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I bought my first corvette, a 1985 C4, back in 2013. Paid way too much for it, then spent way too much trying to get the 105,000 mile L98 running correctly. After replacing all the sensors, computer, cleaning injectors and throttle body, new radiator and water pump, it was running but with a solid miss. Pulled off the valve covers and found the #8 cylinder with an exhaust valve stuck open. Pulled the heads and installed a used set of World Products heads I had laying around, and finally had a good running car. Built my own custom exhaust with 40 series mufflers and a set of dual tips from the e store. Car sat for a couple years, then the alternator crapped out and messed up the digital dash. Since the interior is shot and the body needs a good paint job, I was stuck with either parting it out to get a small portion of my investment back, or do the swap and restore the car. I decided on the swap. I was able to fix the dash with a new power supply and new film on the LCD displays so that sealed the deal. Picked up a 113,000 mile LQ4, a 4L60E with unknown miles, and decided on the Holley Terminator X Max fuel management system with trans control. The plan is to rebuild the engine by breaking the glaze on the cylinders and reuse the pistons, rods and crank with new rings and bearings. Everything looked real nice when I broke it down, no cylinder ridge and still has some cross hatch left. I plan to run a 400 grit ball hone through the cylinders, then clean and paint the block and put it back together using rebuilt 706 heads. There is an article out on the webs of an LQ4 making 480hp with 473lb/ft with these heads, and streetable torque with my horsepower goal should make a great weekend warrior. I'm very undecided on the cam, being only familiar with the Gen 1 Chevy and Pontiac engines. I'd like to make 450 hp. I also plan on using the adapter that lets you attach the original tail shaft to the 4L60E, although its fairly expensive. Here are some pics of the project.
This is my first time posting anywhere about any project so bear with me. I have over 20+ years experience building on cars, mostly Firebirds and Trans Ams. However, I have never messed with anything fuel injected/computer controlled, but that doesn't mean I won't give it a shot. I've always loved the look of a C4, and jumped on this one. I understand the 85's are set up as a mostly stand alone computer system, so that will help with the switch to the Holley system. I have a fair amount of electrical experience and skill (dad was an electrical engineer) and can weld, do body work and paint. Here is a pic of my 81 Trans Am that I did a frame off restoration and installed a 383 with Vortec heads. I went 13.3 at 105mph at the local track, and that was on street tires spinning through the 60ft mark.
Anyway, thanks for looking at my post. I will be adding more info/pics as I go. Any suggestions/comments are much appreciated. I've been looking at a couple other build threads and hope to learn from them and others, and share my experience as well as assist others with any questions.
Great thread thanks for sharing, I look forward to following your progress! Awesome to see anothee C4 LS swap happening . I'm sure your car is going to be fantastic when the swap's done.
Have you decided on a Cam and the other valvetrain parts?
I haven't decided on the cam but will probably go with a comp cams xfi type. Definitely going with heavier pushrods. I'll probably go with the stock rockers and do the trunnion upgrade.
I haven't decided on the cam but will probably go with a comp cams xfi type. Definitely going with heavier pushrods. I'll probably go with the stock rockers and do the trunnion upgrade.
Cool, look forward to seeing what you choose
Also don't forget to get some new valve spring too.
I am considering a cam with more duration and slightly more lift than the one in the article. Based on my experience with the early chevys and from what I've read on this and other forums, a 230 or more duration type cam would get me where I want to be. But I also understand that LS heads flow much better than the earlier style heads. That is where my questions lie.
Intakes are another question mark. There are setups on the e store that have a fabricated sheet metal intake with fuel rails and throttle body for about $500 but what kind of torque/hp can be expected from these Chinese knock offs? FAST intakes are stupid expensive. I hear that aluminum intakes can have a heat soak factor. Lots of questions and research.....
As far as springs i am looking at PAC 1219's. I have my heads in at D&D Machine here in Cincinnati getting cleaned and pressure checked. Once I get the green light it'll be new valves and the springs listed above. Should know more Wednesday on that.
One thing I am excited about is to install/utilize the Holley Terminator system. I've managed to set up an output for the speedometer on my laptop and will need to upload that to the ecm when the time comes. THAT is something I've never attempted. Cool stuff and can't wait to try!
I am considering a cam with more duration and slightly more lift than the one in the article. Based on my experience with the early chevys and from what I've read on this and other forums, a 230 or more duration type cam would get me where I want to be. But I also understand that LS heads flow much better than the earlier style heads. That is where my questions lie.
Intakes are another question mark. There are setups on the e store that have a fabricated sheet metal intake with fuel rails and throttle body for about $500 but what kind of torque/hp can be expected from these Chinese knock offs? FAST intakes are stupid expensive. I hear that aluminum intakes can have a heat soak factor. Lots of questions and research.....
230 duration as I understand it is sort of the line where you go from primarily street oriented to performance oriented. meaning 230 and under is more street use, once you get much over 230 your starting to get more into a track oriented cam. Most people seem to say a high 220's to low 230's duration is a good compromise.
