400 sbc in LeMans making ticking sound

musicman6120 · Member

400 sbc in LeMans making ticking sound

73SC · A Poncho Legend!

Based on what you have done it seems that exhaust leaks are the next area to investigate. I had a Monza with a small block that ticked like crazy and in the end it was a bad header gasket and loose header bolts. Of course the engine had to be lifted to repair this since the engine was shoehorned in there and the headers were in three pieces.

67curves · Addicted!

If the noise is from the back of the engine, maybe a cracked flex plate.

CdnGMfan · Canadian Poncho Superstar!

I don't suppose you are running the 74 smog pump or at least the original 74 exhaust manifolds with the smog tubes. Dad had a 74 Biscayne with a 350 that started ticking all the time. We took it to his old-time mechanic Roy, who must have been 70 years old at the time. What sounded to us like a lifter noise ended up being a small perforation in the smog tubes. Roy took off the complete smog setup (I should have kept it...), plugged the holes in the manifolds where the smog tubes went in and, no more ticking!

Attached is exactly what a stock 73 or 74 small block Chevy looked like fully dressed and in production form. Our 74 engine looked exactly like this, as would a 400 SBC. Note the tubes about the exhaust manifolds. They were the culprits. If the smog was removed and the holes were epoxied, perhaps the epoxy is blowing out.

ARCADIAN · Poncho Master!

Check the header gasket around each cylinder.You should see a bit of black/grey mark (exhaust) in this area.Sometimes the gasket burns through between the cylinders as the Mr.Gasket type get very hard and brittle from heat. I had this problem once and replaced the gaskets with carbon fiber ones from Percy's and no more blown gasket.

long stroke · Canadian Poncho Superstar!

I find the whole smog pump thing very interesting because my original 1974 Chev 400 V-8 small block never came with one. My dad bought the car new ( 74 Chev Caprice Estate wagon ) and the car and motor have never been molested. Cam, why is it some 74 400's had smog pumps and others did not. My 74 Chev was built in Oshawa, could the U.S. built 400's have smog pumps only? Here are some photos of my 74 Chev 400 V8. Cheers. George.

CdnGMfan · Canadian Poncho Superstar!

long stroke wrote:
I find the whole smog pump thing very interesting because my original 1974 Chev 400 V-8 small block never came with one. My dad bought the car new ( 74 Chev Caprice Estate wagon ) and the car and motor have never been molested. Cam, why is it some 74 400's had smog pumps and others did not. My 74 Chev was built in Oshawa, could the U.S. built 400's have smog pumps only? Here are some photos of my 74 Chev 400 V8. Cheers. George.

George, all 1974 Big Chevrolet engines and models came with a smog pump - except the LT4 400 4-barrel. The 400 2-barrel (LF6) was standard in the Caprice Classic series and optional on all others and used the smog pump, however all the wagons used the 400 4-barrel (LT4) exclusively as a standard engine and did not come with a smog pump unless it was a California car.

Incidently in California for 1974 they didn't offer any 2-barrel Chevy V8 engines, only the 4-barrel versions could pass the strict emissions tests (presumably due in part to the small 1.38" primaries vs. the 1.69" venturies of the 2-barrel carbs.) The Quadrajets in California carried different part #s so there were other calibrations as well. Getting stuff emissions-certified for sale was a panic back then, and with California being especially demanding they concentrated on the tweaking the Quadrajet with its smaller 1.38" primaries.

In 49 states plus Canada you got the L65 350-2, LF6 400-2 or the LS4 454-4, plus the LT4 400-4 exclusive to wagons. California got the LM1 350-4, LT4 400-4 and the LS4 454-4. Canada also was unique in that Biscayne, Bel Air & Impala coupes & sedans in Canada offered a 350-4, the LM1 with single exhaust. The Canadian LM1s used a smog pump, as did all California engines.

The L48 350-4 with dual exhausts on Chevelles & Monte Carlos (plus Canadian Lemans) were exclusive to Canada that year.

-- Edited by CdnGMfan on Friday 27th of June 2014 12:24:43 AM

73SC · A Poncho Legend!

Cam is bang on on Canadian LeMans, our first 73 with L48 had the set up as shown ion the photo. By trade in time in 76 it was starting to leak, tick and hiss. The car I have now had the tubes brazed closed on one side and still had the piping on the other albeit leaking and ticking when I git it in 2004. The AIR brackets and pulleys were in the trunk in a box.

long stroke · Canadian Poncho Superstar!

Cam, thank you for all the clarification on the 400 Chev V-8 and smog pumps. My wagon certainly is a four barrel 400 and i am very thankful it never came with that silly smog pump. I look at a smog pump as just another device to maintain, another device to break down and another device to cost you money. Plus it puts more drag on the motor and look at that.............. it leaks exhaust too. I will admit though, it is neat to look at on an engine. Cheers. George.