I've got a 91 corvette 6spd manual. Over the weekend it suffered the cylinder #7 head gasket failure so I'm getting ready to fix it. I figure though that while it's out I'll add on my headers and cam now while I'm in there. However, I'm not sure about fitment with the LT4 Hot cam kit (P/N 12480002). With 1.6 rocker arms would I need different length pushrods? I'm coming from a long line of DOHC cars and I'm not sure how to calculate out the finer details such as push rod length. To my understanding this kit is a compatible fit with no major modifications, however I'm wondering what else I need to add to my cart to fit the cam.

Thanks!

 

I've been running a hot cam with 1.6 roller rockers and stock length pushrods for almost 20 years, Works for me.

 

If you want to get your pushrod lengths juuuuuust right, you can buy an adjustable pushrod length checker tool at Summit for less than $20.

 

Every component has a tolerance. $20 is cheap to check.

 

You can really dial it in but chances are you'll find 7.2 (7.3? I forget stock length) gives the best sweep on the valve tip... I used no stock components on mine and was going to order what the head manufacturer reccomended... but did the check instead and it came back to exactly what length they called for. But it never hurts to check. The kit was designed to be a drop in by a guy or dealer... so I highly doubt they would be checking things that close. But it is the right thing to do.

 

Check with someone like Rklessdriver who builds engines..... But I dont believe it changes just with a rocker arm. The difference in the rocker 1.5 vs 1.6 is on the valve side of the pivot. I think the push rod side stays the same.
I can tell you, I ran 1.6 with no other change....
Also, in order to actually check it, in addition to an adjustable rod, you need a test spring. Much more involved then just a rod.

 

OP is talking about a Cam change as well, but only changing the rocker would not cause a change in push rod length...

As ​​​@84 4+3 said, it is designed as a drop in kit. I don't think you are goign to have a leght issue because if there was they would either include the push rods in the kit or the many that have installed this kit would probably have spread the word wide on the internet about what they needed to complete the install.

Still, having the items around to check is cheap insurance again a catastrophic failure causing you to have to redo the job.

 

I used the adj. checker myself but I have a '96 LT4 to begin with before HOT cam so not sure of the same distance as LT1. Agree you need to observe witness mark on top of valve stem with adj. checker to be sure valve not pushing sideways and wearing guide. Not difficult and then you can order exact length needed.

 

I went with the stock push rods on my 95 but we did replace all of the lifters. Also went with the HD timing chain & sprocket kit.

 

After about 40k miles I had occassion to inspect the lt4 extreme duty chain. No apparent slack from any wear.
None!

 

One advantage of getting aftermarket pushrods, even if they end up being the same length, is stiffness. The stock LT1 pushrods on the impalas were kind of flexible. I don't remember anyone having catastrophic engine damage from stock pushrods, but we did note that guys who used stiffer pushrods with moderate cams (like the HOT cam) tended to make 10-15 more hp on the dyno. We always assumed this was from better valve train control.

 

As has been said on here if you are changing the rocker arms to a different style/brand there is a good chance you will need to change the pushrods to match. I just did LT4 kit on mine and I had to go shorter on my pushrods. 7.3 to 7.2. I used a sharpie on the top of 2 valves and rolled it through a few times and it showed me where it was lining up. There are a few videos on it out there on the web. I followed the summit one. A rod length checker would be a good investment. Even if its a one time use its worth it.

 

You can get a better quality Lunati kit, including pushrods, with a custom grind cam from Lloyd Elliot for comparable cost.

 

I did just that, Lloyd Elliot cam, Lunati springs, studs, VooDoo adjustable guided roller rockers. I can't vouch for it being less expensive (it wasn't) because I had to purchase different shims, retainers, pushrods, valve covers (VooDoo rockers were hitting the stock composite valve covers), to get everything on my stock LT4 aligned properly.
But my car really hauls the goods compared to stock. And Lloyd Elliot is a great, knowledgeable person who will try and help you if you end up having any issues.

 

out of curiosity, what valve covers did you get?

 

I purchased the Canton 65-208 covers. They are nicely built covers but it required a bit of work to fit correctly. The covers gave me the clearance I needed for the VooDoo adjustable roller rocker arms.
-I removed the air injection because the passenger side tubing is in the way of the taller valve cover. I fabricated a small block off plate to cover the air injection port on the back of my intake manifold. Also I needed to remove the air injection trouble code reporting from my PCM with my JET tuner. (I was going to fabricate new longer stainless steel tubing and bend the tubing to clear the valve covers but it seemed like too much work and I don't have to worry about emissions testing).
-I had to grind some material on the alternator housing to clear the valve cover on the driver's side.
-I needed to fabricate a new bracket that goes from the intake manifold to the back of the alternator and AC compressor.
-I plumbed a hose from the breather port on the throttle body (passenger side) to the driver's side valve cover because Canton relocated the hole on the driver's side valve cover.
-The plastic Corvette fuel injector rail covers won't fit because the Canton covers are taller than stock. I bought some threaded rod (to replace the stock mounting studs for the plastic covers) and cut them to the appropriate length to make those covers work again.

 

I think I bought OP's 1991

Attached service history document shows headgasket repair and LT4 hot cam kit install in September of 2020

Car also has things like cut air filter lid and K&N filter that indicate previous owner knew how to Google.