As far as lift do you have a flow chart for the heads? Unless your going roller rockers I've heard you want to stick to .600 lift or less but if your heads get max flow at .550 lift then you only need that much, so a head flow chart is important in picking a cam. Additionally, the head flow chart will tell you how much split you need between intake and exhaust duration based on how much the intake and exhaust flow.
Of course the type of intake you pick will also have an effect on where you make your power. So i'd suggest planning out all the components so they work together to make power in the RPM band you choose. I had the same dilema as you regarding the intake. I'd shy away from the aluminum intakes because of heat soak, the sheet metal ones seemed to me like they are tuned for quite high rpm operation which was not ideal for me. There is a half decent Dorman LS2 intake avalible now that is better than an LS6 but not quite as good as a FAST. Its about $450. I ended up just watching ebay and found a Tony Mamo ported FAST 90 for $500, I was the only one that bid so I got it for the min bid price ($500). Of course there is also the option of LS3 heads and intake since you have a 4.00 bore. But with LQ4 pistons your conpression won't be all that great with LS3 stuff.
Once you have everything but the cam choosen out i'd suggest you send PAT.G an email and have him custom spec you a cam for your combo and intended use. He will also give you advice on valve springs for the cam he specs. It only costs $25 to get the specs ($40 for next day service). If you like the specs you can get it ground by TSP or cam motion.If you don't like them then you only lost $25.
Ya that'a a good article It was one I looked at a while back when I was deciding on what intake to get. Wish they had tested a FAST 90/92 like I have, but I imagine it is somewhere between the FAST 78 and FAST 102 for performance.
After reading the article are you leaning towards a particular intake?
Based on price and performance the speedmaster setup doesn't look bad, kind of a middle of the road in both fronts. I've been looking and the fast intakes are still too high to justify the price, even used ones are going for $600+. I'll give it some time and see if I run across a deal.
In the past on the older engines I've always gone with full roller rockers but havent seen much about using them on LS engines. The trunnion upgrade is about $145 and I've seen full rollers around $160. Anybody have info/thoughts on this?
Based on price and performance the speedmaster setup doesn't look bad, kind of a middle of the road in both fronts. I've been looking and the fast intakes are still too high to justify the price, even used ones are going for $600+. I'll give it some time and see if I run across a deal.
In the past on the older engines I've always gone with full roller rockers but havent seen much about using them on LS engines. The trunnion upgrade is about $145 and I've seen full rollers around $160. Anybody have info/thoughts on this?
It sort of depends on who you talk to but from my reading it seems most feel roller rockers add to much weight over the valve steam and a trunion upgrade is best up to .600 lift. if you need more than that TSP seems to have some nice formed steel roller tip rockers. Shy away from aluminum roller rockers as most say they are heavier and likely to experience metal fatigue. Also steer clean of the comp truniom upgrade, lots of people have had those fail.
I did the CHE bronze bushing trunions on my stock rockers seemed very nice quality and good reviews but I have not started the engine yet...
A 230 cam in a lq4 will put you at 450 easy so long as you have decent heads. You honestly could get away with a 224 and still probably be about there. But anyway. 230 is very doable. Even with a ls, 230 is a little on the rowdy side. Not bad, just fun lol.
I have a LQ9/700R 85 vette, FAST stand alone, ev6 LS3 injectors, speedmaster intake, 102mm throttle body, headers. I would install the LS2/LQ9 pistons (and since the engine is apart, LS2 pistons are cheap) and run the larger intake runner/intake valve 243/799/317 heads (210cc runner). The 706 heads will work fine (200cc runner)., I would also run the newer C4 rad support (slanted rad), so you can have a cleaner cold air set-up. My original dream was going to run a turbo, but not sure if its going to happen.
Hey my bad double post all that, but I found a cool build package from Texas Speed. Sounds really rowdy set-up. LS3 head, TSP stage 1 cam (225/236 .629/.615). I bet its at least 450HP
Thank you to everyone for the advice and info. And thank you Mike for sharing your car build. Looks nice! I'm considering the speedmaster as well for the intake. Looking at summit and comp cams at around the 230 duration mark and close to .600 lift. I may get a spec from Pat G as Dmittz suggested.
Looking at also changing the rear gears from the stock 2.xx to 3.23 or 3.42. Maybe even change the differential and cover to something more beefy. Will this help the D36 rear in terms of strength? I don't plan on using slicks but still don't want to blow out the rear end.
Last edited by banditt1979; Feb 29, 2020 at 02:19 PM.
I'd suggest using a gear ratio/ rpm/ speed calculator when choosing the rear gears so you can figure out good cruising rpm and shift points. Tremec has a good one on their website.
If your just cuising on the street, i'd think the D36 is ok. But since your going to swap gears anyway, it might be a good time to find a good used D44 with 3.45 gears. You may need a new driveshaft and D44 C beam though... Depends how your going to use the car and how much money you want to spend.
1985 C4 LQ4/4L60E conversion
. I'm sure your car is going to be fantastic when the swap's done.
