Greenfire

iTrader: (2)

I had a guy build my engine for me and I have a few questions for you guru's out there, b/c this guy is saying the below would not work for my set up which is a 383 LT4.

We originally agreed on these heads when they were bought to change out the springs. An email from the builder of the heads:This is a set of LT-4 heads I did a few years back for a blown 355. They were never installed. I no longer have the flowsheet as it is was on my dos PT software...which nothing will run any longer. From the build sheet Target intake was 282 @ .500 and 291 @ .600. Exhaust 193 @ .500 and 202 @ .600. The heads were originally built with 985 comp springs installed @ 1.750. As you can see they are lift limited. The customer is willing to install new springs if necessary.

We planned to swap the 985 springs out and install the PAC 1218 springs as suggested to us for better lift.

The emails below are from the guy that built my engine, arguing that the 985 comp springs were the better spring for the build:

With the 1.6 roller rockers, the beehive springs would not
work the actual valve lift is .611 on exhaust. The springs
supplied with the heads would not bind or hit the seals.

As far as the springs, the springs that are on there will work best for
the combination of valve train components that you got. The lift on the
cam was OK for 1.5 rockers, but with the cam lift and the 1.6 rockers it
was too much for the beehive springs and retainers that were sent. At
.611 lift, the spring retainers were going to hit the top of the seals,
and there was a chance of pring bind at igh RPM. If I increased the
installed heigth, the seat pressure would have been lower than I think
is acceptable. the springs on the heads are double springs plus a
damper, which i think will work better with the cam you bought.

We don't know if the builder tried to install the springs at 1.750 height as suggested by the guy who cut the cam and sent the beehive springs with the cam.

The Cam specs are below:

Intake Exhaust
.570 .571

Intake Exhaust
236 248

LSA 108.5

Let me know if you all need more information.

Thanks for your help.

Pampered-Z

611 is allot of lift for the beehives? You're probably going to be pushing them to their limits. I know with a GM847 and 1.6 on stock heads we were real close to coil bind, so we opt'd for 1.5 just to give us a bit of saftey.

* Note sure, i can't confirm the new style of them will go to 650 lift? * The ones we installed a few years back were close to bind at 600.

But honestly, I'm not a big fan of single springs, if a spring fails you run a good change of dropping the valve into the engine. I would go with the double/dampner springs rated to over 611, more towards 650 lift. For the cost of getting the heads cut to accept them is money well invested in my mind.

From the specs on that cam , you're going to be spinning that engine pretty high. I'd want to stay away from a single pring and possible valve float/bounch.

Greenfire

iTrader: (2)

Thanks for the reply, well noted!

Greenfire

iTrader: (2)

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BlackScreaminMachine

iTrader: (17)

With Bee hive you need NSA rockers, the newer comp 918's go to .625" lift, even the older ones could be pushed beyond the recommended .600" lift if installed height was done correctly.

Yeahdoug

Would the 1218 work at .610" lift, most likely. But if it was me I'd get a set of 1518s for the extra insurance.

Greenfire

iTrader: (2)

Thanks for the reply's guys. I am planning to replace the springs on the heads when I get back from my deployment in January. The install height for the Beehives should have been as stated above 1.750. I am at odds right now with the builder so that is a question I need to ask him if he even tried installing them at that height.

Thanks again for the advice.

Greenfire

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koolaid_kid

iTrader: (21)

I was under the impression that NSA vs. SA had more to do with RPMs rather than spring type. Please feel free to explain.

StealthFormula

iTrader: (35)

Just to throw out there....The PAC 1518's are the same as the 1218's except that they are nitrided for extra strength and are rated to a .650" lift vs. .600" with the 1218's. I run the 1518's myself.

Greenfire

iTrader: (2)

I got another email from my builder about the springs:

I tried 1.750 (which was what was written on the box) and with 1.6
rockers it would hit solid height (and it appeared to hit the top of the
valve seal). If I installed them at 1.800 (which is what the web site
recommends), the seat presseure looked way to low.

That's the only reason I didn't use them. The cam guy said the 985's
were too soft, but if you look at the specs they are stronger (higher
seat pressure and higher spring rate).


I asked the builder how low was the seat pressure, he has yet to get back to me on that question.

Greenfire

iTrader: (2)

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Greenfire

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IllusionalTA

iTrader: (9)

should have just brought me the car.. i"d be pimpin' a 383LT4 right now..