stevieturbo

Ive recently swapped from a 382, to a 346 after some engine problems.

All other aspects of my build are the same however ( albeit cam timing re-set due to chain stretch )

I did also swap the crank pulley for a different one, which should be 8.5", but is fractionally bigger than my previous one of same size ( belt was harder to put on )

Initial testing on the road, seen me make an easy 15psi at 5000rpm. It was difficult to test above this due to lack of traction, then it started raining, so that put a stop to that. But I did see 20+psi a couple of times at 6500rpm.

So I went racing on friday, half untested on a semi-new engine. All weekend Ive been struggling to make say 18-19psi.

I was consistently making this with my 382, same blower speeds.

Power above 6000rpm doesnt feel that great, and it certainly doesnt pull hard to 7k, whereas before it was fairly good up there.

Could this lack of boost be valvetrain related ? I see no obvious signs of belt slippage, and I dont honestly believe I have any slippage.

This thing should be hitting like 68k at 7000rpm, so I had expected an easy 20+psi, and I did see this briefly on the road before the weather turned shitty.

As for power.....I dumped more meth in for this build. But I was only trapping 138mph or thereabouts.

I know its a smaller engine, but Im way down on power over my 382, for same blower speeds.

Where has my boost gone !!!!

Pro Stock John

iTrader: (34)

Same valvesprings? Same cam?

ty_ty13

iTrader: (42)

tighten the belt back up...

stevieturbo

I did, made no difference. There is also no visible dust from the belt.

PSJ.

Same heads, same springs, same cam, same stock lifters I have been using since I went LSx. ( admittedly used lifters at that point too )
Same 1.7 YT's too

Not 100% sure on lifter pre-load, but I'd say its probably more than it should be. I did measure, but damned if I can remember, but it could easily be 0.080-0.090"

Im using 7.400" pushrods, but do have a set of 7.350"s albeit -1 that broke a few days after I built my 382 over a year ago...hence using the 7.4's

I had fully intended to use a set of 1.75 Jesel SS non-adj this time around...

But no surprise, they wouldnt fit with my heads, and when modified to fit, would require some very short pushrods ( circa 7.25-7.30" ) all of which seems strange. Although I am on Edelbrock heads..
Surely Jesel arent so sort sighted to build rockers that literally will only work with stock heads ?

ty_ty13

iTrader: (42)

was it very hot out... sometimes the DA will effect the boost i get...

stevieturbo

not especially...

Its even stranger, given its same blower speed and a smaller engine. Even my 382 was consistently making more boost than this 346 is ?

Bost patterns with the 346 were consistent all weekend. Made about 10 passes on friday, then another 10 or so on Sunday ( different venue ) along with a standing mile.

In the mile, boost started tailing around 6200rpm+. No sharp drops, just a gradual decrease as the rpm's rose to max of 6600rpm ( 190.7mph standing mile )

alwaysinboost

steve have you done a boost leak test recently??

stevieturbo

as in to test plumbing ?

Nope...but given I have just rebuilt, and all hoses and clamps are sound, I dont think that side of things is leaking. Pipe routes are short, and easily visible.

But it is a test I can do.

Although oddly, some of the boost readings pre-post IC as measured in the end tanks, would be slightly higher than expected compared to MAP.

Id need to check my logs more carefully, to check the discrepancy between them.

alwaysinboost

nothing against you personally but everyone always says "everything looks fine" or "all my clamps are tight" but there is NO WAY you can look at a pipe and tell if its leaking or not. The only way to be 100% sure is to pressurize the intake track. People would be AMAZED at how many leaks they infact do have if they never pressurized their system. there are SO MANY places there could be a leak, a couple could have a pin hole, there could be gaps in the welding on an intercooler or manifold are just a few that come to mind.

on this turbo system I built below there was no more then 4' of IC piping total and I had at least 1/2 a dozen leaks in the most inconspicuious places (pin holes in couplers, injector bungs, TB to manifold connection just to name a few). there would have been no way just by looking at a connection I could have spotted a leak! again nothing against you personally, just trying to hammer my point accross.

stevieturbo

I fully understand. I have previously pressure tested my IC, and pipework, so at that time, everything was sound.

But yes, anything can happen since then, especially to the silicone couplers etc. I will do a test on them just in case.

alwaysinboost

Cool, just make sure you do it @ the compressor inlet and that you don't remove any plumbing or hoses to do the test, except for your intake obviously. you want to leave EVERYTHING intact just like you would drive the car on the street. I forget if you car is turbo'ed or not, if it is and you have an MBC you will need to tighten it down a few turns otherwise it will bleed pressure off on you.

stevieturbo

Boost leak test done as far as the TB.

One leak detected, and sorted ( pre IC clamp not tight enough )

However, boost patterns remain pretty much the same. It seems to hit 18psi circa 6200rpm, but circa 6300rpm, boost always drops, and sort of flatlines at say 13-14psi

It will not regain boost, although the car will continue to accelerate to 7000rpm ( 4th gear runs )
Engine also feels pretty crap at that point.

Could it be valve float/bounce ? or lifters pumping up a bit ?

stevieturbo

update....

I am in the middle of removing the engine, and did another test.

I removed the rockers, and did a pressure test on the intake.

As expected, leaks....first of which are the rocker bolt holes lol.

Next up, TB flange has some very slight leaks, intake at circa 6psi. The TPS is also letting a bit of air out ( Accufab/Ford 85mm TB ), well a lot really.

But....more worrying, is some of the intake valves seem to be making a very poor seal. Ive removed 6 plugs ( not cyl 6 and 8, too awkward with headers on ) and pretty much all the intake valves are letting air past. With the front cylinders 1 and 2 letting quite a bit past.

Not really sure how this would affect performance ??

I havent done a compression test.

jeejee

iTrader: (3)

any udates ?

stevieturbo

Yes...engine is in bits !!!!

Seeing as the valves werent sealing very well, I stripped the heads and have ground them back in again. 2 exhaust valves are pitted a little, so these will be replaced.
Generally, the seats werent good and clean at all...

Id say this obviously covers the lost boost side of things. Id also say its partly, if not all to do with me having insufficient lifter pre-load ??
Causing early valve float...which in turn wont do the seats any good.

So the heads will be perfect again very soon...

Im in the process of getting a custom set of JE pistons to rebuild as a 383 with 9.35:1 CR instead of my 8.7:1.

New 1.75 Jesel rockers to replace the 1.7 YT's, Morels and generally a nice rebuild.

redvictor

Stevie,are you on pump gas?

stevieturbo

Yes, albeit with methanol injection when racing. 97 RON BP Ultimate normally, although when on the mainland, I use V-power when I can find it.

Dont bother with meth on the road...no need for it really.

redvictor

just thought that maybe you should look at using Powerpour when you move the compression up.......
Works well for me....

stevieturbo

What is Powerpour ?

Im not going too high, aiming for 9.35-9.4:1 CR this time around. Compared to what ive heard some guys run recently, and the boost they make....mine is pretty tame !!!

redvictor

it's a bit different on pump.Use too much compression and you'll be on the edge of det for sure.I kept my compression low and use the boost to compensate.
http://www.webster-race-engineering.co.uk/powerpour.htm It's not an octane booster but a burn retarder.
Pretty much all the Street Eliminator racers use it.I tested it on the dyno as well as run it..