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Engine SwapEverything about swapping an engine into your Third Gen.....be it V6, V8, LTX/LSX, crate engine, etc. Pictures, questions, answers, and work logs.
We have an '89 RS with a sweet little 305 (all stock). She runs good, but we want more HP. My uncle gave us a 350 engine from 1996 Chevy truck. It is all stock with original Vortec heads; no intake. It is a little rough, but we are totally rebuilding it. Our goal is 400 hp. We need some help on this task and we have a lot of questions. He also gave us some cast heads (3970126), port and polished 2.02 int.-1.95 ex. Are these heads worth putting money into to rebuild or should I keep and rebuild the votecs or buy new heads?
Last edited by AKA Greg; May 13, 2017 at 07:10 AM.
Reason: Miss type
It is fairly easy to make 400Hp on Vortec heads with new springs. The 96-2000 vortec heads are the best iron head chevy ever made stock. Ditch the 126 heads they are not nearly as good, bring the others to a shop, have them checked for cracks and have screw in studs installed and good springs installed leave the valves the stock size.
Keep the cam roller maybe something like comps 12-432-8 and you will have a great machine.
We are doing a complete rebuild with new bearings, lifters, rebuild the heads, etc...I was going to install a 488 cam - then have the cylinders bored over .030.
Can you post a link to the cam. Either way it will make more power with vortec heads vs the 126 heads. Make sure you get proper pistons not crapper re builder pistons that sit too low.
Grab an RPM performer or Air gap or clone of either one if you are going carbed.
It is fairly easy to make 400Hp on Vortec heads with new springs. The 96-2000 vortec heads are the best iron head chevy ever made stock. Ditch the 126 heads they are not nearly as good, bring the others to a shop, have them checked for cracks and have screw in studs installed and good springs installed leave the valves the stock size.
Keep the cam roller maybe something like comps 12-432-8 and you will have a great machine.
Thanks! We want to go 400-425 HP and I been hearing the same...dump the old 126 cast heads. Do you think .030 over bore is good or should we go .060?
We are not using anything from the 305. All new or rebuilt.
Can you post a link to the cam. Either way it will make more power with vortec heads vs the 126 heads. Make sure you get proper pistons not crapper re builder pistons that sit too low.
Grab an RPM performer or Air gap or clone of either one if you are going carbed.
This is the cam we were looking at...but not into it far enough. I will get better informed from guys like you before I buy the kit.
Can you post a link to the cam. Either way it will make more power with vortec heads vs the 126 heads. Make sure you get proper pistons not crapper re builder pistons that sit too low.
Grab an RPM performer or Air gap or clone of either one if you are going carbed.
Thanks! We want to go 400-425 HP and I been hearing the same...dump the old 126 cast heads. Do you think .030 over bore is good or should we go .060?
We are not using anything from the 305. All new or rebuilt.
Stay 30 it is safer. Besides the vortec heads will make way more difference than 5cuin
Think of it this way stock 170CC vorted heads flow better than some of the older large port bowtie "performance" heads. They can support 400hp with zero porting or valve changes.
Stay 30 it is safer. Besides the vortec heads will make way more difference than 5cuin
Think of it this way stock 170CC vorted heads flow better than some of the older large port bowtie "performance" heads. They can support 400hp with zero porting or valve changes.
Thanks midias! We are going to get the Votec Heads reconditioned, add a 282hr CAM, bore it out .030 and get a good RPM Performer Intake.
~What kind of pistons and ring set should I look for?
Great! I need the set (with lifters). Wow, you guys are helping me a lot. We will have an awesome machine when we're done. My 20 yr old son and I are building this engine together.
You want a set of pistons with a 1.56 compression height not a 1.54 Shoot for a 9.5:1 compression and it should help you stay away from other issues.
Here is a calculator.
You can get lifter kits from comp but you may be able to reuse yours. Give comp a call I am sure they have a kit. Make sure to tell them it is not a retrofit
Make sure those are actually vortec heads. Vortecs didn't come until 1996, so they would have to had swapped them over if that block is a 92.
I made about 420 hp with my vortec setup. Vortec heads, with beehives and a comp 280xfi/hr, on a low compression l98 factory block.
86mph in the 1/8 with a 3524lb car.
I was told it was a 92 engine...I am checking the block number tonight. The engine might be a mid to late 90's. You're right about the Vortec heads though...1996 and up. Thanks for your input. We are just getting started and I am not made of $ so, this will take a year or so to complete. Thanks irocman7!
I was told it was a 92 engine...I am checking the block number tonight. The engine might be a mid to late 90's. You're right about the Vortec heads though...1996 and up. Thanks for your input. We are just getting started and I am not made of $ so, this will take a year or so to complete. Thanks irocman7!
No problem, love helping and seeing how other people do with similar setups. There are quite a few vortec guys on here. Nothin better than cheap power.
