it on pump gas. So yes that's what I'm going for right now until I can get me a set of aluminum canfield heads and build another engine.

 

thats cool i never thought of that (both the 305 heads and the ls1 valvestrain) i wish i would thought of that

 

nice on the 1.7 rr's...

i'm still working on mating a ls1 intake to gen 1 heads....

 

yes, 305 heads are fine. there are a few guys on here who keep saying otherwise but, fact is they are ok, on a 350. you just need to run 93 oct. and have a good con. cooling system nothing special. I ran 305 heads on my old 350 l98 still have the 350 and there are no problems with it the 400 was just a deal I could not pass on

 

Why would you wanna do that? The intake is the single most restrictive part on an LS1.

 

I think he was being sarcastic

Thats a great idea, putting the 1.7 rockers on there... but how well do the valve covers fit over? I know that if you put BBC rockers (also 1.7) on a sbc head, you have to beat out the stamped abc valve covers so the rockers don't hit them.

Do normal sbc valve covers fit well with those rockers?

 

Pretty cool. Have you actually ran that yet? Be interesting what kind of gains it gives. ODB eh....surprised this hasn't started a flame war.

 

It's not running yet because the heads are still getting worked on. Today the EGR holes in the exhaust ports got welded up and more porting has to be done. I tried a stock valvecover on one today and it fits fine. These 305 heads are older and can't use the centerbolt covers that my 89 came with, so I'm not using the 89 covers.

 

Here's a picture of the filled EGR holes. I'm happy with how they came out. Now they just have to be re-ported and some holes epoxied in and I can run them.

 

how much money have you spent on this??

 

yeah i think he was being sarcastic too...

but while yes the LS1 intake might be the most restrictive part of an LS1 intake... that restriction still is at around 260 cfm!!!

 

260 cfm might be a lot, but it's horrible when my heads flow very close to 300 cfm. I still don't see why you would go through all that trouble to put on ls1 rockers when they don't even have roller tips. Why not just get a set of fuller roller comps or similar?

 

LS6 manifolds flow about 275 cfm and that is the intake alone... i haven't seen any studies of people flowing the intake when matched to the heads... but a lot of those cars are running just fine w/ heads flowing 300 and an intake that flow 275...

 

No doubt, and my heads/cam LS1 is one of them, but would it run even better with a better intake manifold? Yes. Does it run better with my yella terras? Yes. It would have been a whole lot easier and you would get more performance out of a set of fuller roller rockers made for the gen 1 block. Just my opinion, what do I know.

 

i am not disagreeing w/ you on the whole LS1 intake restriction. yes they desperately need to come up w/ an itake that will flow for the LS1s that isn't on a "race only" level. i know there are guys making the sheet metal intakes and that is great, and worth about 40 hp up near 7K rpm, and that is great but that is absolutely worthless on a street car.

i also agree that it would be better to get a set of the full roller rockers for the Gen 1s than just using the stocker LS1 rockers...

 

I think it's around $500 in parts. It would've been cheaper but my cam has .503 lift and .570 lift with 1.7 rockers, so I had to buy new springs to keep them from binding and still have enough seat pressure.

 

thats amazing

 

Verry interesting. 2thumbs up for doing somethign Diff.

not to get off topic but did you ever get the injectors problems fixed befor the tear down?

 

Thanks
and NO I didn't, but I've ordered a new set from SLP. I think they are supposed to be 25 lb for LS1 cars.

 

So the 1.7 ratio roller rockers are from an LS1?

Since you're using guide plates, I'm guessing these rockers are non-self aligning, is that true?

Anyone have an idea if these would be fine for a stock cam in a '91 GTA if I replaced the springs or would I have to pull the head to check clearances?