I should be getting a 383 with a cc306. 9.5 compression with a 64cc head. Im looking at the Dart Pro 1 heads with 230cc intake runners they flow 307/207 at 700 lift. Here they are on ebay http://cgi.ebay.com/ebaymotors/ws/eB...931065409&rd=1 . Are these heads too big for a 383? Should I go with something smaller like a 215cc runner? What about with 200 shot of nitro?

For those wondering I can convert this head to fit on a LT1.

 

9.5:1 with a 306 will be a dog. You should be thinking more in the 11:1 range.

Rich

 

Sounds like a real mismatch in parts.... the intake runner is way too big and is going to kill the bottom end performance, the cam is "mild" for a 383, and the lift isn't anywhere near enough to support heads that flow well at 0.700" lift. And as Rich mentioned, there is not reason to drop your compression ratio. The heads might not be that great for nitrous, since the exhaust flows less than 70% of the intake. You can get similar flow numbers out of LT4 heads, and end up with much smaller intake runner volume.

 

Ok so a 230cc runner is too big. But I can also get these heads in 215cc runner with 64cc chamber that can be milled some to achieve a smaller chamber for compression about lower 10's. I can also opt for cam bigger like 246/246 600/600 111LS (just pulled it out of my head) Here is the 215cc runner head http://cgi.ebay.com/ebaymotors/ws/eB...930072719&rd=1 I dont know what these flow but I should be able to find out. I can also port out the exaust if they are split so badly for nitro. But will these heads be good all around for street n/a and nitro at the track?

I also have plenty of time before I start this project so no rush

 

Agree! It's one of those combos that sounds way off.

What intake do you plan to use? A big advantage to Gen I heads is the choice of intakes, but the choices will be adapting the LTx intake or converting a Gen I. The former isn't too difficult, but negates a lot of the advantage of going Gen I. The latter is do-able, but somewhat involved and necessitates either a carb conversion, some major work with the stock PCM, or a new engine management system. It adds up to time, money, and frustration.

I am still of the opinion that unless you can do all the work yourself and enjoy wrenching and problem solving as much as driving that a Gen I head on a 4th gen LT1 is not a logical swap. Either go all the way and swap in a complete Gen I or stick with an LT1 head.

Rich

 

If this is an LT1 Block that these are going onto , wouldnt the LT4s ported make the parts fit and availability better? After you dump the money in the Pro 1 heads to convert them to an LT1 youre close to a very nice ported set of LT4s.

More compression, the LT4 heads come with a smaller chamber and will boost the compression up closer to the 11:1 mark.

I'd go with a more 383 specific cam. I like my GM 847 but I'm leaving alot on the table there.

 

It is a LT1 gen 2 motor that I will be using. I was plaing on using the lt1 intake (whats that lt4 intake in Summit that says its compatable with lt1 heads?) Because it will be a lot cheaper to stay with what I already have. Sure ive looked at the gen 1 intake design and it looks much better but affordablilty comes into play. I also looked into the L98 intakes but saw it was not really good for much past 5500 rpm.

The reason why i dont go with a lt4 head is because of cost. The lt4 kit cost a little over 2 grand. When these heads only cost 1000. I would do everything needed to convert them to the LT1 block myself. I also dont like going with a lower compression but these heads only come in 64cc chambers. What I can do is get the impala head gasket and shave the heads a little to make that up somewhat.

Oh yea I love wrenching around. Me and Black_95Formula are just finishing a 383 swap. Now im in the process of taking a transmission out of a 2000 Grand prix ( has to come out the bottem with motor and k-member at once), I have ported heads rebuilt manual trans. Basically what I am trying to say I have no prob wrenching around into some serious work like this.

 

I don't know if the LT1 or the LT4 intake matches up better with the Dart heads. In either case, I am sure you will need to do some porting and perhaps welding to match the ports. The intake will need to be modified to bolt up to the heads as well.

If you can port heads, why not buy a set of LT1 heads (usually in the $250-300 range) and port them yourself?

Rich

 

I do have a set of LT1 heads I ported out with stock valves in the basement. In Mass there is only expensive machine work. Nearly 400 to get bigger valves. Get this, 600 to bore a block .030 over. Black_95Formula paid 1550 to have his 383 kit installed in his block (we even brought him the block and took it back to avoid any shipping costs). Its just plain rape around here. I dont justify putting money into heads that will only flow a max of 270-280 (If im that good, doubt it) The pro 1's should be around 300 cfm at .600 ported a little I hope.

I also thought it was not a good idea to use ported LT1's heads with a 383 since the runner are too small. Especially with a 200 shot. Do you think ported lt1 heads will be able to support this?

To match a gen 1 head to gen 2 block I think that all that needs to be done is drill and tap at the back of the head for coolant crossover, port out the coolant passages on deck side. fill in (weld in) the coolant passages on the intake side. Port match intake to head and drill new bolt holes to match head. Im pretty sure the intake runners on the head and intake will match up nicly with some porting.

 

Holy Cow!!!

My machineshop bill for my 383, was 900$ and that included the machinework to the heads, and the rings and bearings ( they get good prices)

I had everything hot tanked , including all my accessory bolts and barackets.
They balanced my assembly and even did some mods to the crank (nitriding the journals), they painted my lifter valley for me after enlarging the drainback holes at the back, all freeze plugs and cam bearings installed and purchased,they offered to assemble it for me for another 150, but I can do that easily enough.