Hey Everyone.

Ive read alot about LT1 cams in the TBI engine, but havnt read much about them in a TPI Engine.

Ive got a LT1 cam *.447 lift), and ( i think) the mechanical ability to get it in.

The swap is underway at the moment, and the engine is stripped down as i await cam lube to put the new cam in.

How my question is regarding What difference this will make, and what need to be changed.

I am planning on putting these in the car with the swap:
Summit 1.6 Roller Rockers
BBK AFPR
Fel-Pro Gaskets
LT1 Lifters (already have these)
Air Foil

My question is regarding my Max. Lift with stock 081 heads and valve springs.

Whats the max. lift these heads will take? (aft.market valve springs)
Whats the max. lift these heads will take with stock springs?

Would you reccomend changing the springs? My engine has 140 000miles, but a main brearing was spun at 100k and the bottom end is fresh.

I know people tell me it isnt worth putting much into this engine, but im looking for a quick reliable engine.

One last question:
Is it worth it to pull the heads off to change the valve springs and clean up the heads if the engine is apart?
The engine is still in the car at the moment, but is basically bolted to tranny and mounts, as the rest has been taken apart.
Keeping in mind in a 16 year old with a tight budget, but i know i can afford the parts ive picked out.

Thanks for the help.

Sheldon

 

It will definetly be worth pulling the heads to clean them up. Run a thim shim head gasket when you reinstall them. Bolts, gaskets, new springs (just get the generic .550 lift Z28 springs they're on eBay and other places cheap), and bits for porting/cleaning the heads will be a great investment. You should also look into porting the base. If you need any advice on it just post up or search. You will probably need to feed the car more fuel pressure and perhaps a little more base timing with the new cam and ported heads. Good luck on it.

 

I did the LT1 cam into a LB9 a while back.
Everything worked out great.
I didn't do the 1.6 rockers, so I can't tell you if there will be a spring binding problem.
It was a very worth while swap for me since I had a lobe come apart on the original cam.

 

Your total lift with the 1.6 rockers will be .477, I would recommend the steel 1.6 roller tip rockers as opposed to the Summit aluminum body rockers for a daily driver and this will save you some money.

 

So i probably cant get away with 1.6 rockers without the springs binding?

Thanks,

Sheldon

 

They won't bind but the stockers will be close. Those stock springs are probably to weak to handle the new cam anyhow and should definetly be changed. I believe stock springs will bind at .480 but the real issue is that they have very little seat pressure (I believe 70 lbs) and for how cheap upgrades are I'de definetly go with a new set.

 

If you're at 140K on the motor, springs should be your first thought ahead of a cam. If you're going to cam the motor port your intake too so you'll get the most out of it. Easy power since it's off and you're gonna have to change gaskets anyways.

 

I put in the xe258hr cam(Bigger than the LT1 cam)
It has .480/.487 lift. The stock springs worked until I put on 1.6 roller rockers.
That elevated the lift to .512/.519. Then I had to switch to the comp spring(part#981-16), the stock springs started to float at about 4800rpm

 

.470-.480” lift is usually right around where you nee dot actually check things with stock springs/hardware. That is assuming that it’s in good shape… you really don’t want to use borderline hardware with 140K miles. So the answer to that is replace them with a decent spring kit.

Past that, I have to ask, why? LT1 and TPI cams tend to have slightly different numbers but for the most part are very similar. The biggest difference is that the LT1’s used a greater LSA (117*), which would tend to give a slightly flatter power band where the tighter LSA/greater overlap of the TPI version will give you a fatter midrange, where its’ most useful.

For that most part the only way I see you gaining anything with this swap is if our original setup had the peanut cam in it.

What shim gaskets have you had luck with? None are intended to be used with late model, light weight heads (basically anything mid/late 70’s and up).

 

Thanks for the info everyone!

I am actually doing this cam swap mainly because i had the cam avaliable for cheap, it will wake up my 305 a bit, and im only 16, so the learning experience is amazing.

I will check all of my springs, if i can get away with .480/.491 lift without damaging anything, then i will leave springs stock.

The original cam in my car
Int/Exh 179/194 Lift .350/.384

On the new cam:
Int/Exh 202/208 Lift .460/.460 (with 1.5 rockers)

Im thinking it will bring up the performance a bit.

I also need this engine to be a streetable engine, as its my DD.

I will post up a bunch of pictures when im done, but its been fun doing all of this so far.

Thanks for the input guys.

Sheldon

 

No, they will pound the seals to pieces. Maximum lift .460 (verified)

 

The locals run the Felpro rubber coated metal shim gaskets. I may be misleading saying metal shim, I just know it's a very thin gasket with a rubber coating. I was told by my mechanic to run these on a 305. I never ended up building the 305 so I've never had experience with them on there. As for the seal pounding, Dyno Don knows his stuff I'de trust him on that one. How do you remedy that Don? Run a different seal? Or do you have to get different retainers?