Need tips for putting engine together

[Joe R.]

I'm getting ready to start assembling my L72 (427 / 425) engine. The short block is done, the heads are done (valve train installed). Does anyone have any advice for me? For example, I've heard that the heat tube through the intake manifold should be blocked off because the gas in the carb tends to boil on a long drive with hot weather. Also, it has a new cam. Comp Cams recommends degreeing the cam. The machinist that built the short block says that he didn't do it because it will not be raced. Should I degree the cam?

Thanks,
Joe

[Tom D.]

Re: Need tips for putting engine together

There are several CD videos avail. I have used "How to Build Your Chevy Engines like a Pro". This is from a guy in CA who is on e-bay all the time.

I'll get the name if I can find it - It's not on the CD copies. He always sends an extra (free) CD showing a car show, demolition derby in Turlock, or the like.

td

[Joel F.]

Re: Need tips for putting engine together

His name is Ron Crisafulli. I think his ebay id is CFA-services

The DVD is good (especially for the price) but does not cover everything. But if you are buttoning up a short block it should cover your needs.

[Bill M.]

Re: Need tips for putting engine together

For example, I've heard that the heat tube through the intake manifold should be blocked off

Thanks,
Joe

I had a heat problem with my 65 396, so I installed an oil shield under the manifold, blocked the heat risers, and wired open the heat riser valve in 1978. I have had no problems with those changes, but my car is only driven in 50 degree or warmer weather. I would probably have carburetor icing in colder damp weather.

[Joe L.]

Re: Need tips for putting engine together

I'm getting ready to start assembling my L72 (427 / 425) engine. The short block is done, the heads are done (valve train installed). Does anyone have any advice for me? For example, I've heard that the heat tube through the intake manifold should be blocked off because the gas in the carb tends to boil on a long drive with hot weather. Also, it has a new cam. Comp Cams recommends degreeing the cam. The machinist that built the short block says that he didn't do it because it will not be raced. Should I degree the cam?

Thanks,
Joe

Joe-----


If you block the heat cross-over in the intake manifold you will lose functionality of the choke. 1966 was the first year for the divorced style choke on big blocks and the divorced style choke requires the heat cross-over.

Notwithstanding the above, it still might be a very good idea to get rid of the cross-over. I think the elimination of the cross-over has more benefits than detriments. You may not even need a choke but, if you do, you can convert to an electric choke. However, if you eliminate the cross-over, you MUST also do one of the following:

1) remove the heat riser valve and install a spacer, or;

2) PERMANENTLY wire open the heat riser valve, or;

3) remove the valve plate ("butterfly valve") from the heat riser valve assembly.

[Bill M.]

Re: Need tips for putting engine together

Joe-----


If you block the heat cross-over in the intake manifold you will lose functionality of the choke. 1966 was the first year for the divorced style choke on big blocks and the divorced style choke requires the heat cross-over.

Notwithstanding the above, it still might be a very good idea to get rid of the cross-over. I think the elimination of the cross-over has more benefits than detriments. You may not even need a choke but, if you do, you can convert to an electric choke. However, if you eliminate the cross-over, you MUST also do one of the following:

1) remove the heat riser valve and install a spacer, or;

2) PERMANENTLY wire open the heat riser valve, or;

3) remove the valve plate ("butterfly valve") from the heat riser valve assembly.

My '65 Corvette has a '66 427/425 intake with the divorced style choke Joe mentions. I don't use a choke.

Joe: Thanks for the clarification.

[Michael H.]

Re: Need tips for putting engine together

Notwithstanding the above, it still might be a very good idea to get rid of the cross-over. I think the elimination of the cross-over has more benefits than detriments. You may not even need a choke .

I agree. I haven't had an operating choke on my 425 HP in the last 25 years and I definitely don't miss it.

[Clem Z.]

Re: Need tips for putting engine together

i started blocking the heat riser crossovers in my 41 ford using copper pennies and that was in 1952 and have done it to every performance vehilcle i have had since then and i live in Pa and drove the cars in the winter. the only problem i ever had was when i had to leave the car out side over night in the winter it was a little slow warming up. if you want heated intake in the winter just tap both sides of the intake thru the heat riser passage and run your heater hose in one side and out the other.

[Duke W.]

Re: Need tips for putting engine together

Assuming the choke heat stove is located on the RH side of the inlet manifold, just block the heat riser passage on the LH side.

This creates a dead end passage that allows exhaust gas/heat up the choke stove side, which should yield proper choke operation, but will significantly decrease the amount of heat that reaches the base of the carburetor because exhaust gas cannot flow through.

Duke

[Joel F.]

Re: Need tips for putting engine together

This creates a dead end passage that allows exhaust gas/heat up the choke stove side, which should yield proper choke operation, but will significantly decrease the amount of heat that reaches the base of the carburetor because exhaust gas cannot flow through.

Interesting concept Duke. Has anyone done this and was it an improvement?

[Duke W.]

Re: Need tips for putting engine together

...not that I'm aware of. I've recommended it a number of times, but to my knowledge, no one has tried it. Someone needs to in order to see how it works.

It's not a major effort and can be easily reversed.

Note that blocking one or both sides of the heat riser passage requires that the heat riser valve be securely held open all the time. Otherwise the RH exhaust is effectively blocked with a closed valve.

Duke

[Joe R.]

Re: Need tips for putting engine together

Guys,

Thanks for the advice. I'm now planning to block off the left side with a stainless plate and remove the innards of the heat riser. I'll report back the results.

Joe

[William V.]

Re: Need tips for putting engine together

Joe

I like to degree a cam on #1 for street engines. This way you know where the cam timing is and you can slightly adjust for best street performance an economy. However, when building a race engine it's best to degree the cam for each cylinder. Should the cam cut be slightly off grind for one or more cylinders a slight power loss will occur and you lose the race . You would never detect this slight power loss on a street engine. I just finished building a small block street stroker using a Comp Cam and the degree on #1 was right on.

Good luck

Bill

[William B.]

Re: Need tips for putting engine together

This is the engine that requires the engine builder to notch the cam at the rear oiling journal, a lot of engine builders miss this because it was a 1 year only thing.

[Duke W.]

Re: Need tips for putting engine together

It was a two year deal - '65 and '66. These year big blocks require a circumferential groove, not a "notch" (like the '55-'56 small blocks) in the rear bearing journal and a unique "three-hole" bearing. No groove and/or a later single hole bearing will cause upper end oil starvation, which could damage the valve train.

This subject was thoroughly vetted within the last year, and the thread included good photos of the two bearings and I think part numbers.

Duke