The block casting number should be 10243880. Also known as the 880's.
I am now running an 880 4 bolt main 383. Good motors.
You want a set of pistons with a 1.56 compression height not a 1.54 Shoot for a 9.5:1 compression and it should help you stay away from other issues.
Here is a calculator.
You can get lifter kits from comp but you may be able to reuse yours. Give comp a call I am sure they have a kit. Make sure to tell them it is not a retrofit
We are starting to pull the heads this weekend (hopefully). I will see what needs replaced and what can be used from this engine. The original owner of the engine replaced it due to a tick inside somewhere. We won't know until we start taring into it. It is still cold here in Ohio, but when it warms up my son and I are jumping into it.
Last edited by AKA Greg; Mar 17, 2017 at 11:51 AM.
Totally missed the 92 vortec engine thing. Definately get a head casting number. If its not a vortec head then you will need to reconsider this approach lol. Stock tbi heads likely will not support 400 hp
Totally missed the 92 vortec engine thing. Definately get a head casting number. If its not a vortec head then you will need to reconsider this approach lol. Stock tbi heads likely will not support 400 hp
Yep, checking the numbers on the heads and block tonight. Thanks guys.
We removed the heads today. Some forums say the heads I have shown here (10239906) are good and others say they should be replaced with new aluminum vortec heads to reach the 400 to 425 horsepower we are looking for.
We removed the heads today. Some forums say the heads I have shown here (10239906) are good and others say they should be replaced with new aluminum vortec heads to reach the 400 to 425 horsepower we are looking for.
That article was denunked a few years back, surprised its still floating around.. I'm running the 906s myself. Same flow numbers between all of them
Plan on upgrading the valve train, I went with beehive valve springs comp retainers, and arp screw in studs. It was less than 300 with the machine work.
All the ones I have seen cracked, were cracked right in the middle between the two water jackets. When you pop those off clean that area with a wire brush and check.
That article was denunked a few years back, surprised its still floating around.. I'm running the 906s myself. Same flow numbers between all of them
Plan on upgrading the valve train, I went with beehive valve springs comp retainers, and arp screw in studs. It was less than 300 with the machine work.
All the ones I have seen cracked, were cracked right in the middle between the two water jackets. When you pop those off clean that area with a wire brush and check.
I am taking these 902 to be machined, valves and springs, replace the pressed studs with threaded, and the deck skim cut. Also having the cylinders bored .03 over. Thanks for clearing that up for me.
It is fairly easy to make 400Hp on Vortec heads with new springs. The 96-2000 vortec heads are the best iron head chevy ever made stock. Ditch the 126 heads they are not nearly as good, bring the others to a shop, have them checked for cracks and have screw in studs installed and good springs installed leave the valves the stock size.
Keep the cam roller maybe something like comps 12-432-8 and you will have a great machine.
From what I have been reading as I research the vortec heads, the comp 12-432-8 will not work. It has too much lift. With new beehive springs on the 906 vortec I will only have .5 lift, so .47 intake (gives .030 clearance). I would need a different cam for this head...right?
I found a good price on a 383 Stroker Kit. We are getting the short block overhauled to be a 383. But 1st the heads are off to the machine shop to be checked and machined.
Awesome. I hope she runs and sounds great for you. We've hit a wall for now...summer is near and cruise ins and shows are the plan for a few months. We will get back into it later this year. Now it's time to drive.
This is the 383 stroker kit we want to install. We have to modify the block to add clearance for the bigger stroke.
If you go with 383 stroker kit then your 400hp goal will be a bit easier. xe282h or even a xe272 cam, a 750cfm carb, performer rpm intake, and if you can work those heads a bit.
Personally I think a 272 cam would be fine for you if your are not all out drag racing the car. A 282 is pretty big and really moves your tq range arround and pushes that peak rpm up alot. I suppose it also goes into play what rear end gears you have and trans(tq converter stall)...exc. Now saying that, I wish the PO that had my engine before put a larger cam into it.... the xe268 is way too small for me personally when drag racing. If you do go with a xe282 then make sure to keep the compression ratio static at 10:1 or more. It will really help with a cam that size.
Personally i have a 385, 11.1:1 compression, eagle rotating assembly, 750 cfm carb, 1.6 roller t rockers, xe268 cam, Dart Iron heads 200/80 cc runners 23* and make 12.10 passes at 110mph so about 400hp or a touch more. I know you are trying to stay a bit lower compression wise. 10:1 would be about right for you if you plan to drive it around alot and retain iron vortec heads. Just run 93 octane if its available .
Last edited by fasteddi; May 18, 2017 at 05:08 PM.
Thanks fasteddi. I will keep this in mind. I appreciate all of the info I am getting from all of the veteran motor heads. This is the biggest undertaking we have attempted, but will be worth it when we finish.
